ORCID Profile
0000-0002-5189-4046
Current Organisations
Peter MacCallum Cancer Institute
,
University of Wollongong
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Main Group Metal Chemistry | Inorganic Chemistry | Bioinorganic Chemistry | Biologically Active Molecules
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Medical and Health Sciences |
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.IJROBP.2012.11.035
Abstract: The use of image guidance protocols using soft tissue anatomy identification before treatment can reduce interfractional variation. This makes intrafraction clinical target volume (CTV) to planning target volume (PTV) changes more important, including those resulting from intrafraction bladder filling and motion. The purpose of this study was to investigate the required intrafraction margins for soft tissue image guidance from pretreatment and posttreatment volumetric imaging. Fifty patients with muscle-invasive bladder cancer (T2-T4) underwent an adaptive radiation therapy protocol using daily pretreatment cone beam computed tomography (CBCT) with weekly posttreatment CBCT. A total of 235 pairs of pretreatment and posttreatment CBCT images were retrospectively contoured by a single radiation oncologist (CBCT-CTV). The maximum bladder displacement was measured according to the patient's bony pelvis movement during treatment, intrafraction bladder filling, and bladder centroid motion. The mean time between pretreatment and posttreatment CBCT was 13 minutes, 52 seconds (range, 7 min 52 sec to 30 min 56 sec). Taking into account patient motion, bladder centroid motion, and bladder filling, the required margins to cover intrafraction changes from pretreatment to posttreatment in the superior, inferior, right, left, anterior, and posterior were 1.25 cm (range, 1.19-1.50 cm), 0.67 cm (range, 0.58-1.12 cm), 0.74 cm (range, 0.59-0.94 cm), 0.73 cm (range, 0.51-1.00 cm), 1.20 cm (range, 0.85-1.32 cm), and 0.86 cm (range, 0.73-0.99), respectively. Small bladders on pretreatment imaging had relatively the largest increase in pretreatment to posttreatment volume. Intrafraction motion of the bladder based on pretreatment and posttreatment bladder imaging can be significant particularly in the anterior and superior directions. Patient motion, bladder centroid motion, and bladder filling all contribute to changes between pretreatment and posttreatment imaging. Asymmetric expansion of CTV to PTV should be considered. Care is required in using image-guided radiation therapy protocols that reduce CTV to PTV margins based only on daily pretreatment soft tissue position.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 02-2021
Publisher: Wiley
Date: 20-05-2014
DOI: 10.1118/1.4875698
Abstract: The purpose of this investigation was to assess the angular dependence of a commercial optically stimulated luminescence dosimeter (OSLD) dosimetry system in MV x-ray beams at depths beyond d(max) and to find ways to mitigate this dependence for measurements in phantoms. Two special holders were designed which allow a dosimeter to be rotated around the center of its sensitive volume. The dosimeter's sensitive volume is a disk, 5 mm in diameter and 0.2 mm thick. The first holder rotates the disk in the traditional way. It positions the disk perpendicular to the beam (gantry pointing to the floor) in the initial position (0°). When the holder is rotated the angle of the disk towards the beam increases until the disk is parallel with the beam ("edge on," 90°). This is referred to as Setup 1. The second holder offers a new, alternative measurement position. It positions the disk parallel to the beam for all angles while rotating around its center (Setup 2). Measurements with five to ten dosimeters per point were carried out for 6 MV at 3 and 10 cm depth. Monte Carlo simulations using GEANT4 were performed to simulate the response of the active detector material for several angles. Detector and housing were simulated in detail based on microCT data and communications with the manufacturer. Various material compositions and an all-water geometry were considered. For the traditional Setup 1 the response of the OSLD dropped on average by 1.4% ± 0.7% (measurement) and 2.1% ± 0.3% (Monte Carlo simulation) for the 90° orientation compared to 0°. Monte Carlo simulations also showed a strong dependence of the effect on the composition of the sensitive layer. Assuming the layer to completely consist of the active material (Al2O3) results in a 7% drop in response for 90° compared to 0°. Assuming the layer to be completely water, results in a flat response within the simulation uncertainty of about 1%. For the new Setup 2, measurements and Monte Carlo simulations found the angular dependence of the dosimeter to be below 1% and within the measurement uncertainty. The dosimeter system exhibits a small angular dependence of approximately 2% which needs to be considered for measurements involving other than normal incident beams angles. This applies in particular to clinical in vivo measurements where the orientation of the dosimeter is dictated by clinical circumstances and cannot be optimized as otherwise suggested here. When measuring in a phantom, the proposed new setup should be considered. It changes the orientation of the dosimeter so that a coplanar beam arrangement always hits the disk shaped detector material from the thin side and thereby reduces the angular dependence of the response to within the measurement uncertainty of about 1%. This improvement makes the dosimeter more attractive for clinical measurements with multiple coplanar beams in phantoms, as the overall measurement uncertainty is reduced. Similarly, phantom based postal audits can transition from the traditional TLD to the more accurate and convenient OSLD.
Publisher: Wiley
Date: 03-02-2009
DOI: 10.1118/1.3070539
Abstract: In applying 3D conformal radiation therapy to a tumor clinical target volume (CTV), a margin is added around the CTV to account for any sources of error in the application of treatment which may result in misalignment between the CTV and the dose distribution actually delivered. The volume enclosed within the CTV plus the margin is known as the PTV, or planning target volume. The larger the errors are anticipated to be, the wider the margin will need to be to accommodate those errors. Based on the approach of van Herk et al. ["The probability of correct target dosage: Dose-population histograms for deriving treatment margins in radiotherapy," Int. J. Radiat. Oncol. Biol., Phys. 47(4), 1121-1135 (2000)] this paper develops the mathematical theory behind the calculation of the margin width required to ensure that the entire CTV receives sufficiently high dose with sufficiently high probability. The margin recipe developed not only considers the magnitude of the errors but also includes a term to adjust for curved CTV surfaces. In doing so, the accuracy of the margin recipe is enhanced yet remains mathematically concise enough to be readily implemented in the clinical setting. The results are particularly relevant for clinical situations in which the uncertainties in treatment are large relative to the size of the CTV.
Publisher: Elsevier BV
Date: 11-2001
DOI: 10.1016/S0360-3016(01)01689-3
Abstract: To examine whether changes in the effective doubling time of tumor cells during irradiation of head-and-neck cancer are linked to accumulating dose. Optimal fitting of the results of four apparently iso-effective regimens in three recently reported randomized controlled trials (continuous hyperfractionated accelerated radiation therapy [CHART], Radiation Therapy Oncology Group [RTOG] 90-03, and Trans-Tasman Radiation Oncology Group [TROG] 91.01) was attempted using two different types of model of the change in effective doubling time that may occur during treatment. The first involved the traditional approach where doubling time changes at specific times after the start of treatment regardless of fractionation used (''fixed response time'' models). The second is where changes in doubling time are linked to accumulating biologic dose (''cellular depletion'' models). Changes in effective doubling time occur during radiotherapy for head-and-neck cancer. Data from the three trials can be fitted successfully by functions that imply a continuous reduction in effective doubling time. Models linking the reductions in effective doubling time to the cellular depletion that occurs in the tumor during radiotherapy fit the data satisfactorily. Effective doubling time ultimately reduces to 2 days, or slightly less, during high-dose radiotherapy regimens designed to cure squamous head-and-neck cancer. If the assumption of iso-effectivity is justified then this study indicates that the ''repopulation phenomenon'' may be best described by a function that depicts a reduction in effective tumor cell doubling time that decreases continuously during treatment down to a certain minimum value. Furthermore, this reduction may be linked to cellular depletion.
Publisher: Wiley
Date: 22-06-2021
DOI: 10.1002/ACM2.13319
Abstract: This study aimed to develop a physical geometric phantom for the deformable image registration (DIR) credentialing of radiotherapy centers for a clinical trial and tested the feasibility of the proposed phantom at multiple domestic and international institutions. The phantom reproduced tumor shrinkage, rectum shape change, and body shrinkage using several physical phantoms with custom inserts. We tested the feasibility of the proposed phantom using 5 DIR patterns at 17 domestic and 2 international institutions (21 datasets). Eight institutions used the MIM software (MIM Software Inc, Cleveland, OH) seven used Velocity (Varian Medical Systems, Palo Alto, CA), and six used RayStation (RaySearch Laboratories, Stockholm, Sweden). The DIR accuracy was evaluated using the Dice similarity coefficient (DSC) and Hausdorff distance (HD). The mean and one standard deviation (SD) values (range) of DSC were 0.909 ± 0.088 (0.434–0.984) and 0.909 ± 0.048 (0.726–0.972) for tumor and rectum proxies, respectively. The mean and one SD values (range) of the HD value were 5.02 ± 3.32 (1.53–20.35) and 5.79 ± 3.47 (1.22–21.48) (mm) for the tumor and rectum proxies, respectively. In three patterns evaluating the DIR accuracy within the entire phantom, 61.9% of the data had more than a DSC of 0.8 in both tumor and rectum proxies. In two patterns evaluating the DIR accuracy by focusing on tumor and rectum proxies, all data had more than a DSC of 0.8 in both tumor and rectum proxies. The wide range of DIR performance highlights the importance of optimizing the DIR process. Thus, the proposed method has considerable potential as an evaluation tool for DIR credentialing and quality assurance.
Publisher: SAGE Publications
Date: 08-2014
Abstract: Motion management strategies are important during stereotactic ablative body radiotherapy for abdominal targets. The kidney is a mobile retroperitoneal organ that moves with respiration. A review of the literature was performed to investigate the reported degree of kidney motion associated with various breathing conditions. A structured search was performed using Medline from January 1970 to May 2013 for all publications describing cranial-caudal kidney motion. Relevance to radiotherapy practice was reviewed based on any breathing instructions and/or immobilization equipment that could affect breathing pattern. Studies were categorized under three types of breathing conditions: Forced-shallow, breath-hold/deep and free. A total of 25 publications were identified describing cranial-caudal kidney motion with a combined total of 415 participants. Three publications described forced-shallow breathing using prone positioning or abdominal compression plates. Prone positioning, compared to supine positioning, did little to minimise kidney motion, however use of compression plates can result in kidney motion of less than 5 mm. Eight publications described deep breathing/breath hold techniques that showed average kidney motion ranging between 10 mm-40 mm. Fifteen publications investigated kidney motion under free breathing with the majority reporting mean motion of less than 10 mm. Kidney movement of up to 8.1 mm in the anterior posterior direction and 6.2 mm laterally were reported with no indications that breathing technique can influence the extent of this motion. In summary, kidney movement is complex and consideration should be made to ensure that motion management strategies provide the desired radiotherapy benefit. There are limited publications on the effectiveness of abdominal compression on reducing kidney motion which warrant further investigation in this area.
Publisher: Elsevier BV
Date: 04-2008
Publisher: Elsevier
Date: 2006
Publisher: American Society of Clinical Oncology (ASCO)
Date: 20-06-2007
DOI: 10.1200/JCO.2007.25.18_SUPPL.18503
Abstract: 18503 Background Breast cancer risk after mantle irradiation has prompted concern regarding the use of IFRT for ESHL. As breast cancer risk is radiation dose related, reliable estimates of breast radiation dose from IFRT might aid in idual patient risk assessment. However, estimates of breast dose from radiation scatter/leakage beyond the involved field, using standard computer algorithms, are of uncertain accuracy. The aims of this study were to compare computer estimates with measured breast dose, and to compare breast dose from mantle and neck IFRT. Methods A phantom with breast tissue equivalent was used to determine breast dose using computerized treatment planning (CMS XiO), and to perform measurements within the phantom breast tissue using thermoluminescent dosimetry (TLD). These measurements were made for mantle fields and (neck) IFRT. Results Computer estimates and TLD measurements of breast dose in centigray (cGY) are shown for IFRT and mantle treatment, for a prescribed dose of 3000cGy, using 6MV X-rays from a Varian 21eX linear accelerator. Conclusions Breast dose from neck IFRT was lower than from mantle treatment by an order of magnitude, but being well outside the treatment field, was not accurately estimated by our computer algorithm. Work in progress will examine breast dose from mediastinal IFRT and involved node irradiation. Modifications to the planning algorithm may improve accuracy of dose estimates at a distance from the primary field, allowing routine breast dose estimates for patients. Ultimately, utilisation of dose-risk data may allow risk modelling and risk-benefit analysis of IFRT for ESHL in in idual patients. [Table: see text] No significant financial relationships to disclose.
Publisher: Elsevier BV
Date: 06-1997
DOI: 10.1016/S0167-8140(97)00059-5
Abstract: Hair cortical cell counting (HCCC) represents a non-invasive, in-vivo measure of cell kill in the human integument. Sixty-six patients undergoing conventionally fractionated, external beam radiotherapy for early stage carcinoma of the prostate had groin hair s les counted. This technique is a sensitive and reproducible measure of radiation effect and may have applicability as an in-vivo prediction tool or in the field of biological dosimetry. A repopulative follicular response occurring at 3-4 weeks may explain flattening of the dose response curve.
Publisher: IOP Publishing
Date: 04-2017
Publisher: IEEE
Date: 04-2007
Publisher: Wiley
Date: 11-01-2013
DOI: 10.1118/1.4773310
Abstract: Stereotactic lung radiotherapy is complicated by tumor motion from patient respiration. Four-dimensional CT (4DCT) imaging is a motion compensation method used in treatment planning to generate a maximum intensity projection (MIP) internal target volume (ITV). Image guided radiotherapy during treatment may involve acquiring a volumetric cone-beam CT (CBCT) image and visually aligning the tumor to the planning 4DCT MIP ITV contour. Moving targets imaged with CBCT can appear blurred and currently there are no studies reporting on the effect that irregular breathing patterns have on CBCT volumes and their alignment to 4DCT MIP ITV contours. The objective of this work was therefore to image a phantom moving with irregular breathing patterns to determine whether any configurations resulted in errors in volume contouring or alignment. A Perspex thorax phantom was used to simulate a patient. Three wooden "lung" inserts with embedded Perspex "lesions" were moved up to 4 cm with computer-generated motion patterns, and up to 1 cm with patient-specific breathing patterns. The phantom was imaged on 4DCT and CBCT with the same acquisition settings used for stereotactic lung patients in the clinic and the volumes on all phantom images were contoured. This project assessed the volumes for qualitative and quantitative changes including volume, length of the volume, and errors in alignment between CBCT volumes and 4DCT MIP ITV contours. When motion was introduced 4DCT and CBCT volumes were reduced by up to 20% and 30% and shortened by up to 7 and 11 mm, respectively, indicating that volume was being under-represented at the extremes of motion. Banding artifacts were present in 4DCT MIP images, while CBCT volumes were largely reduced in contrast. When variable litudes from patient traces were used and CBCT ITVs were compared to 4DCT MIP ITVs there was a distinct trend in reduced ITV with increasing litude that was not seen when compared to true ITVs. Breathing patterns with a rest period following expiration resulted in well-defined superior edges and were better aligned using an edge-to-edge alignment technique. In most cases, sinusoidal motion patterns resulted in the closest agreements to true values and the smallest misalignments. Strategies are needed to compensate for volume losses at the extremes of motion for both 4DCT MIP and CBCT images for larger and varied litudes, and for patterns with rest periods following expiration. Lesions moving greater than 2 cm would warrant larger treatment margins added to the 4DCT MIP ITV to account for the volume being under-represented at the extremes of motion. Lesions moving with a rest period following expiration would be better aligned using an edge-to-edge alignment technique. Sinusoidal patterns represented the ideal clinical scenario, reinforcing the importance of investigating clinically relevant motions and their effects on 4DCT MIP and CBCT volumes. Since most patients do not breathe sinusoidally this may lead to misinterpretation of previous studies using only sinusoidal motion.
Publisher: Elsevier BV
Date: 03-2013
DOI: 10.1016/J.RADONC.2013.02.010
Abstract: To investigate the impact of treatment delays on radiation therapy (RT) target volumes and overall survival (OS) in patients with non-small cell lung cancer (NSCLC) who underwent two baseline FDG PET/CT scans. Patients underwent a staging (PET1) and RT planning (PET2) FDG PET/CT scan. At PET1 all patients were eligible for radical chemo-RT. OS and progression-free survival (PFS) were compared for patients remaining eligible for radical RT and those treated palliatively because PET2 showed progression. RT target volumes were contoured using PET1 and PET2. Normal tissue doses were compared for patients remaining eligible for radical RT. Eighty-two patients underwent PET2 scans between October 2004 and February 2007. Of these, 21 had a prior PET1 scan, median 23 days apart (range 8-176 days). Six patients (29%) were unsuitable for radical RT after PET2 five received palliative treatment and one received no treatment. Patients treated palliatively had significantly worse OS and PFS than patients treated radically p<0.001. Mean RT tumour volume increased from 105cc to 198cc (p<0.005) between scans. Disease progression while awaiting initiation of curative RT in NSCLC is associated with larger treatment volumes and worse survival.
Publisher: Elsevier BV
Date: 10-2012
DOI: 10.1016/J.CLON.2012.04.004
Abstract: To compare the treatment time and cost of prostate cancer fiducial marker image-guided radiotherapy (IGRT) using orthogonal kilovoltage imaging (KVI) and automated couch shifts and orthogonal electronic portal imaging (EPI) and manual couch shifts. IGRT treatment delivery times were recorded automatically on either unit. Costing was calculated from real costs derived from the implementation of a new radiotherapy centre. To derive cost per minute for EPI and KVI units the total annual setting up and running costs were ided by the total annual working time. The cost per IGRT fraction was calculated by multiplying the cost per minute by the duration of treatment. A sensitivity analysis was conducted to test the robustness of our analysis. Treatment times without couch shift were compared. Time data were analysed for 8648 fractions, 6057 from KVI treatment and 2591 from EPI treatment from a total of 294 patients. The median time for KVI treatment was 6.0 min (interquartile range 5.1-7.4 min) and for EPI treatment it was 10.0 min (interquartile range 8.3-11.8 min) (P value < 0.0001). The cost per fraction for KVI was A$258.79 and for EPI was A$345.50. The cost saving per fraction for KVI varied between A$66.09 and A$101.64 by sensitivity analysis. In patients where no couch shift was made, the median treatment delivery time for EPI was 8.8 min and for KVI was 5.1 min. Treatment time is less on KVI units compared with EPI units. This is probably due to automation of couch shift and faster evaluation of imaging on KVI units. Annual running costs greatly outweigh initial setting up costs and therefore the cost per fraction was less with KVI, despite higher initial costs. The selection of appropriate IGRT equipment can make IGRT practical within radiotherapy departments.
Publisher: American Association for Cancer Research (AACR)
Date: 10-2016
DOI: 10.1158/1078-0432.CCR-16-0138
Abstract: Purpose: To study the response of irradiated and out-of-field normal tissues during localized curative intent radiotherapy. Experimental Design: Sixteen patients with non–small cell lung carcinoma (NSCLC) received 60 Gy in 30 fractions of definitive thoracic radiotherapy with or without concurrent chemotherapy. Peripheral blood lymphocytes (PBL) and eyebrow hairs were s led prior, during, and after radiotherapy. Clinical variables of radiotherapy dose/volume, patient age, and use of chemoradiotherapy were tested for association with γ-H2AX foci, a biomarker of DNA damage that underlies cellular response to irradiation. Results: Radiotherapy induced an elevation of γ-H2AX foci in PBL, representing normal tissues in the irradiated volume, 1 hour after fraction one. The changes correlated directly with mean lung dose and inversely with age. γ-H2AX foci numbers returned to near baseline values in 24 hours and were not significantly different from controls at 4 weeks during radiotherapy or 12 weeks after treatment completion. In contrast, unirradiated hair follicles, a surrogate model for out-of-field normal tissues, exhibited delayed “abscopal” DNA damage response. γ-H2AX foci significantly increased at 24 hours post-fraction one and remained elevated during treatment, in a dose-independent manner. This observed abscopal effect was associated with changes in plasma levels of MDC/CCL22 and MIP-1α/CCL3 cytokines. No concordant changes in size and concentration of circulating plasma exosomes were observed. Conclusions: Both localized thoracic radiotherapy and chemoradiotherapy induce pronounced systemic DNA damage in normal tissues. In idual assessment of biologic response to dose delivered during radiotherapy may allow for therapeutic personalization for patients with NSCLC. Clin Cancer Res 22(19) 4817–26. ©2016 AACR. See related commentary by Verma and Lin, p. 4763
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.IJROBP.2015.01.034
Abstract: To develop a mathematical tool that can update a patient's planning target volume (PTV) partway through a course of radiation therapy to more precisely target the tumor for the remainder of treatment and reduce dose to surrounding healthy tissue. Daily on-board imaging was used to collect large datasets of displacements for patients undergoing external beam radiation therapy for solid tumors. Bayesian statistical modeling of these geometric uncertainties was used to optimally trade off between displacement data collected from previously treated patients and the progressively accumulating data from a patient currently partway through treatment, to optimally predict future displacements for that patient. These predictions were used to update the PTV position and margin width for the remainder of treatment, such that the clinical target volume (CTV) was more precisely targeted. Software simulation of dose to CTV and normal tissue for 2 real prostate displacement datasets consisting of 146 and 290 patients treated with a minimum of 30 fractions each showed that re-evaluating the PTV position and margin width after 8 treatment fractions reduced healthy tissue dose by 19% and 17%, respectively, while maintaining CTV dose. Incorporating patient-specific displacement patterns from early in a course of treatment allows PTV adaptation for the remainder of treatment. This substantially reduces the dose to healthy tissues and thus can reduce radiation therapy-induced toxicities, improving patient outcomes.
Publisher: MDPI AG
Date: 04-09-2020
Abstract: Thoracic radiotherapy (RT) is required for the curative management of inoperable lung cancer, however, treatment delivery is limited by normal tissue toxicity. Prior studies suggest that using radiation-induced DNA damage response (DDR) in peripheral blood mononuclear cells (PBMC) has potential to predict RT-associated toxicities. We collected PBMC from 38 patients enrolled on a prospective clinical trial who received definitive fractionated RT for non-small cell lung cancer. DDR was measured by automated counting of nuclear γ-H2AX foci in immunofluorescence images. Analysis of s les collected before, during and after RT demonstrated the induction of DNA damage in PBMC collected shortly after RT commenced, however, this damage repaired later. Radiation dose to the tumour and lung contributed to the in vivo induction of γ-H2AX foci. Aliquots of PBMC collected before treatment were also irradiated ex vivo, and γ-H2AX kinetics were analyzed. A trend for increasing of fraction of irreparable DNA damage in patients with higher toxicity grades was revealed. Slow DNA repair in three patients was associated with a combined dysphagia/cough toxicity and was confirmed by elevated in vivo RT-generated irreparable DNA damage. These results warrant inclusion of an assessment of DDR in PBMC in a panel of predictive biomarkers that would identify patients at a higher risk of toxicity.
Publisher: Wiley
Date: 06-2013
DOI: 10.1118/1.4815049
Publisher: Oxford University Press (OUP)
Date: 22-11-2015
DOI: 10.1093/RPD/NCV480
Abstract: Production of radioisotopes in medical linear accelerators (linacs) is of concern when the beam energy exceeds the threshold for the photonuclear interaction. Staff and patients may receive a radiation dose as a result of the induced radioactivity in the linac. Gamma-ray spectroscopy was used to identify the isotopes produced following the delivery of 18 MV photon beams from a Varian 21EX and an Elekta Synergy. The prominent radioisotopes produced include
Publisher: Wiley
Date: 03-2014
DOI: 10.1118/1.4865786
Abstract: On 1 July 2012, the Australian Clinical Dosimetry Service (ACDS) released its Optically Stimulated Luminescent Dosimeter (OSLD) Level I audit, replacing the previous TLD based audit. The aim of this work is to present the results from this new service and the complete uncertainty analysis on which the audit tolerances are based. The audit release was preceded by a rigorous evaluation of the InLight® nanoDot OSLD system from Landauer (Landauer, Inc., Glenwood, IL). Energy dependence, signal fading from multiple irradiations, batch variation, reader variation, and dose response factors were identified and quantified for each in idual OSLD. The detectors are mailed to the facility in small PMMA blocks, based on the design of the existing Radiological Physics Centre audit. Modeling and measurement were used to determine a factor that could convert the dose measured in the PMMA block, to dose in water for the facility's reference conditions. This factor is dependent on the beam spectrum. The TPR20,10 was used as the beam quality index to determine the specific block factor for a beam being audited. The audit tolerance was defined using a rigorous uncertainty calculation. The audit outcome is then determined using a scientifically based two tiered action level approach. Audit outcomes within two standard deviations were defined as Pass (Optimal Level), within three standard deviations as Pass (Action Level), and outside of three standard deviations the outcome is Fail (Out of Tolerance). To-date the ACDS has audited 108 photon beams with TLD and 162 photon beams with OSLD. The TLD audit results had an average deviation from ACDS of 0.0% and a standard deviation of 1.8%. The OSLD audit results had an average deviation of -0.2% and a standard deviation of 1.4%. The relative combined standard uncertainty was calculated to be 1.3% (1σ). Pass (Optimal Level) was reduced to ≤2.6% (2σ), and Fail (Out of Tolerance) was reduced to >3.9% (3σ) for the new OSLD audit. Previously with the TLD audit the Pass (Optimal Level) and Fail (Out of Tolerance) were set at ≤4.0% (2σ) and >6.0% (3σ). The calculated standard uncertainty of 1.3% at one standard deviation is consistent with the measured standard deviation of 1.4% from the audits and confirming the suitability of the uncertainty budget derived audit tolerances. The OSLD audit shows greater accuracy than the previous TLD audit, justifying the reduction in audit tolerances. In the TLD audit, all outcomes were Pass (Optimal Level) suggesting that the tolerances were too conservative. In the OSLD audit 94% of the audits have resulted in Pass (Optimal level) and 6% of the audits have resulted in Pass (Action Level). All Pass (Action level) results have been resolved with a repeat OSLD audit, or an on-site ion chamber measurement.
Publisher: IOP Publishing
Date: 24-03-2011
Publisher: Wiley
Date: 08-1996
DOI: 10.1118/1.597873
Abstract: Clinical applications of electrons may involve oblique incidence of beams, and although dose variations for angles up to 60 degrees from normal incidence are well documented, no results are available for highly oblique beams. Surface dose measurements in highly oblique beams were made using parallel-plate ion chambers and both standard LiF:Mg, Ti and carbon-loaded LiF Thermoluminescent Dosimeters (TLD). Obliquity factors (OBF) or surface dose at an oblique angle ided by the surface dose at perpendicular incidence, were obtained for electron energies between 4 and 20 MeV. Measurements were performed on a flat solid water phantom without a collimator at 100 cm SSD. Comparisons were also made to collimated beams. The OBFs of surface doses plotted against the angle of incidence increased to a maximum dose followed by a rapid dropoff in dose. The increase in OBF was more rapid for higher energies. The maximum OBF occurred at larger angles for higher-energy beams and ranged from 73 degrees for 4 MeV to 84 degrees for 20 MeV. At the dose maximum, OBFs were between 130% and 160% of direct beam doses, yielding surface doses of up to 150% of Dmax for the 20 MeV beam. At 2 mm depth the dose ratio was found to increase initially with angle and then decrease as Dmax moved closer to the surface. A higher maximum dose was measured at 2 mm depth than at the surface. A comparison of ion chamber types showed that a chamber with a small electrode spacing and large guard ring is required for oblique dose measurement. A semiempirical equation was used to model the dose increase at the surface with different energy electron beams.
Publisher: SAGE Publications
Date: 2021
DOI: 10.1177/16094069211008333
Abstract: Australia has one of the highest asthma prevalence rates in the world, with this chronic and debilitating condition affecting one in nine people. The health and mental wellbeing of young people with asthma are worse than not only their peers without asthma but also worse than that of people with asthma at other ages. Psychological interventions could be beneficial in treating symptoms of elevated psychological distress in patients with asthma. However, evidence suggests that engagement with mental health services is low in this population. Technology-based solutions that engage youth may overcome barriers to service uptake for both mental health and asthma management. To fast-track the successful translation of evidence-based treatment into practice, interactive, mixed-reality technologies such as augmented reality (AR), virtual reality (VR) and holographic technology may provide a novel, low-cost solution, yet to date, methodological rigor in the evaluation of mixed reality for this purpose is lacking. To evaluate the perceived usability and acceptability of these technologies, mixed reality tools will be developed by the author team to deliver a component of a psychological intervention for treatment of elevated psychological distress among young people with asthma. Qualitative research will be conducted through one-on-one interviews with young people with asthma, parents/caregivers of young people with asthma, and with health professionals, during which participants will have time to interact with the resources. Moderator guides will be used to direct interviews, and will be supplemented with a questionnaire, including Likert-type measures of usability and acceptability to facilitate triangulation of data. Understanding and data obtained through this study will be used to develop version 2.0 mixed reality tools, which will be tested for feasibility in a RCT. Improving access to and uptake of evidence-based treatments for elevated psychological distress in young people with asthma may reduce the burden of this highly prevalent disease.
Publisher: Informa UK Limited
Date: 11-2019
DOI: 10.1111/CP.12185
Publisher: IOP Publishing
Date: 26-06-2013
Publisher: Wiley
Date: 22-11-2019
Abstract: In the 4DCT era, the definition of lung organ-at-risk (OAR) volumes for dose-volume histogram (DVH) calculation is unclear, introducing potential for variability in practice. We aimed to identify definitions used clinically and evaluate the magnitude of DVH differences between these. We surveyed Australian & New Zealand departments about lung radiotherapy protocols including lung OAR volume definition. We used these definitions to calculate lung DVHs on 10 patients prescribed lung IMRT (60-66 Gy/30-33 fractions). We calculated mean lung dose (MLD), V20 and V30 for 'Lungs - PTV', 'Lungs - CTV', 'Lungs - iGTV' (internal GTV in all respiratory phases) and 'Lungs - GTV_EX' (expiratory phase). The response rate was 39% (34/88). 14% and 29% of departments did not have a departmental protocol for OAR and tumour volume delineation, respectively. All permutations for lung OAR volumes were used with no clear preference. For conventional radiotherapy (n = 27), this included Lungs alone (n = 1), Lungs - PTV (n = 6), Lungs - CTV (n = 2), Lungs - iGTV (n = 6), Lungs - GTV in single phase (n = 5) and in idual clinician preference (n = 7). The different lung OAR volumes resulted in MLD difference ranging from 0.9 to 4.15 Gy, V20 from 1.5% to 6.6% and V30 from 1.34% to 7.11%. The largest differences between subtraction of GTV_EX and iGTV were 0.32 Gy, 0.43% and 0.46% for MLD, V20 and V30, respectively. A significant number of departments lacked lung cancer radiotherapy contouring protocols. Lung OAR volume definition was variable between and within departments. Potentially clinically significant differences in lung DVH parameters were seen according to the volume used.
Publisher: Elsevier BV
Date: 05-2023
Publisher: IOP Publishing
Date: 08-2019
DOI: 10.1088/1742-6596/1305/1/012048
Abstract: The utility of gel dosimeters is sought to be improved upon in this study which proposes a target region of different X-ray CT contrast that is dose sensitive. The changes in the physico-chemical makeup of nPAG caused by the addition of the X-ray imaging Iodine based contrast agent Isovue are explored. The impact of this change on dose measurements is also discussed. The increase in HU as it correlates with increasing Isovue concentration is detailed, along with the dosimetric changes that occur, namely the steepness of the dose response curve and general shape of the percentage depth dose curve. It is noted that diffusion of Isovue from one gel region to another has significant dosimetric impact and the experimental method was constructed and conducted with this in mind. Further refinement and optimisation of the Isovue nPAG formulation will lead to a target region dosimeter that can be contoured on X-ray CT and used in the improvement of planning protocols, especially in cases that involve motion and deformation of target volumes.
Publisher: Elsevier BV
Date: 02-2015
Publisher: Wiley
Date: 06-2016
DOI: 10.1118/1.4956403
Publisher: Elsevier BV
Date: 09-2022
Publisher: American Society of Clinical Oncology (ASCO)
Date: 05-2017
Publisher: Elsevier BV
Date: 02-1993
DOI: 10.1016/0167-8140(93)90097-R
Abstract: Thermoluminescence dosimetry (TLD) for radiotherapy treatment verification is performed in the Prince of Wales Hospital in Sydney for a wide range of applications: (A) to determine the dose in difficult treatment geometries, (B) to record the dose to critical organs, and (C) to monitor special treatments such as total body irradiation (TBI). TLD measurements were performed with the aim to investigate cases where dose prediction is difficult and not as part of a routine verification procedure. We reviewed 1058 reports of TLD performed during the treatment of 502 patients between 1986 and 1991 to evaluate how the TLD results compare with the dose determined by the treatment plan. Reasons for possible discrepancies should be identified. In 19% of all investigated cases a discrepancy of more than 10% was found between expected and measured doses. The discrepancies could be ided into three groups: (1) errors made in the TLD determination or evaluation, such as placement errors of the TLD chips (21% of all discrepancies) (2) mistakes made during the patient set-up, such as insufficient shielding or inadequate patient immobilisation (30%) (3) inadequate treatment planning and dose calculation procedure, such as wrong inverse square law corrections or errors due to limitations of the two-dimensional treatment planning system used (41% of all). In 8% of all discrepancies the reason remained unclear. A number of changes to treatment plans and modalities (e.g. changed scrotal shield, modified bolus) were introduced due to TLD results. The increasing number of TLD requests per year attests to the value of TLD as a treatment verification method in clinical practice.
Publisher: IOP Publishing
Date: 24-03-2014
Publisher: Wiley
Date: 30-07-2009
DOI: 10.1111/J.1754-9485.2009.02097.X
Abstract: Inconsistencies in contouring target volumes for partial breast irradiation (PBI) may result in geographical misses and compromise treatment outcomes. The present study aimed to (1) determine the variability of the target volumes contoured and treatment plans generated by participating centres in credentialing for participation in a multicentre PBI trial and (2) assess dosimetric changes when standardized target volumes were used. The CT image sets of two de-identified patients post-breast conserving surgery were used. Contouring of the target volumes for the two cases was performed and a treatment plan as per protocol specifications was generated for each case by the seven participating centres. Planning of both cases was repeated by five centres using a set of standardized target volumes to evaluate resulting dosimetric changes in the treatment plans. The surgical cavity, the part of the planning target volume used for dose evaluation and ipsilateral whole breast volumes contoured by the centres varied by 25%, 16% and 21% (1 standard deviation), respectively. The dosimetric variations found when the standardized target volumes were used were smaller than those noted when centre-specific volumes were used. The volumes of the ipsilateral lungs receiving 30% of the prescribed dose and the volumes of the ipsilateral whole breasts receiving 95% and 50% of the prescribed dose were reduced in the treatment plans developed using the standardized target volumes. Given the impact of contouring on dose distributions, quality assurance procedures in clinical trials of PBI need to take into account both the technical approaches and the contouring.
Publisher: Bioscientifica
Date: 31-07-2012
DOI: 10.1530/ERC-12-0176
Abstract: Radioiodine-131 ( 131 I) is widely used for diagnosis and treatment of benign thyroid diseases. Observational studies have not been conclusive about the carcinogenic potential of 131 I and we therefore conducted a meta-analysis. We performed a literature search till September 2011 which included 131 I as a diagnostic or treatment modality ( 131 I for treatment of thyroid cancer was excluded). Data on 64 different organ or organ group subsets comprising 22 029 exposed subjects in the therapeutic cohorts and 24 799 in the diagnostic cohorts in seven studies were included. Outcome was pooled as the relative risk (RR) using both standard and bias adjusted methods. Quality assessment was performed using a study-specific instrument. No increase in overall (RR 1.06, 95% CI: 0.94–1.19), main organ group or combined organ group (four groups known to concentrate 131 I RR 1.11, 95% CI: 0.94–1.31) risks was demonstrable. In idual organs demonstrated a higher risk for kidney (RR 1.70, 95% CI: 1.15–2.51) and thyroid (RR 1.99, 95% CI: 1.22–3.26) cancers with a strong trend for stomach cancer (RR 1.11, 95% CI: 0.92–1.33). A thyroid dose effect was seen for diagnostic doses. While there is no increase in the overall burden of cancer, an increase in risk to a few organs is seen which requires substantiation. The possible increase in thyroid cancer risk following diagnostic 131 I use should no longer be of concern given that it has effectively been replaced by the use of 99mTc-pertechnetate.
Publisher: Springer Science and Business Media LLC
Date: 28-09-2012
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.IJROBP.2014.07.043
Abstract: To describe our 3-dimensional conformal planning approaches and report early toxicities with stereotactic body radiation therapy for the management of primary renal cell carcinoma. This is an analysis of a phase 1 trial of stereotactic body radiation therapy for primary inoperable renal cell carcinoma. A dose of 42 Gy/3 fractions was prescribed to targets ≥5 cm, whereas for <5 cm 26 Gy/1 fraction was used. All patients underwent a planning 4-dimensional CT to generate a planning target volume (PTV) from a 5-mm isotropic expansion of the internal target volume. Planning required a minimum of 8 fields prescribing to the minimum isodose surrounding the PTV. Intermediate dose spillage at 50% of the prescription dose (R50%) was measured to describe the dose gradient. Early toxicity (<6 months) was scored using the Common Terminology Criteria for Adverse Events (v4.0). From July 2012 to August 2013 a total of 20 patients (median age, 77 years) were recruited into a prospective clinical trial. Eleven patients underwent fractionated treatment and 9 patients a single fraction. For PTV targets 100 cm(3) the median beam number used was 10 (4 noncoplanar) for an average R50% value of 4.3. The R50% was inversely proportional to decreasing PTV volume (r=-0.62, P=.003) and increasing total beams used (r=-0.51, P=.022). Twelve of 20 patients (60%) suffered grade ≤2 early toxicity, whereas 8 of 20 patients (40%) were asymptomatic. Nausea, chest wall pain, and fatigue were the most common toxicities reported. A 3-dimensional conformal planning technique of 8-10 beams can be used to deliver highly tolerable stereotactic ablation to primary kidney targets with minimal early toxicities. Ongoing follow-up is currently in place to assess long-term toxicities and cancer control.
Publisher: IOP Publishing
Date: 08-2019
Publisher: Elsevier BV
Date: 07-2021
Publisher: Wiley
Date: 06-2010
DOI: 10.1118/1.3469364
Publisher: Springer Science and Business Media LLC
Date: 26-08-2019
DOI: 10.1007/S13246-019-00789-8
Abstract: We propose a simple and efficient method to measure beam attenuation in one or two dimensions using an amorphous silicon electronic portal imaging device (a-Si EPID). The proposed method was validated against ionization chamber measurements. Beam attenuation through treatment couches (Varian Medical Systems) and immobilization devices (CIVCO Radiotherapy, USA) was examined. The dependency of beam attenuation on field size, photon energy, thickness of the couch, and the presence of a phantom were studied. Attenuation images were derived by computing the percentage difference between images obtained without and with a couch or immobilization devices determining the percentage of attenuation at the center and the mean attenuation. The beam attenuation measurements obtained with an a-Si EPID and an ionization chamber agreed to within ± 0.10 to 1.80%. No difference was noted between the center and mean of an attenuated image for a small field size of 5 × 5 cm
Publisher: Wiley
Date: 27-11-2012
DOI: 10.1118/1.4762564
Abstract: Complex radiotherapy fields delivered using a tertiary multileaf collimator (MLC) often feature small open segments surrounded by large areas of the beam only shielded by the MLC. The aim of this study was to test the ability of two modern dose calculation algorithms to accurately calculate the dose in these fields which would be common, for ex le, in volumetric modulated arc treatment (VMAT) and study the impact of variations in dosimetric leaf gap (DLG), focal spot size, and MLC transmission in the beam models. Nine test fields with small fields (0.6-3 cm side length) surrounded by large MLC shielded areas (secondary collimator 12 × 12 cm(2)) were created using a 6 MV beam from a Varian Clinac iX linear accelerator with 120 leaf MLC. Measurements of output factors and profiles were performed using a diamond detector (PTW) and compared to two dose calculations algorithms anisotropic analytical algorithm [(AAA) and Acuros XB] implemented on a commercial radiotherapy treatment planning system (Varian Eclipse 10). Both calculation algorithms predicted output factors within 1% for field sizes larger than 1 × 1 cm(2). For smaller fields AAA tended to underestimate the dose. Profiles were predicted well for all fields except for problems of Acuros XB to model the secondary penumbra between MLC shielded fields and the secondary collimator. A focal spot size of 1 mm or less, DLG 1.4 mm and MLC transmission of 1.4% provided a generally good model for our experimental setup. AAA and Acuros XB were found to predict the dose under small MLC defined field segments well. While DLG and focal spot affect mostly the penumbra, the choice of correct MLC transmission will be essential to model treatments such as VMAT accurately.
Publisher: Frontiers Media SA
Date: 14-06-2018
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 09-2021
Publisher: Wiley
Date: 25-02-2022
DOI: 10.1002/ACM2.13548
Abstract: Immobilization devices are used to obtain reproducible patient setup during radiotherapy treatment, improving accuracy, and reducing damage to surrounding healthy tissue. Additive manufacturing is emerging as a viable method for manufacturing and personalizing such devices. The goal of this study was to investigate the dosimetric and mechanical properties of a recent additive technology called multi‐jet fusion (MJF) for radiotherapy applications, including the ability for this process to produce full color parts. Skin dose testing included 50 s les with dimensions 100 mm × 100 mm with five different thicknesses (1 mm, 2 mm, 3 mm, 4 mm, and 5 mm) and grouped into colored (cyan, magenta, yellow, and black (CMYK) additives) and non‐colored (white) s les. Results using a 6 MV beam found that surface dose readings were predominantly independent of the colored additives. However, for an 18 MV beam, the additives affected the surface dose, with black recording significantly lower surface dose readings compare to other colors. The accompanying tensile testing of 175 s les designed to ASTM D638 type I standards found that the black agent resulted in the lowest ultimate tensile strength (UTS) for each thickness of 1–5 mm. It was also found that the print orientation had influence on the skin dose and mechanical properties of the s les. When all data were combined and analyzed using a multiple‐criteria decision‐making technique, magenta was found to offer the best balance between high UTS and low surface dose across different thicknesses and orientations, making it an optimal choice for immobilization devices. This is the first study to consider the use of color MJF for radiotherapy immobilization devices, and suggests that color additives can affect both dosimetry and mechanical performance. This is important as industrial additive technologies like MJF become increasingly adopted in the health and medical sectors.
Publisher: Wiley
Date: 29-09-2018
DOI: 10.1002/ACM2.12457
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.MEDDOS.2013.03.001
Abstract: Stereotactic ablative body radiotherapy (SABR) for primary renal cell carcinoma (RCC) targets requires motion management strategies to verify dose delivery. This case study highlights the effect of a change in patient breathing litude on the dosimetry to organs at risk and target structures. A 73-year-old male patient was planned for receiving 26Gy of radiation in 1 fraction of SABR for a left primary RCC. The patient was simulated with four-dimensional computed tomography (4DCT) and the tumor internal target volume (ITV) was delineated using the 4DCT maximum intensity projection. However, the initially planned treatment was abandoned at the radiation oncologist's discretion after pretreatment cone-beam CT (CBCT) motion verification identified a greater than 50% reduction in superior to inferior diaphragm motion as compared with the planning 4DCT. This patient was resimulated with respiratory coaching instructions. To assess the effect of the change in breathing on the dosimetry to the target, each plan was recalculated on the data set representing the change in breathing condition. A change from smaller to larger breathing showed a 46% loss in planning target volume (PTV) coverage, whereas a change from larger breathing to smaller breathing resulted in an 8% decrease in PTV coverage. ITV coverage was similarly reduced by 8% in both scenarios. This case study highlights the importance of tools to verify breathing motion prior to treatment delivery. 4D image guided radiation therapy verification strategies should focus on not only verifying ITV margin coverage but also the effect on the surrounding organs at risk.
Publisher: Wiley
Date: 11-2021
DOI: 10.1002/MP.15290
Abstract: To investigate multiple deep learning methods for automated segmentation (auto‐segmentation) of the parotid glands, submandibular glands, and level II and level III lymph nodes on magnetic resonance imaging (MRI). Outlining radiosensitive organs on images used to assist radiation therapy (radiotherapy) of patients with head and neck cancer (HNC) is a time‐consuming task, in which variability between observers may directly impact on patient treatment outcomes. Auto‐segmentation on computed tomography imaging has been shown to result in significant time reductions and more consistent outlines of the organs at risk. Three convolutional neural network (CNN)‐based auto‐segmentation architectures were developed using manual segmentations and T2‐weighted MRI images provided from the American Association of Physicists in Medicine (AAPM) radiotherapy MRI auto‐contouring (RT‐MAC) challenge dataset ( n = 31). Auto‐segmentation performance was evaluated with segmentation similarity and surface distance metrics on the RT‐MAC dataset with institutional manual segmentations ( n = 10). The generalizability of the auto‐segmentation methods was assessed on an institutional MRI dataset ( n = 10). Auto‐segmentation performance on the RT‐MAC images with institutional segmentations was higher than previously reported MRI methods for the parotid glands (Dice: 0.860 ± 0.067, mean surface distance [MSD]: 1.33 ± 0.40 mm) and the first report of MRI performance for submandibular glands (Dice: 0.830 ± 0.032, MSD: 1.16 ± 0.47 mm). We demonstrate that high‐resolution auto‐segmentations with improved geometric accuracy can be generated for the parotid and submandibular glands by cascading a localizer CNN and a cropped high‐resolution CNN. Improved MSDs were observed between automatic and manual segmentations of the submandibular glands when a low‐resolution auto‐segmentation was used as prior knowledge in the second‐stage CNN. Reduced auto‐segmentation performance was observed on our institutional MRI dataset when trained on external RT‐MAC images only the parotid gland auto‐segmentations were considered clinically feasible for manual correction (Dice: 0.775 ± 0.105, MSD: 1.20 ± 0.60 mm). This work demonstrates that CNNs are a suitable method to auto‐segment the parotid and submandibular glands on MRI images of patients with HNC, and that cascaded CNNs can generate high‐resolution segmentations with improved geometric accuracy. Deep learning methods may be suitable for auto‐segmentation of the parotid glands on T2‐weighted MRI images from different scanners, but further work is required to improve the performance and generalizability of these methods for auto‐segmentation of the submandibular glands and lymph nodes.
Publisher: Springer International Publishing
Date: 2022
Publisher: Elsevier BV
Date: 07-2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2005
Publisher: Elsevier BV
Date: 06-2021
Publisher: Springer Science and Business Media LLC
Date: 27-06-2022
DOI: 10.1186/S13014-022-02041-2
Abstract: Delivered organs at risk (OARs) dose may vary from planned dose due to interfraction and intrafraction motion during kidney SABR treatment. Cases of bowel stricture requiring surgery post SABR treatment were reported in our institution. This study aims to provide strategies to reduce dose deposited to OARs during SABR treatment and mitigate risk of gastrointestinal toxicity. Small bowel (SB), large bowel (LB) and stomach (STO) were delineated on the last cone beam CT (CBCT) acquired before any dose had been delivered (PRE CBCT) and on the first CBCT acquired after any dose had been delivered (MID CBCT). OAR interfraction and intrafraction motion were estimated from the shortest distance between OAR and the internal target volume (ITV). Adaptive radiation therapy (ART) was used if dose limits were exceeded by projecting the planned dose on the anatomy of the day. In 36 patients, OARs were segmented on 76 PRE CBCTs and 30 MID CBCTs. Interfraction motion was larger than intrafraction motion in STO (p-value = 0.04) but was similar in SB (p-value = 0.8) and LB (p-value = 0.2). LB was inside the planned 100% isodose in all PRE CBCTs and MID CBCTs in the three patients that suffered from bowel stricture. SB D0.03cc was exceeded in 8 fractions (4 patients). LB D1.5cc was exceeded in 4 fractions (2 patients). Doses to OARs were lowered and limits were all met with ART on the anatomy of the day. Interfraction motion was responsible for OARs overdosage. Dose limits were respected by using ART with the anatomy of the day.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2001
DOI: 10.1109/23.983173
Publisher: Elsevier BV
Date: 1996
Publisher: Wiley
Date: 02-11-2016
Abstract: Cone-beam computed tomography (CBCT) is a valuable image-guidance tool in radiation therapy (RT). This study was initiated to assess the accuracy of CBCT for quantifying non-small cell lung cancer (NSCLC) tumour volumes compared to the anatomical 'gold standard', CT. Tumour regression or progression on CBCT was also analysed. Patients with Stage I-III NSCLC, prescribed 60 Gy in 30 fractions RT with concurrent platinum-based chemotherapy, routine CBCT and enrolled in a prospective study of serial PET/CT (baseline, weeks two and four) were eligible. Time-matched CBCT and CT gross tumour volumes (GTVs) were manually delineated by a single observer on MIM software, and were analysed descriptively and using Pearson's correlation coefficient (r) and linear regression (R Of 94 CT/CBCT pairs, 30 patients were eligible for inclusion. The mean (± SD) CT GTV vs CBCT GTV on the four time-matched pairs were 95 (±182) vs 98.8 (±160.3), 73.6 (±132.4) vs 70.7 (±96.6), 54.7 (±92.9) vs 61.0 (±98.8) and 61.3 (±53.3) vs 62.1 (±47.9) respectively. Pearson's correlation coefficient (r) was 0.98 (95% CI 0.97-0.99, ρ < 0.001). The mean (±SD) CT/CBCT Dice's similarity coefficient was 0.66 (±0.16). Of 289 CBCT scans, tumours in 27 (90%) patients regressed by a mean (±SD) rate of 1.5% (±0.75) per fraction. The mean (±SD) GTV regression was 43.1% (±23.1) from the first to final CBCT. Primary lung tumour volumes observed on CBCT and time-matched CT are highly correlated (although not identical), thereby validating observations of GTV regression on CBCT in NSCLC.
Publisher: IOP Publishing
Date: 2019
Publisher: Elsevier BV
Date: 08-2021
Publisher: Wiley
Date: 06-2010
DOI: 10.1118/1.3468440
Publisher: Wiley
Date: 06-2015
DOI: 10.1118/1.4923938
Publisher: Medknow
Date: 2013
Publisher: Wiley
Date: 06-2016
DOI: 10.1118/1.4956743
Publisher: American Physical Society (APS)
Date: 12-08-2005
Publisher: MDPI AG
Date: 27-10-2017
Publisher: Elsevier BV
Date: 05-2011
Publisher: Elsevier BV
Date: 11-2017
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Publisher: Elsevier BV
Date: 05-2012
Publisher: Wiley
Date: 12-1985
DOI: 10.1177/019459988509300620
Abstract: Many large studies have complex advisory committee structures, yet there is no empirical evidence regarding their optimal composition, scope and contribution. The aim of this study was to inform the committee and advice infrastructure for future research studies. In the context of a five-year study funded by the UK National Institute for Health Research, three advisory committees were formed. In addition, advice was obtained from in idual experts. All recommendations received in the start-up phase (first seven months) of the study were recorded, along with the decision about implementation of the recommendation. A particular focus was on the impact of public involvement. A total of 172 recommendations were made, including 70 from 20 in idual experts. The recommendations were grouped into five emergent themes: Scientific, Pragmatic, Resources, Committee and Collaboration. Most recommendations related to strengthening existing components or adding new components to the study protocol. Very few recommendations either proposed removing study components or contradicted other recommendations. Three 'implementation criteria' were identified: scientific value, pragmatic feasibility, and paradigmatic consistency. 103 (60%) of recommendations were implemented and 25 (15%) were not implemented. The benefits identified by the research team were improved quality and confidence, and the costs were increased cognitive demands, protocol revision time, and slower progress. The findings are discussed in the context of the wider literature on public involvement in research. Six recommendations are identified. First, have a clear rationale for each advisory committee expressed as terms of reference, and consider the best balance between committees and in idual consultation with experts. Second, an early concern of committees is inter-committee communication, so consider cross-representation and copying minutes between committees. Third, match the scope of advisory committees to the study, with a less complex advisory structure for studies with more finalised designs. Fourth, public involvement has a mixed impact, and relies on relationships of trust, which take time to develop. Fifth, carefully consider the match between the scientific paradigm applied in the study and the contribution of different types of knowledge and expertise, and how this will impact on possibilities for taking on advice. Finally, responding to recommendations uses up research team resources, and the costs can be reduced by using the three implementation criteria.
Publisher: Informa UK Limited
Date: 02-04-2015
Publisher: Wiley
Date: 18-11-2021
DOI: 10.1002/ACM2.13473
Abstract: The deep inspiration breath‐hold (DIBH) technique assists in sparing the heart, lungs, and liver during breast radiotherapy (RT). The quality of DIBH is currently assessed via surrogates which correlate to varying degrees with the patient's internal anatomy. Since modern linacs are equipped with an electronic portal imaging device (EPID), images of the irradiated anatomy streamed from EPIDs and analyzed in real time could significantly improve assessment of the quality of DIBH. A system has been developed to quantify the quality of DIBH during tangential breast RT by analyzing the “beam's eye view” images of the treatment fields. The system measures the lung depth (LD) and the distance from the breast surface to the posterior tangential radiation field edge (skin distance, SD) at three user‐defined locations. LD and SD measured in real time in EPID images of two RT phantoms showing different geometrical characteristics of their chest wall regions (computed tomography dose index [CTDI] and “END‐TO‐END” stereotactic body radiation therapy [E2E SBRT]) were compared with ground truth displacements provided by a precision motion platform. Performance of the new system was evaluated via static and dynamic (sine wave motion) measurements of LD and SD, covering clinical situations with stable and unstable breath‐hold. The accuracy and precision of the system were calculated as the mean and standard deviation of the differences between the ground truth and measured values. The accuracy of the static measurements of LD and SD for the CTDI phantom was 0.31 (1.09) mm [mean (standard deviation)] and –0.10 (0.14) mm, respectively. The accuracy of the static measurements for E2E SBRT phantom was 0.01 (0.18) mm and 0.05 (0.08) mm. The accuracy of the dynamic LD and SD measurements for the CTDI phantom was –0.50 (1.18) mm and 0.01 (0.12) mm, respectively. The accuracy of the dynamic measurements for E2E SBRT phantom was –0.03 (0.19) mm and 0.01 (0.11) mm.
Publisher: IEEE
Date: 08-2008
Publisher: IOP Publishing
Date: 04-09-2004
Publisher: Elsevier BV
Date: 11-2017
Publisher: Springer Science and Business Media LLC
Date: 25-06-2018
DOI: 10.1007/S13246-018-0659-2
Abstract: This commentary reports on a forum held in October 2017 in Hobart, Tasmania, attended by 20 Australasian medical physicists, to consider the future role of medical physics, as well as non-medical physics and allied disciplines, in oncology research. Attendees identified important areas of oncology research which physicists can be contributing to, with these evaluated in the context of a set of "Provocative Questions" recently generated by the American Association of Physicists in Medicine. Primary perceived barriers to participation in research were identified, including a "lack of knowledge of cancer science", together with potential solutions. Mechanisms were considered for engagement with the broader scientific community, consumers, advocates and policy makers. In considering future opportunities in oncology research for medical physicists, it was noted that a professional need to focus on the safety and accuracy of current treatments applied to patients, encouraging risk-aversion, is somewhat in competition with the role of physical scientists in the exploration and discovery of new concepts and understandings.
Publisher: Oxford University Press (OUP)
Date: 11-2020
DOI: 10.1093/RPD/NCAA212
Abstract: Thermoluminescence dosimetry (TLD) has a long history of applications in medicine. However, despite its versatility and sensitivity its use is anecdotally diminishing, at least in part due to the complexity and work intensity of a quality TLD service. The present paper explores the role of TLD in medicine using a common inquiry methodology (5W1H) which systematically asks ‘Who, What, When, Where, Why and How’ to identify what role TLD could and should play in medical applications.
Publisher: Oxford University Press (OUP)
Date: 11-2020
DOI: 10.1093/RPD/NCAA213
Abstract: If the first decade of the new millennium saw the establishment of a more solid foundation for the use of the Optically Stimulated Luminescence (OSL) in medical dosimetry, the second decade saw the technique take root and become more widely used in clinical studies. Recent publications report not only characterization and feasibility studies of the OSL technique for various applications in radiotherapy and radiology, but also the practical use of OSL for postal audits, estimation of staff dose, in vivo dosimetry, dose verification and dose mapping studies. This review complements previous review papers and reports on the topic, providing a panorama of the new advances and applications in the last decade. Attention is also dedicated to potential future applications, such as LET dosimetry, 2D/3D dosimetry using OSL, dosimetry in magnetic resonance imaging-guided radiotherapy (MRIgRT) and dosimetry of extremely high dose rates (FLASH therapy).
Publisher: Oxford University Press (OUP)
Date: 07-1996
Publisher: Wiley
Date: 06-2006
DOI: 10.1118/1.2241923
Publisher: Elsevier BV
Date: 04-2022
Publisher: IOP Publishing
Date: 2019
Publisher: Elsevier BV
Date: 10-2023
Publisher: Informa UK Limited
Date: 14-09-2018
Publisher: IOP Publishing
Date: 15-02-2002
DOI: 10.1088/0031-9155/47/5/303
Abstract: As an alternative to standard treatment of superficial lesions with surgery and/or superficial/orthovoltage x-ray irradiation, radioactive moulds can be used. However, close proximity of the source to the treatment region leads to significant dose inhomogeneities in the tissue. Analytical and fast numerical methods have been developed that can calculate a corresponding flattening filter that evens out the dose distribution at the surface. Monte Carlo transport calculations were used to enable accurate treatment of the transport through the geometry. It was found that the use of pre-calculated transport parameters like dependence of the attenuation coefficient and scattering with depth is required for fast calculation of the flattening filter shape. Only 1-2 iterations were needed for a successful convergence to the filter shape that flattens out the dose distribution at the surface to within 1%. The developed methods are very general and could be applied with some minor modifications to other problems, where shaping of the irradiation field is required.
Publisher: IOP Publishing
Date: 15-02-2002
DOI: 10.1088/0031-9155/47/5/302
Abstract: Radioactive sources in close contact offer an alternative to superficial radiation in the treatment of skin lesions. A flattening filter was designed for a lead surface applicator to improve the skin dose distribution of a high dose rate (HDR) brachytherapy unit (Nucletron). At three heights from the opening (10, 15 and 25 mm) of the cylindrical applicator, the 192Ir source can be driven into the centre of the applicator. Thin sheets of lead foil (0.2 mm) were cut into circular shapes and placed in the opening to build a cylindrical cone that acts as a flattening filter. The shape of the cone was optimized in an iterative process using a spreadsheet and the resulting dose distribution under the applicator was determined using radiosensitive film. The use of the filter improved the dose distribution in a plane perpendicular to the beam axis to be within +/- 5% of the central axis dose. The present applicator and flattening filter together with an HDR brachytherapy unit offer an alternative for skin irradiation where a superficial unit is not available or will be replaced with a more flexible device. As the depth dose characteristics can be modified using different source-to-surface distances, the dose throughout the patient's skin can be shaped as desired by the radiation oncologist using a compensator design type approach.
Publisher: Springer Science and Business Media LLC
Date: 06-11-2014
DOI: 10.1007/S00259-013-2607-4
Abstract: Our group has previously reported on the use of (68)Ga-ventilation erfusion (VQ) PET/CT scanning for the diagnosis of pulmonary embolism. We describe here the acquisition methodology for (68)Ga-VQ respiratory gated (4-D) PET/CT and the effects of respiratory motion on image coregistration in VQ scanning. A prospective study was performed in 15 patients with non-small-cell lung cancer. 4-D PET and 4-D CT images were acquired using an infrared marker on the patient's abdomen as a surrogate for breathing motion following inhalation of Galligas and intravenous administration of (68)Ga-macroaggregated albumin. Images were reconstructed with phase-matched attenuation correction. The lungs were contoured on CT and PET VQ images during free-breathing (FB) and at maximum inspiration (Insp) and expiration (Exp). The similarity between PET and CT volumes was measured using the Dice coefficient (DC) comparing the following groups (1) FB-PET/CT, (2) InspPET/InspCT, (3) ExpPET/Exp CT, and (4) FB-PET/AveCT. A repeated measures one-way ANOVA with multiple comparison Tukey tests were performed to evaluate any difference between the groups. Diaphragmatic motion in the superior-inferior direction on the 4-D CT scan was also measured. 4-D VQ scanning was successful in all patients without additional acquisition time compared to the nongated technique. The highest volume overlap was between ExpPET and ExpCT and between FB-PET and AveCT with a DC of 0.82 and 0.80 for ventilation and perfusion, respectively. This was significantly better than the DC comparing the other groups (0.78-0.79, p < 0.05). These values agreed with a visual inspection of the images with improved image coregistration around the lung bases. The diaphragmatic motion during the 4-D CT scan was highly variable with a range of 0.4-3.4 cm (SD 0.81 cm) in the right lung and 0-2.8 cm (SD 0.83 cm) in the left lung. Right-sided diaphragmatic nerve palsy was observed in 3 of 15 patients. (68)Ga-VQ 4-D PET/CT is feasible and the blurring caused by respiratory motion is well corrected with 4-D acquisition, which principally reduces artefact at the lung bases. The images with the highest spatial overlap were the combined expiration phase or FB PET and average CT. With higher resolution than SPECT/CT, the PET/CT technique has a broad range of potential clinical applications including diagnostic algorithms for patients with suspected pulmonary embolism, preoperative evaluation of regional lung function and improving assessment or understanding of pulmonary physiology in the vast range of pulmonary diseases.
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.IJROBP.2010.06.061
Abstract: To determine the advantages and disadvantages of daily online adaptive image-guided radiotherapy (RT) compared with conventional RT for muscle-invasive bladder cancer. Twenty-seven patients with T2-T4 transitional cell carcinoma of the bladder were treated with daily online adaptive image-guided RT using cone-beam computed tomography (CBCT). From day 1 daily soft tissue-based isocenter positioning was performed using CBCT images acquired before treatment. Using a composite of the initial planning CT and the first five daily CBCT scans, small, medium, and large adaptive plans were created. Each of these adaptive plans used a 0.5-cm clinical target volume (CTV) to planning target volume expansion. For Fractions 8-32, treatment involved daily soft tissue-based isocenter positioning and selection of suitable adaptive plan of the day. Treating radiation therapists completed a credentialing program, and one radiation oncologist performed all the contouring. Comparisons were made between adaptive and conventional treatment on the basis of CTV coverage and normal tissue sparing. All 27 patients completed treatment per protocol. Bladder volume decreased with time or fraction number (p < 0.0001). For the adaptive component (Fractions 8-32) the small, medium, large, and conventional plans were used in 9.8%, 49.2%, 39.5%, and 1.5% of fractions, respectively. For the adaptive strategy, 2.7% of occasions resulted in a CTV V95 45 Gy was 29% (95% confidence interval, 24-35%) less with adaptive RT compared with conventional RT. The mean volume of normal tissue receiving >5 Gy was 15% (95% confidence interval, 11-18%) less with adaptive RT compared with conventional RT. Online adaptive radiotherapy is feasible in an academic radiotherapy center. The volume of normal tissue irradiated can be significantly smaller without reducing CTV coverage.
Publisher: Elsevier BV
Date: 05-2023
Publisher: Springer Berlin Heidelberg
Date: 2009
Publisher: Springer Science and Business Media LLC
Date: 14-12-2014
Publisher: Department of Biomedical Imaging, University of Malaya, Malaysia
Date: 2007
DOI: 10.2349/BIIJ.3.1.E17
Publisher: Elsevier BV
Date: 12-1995
Publisher: Elsevier BV
Date: 05-1995
DOI: 10.1016/0167-8140(95)01545-R
Abstract: The purpose of this study was to determine the influence of changes in dose rate over the range 0.8-240 Gy/h on acute oropharyngeal mucosal reactions in human subjects, and to estimate the values of the important parameters that influence these reactions. Sixty-one patients requiring radiotherapy to palliate incurable head and neck cancer were treated on a telecaesium unit, using opposing lateral portals to total midline doses, varying between 30 and 42 Gy in 10 daily fractions over 2 weeks, at dose rates of 0.8, 1.8, 3.0 and 240 Gy/h according to a central composite study design. The severity and time course of reactions were charted at least twice weekly for each patient, using the EORTC/RTOG acute mucosal reaction grading system. Duration of reaction at each grade was observed to provide a more sensitive reflection of effect than the proportion of patients reaching any particular reaction grade. Analysis of duration by direct and indirect methods suggest alpha/beta ratios in the range 7-10 Gy and half-time (t1/2) values in the range 0.27-0.5 h, if mono-exponential repair kinetics are assumed. The t1/2 values are short and raise the question as to whether the repair kinetics of this tissue are well described by a mono-exponential function. Further prospective studies involving multiple daily fraction treatment regimes delivered at high dose rate, in which interfraction interval is deliberately varied, are needed to find out whether the parameters derived from this project are applicable to fractionated treatment courses at high dose rate.
Publisher: Department of Biomedical Imaging, University of Malaya, Malaysia
Date: 2007
DOI: 10.2349/BIIJ.3.1.E16
Publisher: Springer Science and Business Media LLC
Date: 02-05-2019
Publisher: Elsevier BV
Date: 05-2012
Publisher: Wiley
Date: 06-2013
DOI: 10.1118/1.4815090
Publisher: IOP Publishing
Date: 24-03-2014
Publisher: IOP Publishing
Date: 05-1998
DOI: 10.1088/0031-9155/43/5/023
Abstract: Medium-energy x-rays from orthovoltage treatment units are used for a variety of radiotherapy treatments ranging from cutaneous malignancies in the head and neck region to bone metastases. It was the aim of the present study to investigate the dose distribution due to secondary electrons close behind inhomogeneities in these radiation qualities. The dose was assessed in a solid water phantom using three plane-parallel ionization chambers (NE 2532/2, 'Markus' and 'Attix' chamber) and sheets of aluminium, copper, zinc, platinum, lead and bone equivalent material. The depth dose distribution directly behind the inhomogeneity was assessed using sheets of 15 microm thick polyethylene foil. A dose increase was found directly behind inhomogeneities of high atomic number with a rapid dose fall-off over the first 100 microm. The dose downstream of the inhomogeneity was found to increase with increasing beam quality from 120 kVp (HVL 2.8 mm Al) to 250 kVp (HVL 2 mm Cu). In the latter the dose was increased directly behind lead and platinum sheets by up to a factor of eight compared with a solid water depth of similar attenuation. The results of the study demonstrate the importance of using appropriate materials if shielding is in contact with the patient.
Publisher: IOP Publishing
Date: 21-12-2012
DOI: 10.1088/0031-9155/58/2/319
Abstract: Formulae to calculate margins for external beam radiotherapy traditionally treat the radiotherapy regimen for analysis purposes as consisting of a very large number of treatment sessions, each delivering a very small dose. It is assumed that the difference in the calculated margin for an infinitely fractionated regimen, and the margin for real world treatment scenarios with finite fractions per patient, is negligible given the usual large number of fractions used to treat most malignancies. However hypofractionated radiotherapy using five fractions or even fewer is becoming increasingly common, causing the accuracy of traditional margin formulae to break down. This work introduces an algorithm that accurately calculates margins for hypofractionated treatment regimens. A method for estimating an upper limit for the required margin is introduced, and an adjustment to the van Herk formula (van Herk et al (2000 Int. J. Radiat. Oncol. Biol. Phys. 47 1121-35)) is used to provide a lower limit. A single-term mathematical model is then used to interpolate between these limits. Results are compared to those calculated by Monte Carlo simulation, demonstrating that the proposed method yields accurate estimates of the actual margin required (consistently within ~1%) for wide ranges of values of the systematic error, random error and penumbral width, even when the number of fractions per patient is as low as 2.
Publisher: Wiley
Date: 24-08-2011
DOI: 10.1118/1.3626484
Abstract: To assess dose delivery accuracy to clinically significant points in a realistic patient geometry for two separate pelvic radiotherapy scenarios. An inhomogeneous pelvic phantom was transported to 36 radiotherapy centers in Australia and New Zealand. The phantom was treated according to Phase III rectal and prostate trial protocols. Point dose measurements were made with thermoluminescent dosimeters (TLDs) and an ionisation chamber. Comprehensive site-demographic, treatment planning, and physical data were collected for correlation with measurement outcomes. Dose delivery to the prescription point for the rectal treatment was consistent with planned dose (mean difference between planned and measured dose - 0.1 ± 0.3% std err). Dose delivery in the region of the sacral hollow was consistently higher than planned (+1.2 ± 0.2%). For the prostate treatment, dose delivery to the prostate volume was consistent with planned doses (-0.49 ± 0.2%) and planned dose uniformity, though with a tendency to underdose the PTV at the prostate-rectal border. Measured out-of-field doses were significantly higher than planned. A phantom based on realistic anatomy and heterogeneity can be used to comprehensively assess the influence of multiple aspects of the radiotherapy treatment process on dose delivery. The ability to verify dose delivery for two trials with a single phantom was advantageous.
Publisher: SAGE Publications
Date: 2019
Abstract: Additive manufacturing or 3-dimensional printing has become a widespread technology with many applications in medicine. We have conducted a systematic review of its application in radiation oncology with a particular emphasis on the creation of phantoms for image quality assessment and radiation dosimetry. Traditionally used phantoms for quality assurance in radiotherapy are often constraint by simplified geometry and homogenous nature to perform imaging analysis or pretreatment dosimetric verification. Such phantoms are limited due to their ability in only representing the average human body, not only in proportion and radiation properties but also do not accommodate pathological features. These limiting factors restrict the patient-specific quality assurance process to verify image-guided positioning accuracy and/or dose accuracy in “water-like” condition. English speaking manuscripts published since 2008 were searched in 5 databases (Google Scholar, Scopus, PubMed, IEEE Xplore, and Web of Science). A significant increase in publications over the 10 years was observed with imaging and dosimetry phantoms about the same total number (52 vs 50). Key features of additive manufacturing are the customization with creation of realistic pathology as well as the ability to vary density and as such contrast. Commonly used printing materials, such as polylactic acid, acrylonitrile butadiene styrene, high-impact polystyrene and many more, are utilized to achieve a wide range of achievable X-ray attenuation values from −1000 HU to 500 HU and higher. Not surprisingly, multimaterial printing using the polymer jetting technology is emerging as an important printing process with its ability to create heterogeneous phantoms for dosimetry in radiotherapy. Given the flexibility and increasing availability and low cost of additive manufacturing, it can be expected that its applications for radiation medicine will continue to increase.
Publisher: Wiley
Date: 23-03-2021
DOI: 10.1002/ACM2.13215
Publisher: Oxford University Press (OUP)
Date: 09-1999
Publisher: Elsevier BV
Date: 04-2020
Publisher: Springer Science and Business Media LLC
Date: 03-2010
DOI: 10.1007/S13246-010-0005-9
Abstract: Field junctions between megavoltage photon beams are important in modern radiotherapy for treatments such as head and neck and breast cancer. An electronic portal imaging device (EPID) may be used to study junction dose between two megavoltage X-ray fields. In this study, the junction dose was used to determine machine characteristics such as jaw positions and their reproducibility, collimator rotation and the effect of gantry rotation. All measurements were done on Varian linear accelerators with EPID (Varian, Palo Alto, CA). The results show reproducibility in jaw positions of approximately 0.3 mm for repeated jaw placement while EPID readings were reproducible within a standard deviation of 0.4% for fixed jaw positions. Junction dose also allowed collimator rotation error of 0.1 degrees to be observed. Dependence of junction dose on gantry rotation due to gravity was observed the gravity effect being maximum at 180 degrees gantry angle (beam pointing up). EPIDs were found to be reliable tools for checking field junctions, which in turn may be used to check jaw reproducibility and collimator rotation of linacs.
Publisher: Springer Science and Business Media LLC
Date: 06-2012
Publisher: Oxford University Press (OUP)
Date: 07-1996
Publisher: Oxford University Press (OUP)
Date: 07-1996
Publisher: Wiley
Date: 11-10-2011
DOI: 10.1118/1.3641865
Abstract: To quantify movement of prostate cancer patients undergoing treatment, using an in-house developed motion sensor in order to determine a relationship between patient movement and high dose rate (HDR) brachytherapy implant displacement. An electronic motion sensor was developed based on a three axis accelerometer. HDR brachytherapy treatment for prostate is delivered at this institution in two fractions 24 h apart and 22 patients were monitored for movement over the interval between fractions. The motion sensors functioned as inclinometers, monitoring inclination of both thighs, and the inclination and roll of the abdomen. The implanted HDR brachytherapy catheter set was assessed for displacement relative to fiducial markers in the prostate. Angle measurements and angle differences over a 2 s time base were binned, and the standard deviations of the resulting frequency distributions used as a metric for patient motion in each monitored axis. These parameters were correlated to measured catheter displacement using regression modeling. The mean implant displacement was 12.6 mm in the caudal direction. A mean of 19.95 h data was recorded for the patient cohort. Patients generally moved through a limited range of angles with a mean of the exception of two patients who spent in excess of 2 h lying on their side. When tested for a relationship between movement in any of the four monitored axes and the implant displacement, none was significant. It is not likely that patient movement influences HDR prostate implant displacement. There may be benefits to patient comfort if nursing protocols were relaxed to allow patients greater freedom to move while the implant is in situ.
Publisher: IOP Publishing
Date: 2019
Publisher: Springer Singapore
Date: 30-05-2019
Publisher: Elsevier BV
Date: 02-2002
DOI: 10.1016/S0360-3016(01)02682-7
Abstract: Many different factors can affect the accurate delivery of dose to the clinical target volume in radiotherapy. This is particularly important in the context of multicenter clinical trials where different equipment and techniques may be used for supposedly identical treatments. A dosimetric intercomparison employing an anthropomorphic phantom (level III dosimetric intercomparison) can be used to check many of the factors that could affect treatment by mimicking the radiotherapy pathway of a patient as closely as possible. An anthropomorphic phantom (ART) was taken to 18 radiotherapy centers in Australia and New Zealand and treated for two different treatment scenarios based on current clinical trials of the Trans-Tasman Radiation Oncology Group (TROG): a two-field treatment of a carcinoma of the tonsil (TROG 91.01), and a four-field prostate treatment (TROG 96.01). The dose distribution was assessed in two consecutive treatments using thermoluminescence dosimeters (TLDs) placed throughout the target volume and in "critical" structures such as the lens of the eye or the rectum. The study also included a check of absolute dose calibration in a slab phantom (level I dosimetric intercomparison). The influence of a variety of treatment parameters on the dose homogeneity in the target and the measured dose in the target and the critical organs was evaluated. The dose measurements confirmed that in all participating centers the correct dose was delivered to the ICRU reference point (tonsil: 99.8 +/- 2.3% prostate: 100.9 +/- 1.9% [1 SD]). Also the absolute dose calibration and the mean dose in the target volume were within the specified action levels of plus minus 5% for all participating centers. No influence of shielding, beam modifiers, beam weighting, treatment planning approach (CT, 2D, 3D), and type of equipment used on the dose in the target and its homogeneity could be demonstrated. However, treatment technique and energy used influenced the dose to the critical organs. It was shown that the interpretation of results could be improved by including two complementary treatment scenarios and a level I intercomparison with the level III dosimetric intercomparison. The study demonstrated the feasibility of a level III dosimetric intercomparison service at a cost of approximately $1000(US) per center in Australasia. It confirmed that the dose delivered by all participating centers was as intended in the two treatment scenarios chosen. While this provides reassurance to the oncology community and the general public, the service must be extended to all centers and other potentially more complex treatment scenarios. The present study has built the foundation for this by establishing a baseline and action levels and suggesting improvements in phantom design which will be included in future TROG quality assurance exercises.
Publisher: IOP Publishing
Date: 2019
Publisher: Wiley
Date: 23-06-2005
DOI: 10.1118/1.2030994
Publisher: Wiley
Date: 10-2017
Publisher: IOP Publishing
Date: 12-02-2015
DOI: 10.1088/0031-9155/60/5/2091
Abstract: This study aims to investigate the effects of oblique incidence, small field size and inhomogeneous media on the electron dose distribution, and to compare calculated (Elekta/CMS XiO) and measured results. All comparisons were done in terms of absolute dose. A new measuring method was developed for high resolution, absolute dose measurement of non-standard beams using Gafchromic® EBT3 film. A portable U-shaped holder was designed and constructed to hold EBT3 films vertically in a reproducible setup submerged in a water phantom. The experimental film method was verified with ionisation chamber measurements and agreed to within 2% or 1 mm. Agreement between XiO electron Monte Carlo (eMC) and EBT3 was within 2% or 2 mm for most standard fields and 3% or 3 mm for the non-standard fields. Larger differences were seen in the build-up region where XiO eMC overestimates dose by up to 10% for obliquely incident fields and underestimates the dose for small circular fields by up to 5% when compared to measurement. Calculations with inhomogeneous media mimicking ribs, lung and skull tissue placed at the side of the film in water agreed with measurement to within 3% or 3 mm. Gafchromic film in water proved to be a convenient high spatial resolution method to verify dose distributions from electrons in non-standard conditions including irradiation in inhomogeneous media.
Publisher: IOP Publishing
Date: 2019
Publisher: American Physical Society (APS)
Date: 07-03-2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2018
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 04-2018
Publisher: SPIE
Date: 06-05-2004
DOI: 10.1117/12.535988
Publisher: Elsevier BV
Date: 04-2018
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 02-2010
Publisher: European Medical Group
Date: 17-11-2014
DOI: 10.33590/EMJONCOL/10312427
Abstract: There have been significant technological and technical advances in radiotherapy over the last 20 years. This paper presents the pertinent advances and examines their application in contemporary breast cancer (BC) radiotherapy, particularly for reducing the long-term toxicity, using intensity-modulated radiation therapy, image-guided radiation therapy, and management of breathing motion. These modern technologies and techniques enable precise delivery of a highly conformal radiation dose distribution to the target volume in real-time, to optimise tumour control, and minimise treatment toxicity. They have been used for the treatment of BC in selected centres around the world. Although there is insufficient high-level evidence to support their routine application in BC at present, implementation of these technologies has been shown to be feasible, and could result in clinically meaningful long-term benefits for selected patients with BC.
Publisher: CRC Press
Date: 30-10-2017
Publisher: CRC Press
Date: 30-10-2017
Publisher: Wiley
Date: 06-2008
DOI: 10.1111/J.1440-1673.2008.01957.X
Abstract: This study evaluated the variability among six radiation therapy planners in planning radiation treatment for four patients with lung cancer using two treatment protocols. The interplanner variability for target conformity and homogeneity was smaller than the variability among the patients and planning approaches. The same was found for the dose volume indices achieved for most critical structures, indicating that interplanner variability is not likely to be an important source of variation in radiotherapy studies if concise treatment protocols are followed.
Publisher: American Physical Society (APS)
Date: 12-05-2005
Publisher: Public Library of Science (PLoS)
Date: 07-10-2014
Publisher: SAGE Publications
Date: 18-09-2019
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 11-2021
Publisher: Springer Science and Business Media LLC
Date: 23-10-2018
Publisher: Wiley
Date: 30-07-2009
DOI: 10.1111/J.1754-9485.2009.02080.X
Abstract: One of the first steps towards the development of a comprehensive quality program for radiation oncology in Australia has been a survey of practice. This paper reports on the results of the survey that should inform the development of standards for radiation oncology in Australia. A questionnaire of 108 questions spanning aspects of treatment services, equipment, staff, infrastructure and available quality systems was mailed to all facilities providing radiation treatment services in Australia (n = 45). Information of 42 sites was received by June 2006 providing data on 113 operational linear accelerators of which approximately 2/3 are equipped with multi-leaf collimators. More than 75% of facilities were participating in a formal quality assurance (QA) system, with 63% following a nationally or internationally recognised system. However, there was considerable variation in the availability of policies and procedures specific to quality aspects, and the review of these. Policies for monitoring patient waiting times for treatment were documented at just 71% of all facilities. Although 85% of all centres do, in fact, monitor machine throughput, the number and types of efficiency measures varied markedly, thereby limiting the comparative use of these results. Centres identified workload as the single most common factor responsible for limiting staff involvement in both QA processes and clinical trial participation. The data collected in this 'snapshot' survey provide a unique and comprehensive baseline for future comparisons and evaluation of changes.
Publisher: Elsevier BV
Date: 12-2011
Publisher: Wiley
Date: 14-10-2019
DOI: 10.1002/ACM2.12744
Publisher: Elsevier BV
Date: 03-2020
Publisher: Elsevier BV
Date: 05-2009
DOI: 10.1016/J.RADONC.2008.08.016
Abstract: To develop an in vivo dosimetry based investigative action level relevant for a corrective protocol for HDR brachytherapy boost treatment. The dose delivered to points within the urethra and rectum was measured using TLD in vivo dosimetry in 56 patients. Comparisons between the urethral and rectal measurements and TPS calculations showed differences, which are related to the relative position of the implant and TLD trains, and allowed shifts of implant position relative to the prostate to be estimated. Analysis of rectal dose measurements is consistent with implant movement, which was previously only identified with the urethral data. Shift corrected doses were compared with results from the TPS. Comparison of peak doses to the urethra and rectum has been assessed against the proposed corrective protocol to limit overdosing these critical structures. An initial investigative level of 20% difference between measured and TPS peak dose was established, which corresponds to 1/3 of patients which was practical for the caseload. These patients were assessed resulting in corrective action being applied for one patient. Multiple triggering for selective investigative action is outlined. The use of a single in vivo measurement in the first fraction optimizes patient benefit at acceptable cost.
Publisher: Wiley
Date: 04-2012
DOI: 10.1111/J.1754-9485.2011.02324.X
Abstract: The purpose of this study was to compare and evaluate radiotherapy treatment plans using volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) for post-prostatectomy radiotherapy. The quality of radiotherapy plans for 10 patients planned and treated with a seven-field IMRT technique for biochemical failure post-prostatectomy were subsequently compared with 10 prospectively planned single-arc VMAT plans using the same computed tomography data set and treatment planning software. Plans were analysed using parameters to assess for target volume coverage, dose to organs at risk (OAR), biological outcomes, dose conformity and homogeneity, as well as the total monitor units (MU), planning and treatment efficiency. The mean results for the study population are reported for the purpose of comparison. For IMRT, the median dose to the planning target volume, V(95%) and D(95%) was 71.1 Gy, 98.9% and 68.3 Gy compared with 71.2 Gy, 99.2% and 68.6 Gy for VMAT. There was no significant difference in the conformity index or homogeneity index. The VMAT plans achieved better sparing of the rectum and the left and right femora with a reduction in the median dose by 7.9, 6.3 and 3.6 Gy, respectively. The total number of monitor units (MU) was reduced by 24% and treatment delivery time by an estimated 3 min per fraction without a significant increase in planning requirements. VMAT can achieve post-prostatectomy radiotherapy plans of comparable quality to IMRT with the potential to reduce dose to OAR and improve the efficiency of treatment delivery.
Publisher: Elsevier BV
Date: 06-2023
Publisher: CRC Press
Date: 20-12-2010
DOI: 10.1201/B10448
Publisher: Wiley
Date: 11-2012
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576157
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576159
Publisher: Elsevier BV
Date: 10-2021
Publisher: Wiley
Date: 25-10-2019
DOI: 10.1002/MP.13800
Publisher: Springer Science and Business Media LLC
Date: 06-2005
DOI: 10.1007/BF03178706
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.RADONC.2013.04.005
Abstract: To compare the cone-beam CT (CBCT) soft tissue localization disparity between radiation oncologists (RO) and radiation therapy technologists (RTT) in a novel online protocol of image-guided adaptive radiotherapy to the postoperative prostate bed. Using the planning CT and pre-treatment CBCTs from the first week of radiotherapy, four adaptive plans of different sizes were derived for each of eight post-prostatectomy patients. Four ROs collectively defined the reference answer, i.e. the plan of the day and isocentre correction for 40 CBCTs taken in weeks 2-6 of treatment for each patient. RTTs were randomly assigned five of these CBCTs and asked to record their plan of the day selection and isocentre correction. RTT selection and reference answers were compared. The distance between the RTT selection and the reference answer was calculated. A total of 33 RTTs took part in this study. The average difference in CTV volume (reference answer-RTT selection) was 1.32 cm(3) (SD 29 cm(3)) overall. The average difference between reference answer and RTT isocentre coordinates was SI 1mm (SD 4.8mm), LR 1.1mm (SD 4.0mm) and AP -0.2mm (SD 3.9 mm). Distance of superior 8mm, inferior 6mm, left 4mm, right 2mm, anterior 6mm and posterior 6mm covered 100% of the CTV in 90% of fractions. The difference between RTT and RO selection of adaptive volumes is small and can be accounted for in a clinically acceptable CTV to PTV margin. Adaptive post-prostatectomy radiotherapy is feasible, in the setting of an academic center although at the moment, we have insufficient evidence to suggest that margins can yet be reduced with IGART with the current protocol.
Publisher: SAGE Publications
Date: 2014
Abstract: Abdominal stereotactic ablative body radiotherapy is aided by motion management strategies to ensure accurate dose delivery as targets such as the kidney are easily influenced by breathing motion. Commercial devices such as compression plates and dual vacuum technology have been demonstrated to reduce the motion of lung and liver tumors. The aim of this study was to evaluate the effectiveness of a dual vacuum system in reducing kidney motion as well to investigate any relationship between abdominal wall motions with kidney motion. Ten healthy volunteers were set up with and without vacuum compression (Elekta BodyFIX TM ) to simulate free and d ened breathing. Ultrasound imaging was used to visualize kidney motion at the same time an abdominal surface marker was monitored using infrared imaging (Varian, Real Time Position Management). The resulting kidney and abdominal motion tracks were imported into motion analysis (Physmo TM ) and custom built software (Matlab) to calculate litude of motion independent of shifting baselines. Thirty-four kidney datasets were available for analysis, with six datasets unable to be retrieved. With vacuum compression six out of nine participants showed a mean reduction of kidney motion ranging between 1.6 and 8 mm ( p 0.050). One participant showed an increase in motion of 8.2 mm ( p 0.001) with vacuum compression. Two participants showed no significant change ( mm) in kidney motion. No relationship was observed for abdominal wall motion and motion changes in the left kidney ( r = 0.345, p = 0.402) or right kidney ( r = 0.527, p = 0.145). Vacuum compression reduced kidney motion in the majority of participants however larger breathing motion can also result from its use. No pattern emerged regarding which patients may benefit from vacuum immobilization as abdominal wall motion was not found to be an adequate surrogate for kidney motion.
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.RADONC.2013.04.007
Abstract: To compare rates of late gastrointestinal toxicity, late genitourinary toxicity and biochemical failure between patients treated for prostate cancer with implanted fiducial marker image guided radiotherapy (FMIGRT), and those treated without FMIGRT. We performed a single institution retrospective study comparing all 311 patients who received 74 Gy without fiducial markers in 2006 versus all 243 patients who received our updated regimen of 78 Gy with FMIGRT in 2008. Patient records were reviewed 27 months after completing radiotherapy. Biochemical failure was defined using the Phoenix definition. Details of late gastrointestinal and genitourinary toxicities were graded according to CTCAEv4. Moderate/severe toxicity was defined as a grade 2 or higher toxicity. Cumulative incidence and prevalence curves for moderate/severe toxicity were constructed and compared using multistate modeling while biochemical failure free survival was compared using the log rank test. A Cox regression model was developed to correct for confounding factors. Median follow-up time for both groups was 22 months. The hazard ratio for moderate/severe late gastrointestinal toxicity in the non-FMIGRT group was 3.66 [95% CI (1.63-8.23), p=0.003] compared to patients in the FMIGRT group. There was no difference in the hazard ratio of moderate/severe late genitourinary toxicity between the two groups (0.44 [95% CI (0.19-1.00)]), but patients treated with FMIGRT did have a quicker recovery from their genitourinary toxicities HR=0.24 [95% CI (0.10-0.59)]. We were unable to detect any differences in biochemical failure free survival between the cohorts HR=0.60 [95% CI (0.30-1.20), p=0.143]. Despite dose escalation, the use of FMIGRT in radical radiotherapy for prostate cancer significantly reduces the incidence of gastrointestinal toxicity and the duration of late genitourinary toxicity when compared to conventional non-FMIGRT techniques.
Publisher: European Respiratory Society (ERS)
Date: 07-2019
DOI: 10.1183/23120541.00004-2019
Abstract: Patients suitable for radical chemoradiotherapy for lung cancer routinely have radiotherapy (planning) volumes based on positron emission tomography (PET)-computed tomography (CT) imaging alone. Endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA) can identify PET-occult malignancy and benign PET-avid regions. We investigated the impact of EBUS-TBNA on curative-intent radiotherapy in non-small cell lung cancer (NSCLC). A prospective multicentre trial was undertaken, investigating the impact of systematic EBUS-TBNA in addition to PET-CT for patients considered for radical chemoradiotherapy with NSCLC. A subset analysis of patients with discordant findings between PET-CT and EBUS-TBNA was performed. Radiotherapy plans investigated tumour coverage and dose to critical organs at risk (OARs) using PET-CT alone in comparison to PET-CT and EBUS-TBNA. Of 30 patients enrolled, 10 had discordant findings between PET-CT and EBUS-TBNA. EBUS-TBNA-derived plans allowed for reduction in dose to OARs in patients downstaged by EBUS-TBNA, and reduced the risk of geographic miss in treating PET-occult disease in four patients where EBUS-TBNA identified malignant involvement of PET-negative lymphadenopathy. With the addition of EBUS-TBNA to radiotherapy planning, reductions were noted of 5.7%, 3.7% and 12.5% for the risks of symptomatic pneumonitis, mean heart dose and mean oesophageal dose, respectively. This study demonstrates for the first time that systematic EBUS-TBNA prior to radical-intent radiotherapy significantly improves coverage of subclinical disease through detection of PET-occult metastases. Identification of false-positive lymph node involvement in highly selected cases may reduce radiation dose to critical structures, and risk of organ toxicity.
Publisher: Elsevier BV
Date: 1993
Publisher: Elsevier BV
Date: 10-2000
DOI: 10.1016/S0360-3016(00)00708-2
Abstract: The present study modeled data from a large series of experiments originally designed to investigate the influence of time, dose, and fractionation on early and late pathologic endpoints in rat small intestine after localized irradiation. The objective was to obtain satisfactory descriptions of the regenerative response to injury together with the possible relationships between early and late endpoints. Two- and 26-week pathologic radiation injury data in groups of Sprague-Dawley rats irradiated with 27 different fractionation schedules were modeled using the incomplete repair (IR) version of the linear-quadratic model with or without various time correction models. The following time correction models were tested: (1) No time correction (2) A simple exponential (SE) regenerative response beginning at an arbitrary time after starting treatment and (3) A bi-exponential response with its commencement linked to accumulated cellular depletion and fraction size (the 'intelligent response model' [INTR]). Goodness of fit of the various models was assessed by correlating the predicted biological effective dose for each dose group with the observed radiation injury score. (1) The incomplete repair model without time correction did not provide a satisfactory description of either the 2- or 26-week data. (2) The models using SE time correction performed better, providing modest descriptions of the data. (3) The INTR model provided reasonable descriptions of both the 2- and 26-week data, confirming a treatment time dependence of both early and late pathological endpoints. (4) The most satisfactory descriptions of the data by the INTR model were obtained when the regenerative response was assumed to cease 2 weeks after irradiation rather than at the end of irradiation. A fraction-size-dependent delay of the regenerative response was also suggested in the best fitting models. (5) Late endpoints were associated with low-fractionation sensitivity and treatment-time dependence even in animal groups that exhibited minimal early mucosal reactions. Radiation injury scores in this rat small intestinal experimental model cannot be adequately described without time correction. 'Consequential' mechanisms contribute to the development of late effects, even in animals that do not develop severe early mucosal injuries. The initiation of the regenerative response is subject to a fraction-size-dependent mitotic delay and is linked to the level of accumulated cellular depletion. The response does not cease at the end of therapy but probably continues until maximal healing has taken place.
Publisher: Elsevier BV
Date: 10-2015
DOI: 10.1016/J.IJROBP.2015.06.005
Abstract: To investigate (68)Ga-ventilation erfusion (V/Q) positron emission tomography (PET)/computed tomography (CT) as a novel imaging modality for assessment of perfusion, ventilation, and lung density changes in the context of radiation therapy (RT). In a prospective clinical trial, 20 patients underwent 4-dimensional (4D)-V/Q PET/CT before, midway through, and 3 months after definitive lung RT. Eligible patients were prescribed 60 Gy in 30 fractions with or without concurrent chemotherapy. Functional images were registered to the RT planning 4D-CT, and isodose volumes were averaged into 10-Gy bins. Within each dose bin, relative loss in standardized uptake value (SUV) was recorded for ventilation and perfusion, and loss in air-filled fraction was recorded to assess RT-induced lung fibrosis. A dose-effect relationship was described using both linear and 2-parameter logistic fit models, and goodness of fit was assessed with Akaike Information Criterion (AIC). A total of 179 imaging datasets were available for analysis (1 scan was unrecoverable). An almost perfectly linear negative dose-response relationship was observed for perfusion and air-filled fraction (r(2)=0.99, P<.01), with ventilation strongly negatively linear (r(2)=0.95, P<.01). Logistic models did not provide a better fit as evaluated by AIC. Perfusion, ventilation, and the air-filled fraction decreased 0.75 ± 0.03%, 0.71 ± 0.06%, and 0.49 ± 0.02%/Gy, respectively. Within high-dose regions, higher baseline perfusion SUV was associated with greater rate of loss. At 50 Gy and 60 Gy, the rate of loss was 1.35% (P=.07) and 1.73% (P=.05) per SUV, respectively. Of 8/20 patients with peritumoral reperfusion/reventilation during treatment, 7/8 did not sustain this effect after treatment. Radiation-induced regional lung functional deficits occur in a dose-dependent manner and can be estimated by simple linear models with 4D-V/Q PET/CT imaging. These findings may inform future studies of functional lung avoidance using V/Q PET/CT.
Publisher: British Institute of Radiology
Date: 04-2003
DOI: 10.1259/BJR/79291075
Abstract: Many departments still do not use recommended radiographic parameters to X-ray neonates. Direct, accurate dose measurements of in idual examinations may assist a department in justifying technique modifications that provide a substantial dose reduction without a significant loss of image quality. The aim of this study was to investigate dose reduction techniques for neonates in the intensive care unit. Alterations in beam energy (kVp and filtration) and collimation were investigated using specially designed phantoms mimicking a 700 g and 2000 g neonate, and ultrasensitive LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs). Differences in entrance surface dose (ESD) and dose at depth (3 cm or 5 cm) were compared for two, overlapping fields centred in idually on the chest and abdomen (Technique 1) and one large chest-abdomen field (Technique 2 or babygram). The large phantom was irradiated at 54 kVp, 60 kVp and 70 kVp without additional filtration and at 66 kVp and 70 kVp with a rare-earth hafnium filter. Focus-film distance (FFD) and mAs were adjusted to maintain optical density (OD) on each radiograph. The baseline dose at 54 kVp and 100 cm FFD was (46+/-2) micro Gy. Increasing the tube potential from 54 kVp to 70 kVp without additional filtration reduced the ESD by 27%. However, the addition of a 0.05 mm hafnium filter at 66 kVp further reduced the radiation dose by 13%, to produce an ESD of (28+/-2) micro Gy. All contrast details were observable at 66 kVp with hafnium filtration. Technique 1 may lead to an increase in effective dose due to field overlap, which erges at depth, and increased scatter at the periphery of the fields.
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.RADONC.2012.10.019
Abstract: An e-Learning programme appeared useful for providing training and information regarding a multi-centre image guided radiotherapy trial. The aim of this study is to demonstrate the utility of this e-Learning programme. Modules were created on relevant pelvic anatomy, Cone Beam CT soft tissue recognition and trial details. Radiation therapist participants' knowledge and confidence were evaluated before, at the end of, and after at least 6 weeks of e-Learning (long term). One hundred and eighty-five participants were recruited from 12 centres, with 118 in the first, and 67 in the second cohort. One hundred and forty-six participants had two tests (pre and post e-Learning) and 39 of these had three tests (pre, post, and long term). There was an increase confidence after completion of modules (p<0.001). The first cohort pre scores increased from 67 ± 11 to 79 ± 8 (p<0.001) post. The long term same question score was 73 ± 14 (p=0.025, comparing to pre-test), and different questions' score was 77 ± 13 (p=0.014). In the second cohort, pre-test scores were 64 ± 10, post-test same question score 78 ± 9 (p<0.001) and different questions' score 81 ± 11 (p<0.001). e-Learning for a multi-centre clinical trial was feasible and improved confidence and knowledge.
Publisher: Elsevier BV
Date: 09-1995
DOI: 10.1016/0958-3947(95)00009-L
Abstract: About 5% of patients still undergo cancer treatment with superficial (peak energy < or = 120 kVp) X-ray radiation. Dosimetry of these beams is difficult since the maximum dose is delivered at the surface and backscatter contributes significantly to the dose. This is particularly a problem in the difficult geometries encountered in superficial treatments in the head and neck area. It has recently been shown that surface dose measurements in mega-voltage X-ray beams can be performed using TLD (Thermoluminescence Dosimetry) extrapolation. In this technique, LiF TLD chips with a surface area of 3.15 x 3.15 cm2 and three different thicknesses (0.230, 0.099, and 0.038 g/cm2) are used together in the same radiation beam which allows the extrapolation of the measured dose back to the true surface. The energy response curve of the three thicknesses of LiF chips was measured for the energy range of 60kVp, HVL 1.6 mm Al to 300kVp, 4 mm Cu. LiF was found to over respond by a factor of 1.7 at 60kVp HVL 1.6 mm Al with respect to a 6MV photon beam. A feasibility study was carried out on three patients undergoing treatment at 120kVp. Because of the small field sizes involved it was necessary to limit irradiation to one or two chips at a time. The dose fall off in the first millimetre of tissue could be clearly detected. TLD extrapolation, in low to medium energy beams, was found to be useful to assess the dose of patients undergoing treatment for superficial lesions.
Publisher: Springer Science and Business Media LLC
Date: 28-08-2020
DOI: 10.1038/S41467-020-17359-2
Abstract: Sex differences have been observed in multiple facets of cancer epidemiology, treatment and biology, and in most cancers outside the sex organs. Efforts to link these clinical differences to specific molecular features have focused on somatic mutations within the coding regions of the genome. Here we report a pan-cancer analysis of sex differences in whole genomes of 1983 tumours of 28 subtypes as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium. We both confirm the results of exome studies, and also uncover previously undescribed sex differences. These include sex-biases in coding and non-coding cancer drivers, mutation prevalence and strikingly, in mutational signatures related to underlying mutational processes. These results underline the pervasiveness of molecular sex differences and strengthen the call for increased consideration of sex in molecular cancer research.
Publisher: IOP Publishing
Date: 06-08-2004
DOI: 10.1088/0031-9155/49/17/001
Abstract: In many medical procedures where accurate radiation dose measurements are needed, the variation of detector response with x-ray energy is of concern. The response of LiF:Mg,Cu,P TLDs to a range of x-ray energies was analysed in monoenergetic (synchrotron), diagnostic and therapy radiation beams with the aim of implementing this dosimeter into clinical practice where existing dosimetry techniques are limited due to lack of sensitivity or tissue equivalence (e.g. neonatal radiography, mammography and brachytherapy). LiF:Mg,Cu,P TLDs in different forms from two manufacturers (MCP-N: TLD Poland, GR200: SDDML China) were irradiated using x-ray beams covering 10 keV to 18 MVp. Dose readings were compared with an ionization chamber. The effect of different TLD types and annealing cycles on clinical utility was investigated. The measured energy response of LiF:Mg,Cu,P TLDs was fit to a simple model devised by Kron et al (1998 Phys. Med. Biol. 43 3235-59) to describe the variation of TLD response with x-ray energy. If TLDs are handled as recommended in the present paper, the energy response of LiF:Mg,Cu,P deviates by a maximum of 15% from unity and agrees with the model to within 5% or experimental uncertainty between 15 keV and 10 MeV. LiF:Mg,Cu,P TLDs of all forms have consistent and superior energy response compared to the standard material LiF:Mg,Ti and are therefore suitable for a wide range of applications in diagnostic radiology and radiotherapy.
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.IJROBP.2009.09.050
Abstract: To compare volumetric in-room computed tomography (CT) and kilovoltage (kV) cone-beam CT (CBCT) to planar imaging with respect to their ability to localize fiducial markers (FMs) for radiotherapy of prostate cancer. Image guidance options from two linear accelerators were compared in terms of identifying the center of gravity (COG) of FMs from the isocenter: a Siemens Primatom, where the couch is rotated 180 degrees from the treatment isocenter to the in-room CT vs. electronic portal imaging (EPI) and a Varian OBI system, where kV CBCT, EPI, and planar kV radiographs were compared. In all, 387 image pairs (CBCT = 133 CT = 254) from 18 patients were analyzed. A clinical tolerance of 3 mm was predefined as the acceptable threshold for agreement. COG location on in-room CT and EPI was in agreement 96.9%, 85.8%, and 89.0% of the time in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions, respectively, vs. 99.2%, 91.7%, and 93.2% for the CBCT and EPI analysis. The CBCT vs. kV radiographs were in agreement 100% (LR), 85.4% (SI), and 88.5% (AP), and EPI vs. kV radiographs were in agreement 100% (LR), 94.6% (SI), and 91.5% (AP) of the time. Identification of FMs on volumetric or planar images was found to be not equivalent (+/-3 mm) using either linear accelerator. Intrafraction prostate motion, interpretation of FM location, and spatial properties of images are contributing factors. Although in-room CT has superior image quality, the process of realigning the treatment couch to acquire a CT introduces an error, highlighting the benefits of a single isocentric system.
Publisher: Oxford University Press (OUP)
Date: 09-1999
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.CLON.2016.09.019
Abstract: To investigate a relationship between maximum rectal diameter (MRD) on pre-treatment cone beam computed tomography (CBCT) and intra-fraction prostate motion, in the context of an adaptive image-guided radiotherapy (IGRT) method. The MRD was measured on 2125 CBCTs from 55 retrospective patient datasets and related to prostate displacement from intra-fraction imaging. A linear regression model was developed to determine a threshold MRD associated with a high probability of small prostate displacement. Standard and reduced adaptive margin plans were created to compare rectum and bladder normal tissue complication probability (NTCP) with each method. A per-protocol analysis carried out on 1910 fractions from 51 patients showed with 90% confidence that for a MRD≤3 cm, prostate displacement will be ≤5 mm and that for a MRD≤3.5 cm, prostate displacement will be ≤5.5 mm. In the first scenario, if adaptive therapy was used instead of standard therapy, median reductions in NTCP for rectum and bladder were 0.5% (from 9.5% to 9%) and 1.3% (from 6.6% to 5.3%), respectively. In the second scenario, the NTCP for rectum and bladder would have median reductions of 1.1% and 2.6%, respectively. We have identified a potential method for adaptive prostate IGRT based upon predicting small prostate intra-fraction motion by measuring MRD on pre-treatment CBCT.
Publisher: Department of Biomedical Imaging, University of Malaya, Malaysia
Date: 07-2008
DOI: 10.2349/BIIJ.4.3.E33
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.EJMP.2015.01.002
Abstract: To construct a method and software to track gold seed implants in prostate and lung patients undergoing radiotherapy using CBCT image projections. A mathematical model was developed in the MatLab (Mathworks, Natick, USA) environment which uses a combination of discreet cosine transforms and filtering to enhance several edge detection methods for identifying and tracking gold seed fiducial markers in images obtained from Varian (Varian Medical Systems, Palo Alto, USA) and Elekta (Kungstensgatan, Sweden) CBCT projections. Organ motion was captured for 16 prostate patients and 1 lung patient. Image enhancement and edge detection is capable of automatically tracking markers for up to 98% (Varian) and 79% (Elekta) of CBCT projections for prostate and lung markers however inclusion of excessive bony anatomy (LT and RT LAT) inhibit the ability of the model to accurate determine marker location.
Publisher: Springer Science and Business Media LLC
Date: 12-11-2011
DOI: 10.1007/S13246-011-0109-X
Abstract: To assess the effect of lesion motion and respiration rate on Standardised Uptake Value (SUV) and the ability of 4D PET to restore any loss in SUV and distortion of lesion volume on two PET/CT systems. A Perspex phantom with four cylindrical reservoirs filled with (18)F-FDG was used in this study. The cylinders measured 5, 10, 15, and 20 mm in diameter. A GE Discovery STE8 (GE Medical Systems Milwaukee, WI) and a Siemens Biograph 64/40 (Siemens Medical Solutions, Erlangen, Germany) scanner was used to acquire a stationary un-gated PET scan of the phantom. Multiple 10 min list mode 4D PET scans were acquired using the Varian RPM on the GE camera and the Anzai Gating system on the Siemens camera. The phantom was scanned at five different respiratory rates and motion litudes in a sinusoidal fashion, 15 RPM/1 cm, 15 RPM/2 cm, 15 RPM/4 cm, 30 RPM/2 cm and 7.5 RPM/2 cm (RPM-respirations per minute). Each scan was reconstructed into ten bins and as an un-gated static image. The SUVmax, SUVmean and volume were measured for all four reservoirs using Siemens TrueD analysis software. With increasing lesion movement the SUVmax and SUVmean decreased and the volume increased with the SUVmax in the smallest lesion underestimated by up to a factor of four. The SUVmax, SUVmean and volume were mostly recovered using 4D imaging regardless of amount of lesion displacement. The larger lesions showed better count recovery and volume correction than the smaller lesions. The respiratory rate had no effect of SUV or volume. Un-gated imaging of moving lesions decreases apparent SUV in small lesions significantly and overestimates volumes. 4D PET scanning recovers most of the apparent loss in SUV and distortion of volumes.
Publisher: Springer Science and Business Media LLC
Date: 11-01-2021
DOI: 10.1186/S13643-021-01580-1
Abstract: Structural stigma in health systems experienced by consumers diagnosed with Borderline Personality Disorder (BPD) is a widespread phenomenon that causes major health inequities and harm for this population. Structural stigma in this context relates to institutional policies, cultural norms, and organizational practices that limit consumers’ access to health services, quality of care, and capacity to achieve optimal health and well-being. BPD is a serious mental illness with high morbidity and mortality, characterized by instability in interpersonal relationships, self-image, and emotional and behavioral deregulation, which stem from significant traumatic childhood/life events, and/or biological etiologies. The objectives of this scoping review are to explore the international literature on structural stigma in healthcare systems specific to BPD, and to provide an overview of the impact of structural stigma on health services for BPD consumers and their carers/families. This scoping review will follow the Joanna Briggs Institute (JBI) scoping review guidelines. We will search the following electronic databases (from inception onwards): MEDLINE, CINAHL, PsycINFO, Scopus, Cochrane Library, and JBI-Evidence databases. Grey literature will be identified through the Google search engine. We will include all types of literature in English, published and unpublished, including any study design, reviews, clinical practice guidelines, policy reports, and other documents. No restrictions on publication date of sources of evidence will be applied. International literature should examine structural stigma associated with BPD in any healthcare setting such as, outpatients, inpatients, primary health care, or community-based facilities. Two reviewers will independently screen all titles, abstracts, and full-text citations. Quality appraisal of the included sources of evidence will be assessed using the Mixed Methods Appraisal Tool (MMAT) 2018 version. Data analysis will involve quantitative (e.g., frequencies) and qualitative (e.g., thematic analysis) methods. This review is anticipated to enhance both identification and understanding of those structures in health systems (i.e., institutional policies, cultural norms, and practices) that manifest and perpetuate stigma experienced by consumers with BPD and their carers/families. The findings can be used to inform future research, policy, and practice relating to stigma reduction strategies that can be adopted to improve the provision of BPD-responsive services and care for this population. Open Science Framework ( osf.io/bhpg4 ).
Publisher: Elsevier BV
Date: 2020
Publisher: Elsevier BV
Date: 09-2022
Publisher: American Medical Association (AMA)
Date: 10-2021
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.IJROBP.2010.12.016
Abstract: To benchmark the dosimetric quality assessment of prostate intensity-modulated radiotherapy and determine whether the quality is influenced by disease or treatment factors. We retrospectively analyzed the data from 155 consecutive men treated radically for prostate cancer using intensity-modulated radiotherapy to 78 Gy between January 2007 and March 2009 across six radiotherapy treatment centers. The plan quality was determined by the measures of coverage, homogeneity, and conformity. Tumor coverage was measured using the planning target volume (PTV) receiving 95% and 100% of the prescribed dose (V(95%) and V(100%), respectively) and the clinical target volume (CTV) receiving 95% and 100% of the prescribed dose. Homogeneity was measured using the sigma index of the PTV and CTV. Conformity was measured using the lesion coverage factor, healthy tissue conformity index, and the conformity number. Multivariate regression models were created to determine the relationship between these and T stage, risk status, androgen deprivation therapy use, treatment center, planning system, and treatment date. The largest discriminatory measurements of coverage, homogeneity, and conformity were the PTV V(95%), PTV sigma index, and conformity number. The mean PTV V(95%) was 92.5% (95% confidence interval, 91.3-93.7%). The mean PTV sigma index was 2.10 Gy (95% confidence interval, 1.90-2.20). The mean conformity number was 0.78 (95% confidence interval, 0.76-0.79). The treatment center independently influenced the coverage, homogeneity, and conformity (all p < .0001). The planning system independently influenced homogeneity (p = .038) and conformity (p = .021). The treatment date independently influenced the PTV V(95%) only, with it being better at the start (p = .013). Risk status, T stage, and the use of androgen deprivation therapy did not influence any aspect of plan quality. Our study has benchmarked measures of coverage, homogeneity, and conformity for the treatment of prostate cancer using IMRT. The differences seen between centers and planning systems and the coverage deterioration over time highlight the need for every center to determine their own benchmarks and apply clinical vigilance with respect to maintaining these through quality assurance.
Publisher: IOP Publishing
Date: 2017
Publisher: Elsevier BV
Date: 09-2003
Publisher: Springer Science and Business Media LLC
Date: 13-04-2020
Publisher: Springer Science and Business Media LLC
Date: 21-02-2019
DOI: 10.1007/S13246-019-00736-7
Abstract: A family of prototype 2D monolithic silicon-diode array detectors (MP512, Duo, Octa) has been proposed by the Centre for Medical Radiation Physics, University of Wollongong (Australia) for relative dosimetry in small megavoltage photon beams. These detectors, which differ in the topology of their 512 sensitive volumes, were originally fabricated on bulk p-type substrates. More recently, they have also been fabricated on epitaxial p-type substrates. In the literature, their performance has been in idually characterized for quality assurance (QA) applications. The present study directly assessed and compared that of a MP512-bulk and that of a MP512-epitaxial in terms of radiation hardness, long-term stability, response linearity with dose, dose per pulse and angular dependence. Their measurements of output factors, off-axis ratios and percentage depth doses in square radiation fields collimated by the jaws and produced by 6 MV and 10 MV flattened photon beams were then benchmarked against those by commercially available detectors. The present investigation was aimed at establishing, from a medical physicist's perspective, how the bulk and epitaxial fabrication technologies would affect the implementation of the MP512s into a QA protocol. Based on results, the MP512-epitaxial would offer superior radiation hardness, long-term stability and achievable uniformity and reproducibility of the response across the 2D active area.
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.MEDDOS.2014.11.001
Abstract: This is a planning study investigating the dosimetric advantages of gated volumetric-modulated arc therapy (VMAT) to the end-exhale and end-inhale breathing phases for patients undergoing stereotactic treatment of primary renal cell carcinoma. VMAT plans were developed from the end-inhale (VMATinh) and the end-exhale (VMATexh) phases of the breathing cycle as well as a VMAT plan and 3-dimensional conformal radiation therapy plan based on an internal target volume (ITV) (VMATitv). An additional VMAT plan was created by giving the respective gated VMAT plan a 50% weighting and summing the inhale and exhale plans together to create a summed gated plan. Dose to organs at risk (OARs) as well as comparison of intermediate and low-dose conformity was evaluated. There was no difference in the volume of healthy tissue receiving the prescribed dose for the planned target volume (PTV) (CI100%) for all the VMAT plans however, the mean volume of healthy tissue receiving 50% of the prescribed dose for the PTV (CI50%) values were 4.7 (± 0.2), 4.6 (± 0.2), and 4.7 (± 0.6) for the VMATitv, VMATinh, and VMATexh plans, respectively. The VMAT plans based on the exhale and inhale breathing phases showed a 4.8% and 2.4% reduction in dose to 30cm(3) of the small bowel, respectively, compared with that of the ITV-based VMAT plan. The summed gated VMAT plans showed a 6.2% reduction in dose to 30cm(3) of the small bowel compared with that of the VMAT plans based on the ITV. Additionally, when compared with the inhale and the exhale VMAT plans, a 4% and 1.5%, respectively, reduction was observed. Gating VMAT was able to reduce the amount of prescribed, intermediate, and integral dose to healthy tissue when compared with VMAT plans based on an ITV. When summing the inhale and exhale plans together, dose to healthy tissue and OARs was optimized. However, gating VMAT plans would take longer to treat and is a factor that needs to be considered.
Publisher: Oxford University Press (OUP)
Date: 09-1999
Publisher: IOP Publishing
Date: 06-1993
Publisher: Elsevier BV
Date: 11-2004
DOI: 10.1016/J.IJROBP.2004.06.013
Abstract: The evolution of three-dimensional conformal radiation treatment has led to the use of multileaf collimators (MLCs) in intensity-modulated radiation therapy (IMRT) and other treatment techniques to increase the conformity of the dose distribution. A new quality assurance (QA) phantom has been designed to check the handling of MLC settings in treatment planning and delivery. The phantom consists of a Perspex block with stepped edges that can be rotated in all planes. The design allows for the assessment of several MLC and micro-MLC types from various manufacturers, and is therefore applicable to most radiation therapy institutions employing MLCs. The phantom is computed tomography (CT) scanned as is a patient, and QA assessments can be made of field edge display for a variety of shapes and orientations on both radiation treatment planning systems (RTPS) and computed tomography simulators. The dimensions of the phantom were verified to be physically correct within an uncertainty range of 0-0.7 mm. Errors in leaf position larger than 1 mm were easily identified by multiple observers. The MLC geometry phantom is a useful tool in the QA of radiation therapy with application to RTPS, CT simulators, and virtual simulation packages with MLC display capabilities.
Publisher: IOP Publishing
Date: 04-11-2019
Abstract: The extreme customisation and rapid prototyping capabilities of the 3D printing process allows the manufacture of low-cost and patient-specific radiotherapy phantoms for quality assurance purposes. However, the associated printing techniques and materials are experimentally limited and are yet to be quantified in terms of manufacturability. In addition to this, there lacks research in utilising naturally inspired structures, known as triply periodic minimal surfaces (TPMS), as a structural manufacturing basis for these phantoms, enabling material heterogeneity, which is a significant factor in attaining patient-specificity. We propose the use of Gyroid structures for radiotherapy phantom applications to investigate Gyroid-phantom manufacturability, the mathematical definition of Gyroids and their effects on hounsfield units (HU). The printed Gyroid phantoms were assessed for manufacturability using optical microscopy and micro-computed tomography (µCT), and material hounsfield-equivalence using standard medical CT. A mean HU range of -900 to -390 were achieved from the fabricated Gyroid phantoms with varying standard deviation. Compared to traditional printing infills such as grid and slit structures, the Gyroid phantoms were observed to produce isotropic HU and SD at varied scanning orientations, which optimizes CT attenuations in modulating the hounsfield-equivalence of printed structures. This study not only demonstrates the feasibility of manipulating the structural parameters of Gyroids in simulating tissue imaging attenuations but also opens significant research opportunities in fabricating patient-specific phantoms with added pathological features for end-to-end radiotherapy testing.
Publisher: Elsevier BV
Date: 11-2017
Publisher: Society of Nuclear Medicine
Date: 15-05-2014
DOI: 10.2967/JNUMED.113.131631
Abstract: We aimed to prospectively observe cellular metabolism and proliferation in patients with non-small-cell lung cancer (NSCLC) during radical chemoradiation therapy using serial PET/CT with (18)F-FDG and 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT). Twenty patients with stage I-III NSCLC and candidates for radical chemoradiation therapy (60 Gy in 30 fractions over 6 wk) were recruited. (18)F-FDG and (18)F-FLT PET/CT were performed at baseline and during therapy (weeks 2 and 4). Tumor response was assessed semiquantitatively and using visual response criteria. The median and range for primary tumor volume (cm(3)) at baseline on (18)F-FDG were 28 and 2-241, respectively, and on (18)F-FLT 31 and 2-184, respectively. At week 2, (18)F-FDG was 26 (range, 2-164), and (18)F-FLT was 11 (range, 0-111). At week 4, (18)F-FDG was 19 (1-147), and (18)F-FLT was 7 (0-48). The median and range of maximum standardized uptake value (SUVmax) at baseline on (18)F-FDG were 14 and 4-31, respectively, and on (18)F-FLT 6 and 2-12, respectively. Week 2 (18)F-FDG median SUVmax was 10 (2-31), and (18)F-FLT median SUVmax was 3 (1-15) week 4 (18)F-FDG median SUVmax was 10 (2-15), and (18)F-FLT median SUVmax was 2 (2-9). There was fair agreement between visual tumor response on (18)F-FDG and (18)F-FLT during therapy (Cohen's unweighted κ statistic, 0.27 at week 2 and 0.355 at week 4). Cerebral metastases were detected on 1 baseline (18)F-FLT scan, resulting in palliative management. Progressive disease was detected on week 2 scans in 3 patients, resulting in changes to radiation therapy (2 patients) and treatment intent (1 patient). This study demonstrates that (18)F-FLT PET/CT is a more sensitive tracer of early treatment response than (18)F-FDG PET/CT. The ability of these tracers to detect distinct biologic processes may lead to their use as biomarkers for personalized radiation therapy and prognosis in the future.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Wiley
Date: 13-08-2012
DOI: 10.1118/1.4742053
Abstract: The use of time‐resolved four‐dimensional computed tomography (4D‐CT) in radiotherapy requires strict quality assurance to ensure the accuracy of motion management protocols. The aim of this work was to design and test a phantom capable of large litude motion for use in 4D‐CT, with particular interest in small lesions typical for stereotactic body radiotherapy. The phantom of “see‐saw” design is light weight, capable of including various s le materials and compatible with several surrogate marker signal acquisition systems. It is constructed of polymethylmethacrylate (Perspex) and its movement is controlled via a dc motor and drive wheel. It was tested using two CT scanners with different 4D acquisition methods: the Philips Brilliance Big Bore CT (helical scan, pressure belt) and a General Electric Discovery STE PET/CT (axial scan, infrared marker). Amplitudes ranging from 1.5 to 6.0 cm and frequencies of up to 40 cycles per minute were used to study the effect of motion on image quality. Maximum intensity projections (MIPs), as well as average intensity projections (AIPs) of moving objects were investigated and their quality dependence on the number of phase reconstruction bins assessed. CT number discrepancies between moving and stationary objects were found to have no systematic dependence on litude, frequency, or specific interphase variability. MIP‐delineated litudes of motion were found to match physical phantom litudes to within 2 mm for all motion scenarios tested. Objects undergoing large litude motions ( .0 cm) were shown to cause artefacts in MIP and AIP projections when ten phase bins were assigned. This problem can be mitigated by increasing the number of phase bins in a 4D‐CT scan. The phantom was found to be a suitable tool for evaluating the image quality of 4D‐CT motion management technology, as well as providing a quality assurance tool for intercenter/intervendor testing of commercial 4D‐CT systems. When imaging objects with large litudes, the completeness criterion described here indicates the number of phase bins required to prevent missing data in MIPs and AIPs. This is most relevant for small lesions undergoing large motions.
Publisher: Springer Science and Business Media LLC
Date: 22-03-2011
DOI: 10.1007/S13246-011-0063-7
Abstract: A methodology has been developed for a dosimetry inter-comparison of intensity modulated radiation therapy (IMRT) delivery in Australasia. The inter-comparison is part of site credentialing for those sites participating in the prostate fractionated irradiation trial (PROFIT) for intermediate-risk prostate patients developed by the Ontario Clinical Oncology Group and coordinated in Australasia by the Trans Tasman Radiation Oncology Group. Features of the dosimetry inter-comparison design included the use of a dedicated pelvic anthropomorphic phantom, the use of a single CT data set of the phantom including contours and the use of radiochromic film as a dosimeter. Action levels for agreement between measured dose and treatment planning system dose have been proposed based on measurement uncertainty and international experience. A trial run of the dosimetry procedure at the reference centre gave results within the predefined action levels.
Publisher: Frontiers Media SA
Date: 13-03-2023
DOI: 10.3389/FONC.2023.1134884
Abstract: Lutetium-177 [ 177 Lu]-PSMA-617 is a targeted radioligand that binds to prostate-specific membrane antigen (PSMA) and delivers radiation to metastatic prostate cancer. The presence of PSMA-negative/FDG-positive metastases can preclude patients from being eligible for this treatment. Biology-guided radiotherapy (BgRT) is a treatment modality that utilises tumour PET emissions to guide external beam radiotherapy. The feasibility of combining BgRT and Lutetium-177 [ 177 Lu]-PSMA-617 for patients with PSMA-negative/FDG-positive metastatic prostate cancer was explored. All patients excluded from the LuPSMA clinical trial (ID: ANZCTR12615000912583) due to PSMA/FDG discordance were retrospectively reviewed. A hypothetical workflow where PSMA-negative/FDG-positive metastases would be treated with BgRT whilst PSMA-positive metastases would be treated with Lutetium-177 [ 177 Lu]-PSMA-617 was considered. Gross tumour volume (GTV) of PSMA-negative/FDG-positive tumours were delineated on the CT component of the FDG PET/CT scan. Tumours were deemed suitable for BgRT if (1) normalised SUV (nSUV), defined as the ratio of maximum SUV (SUVmax) inside the GTV to mean SUV inside a 5 mm/10 mm/20 mm margin expansion of the GTV, was larger than a pre-specified nSUV threshold and (2) there was no PET avidity inside the margin expansion. In 75 patients screened for Lutetium-177 [ 177 Lu]-PSMA-617 treatment, 6 patients were excluded due to PSMA/FDG discordance and 89 PSMA-negative/FDG-positive targets were identified. GTV volumes ranged from 0.3 cm 3 to 186 cm 3 (median GTV volume = 4.3 cm 3 , IQR = 2.2 cm 3 – 7.4 cm 3 ). SUVmax inside GTVs ranged between 3 and 12 (median SUVmax = 4.8, IQR = 3.9 – 6.2). With nSUV ≥ 3, 67%/54%/39% of all GTVs were suitable for BgRT within 5 mm/10 mm/20 mm from the tumour. Bone and lung metastases were the best candidates for BgRT (40%/27% of all tumours suitable for BgRT with nSUV ≥ 3 within 5 mm from the GTV were bone/lung GTVs). Combined BgRT/Lutetium-177 [ 177 Lu]-PSMA-617 therapy is feasible for patients with PSMA/FDG discordant metastases.
Publisher: Elsevier BV
Date: 07-2015
Publisher: Elsevier BV
Date: 10-2018
Publisher: Wiley
Date: 11-08-2003
DOI: 10.1046/J.1440-1673.2003.01178.X
Abstract: Because many head and neck radiotherapy treatment techniques rely on a junction between X-ray fields, it was the aim of the present study to investigate the use of different junctioning techniques and the affect on the dose across the junction. Techniques in use at nine radiotherapy centres in Australia were investigated using thermoluminescence dosimetry (TLD). The techniques could broadly be ided into two groups: (i) use of the light field to match the fields after moving the patient and (ii) use of asymmetric collimation to create a single isocentre located in the junction. The mean dose at the junction and its reproducibility was studied in five consecutive treatments in each centre using 25 TLD chips placed throughout the junction in an anthropomorphic phantom. There was a tendency for the mono-isocentric technique to deliver a lower, more accurate mean dose at the junction (Group I: 1.22 Gy (n = 8) vs Group II: 0.96 Gy (n = 5) for 1 Gy planned, some centres contributed to both technique) with greater reproducibility (Group I: 9.6%, Group II: 5.1% of the mean dose). We conclude that a mono-isocentric treatment technique has the potential to deliver a more accurate and reproducible dose distribution at the field junction of photon beams in head and neck treatment.
Publisher: Elsevier BV
Date: 05-2011
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 11-1996
DOI: 10.1016/S0167-8140(96)01795-1
Abstract: Prediction of skin reactions requires knowledge of the dose at various depths in the human skin. Using thermoluminescence dosimeters of three different thicknesses, the dose can be extrapolated to the surface and interpolated between the different depths. A TLD holder was designed for these TLD extrapolation measurements on patients during treatment which allowed measurements of entrance and exit skin dose with a day to day variability of +/-7% (S.D. of mean reading). In a pilot study on 18 patients undergoing breast irradiation, it was found that the angle of incidence of the radiation beam is the most significant factor influencing skin entrance dose. In most of these measurements the beam exit dose contributed 50% more to the surface dose than the entrance dose.
Publisher: Oxford University Press (OUP)
Date: 09-1999
Publisher: IOP Publishing
Date: 17-06-2003
DOI: 10.1088/0031-9155/48/13/306
Abstract: Helical tomotherapy (HT) is a novel treatment approach where the ring gantry irradiation geometry of a helical CT scanner is combined with an intensity-modulated megavoltage x-ray fan beam. An inverse treatment planning system (TomoTherapy Inc., Madison) was used to optimize the treatment plans for ten randomly selected prostate patients. Five different sets of margins (2, 5, 7.5 and 10 mm uniform 3D margins and a non-uniform margin of 5 to 10 mm) were employed for the prostate (GTV2) and seminal vesicles (GTV1). The dose distribution was evaluated in targets, rectum, bladder and femoral heads. HT plans are characterized by a rapid dose fall off around the target in all directions resulting in low doses (less than 30% of the dose at ICRU reference point) to the femurs in all cases. Up to a margin of 5 mm for target structures, it was always possible to satisfy the requirements for dose delivery set by RTOG protocol P-0126. Using a 'class solution', HT plans require minimal operator interaction and result in excellent sparing of normal structures in prostate radiotherapy.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Springer Science and Business Media LLC
Date: 06-2010
DOI: 10.1007/S13246-010-0019-3
Abstract: Dosimetry for intraoperative radiotherapy (IORT) after wide local excision for breast cancer using a 50 kV X-ray needle (Intrabeam) was performed in vivo using thermoluminescence dosimetry. Eight LiF:Mg,Ti chips were placed on the skin around the incision site after wide local excision while the tumour bed was irradiated to a prescribed dose of 5 Gy 10 mm from the applicator surface. The maximum and mean measured skin dose for 57 patients ranged from 0.64 to 7.1 Gy and 0.56 to 4.78 Gy, respectively, reflecting different tissue thicknesses overlying the applicator. The average maximum dose of 2.93+/-1.46 Gy was below the threshold for severe radiation skin toxicity.
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.RADONC.2013.12.004
Abstract: To study prostate bed deformation, and compare coverage by 5 mm and 10mm posterior expansion PTV margins. Fifty patients who completed post-prostatectomy radiotherapy had two expansion margins applied to the planning CT CTV: PTV10 (10 mm isometrically) and PTV5 (5 mm posteriorly, 10 mm all other directions). The CTV was then contoured on 477 pre-treatment CBCTs, and PTV5 and PTV10 coverage of each CBCT-CTVs was assessed. The maximum distance from the planning CT CTV to the combined CTV of all CBCTs including the planning CT CTV was measured for the superior part of the prostate bed, and the inferior part of the prostate bed, for every patient. The mean difference between largest and smallest CBCT-CTVs per patient was 18.7 cm(3) (range 6.3-34.2 cm(3)). Out of 477 CBCTs, there were 43 anterior geometric geographical misses for either PTV with a mean volume of 2.25 cm(3) (range 0.01-18.88 cm(3)). For PTV10, there were 26 posterior geometric geographical misses with a mean volume of 1.37 cm(3) (0.01-11.02 cm(3)). For PTV5, there were 46 posterior geometric geographical misses with a mean volume of 3.22 cm(3) (0.01-19.82 cm(3)). The maximum edge-to-edge distance for the superior prostate bed was anterior 19 mm, posterior 16 mm, left and right 7 mm. The maximum edge-to-edge distance for the inferior prostate bed was anterior 4mm, posterior 12 mm, left and right 7 mm. This study supports differential margins for the superior and inferior portions of the prostate bed. Because of the large deformation of CTV volume seen, adaptive radiotherapy solutions should be investigated further.
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.EURURO.2018.06.004
Abstract: Stereotactic ablative body radiotherapy (SABR) is an emerging treatment option for oligometastatic prostate cancer. However, limited prospective evidence is available. To determine the safety and feasibility of single fraction SABR for patients with oligometastatic prostate cancer. Secondary endpoints were local and distant progression-free survival (LPFS and DPFS), toxicity, quality of life (QoL), and prostate-specific antigen response. In a prospective clinical trial, patients were screened with computed tomography, bone scan, and sodium fluoride positron emission tomography scan and had one to three oligometastases. Kaplan-Meier methods were used to determine LPFS and DPFS. Toxicity was graded using Common Terminology Criteria for Adverse Event version 4.0. QoL was assessed using European Organization for Research and Treatment of Cancer QLQ-C30 and QLQ-BM22 at 1, 3,12, and 24 mo. A single fraction of 20-Gy SABR to each lesion. Between 2013 and 2014, 33 consecutive patients received SABR to a total of 50 oligometastases and were followed for 2 yr. The median age was 70 yr. The Gleason score was ≥8 in 15 patients (45%). Twenty patients had bone only, 12 had node only, and one had mixed disease. SABR was feasible and delivered as planned in 97% of cases. There was one grade 3 adverse event (3.0%, vertebral fracture). No patient died. The 1 and 2-yr LPFS was 97% (95% confidence interval [CI]: 91-100) and 93% (95% CI: 84-100), and DPFS was 58% (95% CI: 43-77) and 39% (95% CI: 25-60), respectively. In those not on androgen deprivation therapy (ADT n=22), the 2-yr freedom from ADT was 48%. There was no significant difference from baseline QoL observed. Limitations include small s le size, limited duration of follow-up, and lack of a control arm. A single SABR session was feasible and associated with low morbidity in this cohort. Over one-third of patients did not progress and were free from ADT at 2-yr. QoL measures were maintained with this treatment strategy. This clinical trial investigated single treatment stereotactic radiotherapy for low volume advanced prostate cancer. The approach was found to be safe with avoidance of hormone therapy in almost half of the participants at 2 yr.
Publisher: Oxford University Press (OUP)
Date: 09-1999
Publisher: Wiley
Date: 10-09-2013
DOI: 10.1118/1.4819945
Abstract: Deformable image registration (DIR) has become a key tool for adaptive radiotherapy to account for inter- and intrafraction organ deformation. Of contemporary interest, the application to deformable dose accumulation requires accurate deformation even in low contrast regions where dose gradients may exist within near-uniform tissues. One expects high-contrast features to generally be deformed more accurately by DIR algorithms. The authors systematically assess the accuracy of 12 DIR algorithms and quantitatively examine, in particular, low-contrast regions, where accuracy has not previously been established. This work investigates DIR algorithms in three dimensions using deformable gel (DEFGEL) [U. J. Yeo, M. L. Taylor, L. Dunn, R. L. Smith, T. Kron, and R. D. Franich, "A novel methodology for 3D deformable dosimetry," Med. Phys. 39, 2203-2213 (2012)], for application to mass- and density-conserving deformations. CT images of DEFGEL phantoms with 16 fiducial markers (FMs) implanted were acquired in deformed and undeformed states for three different representative deformation geometries. Nonrigid image registration was performed using 12 common algorithms in the public domain. The optimum parameter setup was identified for each algorithm and each was tested for deformation accuracy in three scenarios: (I) original images of the DEFGEL with 16 FMs (II) images with eight of the FMs mathematically erased and (III) images with all FMs mathematically erased. The deformation vector fields obtained for scenarios II and III were then applied to the original images containing all 16 FMs. The locations of the FMs estimated by the algorithms were compared to actual locations determined by CT imaging. The accuracy of the algorithms was assessed by evaluation of three-dimensional vectors between true marker locations and predicted marker locations. The mean magnitude of 16 error vectors per s le ranged from 0.3 to 3.7, 1.0 to 6.3, and 1.3 to 7.5 mm across algorithms for scenarios I to III, respectively. The greatest accuracy was exhibited by the original Horn and Schunck optical flow algorithm. In this case, for scenario III (erased FMs not contributing to driving the DIR calculation), the mean error was half that of the modified demons algorithm (which exhibited the greatest error), across all deformations. Some algorithms failed to reproduce the geometry at all, while others accurately deformed high contrast features but not low-contrast regions-indicating poor interpolation between landmarks. The accuracy of DIR algorithms was quantitatively evaluated using a tissue equivalent, mass, and density conserving DEFGEL phantom. For the model studied, optical flow algorithms performed better than demons algorithms, with the original Horn and Schunck performing best. The degree of error is influenced more by the magnitude of displacement than the geometric complexity of the deformation. As might be expected, deformation is estimated less accurately for low-contrast regions than for high-contrast features, and the method presented here allows quantitative analysis of the differences. The evaluation of registration accuracy through observation of the same high contrast features that drive the DIR calculation is shown to be circular and hence misleading.
Publisher: Wiley
Date: 06-2002
Publisher: ASME International
Date: 12-10-2020
DOI: 10.1115/1.4044460
Abstract: Anthropomorphic radiotherapy phantoms require tissue-equivalent materials to achieve Hounsfield units (HU) that are comparable to those of human tissue. Traditional manufacturing methods are limited by their high-cost and incompatibility with patient-specific customization. Additive manufacture (AM) provides a significant opportunity to enable manufacture of patient-specific geometries at relatively low cost. However, AM technologies are currently limited in terms of available material types, and consequently enable very little variation in achievable HU when standard manufacturing parameters are used. This work demonstrates a novel method whereby the partial volume effect (PVE) is utilized to control the HU of an AM material, in particular, enabling low HU in the range typical of lung tissue. The method enables repeatable design of lung HU and is compatible with commercial machines using standard print parameters. A custom algorithm demonstrates the clinical application of the method, whereby patient-specific computed tomography (CT) data are algorithmically calibrated according to AM print parameters and confirmed to be robust as a custom anthropomorphic radiotherapy phantoms.
Publisher: IOP Publishing
Date: 29-09-2020
Abstract: 3D printing provides new opportunities to create devices used during radiotherapy treatments, yet little is known about the effect process parameters play on the proposed devices. This study investigates the combined influence of infill pattern, infill density and print orientation on surface dose, as well as on the mechanical properties of 3D printed s les, identifying the optimal infill patterns for use in radiotherapy devices including immobilisation. Fused deposition modelling (FDM) was used to produce sixty s les in two orientations for surface dose measurement, utilising ten different infill patterns. Surface dose testing was performed using a Varian Trubeam linear accelerator with a 6 MV photon beam. A further one hundred and twenty tensile test s les, designed according to ASTM D638 type I standards, were evaluated using a 50 KN Instron 5969. On average, horizontally printed s les had a lower surface dose measurement compared to the vertically orientated s les, with the Stars infill pattern recording the lowest surface dose values in the horizontal orientation, while the Hilbert Curve recorded the lowest surface dose in the edge orientation. Tensile tests revealed the 3D Honeycomb infill pattern to have the highest ultimate tensile strength (UTS) in both horizontal and edge orientations. Overall, the Stars infill pattern exhibited the optimal balance of low surface dose and above average UTS. This study shows how infill patterns can significantly affect dosimetry and mechanical performance of 3D printed radiotherapy devices, and the data can be used by design engineers, clinicians and medical physicists to select the appropriate infill pattern, density and print orientation based on the functional requirements of a radiotherapy device.
Publisher: Wiley
Date: 2013
DOI: 10.1118/1.4771962
Publisher: Elsevier BV
Date: 11-2022
Publisher: Wiley
Date: 23-11-2018
Publisher: Wiley
Date: 12-10-2021
DOI: 10.1002/ERV.2866
Abstract: Research and theory suggest the aetiological nature and symptomatic profile of eating disorders (EDs) can be explained by multiple factors, including the development of early maladaptive schemas (EMS). Yet, there is lack of consensus regarding the evidence supporting the relationship between EMS and EDs. Therefore, this systematic review aimed to examine existing literature concerning the relationship between different ED diagnoses and EMS to provide a synthesis and evaluation of relevant research. A comprehensive literature search of four electronic databases was conducted and studies were included that examined the association between EMS and EDs. Studies were required to use a variant of Young Schema Questionnaire and establish ED diagnosis or symptomology using self‐report questionnaires or clinical interview. A total of 29 studies were included in the review. Compared to healthy controls and varying clinical populations, in iduals with EDs generally reported significantly higher scores across all EMS except for Entitlement. Furthermore, Unrelenting Standards consistently appeared as a significant EMS across all ED diagnoses whilst Insufficient Self‐Control was significantly lower in ED diagnoses with restrictive behaviour compared to diagnoses with binge eating or purging behaviour. Research supports significant associations between EMS and EDs, which may contribute to our understanding of ED aetiology, including different diagnostic categories. This review underscores the need for studies to explore more gender and age erse s les and highlights important implications for practitioners.
Publisher: Elsevier BV
Date: 04-1998
DOI: 10.1016/S0360-3016(98)00011-X
Abstract: The matching or junctioning of two lateral fields with an anterior field is commonly performed in the treatment of head and neck cancer. A monoisocentric technique utilising asymmetric collimation is potentially associated with improved dosimetry in the plane of the junction due to decreased reliance on operator skill and the avoidance of couch movement. The aim of this study was not only to assess the average dose delivered in the plane of the junction, but also the reproducibility of this dose for the monoisocentric technique and two other commonly used techniques. An anthropomorphic head and neck wax phantom was fashioned to allow the placement of 22 TLD chips in a 2-mm thick transverse plane positioned superior to the potential site of the larynx. Three different treatment techniques were used with the phantom being treated by four different operators a minimum of 20 times for each technique: (1) "straight fields"--using isocentric laterals with an anterior field junctioned in the midline. This technique makes no allowance for ergence (2) "angled fields"--couch and gantry rotation are used to account for ergence (3) "monoisocentric"--using asymmetric collimators to create a single isocenter. For an applied dose of 1 Gy the monoisocentric technique produced a mean dose measured of 1.01 Gy compared with 1.23 and 0.92 Gy for techniques 1 and 2. The reproducibility of the mean dose measured was better for the monoisocentric technique by a factor of 2. The superior reproducibility of the monoisocentric technique was not found to be operator dependent. A monoisocentric technique for the treatment of two laterals and an anterior field in head and neck cancer is likely to be associated with more accurate and reproducible dosimetry in the plane of the junction. Our center has subsequently adopted this technique for matching such fields.
Publisher: Elsevier BV
Date: 12-2009
DOI: 10.1016/J.MEDDOS.2008.11.002
Abstract: The kidneys are dose-limiting organs in abdominal radiotherapy. Kilovoltage (kV) radiographs can be acquired using on-board imager (OBI)-equipped linear accelerators with better soft tissue contrast and lower radiation doses than conventional portal imaging. A feasibility study was conducted to test the suitability of anterior-posterior (AP) non-contrast kV radiographs acquired at treatment time for online kidney position verification. Anthropomorphic phantoms were used to evaluate image quality and radiation dose. Institutional Review Board approval was given for a pilot study that enrolled 5 adults and 5 children. Customized digitally reconstructed radiographs (DRRs) were generated to provide a priori information on kidney shape and position. Radiotherapy treatment staff performed online evaluation of kidney visibility on OBI radiographs. Kidney dose measured in a pediatric anthropomorphic phantom was 0.1 cGy for kV imaging and 1.7 cGy for MV imaging. Kidneys were rated as well visualized in 60% of patients (90% confidence interval, 34-81%). The likelihood of visualization appears to be influenced by the relative AP separation of the abdomen and kidneys, the axial profile of the kidneys, and their relative contrast with surrounding structures. Online verification of kidney position using AP non-contrast kV radiographs on an OBI-equipped linear accelerator appears feasible for patients with suitable abdominal anatomy. Kidney position information provided is limited to 2-dimensional "snapshots," but this is adequate in some clinical situations and potentially advantageous in respiratory-correlated treatments. Successful clinical implementation requires customized partial DRRs, appropriate imaging parameters, and credentialing of treatment staff.
Publisher: Springer Science and Business Media LLC
Date: 04-02-2020
Publisher: Wiley
Date: 10-04-2012
DOI: 10.1111/J.1754-9485.2012.02367.X
Abstract: The Peter MacCallum Cancer Centre has established a stereotactic lung radiosurgery program for the treatment of isolated lung metastases. The aim of this study was to critically assess the technical feasibility of performing stereotactic lung radiosurgery in an Australian institution. A single 26-Gy fraction of radiotherapy was delivered to patients with positron emission tomography (PET) staged solitary lung metastases. Motion management was addressed using four-dimensional computed tomographic simulation, and cone beam CT (CBCT) online soft-tissue matching. Treatments were with multiple coplanar and non-coplanar asymmetric beams. Patients were immobilised in a dedicated stereotactic body cradle. Quality assurance (QA) of treatment plans with both ion chamber and film measurements was performed accounting for patient-specific respiratory motion. Between February 2010 and February 2011, nine patients received stereotactic lung radiosurgery. One grade 1 toxicity and one grade 2 toxicity were recorded after treatment. The mean planning target volume was 22.6 cc. A median of eight beams were delivered per treatment plan (range 7-10) with a median of two non-coplanar beams (range 0-6). At treatment plan QA, the difference between planned and delivered dose was ≤1.76% in all static and dynamic ion chamber recordings. A mid-treatment CBCT was performed at a median time of 21 min, with the mean displacement discrepancy from initial set-up being 0.4 mm (range 0-2 mm). Stereotactic radiosurgery to the lung was both feasible and tolerable at our institution. Intrafractional immobilisation within 2 mm was reproducible. Excellent concordance between planned and delivered treatments was achieved in the phantom QA.
Publisher: Elsevier BV
Date: 03-2012
DOI: 10.1016/J.MEDDOS.2011.01.002
Abstract: Prediction of dose distributions in close proximity to interfaces is difficult. In the context of radiotherapy of lung tumors, this may affect the minimum dose received by lesions and is particularly important when prescribing dose to covering isodoses. The objective of this work is to quantify underdosage in key regions around a hypothetical target using Monte Carlo dose calculation methods, and to develop a factor for clinical estimation of such underdosage. A systematic set of calculations are undertaken using 2 Monte Carlo radiation transport codes (egsnrc and geant4). Discrepancies in dose are determined for a number of parameters, including beam energy, tumor size, field size, and distance from chest wall. Calculations were performed for 1-mm³ regions at proximal, distal, and lateral aspects of a spherical tumor, determined for a 6-MV and a 15-MV photon beam. The simulations indicate regions of tumor underdose at the tumor-lung interface. Results are presented as ratios of the dose at key peripheral regions to the dose at the center of the tumor, a point at which the treatment planning system (TPS) predicts the dose more reliably. Comparison with TPS data (pencil-beam convolution) indicates such underdosage would not have been predicted accurately in the clinic. We define a dose reduction factor (DRF) as the average of the dose in the periphery in the 6 cardinal directions ided by the central dose in the target, the mean of which is 0.97 and 0.95 for a 6-MV and 15-MV beam, respectively. The DRF can assist clinicians in the estimation of the magnitude of potential discrepancies between prescribed and delivered dose distributions as a function of tumor size and location. Calculation for a systematic set of "generic" tumors allows application to many classes of patient case, and is particularly useful for interpreting clinical trial data.
Publisher: Wiley
Date: 11-2014
Publisher: Wiley
Date: 06-2004
Publisher: Elsevier BV
Date: 08-2009
Publisher: American Society of Clinical Oncology (ASCO)
Date: 07-2023
DOI: 10.1200/JCO.23.00150
Abstract: Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. In a randomized phase II clinical trial, the Trans Tasman Radiation Oncology Group compared single- versus multifraction stereotactic ablative body radiotherapy (SABR) in 90 patients with 133 oligometastases to the lung. The study found no differences in safety, efficacy, systemic immunogenicity, or survival between arms, with single-fraction SABR picked as the winner on the basis of cost-effectiveness. In this article, we report the final updated survival outcome analysis. The protocol mandated no concurrent or post-therapy systemic therapy until progression. Modified disease-free survival (mDFS) was defined as any progression not addressable by local therapy, or death. At a median follow-up of 5.4 years, the 3- and 5-year estimates for overall survival (OS) were 70% (95% CI, 59 to 78) and 51% (95% CI, 39 to 61). There were no significant differences between the multi- and single-fraction arms for OS (hazard ratio [HR], 1.1 [95% CI, 0.6 to 2.0] P = .81). The 3- and 5-year estimates for disease-free survival were 24% (95% CI, 16 to 33) and 20% (95% CI, 13 to 29), with no differences between arms (HR, 1.0 [95% CI, 0.6 to 1.6] P = .92). The 3- and 5-year estimates for mDFS were 39% (95% CI, 29 to 49) and 34% (95% CI, 24 to 44), with no differences between arms (HR, 1.0 [95% CI, 0.6 to 1.8] P = .90). In this patient population, where patients receive SABR in lieu of systemic therapy, one-in-three patients are alive without disease in the long term. There were no differences in outcomes by fractionation schedule.
Publisher: Royal College of Psychiatrists
Date: 19-02-2018
DOI: 10.1192/BJB.2017.3
Abstract: Help-seeking is important for patients with suicidal ideation. Currently, a risk management paradigm is used with patients who express suicidality however, this may limit support and increase stigma, reducing future help-seeking. Coping planning is proposed as a paradigm shift that overcomes these problems by focusing on patient needs and strengths. None.
Publisher: Springer Science and Business Media LLC
Date: 04-03-2016
Publisher: Springer Science and Business Media LLC
Date: 26-11-2014
Publisher: Elsevier BV
Date: 07-2021
Publisher: Springer Science and Business Media LLC
Date: 27-07-2022
DOI: 10.1038/S41598-022-16520-9
Abstract: Artificial intelligence and radiomics have the potential to revolutionise cancer prognostication and personalised treatment. Manual outlining of the tumour volume for extraction of radiomics features (RF) is a subjective process. This study investigates robustness of RF to inter-observer variation (IOV) in contouring in lung cancer. We utilised two public imaging datasets: ‘NSCLC-Radiomics’ and ‘NSCLC-Radiomics-Interobserver1’ (‘Interobserver’). For ‘NSCLC-Radiomics’, we created an additional set of manual contours for 92 patients, and for ‘Interobserver’, there were five manual and five semi-automated contours available for 20 patients. Dice coefficients (DC) were calculated for contours. 1113 RF were extracted including shape, first order and texture features. Intraclass correlation coefficient (ICC) was computed to assess robustness of RF to IOV. Cox regression analysis for overall survival (OS) was performed with a previously published radiomics signature. The median DC ranged from 0.81 (‘NSCLC-Radiomics’) to 0.85 (‘Interobserver’—semi-automated). The median ICC for the ‘NSCLC-Radiomics’, ‘Interobserver’ (manual) and ‘Interobserver’ (semi-automated) were 0.90, 0.88 and 0.93 respectively. The ICC varied by feature type and was lower for first order and gray level co-occurrence matrix (GLCM) features. Shape features had a lower median ICC in the ‘NSCLC-Radiomics’ dataset compared to the ‘Interobserver’ dataset. Survival analysis showed similar separation of curves for three of four RF apart from ‘original_shape_Compactness2’, a feature with low ICC (0.61). The majority of RF are robust to IOV, with first order, GLCM and shape features being the least robust. Semi-automated contouring improves feature stability. Decreased robustness of a feature is significant as it may impact upon the features’ prognostic capability.
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.RADONC.2014.07.011
Abstract: To ascertain the rate, type, significance, trends and the potential risk factors associated with radiotherapy incidents in a large academic department. Data for all radiotherapy activities from July 2001 to January 2011 were reviewed from radiotherapy incident reporting forms. Patient and treatment data were obtained from the radiotherapy record and verification database (MOSAIQ) and the patient database (HOSPRO). Logistic regression analyses were performed to determine variables associated with radiotherapy incidents. In that time, 65,376 courses of radiotherapy were delivered with a reported incident rate of 2.64 per 100 courses. The rate of incidents per course increased (1.96 per 100 courses to 3.52 per 100 courses, p 5% deviation in dose (10.50 to 2.75%, p<0.001) had decreased after the introduction of an online electronic reporting system. The following variables were associated with an increased rate of incidents: afternoon treatment time, paediatric patients, males, inpatients, palliative plans, head-and-neck, skin, sarcoma and haematological malignancies. In general, complex plans were associated with higher incidence rates. Radiotherapy incidents were infrequent and most did not result in significant dose deviation. A number of risk factors were identified and these could be used to highlight high-risk cases in the future. Introduction of an online electronic reporting system resulted in a significant increase in the number of incidents being reported.
Publisher: Elsevier BV
Date: 12-2011
Publisher: American Physical Society (APS)
Date: 08-09-2005
Publisher: Elsevier BV
Date: 11-2009
DOI: 10.1016/J.IJROBP.2008.12.039
Abstract: To establish whether (18)F-3'-deoxy-3'-fluoro-L-thymidine ((18)F-FLT) can monitor changes in cellular proliferation of non-small-cell lung cancer (NSCLC) during radical chemo-radiotherapy (chemo-RT). As part of a prospective pilot study, 5 patients with locally advanced NSCLC underwent serial (18)F-FLT positron emission tomography (PET)/computed tomography (CT) scans during treatment. Baseline (18)F-FLT PET/CT scans were compared with routine staging (18)F-FDG PET/CT scans. Two on-treatment (18)F-FLT scans were performed for each patient on Days 2, 8, 15 or 29, providing a range of time points for response assessment. In all 5 patients, baseline lesional uptake of (18)F-FLT on PET/CT corresponded to staging (18)F-FDG PET/CT abnormalities. (18)F-FLT uptake in tumor was observed on five of nine (55%) on-treatment scans, on Days 2, 8 and 29, but not Day 15. A "flare" of (18)F-FLT uptake in the primary tumor of one case was observed after 2 Gy of radiation (1.22 x baseline). The remaining eight on-treatment scans demonstrated a mean reduction in (18)F-FLT tumor uptake of 0.58 x baseline. A marked reduction of (18)F-FLT uptake in irradiated bone marrow was observed for all cases. This reduction was observed even after only 2 Gy, and all patients demonstrated a complete absence of proliferating marrow after 10 Gy. This proof of concept study indicates that (18)F-FLT uptake can monitor the distinctive biologic responses of epithelial cancers and highly radiosensitive normal tissue changes during radical chemo-RT. Further studies of (18)F-FLT PET/CT imaging during therapy may suggest that this tracer is useful in developing response-adapted RT for NSCLC.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Wiley
Date: 10-2010
DOI: 10.1111/J.1754-9485.2010.02203.X
Abstract: We determined Hounsfield numbers, using cone beam CT (CBCT), in the bladder of 27 muscle invasive bladder cancer patients treated with online adaptive radiotherapy using a Varian linear accelerator. The CBCT number of urine was found to increase by 130 from the thinnest to the largest patient (249 mm to 346 mm average diameter) demonstrating the effect of patient size on Hounsfield number in CBCT in vivo.
Publisher: Frontiers Media SA
Date: 18-10-2022
Abstract: The complexity of modern radiotherapy treatment pathways necessitate input from different professions to ensure treatment is delivered safely and as planned. In vivo dosimetry is one method of treatment verification providing the opportunity for both in-field verification or out-of-field measurements. It was the aim of this work to review the impact of an in vivo dosimetry programme with t.he view to justify resources and assist in developing a plan for equipment acquisition. Results of 310 (approximately 2 per 1000 treatment fractions) in vivo measurements were reviewed over a two-year time span. The in vivo dosimetry programme using thermoluminescence (TLD) chips was able to detect three significant treatment errors, amongst some 13 000 patients treated. These errors would likely to have been undetected through other quality assurance measures. Increasing demands in workload were found to be associated with commissioning of new equipment and techniques. A skilled operator with knowledge of TLD physics, treatment planning system (TPS) dose calculation algorithms and radiation transport proved to be essential for appropriate interpretation of TLD results particularly in complex radiation delivery scenarios. TLD continues to play a large role in patient safety and quality assurance at our institution.
Publisher: World Scientific Pub Co Pte Ltd
Date: 07-2018
DOI: 10.1142/S1793545818500141
Abstract: Magnetic resonance imaging (MRI) has been a prevalence technique for breast cancer diagnosis. Computer-aided detection and segmentation of lesions from MRIs plays a vital role for the MRI-based disease analysis. There are two main issues of the existing breast lesion segmentation techniques: requiring manual delineation of Regions of Interests (ROIs) as a step of initialization and requiring a large amount of labeled images for model construction or parameter learning, while in real clinical or experimental settings, it is highly challenging to get sufficient labeled MRIs. To resolve these issues, this work proposes a semi-supervised method for breast tumor segmentation based on super voxel strategies. After image segmentation with advanced cluster techniques, we take a supervised learning step to classify the tumor and nontumor patches in order to automatically locate the tumor regions in an MRI. To obtain the optimal performance of tumor extraction, we take extensive experiments to learn parameters for tumor segmentation and classification, and design 225 classifiers corresponding to different parameter settings. We call the proposed method as Semi-supervised Tumor Segmentation (SSTS), and apply it to both mass and nonmass lesions. Experimental results show better performance of SSTS compared with five state-of-the-art methods.
Publisher: Wiley
Date: 29-05-2014
DOI: 10.1118/1.4888724
Publisher: Springer Berlin Heidelberg
Date: 2000
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.CLON.2014.03.007
Abstract: To measure the difference in cumulative doses received by the bladder (target) and integral doses with different clinical target volume (CTV) to planning target volume (PTV) margins, comparing set-up to skin tattoos versus image-guided radiotherapy to bone or soft tissue. Four plans were generated on each planning computed tomography dataset using the CTV with 5, 10, 15, 20 mm PTV margins using a three-dimensional conformal four-field technique. Set-up data based on skin, bone and soft tissue to the bladder on pre-treatment cone beam computed tomography (CBCT) were recorded. In total, 316 CBCTs were evaluable from 10 bladder cancer patients. Each CBCT was fused to the planning computed tomography dataset using the isocentre corresponding to each of the three pre-treatment matching conditions. The target was contoured on each CBCT and called the CTV of the day and the plan was re-calculated to determine the dose to this. The mean D95 with CTV to PTV margins of 5, 10, 15 and 20 mm for skin set-up was 89.4, 93.0, 97.2, 98.6 for bone 88.8, 92.6, 96.7, 98.6 and for soft tissue 96.3, 98.6, 98.7, 99.5. With soft-tissue matching, the mean (standard deviation) volume of normal tissue receiving 5 Gy with 5, 10, 15 and 20 mm margins was 3899 (1022), 4561 (1142), 5663 (1304) and 6315 (1426) in cm(3). Soft-tissue matching results in superior target coverage and a reduced integral dose to the surrounding tissues. With soft-tissue matching, increasing CTV to PTV margins progressively beyond 5 mm results in modest improvement in CTV coverage, but a large increase in integral dose.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 08-2021
Publisher: IOP Publishing
Date: 19-04-2001
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 03-1999
DOI: 10.1016/S0958-3947(98)00052-1
Abstract: Since 1994, our center has conducted entrance dose measurements on selected patients receiving 6MV x-ray therapy by utilizing a commercial set of p-type semiconductor diodes. We report on three years results representing 386 patients having 1005 measurements and the usefulness of such a system in a radiotherapy department. The 386 patients represent approximately 20% of our total radical treatments. Minimal disruption to patient treatment was achieved. Measurements showed an average variation from expected dose of 0.5% +/- 2.2%. Specific treatment site groups were investigated. Our results show that in vivo dosimetry on a selected group of patients is an effective method of providing an independent verification of dose delivery accuracy.
Publisher: SAGE Publications
Date: 09-01-2016
Abstract: Ga-68-macroaggregated albumin ( 68 Ga-perfusion) positron emission tomography/computed tomography (PET/CT) is a novel imaging technique for the assessment of functional lung volumes. The purpose of this study was to use this imaging technique for functional adaptation of definitive radiotherapy plans in patients with non-small cell lung cancer (NSCLC). This was a prospective clinical trial of patients with NSCLC who received definitive 3-dimensional (3D) conformal radiotherapy to 60 Gy in 30 fx and underwent pretreatment respiratory-gated (4-dimensional [4D]) perfusion PET/CT. The “perfused” lung volume was defined as all lung parenchyma taking up radiotracer, and the “well-perfused” lung volume was contoured using a visually adapted threshold of 30% maximum standardized uptake value (SUVmax). Alternate 3D conformal plans were subsequently created and optimized to avoid perfused and well-perfused lung volumes. Functional dose volumetrics were compared using mean lung dose (MLD), V5 (volume receiving 5 Gy or more), V10, V20, V30, V40, V50, and V60 parameters. Fourteen consecutive patients had alternate radiotherapy plans created based on functional lung volumes. When considering the original treatment plan, the dose to perfused and well-perfused functional lung volumes was similar to that of the conventional anatomical lung volumes with an average MLD of 12.15, 12.67, and 12.11 Gy, respectively. Plans optimized for well-perfused lung improved functional V30, V40, V50, and V60 metrics (all P values .05). The functional MLD of well-perfused lung was improved by a median of 0.86 Gy, P .01. However, plans optimized for perfused lung only showed significant improvement in the functional V60 dose parameter (median 1.00%, P = .04) but at a detriment of a worse functional V5 (median 3.33%, P = .05). This study demonstrates proof of principle that 4D-perfusion PET/CT may enable functional lung avoidance during treatment planning of patients with NSCLC. Radiotherapy plans adapted to well-perfused but not perfused functional lung volumes allow for reduction in dose to functional lung using 3D conformal radiotherapy.
Publisher: Elsevier BV
Date: 05-2022
Publisher: Wiley
Date: 06-2008
DOI: 10.1118/1.2961927
Publisher: IOP Publishing
Date: 02-07-2003
DOI: 10.1088/0031-9155/48/14/307
Abstract: A potential real-time source position verification process for high dose-rate (HDR) brachytherapy treatment is described. This process is intended to provide immediate confirmation that a treatment is proceeding according to plan, so that corrective action can be taken if necessary. We show that three dosimeters are in principle sufficient and demonstrate the feasibility of the process using a diamond detector and an Ir-192 source. An error analysis including all identified sources of error shows that this detector is capable of locating the distance to the source to within 2 mm for distances up to 12 cm. This positional accuracy is less than the diameter of typical HDR catheters indicating that a diamond detector can be used to accurately determine the distance to the source. The uncertainty in the distance is found to increase with distance.
Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.RADONC.2016.01.027
Abstract: To evaluate renal dysfunction after stereotactic ablative body radiotherapy (SABR) for inoperable primary renal cell carcinoma (RCC) using nuclear medicine assessments. In a prospective clinical trial, patients received single fraction renal SABR (26 Gy) for tumours 50% isodoses) may help reduce risk of functional loss.
Publisher: Elsevier BV
Date: 11-2012
Publisher: Wiley
Date: 06-2015
DOI: 10.1118/1.4924975
Publisher: Informa UK Limited
Date: 02-01-2019
DOI: 10.1080/01947648.2019.1586602
Abstract: Medical regulators have a responsibility to protect, promote, and maintain the health and safety of patients. Here, we compare and contrast the processes for addressing concerns about doctors in four countries with legal systems based on English common law: the UK, Australia, the United States, and Canada. The legal provisions underpinning each jurisdiction's disciplinary processes depict distinctive outlooks from the different authorities as each works toward the same goal. The initial stages of the investigation process are broadly similar in all of the jurisdictions examined. Each process, however, has subtle differences with regard to its comparators. Factors include how matters of discipline are framed, the constitution of disciplinary panels, and how the perceived independence of these panels all philosophically affect the public safety remit of each regulator. This work constitutes the first comparison of international regulatory frameworks for the profession of medicine.
Publisher: Springer Science and Business Media LLC
Date: 21-07-2020
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.ZEMEDI.2017.05.002
Abstract: This study examines the difference in surface dose between flat and flattening filter free (FFF) photon beams in the context of breast radiotherapy. The surface dose was measured for 6MV, 6MV FFF, 10MV, 10MV FFF and 18MV photon beams using a thin window ionisation chamber for various field sizes. Profiles were acquired to ascertain the change in surface dose off-axis. Out-of-field measurements were included in a clinically representative half beam block tangential breast field. In the field centres of FFF beams the surface dose was found to be increased for small fields and decreased for large fields compared to flat beams. For FFF beams, surface dose was found to decrease off-axis and resulted in lower surface dose out-of-field compared to flat beams.
Publisher: IEEE
Date: 06-2014
Publisher: IOP Publishing
Date: 05-05-2005
DOI: 10.1088/0031-9155/50/10/014
Abstract: Loose helical delivery is a potential solution to account for respiration-driven tumour motion in helical tomotherapy (HT). In this approach, a treatment is ided into a set of interlaced 'loose' helices commencing at different gantry angles. Each loose helix covers the entire target length in one gantry rotation during a single breath-hold. The dosimetric characteristics of loose helical delivery were investigated by delivering a 6 MV photon beam in a HT-like manner. Multiple scenarios of conventional 'tight' HT and loose helical deliveries were modelled in treatment planning software, and carried out experimentally with Kodak EDR2 film. The advantage of loose helical delivery lies in its ability to produce a more homogeneous dose distribution by eliminating the 'thread' effect-an inherent characteristic of HT, which results in dose modulations away from the axis of gantry rotation. However, loose helical delivery was also subjected to undesirable dose modulations in the direction of couch motion (termed 'beating' effect), when the ratio between the number of beam projections per gantry rotation (n) and pitch factor (p) was a non-integer. The magnitude of dose modulations decreased with an increasing n ratio. The results suggest that for the current HT unit (n = 51), dose modulations could be kept under 5% by selecting a pitch factor smaller than 7. A pitch factor of this magnitude should be able to treat a target up to 30 cm in length. Loose helical delivery should increase the total session time only by a factor of 2, while the planning time should stay the same since the total number of beam projections remains unchanged. Considering its dosimetric advantage and clinical practicality, loose helical delivery is a promising solution for the future HT treatments of respiration-driven targets.
Publisher: SAGE Publications
Date: 20-05-2016
Abstract: Intrafraction organ deformation may be accounted for by inclusion of temporal information in dose calculation models. In this article, we demonstrate a quasi-4-dimensional method for improved risk estimation. Conventional 3-dimensional and quasi-4-dimensional calculations employing dose warping for dose accumulation were undertaken for patients with liver metastases planned for 42 Gy in 6 fractions of stereotactic body radiotherapy. Normal tissue complication probabilities and stochastic risks for radiation-induced carcinogenesis and cardiac complications were evaluated for healthy peripheral structures. Hypothetical assessments of other commonly employed dose/fractionation schedules on normal tissue complication probability estimates were explored. Conventional 3-dimensional dose computation may result in significant under- or overestimation of doses to organ at risk. For instance, doses differ (on average) by 17% (σ = 14%) for the left kidney, by 14% (σ = 7%) for the right kidney, by 7% (σ = 9%) for the large bowel, and by 10% (σ = 14%) for the duodenum. Discrepancies in the excess relative risk range up to about 30%. The 3-dimensional approach was shown to result in cardiac complication risks underestimated by %. For liver stereotactic body radiotherapy, we have shown that conventional 3-dimensional dose calculation may significantly over-/underestimate dose to organ at risk (90%-120% of the 4-dimensional estimate for the mean dose and 20%-150% for D 2% ). Providing dose estimates that most closely represent the actual dose delivered will provide valuable information to improve our understanding of the dose response for partial volume irradiation using hypofractionated schedules. Excess relative risks of radiocarcinogenesis were shown to range up to approximately excess relative risk = 4 and the prediction thereof depends greatly on the use of either 3-dimensional or 4-dimensional methods (with corresponding results differing by tens of percent).
Publisher: Elsevier BV
Date: 08-2021
Publisher: Wiley
Date: 27-07-2012
DOI: 10.1118/1.4736534
Abstract: Strategies for dose accumulation in deforming anatomy are of interest in radiotherapy. Algorithms exist for the deformation of dose based on patient image sets, though these are sometimes contentious because not all such image calculations are constrained by physical laws. While tumor and organ motion has been a key area of study for a considerable amount of time, deformation is of increasing interest. In this work, we demonstrate a full 3D experimental validation of results from a range of dose deformation algorithms available in the public domain. We recently developed the first tissue-equivalent, full 3D deformable dosimetric phantom-"DEFGEL." To assess the accuracy of dose-warping based on deformable image registration (DIR), we have measured doses in undeformed and deformed states of the DEFGEL dosimeter and compared these to planned doses and warped doses. In this way we have directly evaluated the accuracy of dose-warping calculations for 11 different algorithms. We have done this for a range of stereotactic irradiation schemes and types and magnitudes of deformation. The original Horn and Schunck algorithm is shown to be the best performing of the 11 algorithms trialled. Comparing measured and dose-warped calculations for this method, it is found that for a 10 × 10 mm(2) square field, γ(3%∕3mm) = 99.9% for a 20 × 20 mm(2) cross-shaped field, γ(3%∕3mm) = 99.1% and for a multiple dynamic arc (0.413 cm(3) PTV) treatment adapted from a patient treatment plan, γ(3%∕3mm) = 95%. In each case, the agreement is comparable to-but consistently ∼1% less than-comparison between measured and calculated (planned) dose distributions in the absence of deformation. The magnitude of the deformation, as measured by the largest displacement experienced by any voxel in the volume, has the greatest influence on the accuracy of the warped dose distribution. Considering the square field case, the smallest deformation (∼9 mm) yields agreement of γ(3%∕3mm) = 99.9%, while the most significant deformation (∼20 mm) yields agreement of γ(3%∕3mm) = 96.7%. We have confirmed that, for a range of mass and density conserving deformations representative of those observable in anatomical targets, DIR-based dose-warping can yield accurate predictions of the dose distribution. Substantial differences can be seen between the results of different algorithms indicating that DIR performance should be scrutinized before application todose-warping. We have demonstrated that the DEFGEL deformable dosimeter can be used to evaluate DIR performance and the accuracy of dose-warping results by direct measurement.
Publisher: IOP Publishing
Date: 17-04-2012
Publisher: Elsevier BV
Date: 10-2003
Publisher: Wiley
Date: 12-07-2018
DOI: 10.1002/ACM2.12414
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 06-2012
DOI: 10.1016/J.RADONC.2012.03.003
Abstract: Daily variations in bladder filling make conformal treatment of bladder cancer challenging. On-line adaptive radiotherapy with a choice of plans has been demonstrated to reduce small bowel irradiation in single institution trials. In order to support a multicentre feasibility clinical trial on adaptive radiotherapy for bladder cancer (TROG 10.01) a credentialing programme was developed for centres wishing to participate. The credentialing programme entails three components: a facility questionnaire a planning exercise which tests the ability of centres to create three adaptive plans based on a planning and five cone beam CTs and a site visit during which image quality, imaging dose and image guidance procedures are assessed. Image quality and decision making were tested using customised inserts for a Perspex phantom (Modus QUASAR) that mimic different bladder sizes. Dose was assessed in the same phantom using thermoluminescence dosimetry (TLD). All 12 centres participating in the full credentialing programme were able to generate appropriate target volumes in the planning exercise and identify the correct target volume and position the bladder phantom in the phantom within 3mm accuracy. None of the imaging doses exceeded the limit of 5 cGy with a CT on rails system having the lowest overall dose. A phantom mimicking the decision making process for adaptive radiotherapy was found to be well suited during site visits for credentialing of centres participating in a clinical trial of adaptive radiotherapy for bladder cancer. Combined with a planning exercise the site visit allowed testing the ability of centres to create adaptive treatment plans and make appropriate decisions based on the volumetric images acquired at treatment.
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.MEDDOS.2010.02.010
Abstract: The purpose of this study was to evaluate the capabilities of a kilovoltage (kV) on-board imager (OBI)-equipped linear accelerator in the setting of on-line verification imaging for external-beam partial breast irradiation. Available imaging techniques were optimized and assessed for image quality using a modified anthropomorphic phantom. Imaging dose was also assessed. Imaging techniques were assessed for physical clearance between patient and treatment machine using a volunteer. Nonorthogonal kV image pairs were identified as optimal in terms of image quality, clearance, and dose. After institutional review board approval, this approach was used for 17 patients receiving accelerated partial breast irradiation. Imaging was performed before every fraction verification with online correction of setup deviations >5 mm (total image sessions = 170). Treatment staff rated risk of collision and visibility of tumor bed surgical clips where present. Image session duration and detected setup deviations were recorded. For all cases, both image projections (n = 34) had low collision risk. Surgical clips were rated as well as visualized in all cases where they were present (n = 5). The average imaging session time was 6 min, 16 sec, and a reduction in duration was observed as staff became familiar with the technique. Setup deviations of up to 1.3 cm were detected before treatment and subsequently confirmed offline. Nonorthogonal kV image pairs allowed effective and efficient online verification for partial breast irradiation. It has yet to be tested in a multicenter study to determine whether it is dependent on skilled treatment staff.
Publisher: IOP Publishing
Date: 14-01-2010
DOI: 10.1088/0031-9155/55/3/021
Abstract: Despite the highly localized doses that may be delivered via stereotactic radiotherapy, a small dose is nonetheless delivered to out-of-field regions, which may cause detriment to the patient. In this work, a systematic set of dose measurements have been undertaken up to a distance of 45 cm from the isocentre, for stereotactic fields shaped by a BrainLAB mini-multileaf collimator (MMLC) mounted on a Varian 600C linear accelerator. A range of treatment parameters were varied so as to determine the factors of greatest influence and establish relationships with dose. The commercial treatment planning software (TPS) miscalculates the dose to out-of-field regions. Measured dose decreases consistently out to 45 cm, whereas the TPS decreases out to 10-15 cm, at which point the predicted dose is constant. At the 5-10 cm off-axis distance (OAD), measurements indicate doses of about 5-10% of the dose at the isocentre, 1% at 15 cm OAD and 0.1% at 45 cm OAD. There are several observed trends. Greater MMLC field sizes (with static jaw) result in higher out-of-field dose, as do shallower depths. The source-to-surface distance does not greatly influence peripheral dose. However, the results given in this work do indicate that simple treatment arrangements, such as preferable collimator rotation, would in certain cases reduce out-of-field dose by an order of magnitude. Peripheral dose raises questions of treatment optimization, particularly in cases where patients have a long life expectancy in which secondary effects may become manifest, such as in the treatment of paediatric patients or those with a non-malignant primary. For instance, for a 20 Gy hypo-fractionated treatment, dose to out-of-field regions is of the order of cGy-a substantial dose in radiation protection terms.
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 02-2021
Publisher: Wiley
Date: 02-2011
DOI: 10.1111/J.1754-9485.2010.02231.X
Abstract: Positron emission tomography (PET) is a state-of-the-art functional imaging technique used in the accurate detection of cancer. The main problem with the tumours present in the lungs is that they are non-stationary during each respiratory cycle. Tumours in the lungs can get displaced up to 2.5 cm during respiration. Accurate detection of the tumour enables avoiding the addition of extra margin around the tumour that is usually used during radiotherapy treatment planning. This paper presents a novel method to detect and track tumour in respiratory-gated PET images. The approach followed to achieve this task is to automatically delineate the tumour from the first frame using support vector machines. The resulting volume and position information from the first frame is used in tracking its motion in the subsequent frames with the help of level set (LS) deformable model. An excellent accuracy of 97% is obtained using wavelets and support vector machines. The volume calculated as a result of the machine learning (ML) stage is used as a constraint for deformable models and the tumour is tracked in the remaining seven phases of the respiratory cycle. As a result, the complete information about tumour movement during each respiratory cycle is available in relatively short time. The combination of the LS and ML approach accurately delineated the tumour volume from all frames, thereby providing a scope of using PET images towards planning an accurate and effective radiotherapy treatment for lung cancer.
Publisher: IOP Publishing
Date: 28-06-2016
Publisher: Elsevier BV
Date: 12-2023
Publisher: Elsevier BV
Date: 10-2022
Publisher: Springer Science and Business Media LLC
Date: 23-11-2022
DOI: 10.1007/S13246-021-01076-1
Abstract: Vertebral Stereotactic ablative body radiotherapy (SABR) involves substantial tumour density heterogeneities. We evaluated the impact of a linear Boltzmann transport equation (LBTE) solver dose calculation on vertebral SABR dose distributions. A sequential cohort of 20 patients with vertebral metastases treated with SABR were selected. Treatment plans were initially planned with a convolution style dose calculation algorithm. The plan was copied and recalculated with a LBTE algorithm reporting both dose to water (D
Publisher: Wiley
Date: 08-2010
Publisher: Elsevier BV
Date: 04-2015
Publisher: SAGE Publications
Date: 25-06-2018
Publisher: CRC Press
Date: 28-03-2021
Publisher: Elsevier BV
Date: 2014
Publisher: IOP Publishing
Date: 27-01-2023
Abstract: Objective. Functional lung avoidance (FLA) radiotherapy treatment aims to spare lung regions identified as functional from imaging. Perfusion contributes to lung function and can be measured from the determination of pulmonary blood volume (PBV). An advantageous alternative to the current determination of PBV from positron emission tomography (PET) may be from dual energy CT (DECT), due to shorter examination time and widespread availability. This study aims to determine the correlation between PBV determined from DECT and PET in the context of FLA radiotherapy. Approach. DECT and PET acquisitions at baseline of patients enrolled in the HI-FIVE clinical trial (ID: NCT03569072) were reviewed. Determination of PBV from PET imaging ( PBV PET ), from DECT imaging generated from a commercial software (Syngo.via, Siemens Healthineers, Forchheim, Germany) with its lowest ( PBV syngo R = 1 ) and highest ( PBV syngo R = 10 ) smoothing level parameter value ( R ), and from a two-material decomposition (TMD) method ( PBV TMD L ) with variable median filter kernel size ( L ) were compared. Deformable image registration between DECT images and the CT component of the PET/CT was applied to PBV maps before res ling to the PET resolution. The Spearman correlation coefficient ( r s ) between PBV determinations was calculated voxel-wise in lung subvolumes. Main results. Of this cohort of 19 patients, 17 had a DECT acquisition at baseline. PBV maps determined from the commercial software and the TMD method were very strongly correlated [ r s ( PBV syngo R = 1 , PBV TMD L = 1 ) = 0.94 ± 0.01 and r s ( PBV syngo R = 10 , PBV TMD L = 9 ) = 0.94 ± 0.02]. PBV PET was strongly correlated with PBV TMD L [ r s ( PBV PET , PBV TMD L = 28 ) = 0.67 ± 0.11]. Perfusion patterns differed along the posterior-anterior direction [ r s ( PBV PET , PBV TMD L = 28 ) = 0.77 ± 0.13/0.57 ± 0.16 in the anterior osterior region]. Significance . A strong correlation between DECT and PET determination of PBV was observed. Streak and smoothing effects in DECT and gravitational artefacts and misregistration in PET reduced the correlation posteriorly.
Publisher: Medknow
Date: 2013
Publisher: Wiley
Date: 04-2010
Publisher: Wiley
Date: 18-02-2019
DOI: 10.1002/MP.13408
Publisher: Elsevier BV
Date: 05-2017
Publisher: Springer Science and Business Media LLC
Date: 09-2007
DOI: 10.1007/BF03178424
Publisher: Wiley
Date: 08-11-2016
DOI: 10.1002/JMRS.186
Publisher: Informa UK Limited
Date: 18-11-2013
Publisher: Elsevier BV
Date: 10-1996
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.PRRO.2015.08.002
Abstract: Stereotactic ablative body radiation therapy for primary kidney cancer treatment relies on motion management that can quantify both the trajectory of kidney motion and stabilize the patient. A prospective ethics-approved clinical trial of stereotactic treatment to primary kidney targets was conducted at our institution. Our aim was to report on specific kidney tumor motion and the inter- and intrafraction motion as seen on treatment. Patients with tumor size <5 cm received a dose of 26 Gy in 1 fraction and those with tumor size ≥5 cm received 42 Gy in 3 fractions. All patients underwent a 4-dimensional computed tomography planning scan, immobilized in a dual-vacuum system. A conventional linear accelerator cone beam computed tomography scan was used for pre-, mid-, and posttreatment imaging to verify target position. Between July 2012 and October 2014, 33 targets from 32 consecutive patients (24 males/8 females) were treated. Seventeen targets were prescribed 26 Gy/1 fraction and the remaining 16 targets received 42 Gy/3 fractions. Kidney motion at each of the poles was not affected by the presence of tumor (P = .875), nor was the motion statistically different from the corresponding contralateral kidney pole (P = .909). The mean 3-dimensional displacement of the target at mid- and posttreatment was 1.3 mm (standard deviation ± 1.6) and 1.0 mm (standard deviation ± 1.3), respectively. The maximum displacement in any direction for 95% of the fractions at mid- and posttreatment was ≤3 mm. In summary, stereotactic ablative body radiation therapy of primary kidney targets can be accurately delivered on a conventional linear accelerator with protocol that has minimal intrafractional target motion.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2023
DOI: 10.1245/S10434-017-5830-6
Abstract: Postoperative chemoradiation and perioperative chemotherapy using epirubicin/cisplatin/5-fluorouracil (ECF) represent two standards of care for resectable gastric cancer. In the TOPGEAR (Trial Of Preoperative therapy for Gastric and Esophagogastric junction AdenocaRcinoma) trial, we hypothesized that adding preoperative chemoradiation to perioperative ECF will improve survival however, the safety and feasibility of preoperative chemoradiation have yet to be determined. TOPGEAR is an international phase III trial in which patients with adenocarcinoma of the stomach were randomized to perioperative ECF alone or with preoperative chemoradiation. The ECF-alone group received three preoperative cycles of ECF, while the chemoradiation group received two cycles of preoperative ECF followed by chemoradiation. Both groups received three postoperative cycles of ECF. A planned interim analysis of the first 120 patients was conducted, and was reviewed by the Independent Data Safety Monitoring Committee to assess treatment compliance, toxicity/safety, and response rates. The proportion of patients who received all cycles of preoperative chemotherapy was 93% (ECF group) and 98% (chemoradiation group), while 65 and 53%, respectively, received all cycles of postoperative chemotherapy. Overall, 92% of patients allocated to preoperative chemoradiation received this treatment. The proportion of patients proceeding to surgery was 90% (ECF group) and 85% (chemoradiation group). Grade 3 or higher surgical complications occurred in 22% of patients in both groups. Furthermore, grade 3 or higher gastrointestinal toxicity occurred in 32% (ECF group) and 30% (chemoradiation group) of patients, while hematologic toxicity occurred in 50 and 52% of patients. These results demonstrate that preoperative chemoradiation can be safely delivered to the vast majority of patients without a significant increase in treatment toxicity or surgical morbidity.
Publisher: Wiley
Date: 10-10-2013
DOI: 10.1118/1.4824318
Abstract: To create an accurate map of the distribution of radiation dose deposition in healthy and target tissues during radionuclide therapy. Serial quantitative SPECT∕CT images were acquired at 4, 24, and 72 h for 28 (177)Lu-octreotate peptide receptor radionuclide therapy (PRRT) administrations in 17 patients with advanced neuroendocrine tumors. Deformable image registration was combined with an in-house programming algorithm to interpolate pharmacokinetic uptake and clearance at a voxel level. The resultant cumulated activity image series are comprised of values representing the total number of decays within each voxel's volume. For PRRT, cumulated activity was translated to absorbed dose based on Monte Carlo-determined voxel S-values at a combination of long and short ranges. These dosimetric image sets were compared for mean radiation absorbed dose to at-risk organs using a conventional MIRD protocol (OLINDA 1.1). Absorbed dose values to solid organs (liver, kidneys, and spleen) were within 10% using both techniques. Dose estimates to marrow were greater using the voxelized protocol, attributed to the software incorporating crossfire effect from nearby tumor volumes. The technique presented offers an efficient, automated tool for PRRT dosimetry based on serial post-therapy imaging. Following retrospective analysis, this method of high-resolution dosimetry may allow physicians to prescribe activity based on required dose to tumor volume or radiation limits to healthy tissue in in idual patients.
Publisher: Wiley
Date: 04-10-2016
Publisher: Springer Science and Business Media LLC
Date: 05-09-2019
Publisher: Wiley
Date: 02-2009
DOI: 10.1111/J.1754-9485.2009.02047.X
Abstract: The present paper describes the logistics of the 2004-2008 Australasian Level III Dosimetry Intercomparison. Dosimetric intercomparisons (or 'audits') can be used in radiotherapy to evaluate the accuracy and quality of radiation delivery. An intercomparison was undertaken in New Zealand and Australia to evaluate the feasibility and logistics of ongoing dosimetric intercomparisons that evaluate all steps in the radiotherapy treatment process, known as a 'Level III' intercomparison. The study commenced in 2002 with the establishment of a study team, definition of the study protocol, acquisition of appropriate equipment and recruitment of participating radiotherapy centres. Measurements were undertaken between October 2004 and March 2008, and included collation of data on time, costs and logistics of the study. Forty independent Australian and New Zealand radiotherapy centres agreed to participate. Measurement visits were made to 37 of these centres. Data is presented on the costs of the study and the level of support required. The study involved the participation of 16 staff at the study centre who invested over 4000 hours in the study, and of over 200 professionals at participating centres. Recommendations are provided for future phantom-based intercomparisons. It is hoped that the present paper will be of benefit to any centres or groups contemplating similar activities by identifying the processes involved in establishing the study, the potential hazards and pitfalls, and expected resource requirements.
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.RADONC.2005.12.007
Abstract: Lung cancer treatment can be one of the most challenging fields in radiotherapy. The aim of the present study was to compare different modalities of radiation delivery based on a balanced scoring scheme for target coverage and normal tissue avoidance. Treatment plans were developed for 15 patients with stage III inoperable non-small cell lung cancer using 3D conformal technique and intensity-modulated radiotherapy (IMRT). Elective nodal irradiation was included for all cases to create the most challenging scenarios with large target volumes. A 2 cm margin was used around the gross tumour volume (GTV) to generate PTV2 and 1cm margin around elective nodes for PTV1 resulting in PTV1 volumes larger than 1000 cm(3) in 13 of the 15 patients. 3D conformal and IMRT plans were generated on a commercial treatment planning system (TheraPlan Plus, Nucletron) with various combinations of beam energies and gantry angles. A 'dose quality factor' (DQF) was introduced to correlate the plan quality with patient specific parameters. A good correlation was found between the quality of the plans and the overlap between PTV1 and lungs. The patient feature factor (PFF), which is a product of several pertinent characteristics, was introduced to facilitate the choice of a particular technique for a particular patient. This approach may allow the evaluation of different treatment options prior to actual planning, subject to validation in larger prospective data sets.
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.CLON.2022.05.020
Abstract: The aim of TROG 14.04 was to assess the feasibility of deep inspiration breath hold (DIBH) and its impact on radiation dose to the heart in patients with left-sided breast cancer undergoing radiotherapy. Secondary end points pertained to patient anxiety and cost of delivering a DIBH programme. The study comprised two groups - left-sided breast cancer patients engaging DIBH and right-sided breast cancer patients using free breathing through radiotherapy. The primary end point was the feasibility of DIBH, defined as left-sided breast cancer patients' ability to breath hold for 15 s, decrease in heart dose in DIBH compared with the free breathing treatment plan and reproducibility of radiotherapy delivery using mid-lung distance (MLD) assessed on electronic portal imaging as the surrogate. The time required for treatment delivery, patient-reported outcomes and resource requirement were compared between the groups. Between February and November 2018, 32 left-sided and 30 right-sided breast cancer patients from six radiotherapy centres were enrolled. Two left-sided breast cancer patients did not undergo DIBH (one treated in free breathing as per investigator choice, one withdrawn). The mean heart dose was reduced from 2.8 Gy (free breathing) to 1.5 Gy (DIBH). Set-up reproducibility in the first week of treatment assessed by MLD was 1.88 ± 1.04 mm (average ± 1 standard deviation) for DIBH and 1.59 ± 0.93 mm for free breathing patients. Using a reproducibility cut-off for MLD of 2 mm (1 standard deviation) as per study protocol, DIBH was feasible for 67% of DIBH patients. Radiotherapy delivery using DIBH took about 2 min longer than for free breathing. Anxiety was not significantly different in DIBH patients and decreased over the course of treatment in both groups. Although DIBH was shown to require about 2 min longer per treatment slot, it has the potential to reduce heart dose in left-sided breast cancer patients by nearly a half, provided careful assessment of breath hold reproducibility is carried out.
Publisher: Springer Science and Business Media LLC
Date: 06-2009
DOI: 10.1007/BF03178635
Publisher: American Society of Clinical Oncology (ASCO)
Date: 20-09-2012
DOI: 10.1200/JCO.2012.30.27_SUPPL.198
Abstract: 198 Background: The thyroid is not routinely considered an organ at risk in supraclavicular (SC) nodal radiotherapy (RT) for breast cancer. We aim to compare the dosimetric impact of two RT planning techniques on the thyroid: (1) conventional single anterior field to encompass the SC nodal volume defined using clinical and radiological landmarks and (2) 3-dimensional (3D)-conformal planning to encompass the SC nodal volume contoured on planning computed tomography (CT) scans. Methods: The thyroid and SC nodal volumes were contoured on the planning CT datasets of 20 patients who had RT to the breast/chest wall and SC nodes to a dose of 50 Gy in 2-Gy daily fractions. Comparison of the following dosimetric parameters between the techniques was performed: mean and maximum thyroid dose V5, V30, and V50 (percentage of thyroid receiving ≥5, ≥30, and ≥50 Gy respectively) percentage of SC nodal volume receiving 95-107% of the prescribed dose (homogeneity index, HI) and maximum spinal cord dose. Anatomical characteristics that influenced the dose distribution were investigated. Results: The 3D-conformal planning technique significantly increased all dosimetric parameters for the thyroid (p .001) (Table). It improved the mean HI of the SC nodal volume (16% vs. 93.2% p .001) but resulted in a higher spinal cord dose (mean maximum dose 6.1 Gy vs. 30 Gy). The thyroid volume and depth of SC nodes did not influence the differences in the thyroid doses between the two techniques. The depth of SC nodes was significantly associated with the difference seen in the HI of SC nodal volumes between the techniques (p=0.004). Conclusions: The 3D-conformal planning technique improved the dosimetric coverage of the SC nodal volume but increased radiation doses to the thyroid compared to the single field technique. The longer term clinical consequences of radiation to thyroid should be considered in SC nodal irradiation for patients with breast cancer. [Table: see text]
Publisher: Elsevier BV
Date: 08-2023
Publisher: American Physical Society (APS)
Date: 25-10-2005
Publisher: American Physical Society (APS)
Date: 25-10-2005
Publisher: Elsevier BV
Date: 09-2021
Publisher: Oxford University Press (OUP)
Date: 08-2002
DOI: 10.1093/OXFORDJOURNALS.RPD.A006012
Abstract: Dose measurements in brachytherapy 192Ir implants are often difficult due to large dose gradients and complex photon spectra. Therefore, tissue-equivalent detectors with a high spatial resolution, such as the highly promising LiF:Mg,Cu,P thermoluminescent detectors (TLDs) are required. It was the aim of the present work to ascertain if miniature LiF:Mg,Cu,P TLDs can effectively measure the dose distribution around 192Ir implants. 'Pin worm' TLDs (type MCP, diameter 0.6 mm, length 2 mm) were compared with GR-200R (SSDL, Beijing) rods cut in half. The TLDs were tested for reproducibility and energy dependence using high dose rate (HDR) and low dose rate (LDR) brachytherapy units. 192Ir measurements were performed in a tissue equivalent phantom accommodating hollow needles and catheters routinely used in brachytherapy. Pin worms had an average reproducibility of less than +/-2% (1 SD) and a detection limit of less than 10 microGy. The small dimensions of the pin worms allowed their placement within brachytherapy needles and catheters. The measured relative dose distribution was in good agreement with the predictions of a computerised treatment planning system (ADAC Pinnacle) however, limitations in the TLD energy correction did not allow for absolute dose comparison.
Publisher: Informa UK Limited
Date: 15-03-2023
Publisher: IOP Publishing
Date: 11-1998
DOI: 10.1088/0031-9155/43/11/006
Abstract: Accurate dosimetry is particularly difficult for low- to medium-energy x-rays as various interaction processes with different dependences on material properties determine the dose distribution in tissue and radiation detectors. Monoenergetic x-rays from synchrotron radiation offer the unique opportunity to study the dose response variation with photon energy of radiation detectors without the compounding effect of the spectral distribution of x-rays from conventional sources. The variation of dose response with photon energies between 10 and 99.6 keV was studied for two TLD materials (LiF:Mg,Ti and LiF:Mg,Cu,P), MOSFET semiconductors, radiographic and radiochromic film. The dose response at synchrotron radiation energies was compared with the one for several superficial/orthovoltage radiation qualities (HVL 1.4 mm Al to 4 mm Cu) and megavoltage photons from a medical linear accelerator. A calibrated parallel plate ionization chamber was taken as the reference dosimeter. The variation of response with x-ray energy was modelled using a two-component model that allows determination of the energy for maximum response as well as its magnitude. MOSFET detectors and the radiographic film were found to overrespond to low-energy x-rays by up to a factor of 7 and 12 respectively, while the radiochromic film underestimated the dose by approximately a factor of 2 at 24 keV. The TLDs showed a slight overresponse with LiF:Mg, Cu, P demonstrating better tissue equivalence than LiF:Mg, Ti (maximum deviation from water less than 25%). The results of the present study demonstrate the usefulness of monoenergetic photons for the study of the energy response of radiation detectors. The variations in energy response observed for the MOSFET detectors and GAF chromic film emphasize the need for a correction for in idual dosimeters if accurate dosimetry of low- to medium-energy x-rays is attempted.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 04-2019
Publisher: Springer Science and Business Media LLC
Date: 09-2015
Publisher: British Institute of Radiology
Date: 10-2009
DOI: 10.1259/BJR/37579222
Abstract: Cone-beam computed tomography (CBCT) is a three-dimensional imaging modality that has recently become available on linear accelerators for radiotherapy patient position verification. It was the aim of the present study to implement simple strategies for reduction of the dose delivered in a commercial CBCT system. The dose delivered in a CBCT procedure (Varian, half-fan acquisition, 650 projections, 125 kVp) was assessed using a cylindrical Perspex phantom (diameter, 32 cm) with a calibrated Farmer type ionisation chamber. A copper filter (thickness, 0.15 mm) was introduced increasing the half value layer of the beam from 5.5 mm Al to 8 mm Al. Image quality and noise were assessed using an image quality phantom (CatPhan) while the exposure settings per projection were varied from 25 ms/80 mA to 2 ms/2 mA per projection. Using the copper filter reduced the dose to the phantom from approximately 45 mGy to 30 mGy at standard settings (centre eriphery weighting 1/3 to 2/3). Multiple CBCT images were acquired for six patients with pelvic malignancies to compare CBCTs with and without a copper filter. Although the reconstructed image is somewhat noisier with the filter, it features similar contrast in the centre of the patient and was often preferred by the radiation oncologist because of greater image uniformity. The X-ray shutters were adjusted to the minimum size required to obtain the desired image volume for a given patient diameter. The simple methods described here reduce the effective dose to patients undergoing daily CBCT and are easy to implement, and initial evidence suggests that they do not affect the ability to identify soft tissue for the purpose of treatment verification.
Publisher: Elsevier BV
Date: 03-2000
DOI: 10.1016/S0958-3947(00)00036-4
Abstract: On most radiotherapy treatment units, a light field indicates on the patient's skin where the treatment field will irradiate the patient. It was the aim of the present study to investigate the perception of the light field edge by different operators on different surfaces under different lighting conditions. Ten radiation therapists and physicists were asked to mark the light field edge of an 8 x 10-cm2 radiation field from a linear accelerator on prepacked radiographic film. Each operator marked the field 4 times each with the room light turned on and dimmed as usual for patient setup. Two operators marked the field on 5 different surfaces (film envelope, brown solid water, clear plastic used for the manufacturing of immobilization shells, black rubber, and Orfit patient immobilization material). The interoperator reproducibility (+/- 0.39 mm, ISD) was larger than the intraoperator reproducibility (+/- 0.27 mm). The light field was judged consistently to be 0.6 mm smaller in the light room than under dimmed light conditions and the physicists judged the field to be approximately 0.4 mm smaller compared to the radiation therapists' judgement. Compared to the yellow film wrapping, the light field on solid water, black rubber, and the clear plastic were judged to be 0.6 mm smaller by both operators. The same observation was made using a slotted block tray, which also gave the worst reproducibility of perceived field edges. While these systematic errors are relatively small and difficult to correct for, it appears to be important to be at least aware of them, in particular if the light field is used to junction radiation fields with steep penumbras, as commonly done in megavoltage treatments of head & neck and breast cancer.
Publisher: Wiley
Date: 06-2006
DOI: 10.1118/1.2241243
Publisher: Wiley
Date: 07-06-2013
DOI: 10.1118/1.4808151
Abstract: A multi-institution dosimetry intercomparison has been undertaken of prostate intensity modulated radiation therapy (IMRT) delivery. The dosimetry intercomparison was incorporated into the quality assurance for site credentialing for the Trans-Tasman Radiation Oncology Group Prostate Fractionated Irradiation Trial 08.01 clinical trial. An anthropomorphic pelvic phantom with realistic anatomy was used along with multiplanar dosimetry tools for the assessment. Nineteen centers across Australia and New Zealand participated in the study. In comparing planned versus measured dose to the target at the isocenter within the phantom, all centers were able to achieve a total delivered dose within 3% of planned dose. In multiplanar analysis with radiochromic film using the gamma analysis method to compare delivered and planned dose, pass rates for a 5%/3 mm criterion were better than 90% for a coronal slice through the isocenter. Pass rates for an off-axis coronal slice were also better than 90% except for one instance with 84% pass rate. Strengths of the dosimetry assessment procedure included the true anthropomorphic nature of the phantom used, the involvement of an expert from the reference center in carrying out the assessment at every site, and the ability of the assessment to detect and resolve dosimetry discrepancies.
Publisher: Elsevier BV
Date: 09-2001
DOI: 10.1016/S0958-3947(01)00076-0
Abstract: Portal films are an important tool for verification of the shaping and positioning of external radiation fields to the target volume in radiotherapy. One limitation of port films is their inherent lack of contrast, which is due to the low attenuation of the exposing megavoltage radiation by the tissues being imaged. Recently, Kodak introduced a new portal film-cassette system, Kodak EC-L, with much improved contrast compared with conventional film. The aim of this study was to determine if the enhanced contrast of the Kodak EC-L system actually provides better clinical results. To simulate clinical use, port films were taken using an anthropomorphic phantom that was artificially shifted and/or rotated by a predetermined distance. Identical images were taken using a conventional port film system (AGFA-Gevaert Curix MR4 in lead-lined cassette) and the Kodak EC-L system. Twelve different operators (6 physicists and 6 radiation therapists) were asked to diagnose the problem from a total of 20 port films (10 per treatment site), allowing for direct comparison of the 2 types of films. While the diagnosis of the field displacement improved using the Kodak film, it did not speed-up the decision-making process. It was also found that experienced operators were more accurate at evaluating the films. The results indicate that, for the situations studied (head and neck, pelvis), the Kodak system exhibits better contrast and leads to improved decision making.
Publisher: Elsevier BV
Date: 04-2016
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.EJMP.2017.03.022
Abstract: To assess out-of-field dose using three different variants of LiF thermoluminescence dosimeters (TLD) for ten patients who underwent stereotactic ablative body radiotherapy (SABR) for primary renal cell carcinoma (RCC) and compare with treatment planning system (TPS) dose calculations. Thermoluminescent dosimeter (TLD) measurements were conducted at 20, 30, 40 and 50cm from isocentre on ten patients undergoing SABR for primary RCC. Three types of high-sensitivity LiF:Mg,Cu,P TLD material with different Both AAA and PBC showed diminished accuracy for photon doses at increasing distance out-of-field. At 50cm, measured photon dose was 0.3cGy normalised to a 10Gy prescription on average with only small variation across all patients. This is likely due to the leakage component of the out-of-field dose. The LiF:Mg,Cu,P TLD containing
Publisher: Springer Science and Business Media LLC
Date: 23-03-2011
DOI: 10.1007/S13246-011-0067-3
Abstract: Radiochromic film is a self developing two-dimensional dosimeter system that is widely used in radiotherapy. Since its development some 40 years ago many improvements have been made however the sensitivity can vary across the film and a non-linear dose response remains. The former can be addressed using a double exposure technique however this technique assumes that the response is linear so that the dose distribution is incorrectly measured. We are proposing the use of two homogenous exposures one performed prior, the other after the irradiation to be measured. In this 'multiple exposure technique' (MET), the first homogenous exposure can be used to correct for variations in response in different parts of the film, while the second homogenous exposure allows correction for non-linearity of response with dose. The MET was tested with a 60° wedged field and an Intensity Modulated Radiation Therapy fluence map produced by a computerised treatment planning system. In the wedge field measurements, the MET profile showed agreement within 0.6 cGy for 80% of the field compared to ionisation chamber dose values. A comparison of a TPS generated fluence map dose distribution with one measured using conventionally calibrated EBT, and another measured with MET calibrated EBT, showed similar agreement. The MET would be particularly useful for the assessment of highly inhomogenous dose distributions with high maximum dose such as encountered in hypofractionated radiation therapy.
Publisher: Springer Science and Business Media LLC
Date: 08-12-2014
DOI: 10.1007/S13246-013-0235-8
Abstract: Leakage radiation from linear accelerators can make a significant contribution to healthy tissue dose in patients undergoing radiotherapy. In this work thermoluminescent dosimeters (LiF:Mg,Cu,P TLD chips) were used in a focused lead cone loaded with TLD chips for the purpose of evaluating leakage dose at the patient plane. By placing the TLDs at one end of a stereotactic cone, a focused measurement device is created this was tested both in and out of the primary beam of a Varian 21-iX linac using 6 MV photons. Acrylic build up material of 1.2 cm thickness was used inside the cone and measurements made with either one or three TLD chips at a given distance from the target. Comparing the readings of three dosimeters in one plane inside the cone offered information regarding the orientation of the cone relative to a radiation source. Measurements in the patient plane with the linac gantry at various angles demonstrated that leakage dose was approximately 0.01% of the primary beam out of field when the cone was pointed directly towards the target and 0.0025% elsewhere (due to scatter within the gantry). No specific 'hot spots' (e.g., insufficient shielding or gaps at abutments) were observed. Focused cone measurements facilitate leakage dose measurements from the linac head directly at the patient plane and allow one to infer the fraction of leakage due to 'direct' photons (along the ray-path from the bremsstrahlung target) and that due to scattered photons.
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 07-2019
Publisher: Elsevier BV
Date: 08-1996
DOI: 10.1016/S0360-3016(96)00281-7
Abstract: Mucosal underdosing as a result of electron disequilibrium at the air cavity may affect local recurrence rates for T1 and T2 larynx cancers. Secondary build-up properties of high-energy beams have been demonstrated in a slab phantom. It was the aim of this investigation to determine whether significant surface underdosing exists for the mucosa under clinical conditions. Measurements were made using a thermoluminescent dosimetry (TLD) extrapolation technique in an anatomic larynx phantom. The larynx phantom was constructed using tissue and cartilage equivalent material, based on patient cross-sectional anatomy. Three different thicknesses of LiF ribbons, 0.14, 0.39, and 0.89 mm, were placed reproducibly at 12 different positions at the anterior, posterior, and lateral walls on the endolarynx surface. Measured doses were plotted and an extrapolation was made back to the mucosal depth to obtain the dose received at each of the positions. Results were obtained for two different field configurations, opposed laterals and oblique fields, for 6-MV X rays and opposed lateral fields from a telecesium unit. In addition, the larynx surface doses of field sizes from 4 x 6 cm2 to 7 x 6 cm2 were investigated. Surface underdosing was observed owing to the secondary build-up and build-down effect of the air cavity, and the dose measured for the three extrapolation TLDs at any position varied by up to 18%. An average variation of 6% was observed. The surface underdosing was most apparent for the 6-MV opposed lateral beam technique, where mucosa doses down to 76% of the prescribed dose were observed. Mucosal underdosing at the measurement positions was less marked with oblique techniques, telecesium treatment, and increasing field size. Because of underdosing, some surface positions receive < 80% of the prescribed dose. This may contribute to the potential for higher recurrence rates observed with high-energy photons.
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.RADONC.2010.01.010
Abstract: To determine intra-fraction displacement of the prostate gland from imaging pre- and post-radiotherapy delivery of prostate cancer patients with three implanted fiducial markers. Data were collected from 184 patients who had two orthogonal X-rays pre- and post-delivery on at least 20 occasions using a Varian On Board kV Imaging system. A total of 5778 image pairs covering time intervals between 3 and 30 min between pre- and post-imaging were evaluated for intra-fraction prostate displacement. The mean three dimensional vector shift between images was 1.7 mm ranging from 0 to 25 mm. No preferential direction of displacement was found however, there was an increase of prostate displacement with time between images. There was a large variation in typical shifts between patients (range 1 +/- 1 to 6 +/- 2 mm) with no apparent trends throughout the treatment course. Images acquired in the first five fractions of treatment could be used to predict displacement patterns for in idual patients. Intra-fraction motion of the prostate gland appears to be a limiting factor when considering margins for radiotherapy. Given the variation between patients, a uniform set of margins for all patients may not be satisfactory when high target doses are to be delivered.
Publisher: Oxford University Press (OUP)
Date: 08-2002
DOI: 10.1093/OXFORDJOURNALS.RPD.A006022
Abstract: When acquiring data to characterise radiation beams for radiotherapy treatment planning measurements in steep dose gradients such as beam penumbra or dose build-up are often required. A metal oxide semiconductor field effect transistor (MOSFET) with its inherent high spatial resolution was used for penumbra measurements in a 120 kVp X ray beam. The customised MOSFET system features a pulsed readout that allows the acquisition of data points in user defined time intervals of less than 1 s. Using a modified scanning beam data acquisition system the penumbra was acquired on-line in 0.1 mm steps. Measurements were made at different distances behind the beam collimator. From the extrapolation of the penumbra width to a location directly under the block the spatial resolution of the MOSFET system can be estimated to be better than 0.1 mm. This excellent spatial resolution has many potential applications in radiotherapy dosimetry, including the characterisation of multileaf collimator systems.
Publisher: Springer Science and Business Media LLC
Date: 28-09-2014
DOI: 10.1007/S13246-014-0302-9
Abstract: Temporally varying light intensity during acquisition of projection images in an optical CT scanner can potentially be misinterpreted as physical properties of the s le. This work investigated the impact of LED light source intensity instability on measured attenuation coefficients. Different scenarios were investigated by conducting one or both of the reference and data scans in a 'cold' scanner, where the light source intensity had not yet stabilised. Uniform s les were scanned to assess the impact on measured uniformity. The orange (590 nm) light source decreased in intensity by 29 % over the first 2 h, while the red (633 nm) decreased by 9 %. The rates of change of intensity at 2 h were 0.1 and 0.03 % respectively over a 5 min period-corresponding to the scan duration. The normalisation function of the reconstruction software does not fully account for the intensity differences and discrepancies remain. Attenuation coefficient inaccuracies of up to 8 % were observed for data reconstructed from projection images acquired with a cold scanner. Increased noise was observed for most cases where one or both of the scans was acquired without sufficient warm-up. The decrease in accuracy and increase in noise were most apparent for data reconstructed from reference and data scans acquired with a cold scanner on different days.
Publisher: Informa UK Limited
Date: 03-02-2011
Publisher: Wiley
Date: 06-10-2006
DOI: 10.1118/1.2356650
Abstract: Accurate small-field dosimetry has become important with the use of multiple small fields in modern radiotherapy treatments such as IMRT and stereotactic radiosurgery. In this study, we investigate the response of a set of prototype plane-parallel ionization chambers, based upon the Exradin T11 chamber, with active volume diameters of 2, 4, 10, and 20 mm, exposed to 6 MV stereotactic radiotherapy x-ray fields. Our goal was to assess their usefulness for accurate small x-ray field dose measurements. The relative ionization response was measured in circular fields (0.5 to 4 cm diameter) as compared to a 10 x 10 cm2 reference field. A large discrepancy (approximately 40%) was found between the relative response in the smallest plane-parallel chamber and other small volume dosimeters (radiochromic film, micro-metal-oxide-semiconductor field-effect transistor and diode) used for comparison. Monte Carlo BEAMnrc simulations were used to simulate the experimental setup in order to investigate the cause of the under-response and to calculate appropriate correction factors that could be applied to experimental measurements. It was found that in small fields, the air cavity of these custom-made research chambers perturbed the secondary electron fluence profile significantly, resulting in decreased fluence within the active volume, which in turn produces a chamber under-response. It is demonstrated that a large correction to the p(fl) correction factor would be required to improve dosimetric accuracy in small fields, and that these factors could be derived using Monte Carlo simulations.
Publisher: Elsevier BV
Date: 07-1996
DOI: 10.1016/0167-8140(96)01764-1
Abstract: The erythematous response of human skin to radiotherapy has proven useful for testing the predictions of the linear quadratic (LQ) model in terms of fractionation sensitivity and repair half time. No formal investigation of the response of human skin to doses less than 2 Gy per fraction has occurred. This study aims to test the validity of the LQ model for human skin at doses ranging from 0.4 to 5.2 Gy per fraction. Complete erythema reaction profiles were obtained using reflectance spectrophotometry in two patient populations: 65 patients treated palliatively with 5, 10, 12 and 20 daily treatment fractions (varying thicknesses of bolus, various body sites) and 52 patients undergoing prostatic irradiation for localised carcinoma of the prostate (no bolus, 30-32 fractions). Gender, age, site and prior sun exposure influence pre- and post-treatment erythema values independently of dose administered. Out-of-field effects were also noted. The linear quadratic model significantly underpredicted peak erythema values at doses less than 1.5 Gy per fraction. This suggests that either the conventional linear quadratic model does not apply for low doses per fraction in human skin or that erythema is not exclusively initiated by radiation damage to the basal layer. The data are potentially explained by an induced repair model.
Publisher: Elsevier BV
Date: 11-1995
DOI: 10.1016/0360-3016(95)00274-4
Abstract: Carbon-loaded thermoluminescent dosimeters (TLDs) are designed for surface/skin dose measurements. Following 4 years in clinical use at the Mater Hospital, the accuracy and clinical usefulness of the carbon-loaded TLDs was assessed. Teflon-based carbon-loaded lithium fluoride (LiF) disks with a diameter of 13 mm were used in the present study. The TLDs were compared with ion chamber readings and TLD extrapolation to determine the effective depth of the TLD measurement. In vivo measurements were made on patients receiving open-field treatments to the chest, abdomen, and groin. Skin entry dose or entry and exit dose were assessed in comparison with doses estimated from phantom measurements. The effective depth of measurement in a 6 MV therapeutic x-ray beam was found to be about 0.10 mm using TLD extrapolation as a comparison. Entrance surface dose measurements made on a solid water phantom agreed well with ion chamber and TLD extrapolation measurements, and black TLDs provide a more accurate exit dose than the other methods. Under clinical conditions, the black TLDs have an accuracy of +/- 5% (+/- 2 SD). The dose predicted from black TLD readings correlate with observed skin reactions as assessed with reflectance spectroscopy. In vivo dosimetry with carbon-loaded TLDs proved to be a useful tool in assessing the dose delivered to the basal cell layer in the skin of patients undergoing radiotherapy.
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.IJROBP.2013.02.030
Abstract: The delineation of internal target volumes (ITVs) in radiation therapy of lung tumors is currently performed by use of either free-breathing (FB) (18)F-fluorodeoxyglucose-positron emission tomography-computed tomography (FDG-PET/CT) or 4-dimensional (4D)-CT maximum intensity projection (MIP). In this report we validate the use of 4D-PET-MIP for the delineation of target volumes in both a phantom and in patients. A phantom with 3 hollow spheres was prepared surrounded by air then water. The spheres and water background were filled with a mixture of (18)F and radiographic contrast medium. A 4D-PET/CT scan was performed of the phantom while moving in 4 different breathing patterns using a programmable motion device. Nine patients with an FDG-avid lung tumor who underwent FB and 4D-PET/CT and >5 mm of tumor motion were included for analysis. The 3 spheres and patient lesions were contoured by 2 contouring methods (40% of maximum and PET edge) on the FB-PET, FB-CT, 4D-PET, 4D-PET-MIP, and 4D-CT-MIP. The concordance between the different contoured volumes was calculated using a Dice coefficient (DC). The difference in lung tumor volumes between FB-PET and 4D-PET volumes was also measured. The average DC in the phantom using 40% and PET edge, respectively, was lowest for FB-PET/CT (DCAir = 0.72/0.67, DCBackground 0.63/0.62) and highest for 4D-PET/CT-MIP (DCAir = 0.84/0.83, DCBackground = 0.78/0.73). The average DC in the 9 patients using 40% and PET edge, respectively, was also lowest for FB-PET/CT (DC = 0.45/0.44) and highest for 4D-PET/CT-MIP (DC = 0.72/0.73). In the 9 lesions, the target volumes of the FB-PET using 40% and PET edge, respectively, were on average 40% and 45% smaller than the 4D-PET-MIP. A 4D-PET-MIP produces volumes with the highest concordance with 4D-CT-MIP across multiple breathing patterns and lesion sizes in both a phantom and among patients. Freebreathing PET/CT consistently underestimates ITV when compared with 4D PET/CT for a lesion affected by respiration.
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.RADONC.2010.07.023
Abstract: We studied the integral radiation dose in 27 patients who had adaptive radiotherapy for bladder cancer using kilo voltage cone beam CT imaging. Compared to conventional radiotherapy the reduction in margin and choice of best plan of three for the day resulted in a lower total dose in most patients despite daily volumetric imaging.
Publisher: Elsevier BV
Date: 09-2014
Publisher: Wiley
Date: 06-2010
DOI: 10.1118/1.3469098
Publisher: Wiley
Date: 04-2012
DOI: 10.1118/1.3694107
Abstract: Interfraction and intrafraction variation in anatomic structures is a significant challenge in contemporary radiotherapy. The objective of this work is to develop a novel tool for deformable structure dosimetry, using a tissue-equivalent deformable gel dosimeter that can reproducibly simulate targets subject to deformation. This will enable direct measurement of integrated doses delivered in different deformation states, and the verification of dose deforming algorithms. A modified version of the nPAG polymer gel has been used as a deformable 3D dosimeter and phantom to investigate doses delivered to deforming tissue-equivalent geometry. The deformable gel (DEFGEL) dosimeter hantom is comprised of polymer gel in a latex membrane, moulded (in this case) into a cylindrical geometry, and deformed with an acrylic compressor. Fifteen aluminium fiducial markers (FM) were implanted into DEFGEL phantoms and the reproducibility of deformation was determined via multiple computed tomography (CT) scans in deformed and nondeformed states before and after multiple (up to 150) deformations. Dose was delivered to the DEFGEL phantom in three arrangements: (i) without deformation, (ii) with deformation, and (iii) cumulative exposures with and without deformation, i.e., dose integration. Irradiations included both square field and a stereotactic multiple dynamic arc treatment adapted from a patient plan. Doses delivered to the DEFGEL phantom were read out using cone beam optical CT. Reproducibility was verified by observation of interscan shifts of FM locations (as determined via CT), measured from an absolute reference point and in terms of inter-FM distance. The majority (76%) of points exhibited zero shift, with others shifting by one pixel size consistent with setup error as confirmed with a control s le. Comparison of dose profiles and 2D isodose distributions from the three arrangements illustrated complex spatial redistribution of dose in all three dimensions occurring as a result of the change in shape of the target between irradiations, even for a relatively simple deformation. Discrepancies of up to 30% of the maximum dose were evident from dose difference maps for three orthogonal planes taken through the isocenter of a stereotactic field. This paper describes the first use of a tissue-equivalent, 3D dose-integrating deformable phantom that yields integrated or redistributed dosimetric information. The proposed methodology readily yields three-dimensional (3D) dosimetric data from radiation delivery to the DEFGEL phantom in deformed and undeformed states. The impacts of deformation on dose distributions were readily seen in the isodose contours and line profiles from the three arrangements. It is demonstrated that the system is potentially capable of reproducibly emulating the physical deformation of an organ, and therefore can be used to evaluate absorbed doses to deformable targets and organs at risk in three dimensions and to validate deformation algorithms applied to dose distributions.
Publisher: British Institute of Radiology
Date: 12-1998
DOI: 10.1259/BJR.71.852.10319004
Abstract: CT dose varies with both equipment related and operator dependent factors. Thermoluminescence dosimetry (TLD) was employed in two phantoms to investigate the variation in absorbed dose for head CT scans, using a cylindrical head CT dose phantom. Dose profiles were plotted and the computed tomography dose index (CTDI) calculated for a single 10 mm thick slice on 14 CT scanners. An anthropomorphic head phantom was also scanned from the base-of-skull to the vertex using 10/10 mm slices. The absorbed dose measured at the centre of the scan series is reported (Dmid). The mean CTDIw for the 14 scanners was 60.0 mGy, while the mean Dmid was 45.8 mGy. Dmid better represents the absorbed dose in human tissues. The CTDIw and Dmid normalized to mAs varied by up to a factor of 2.2 for the different scanners. Equipment related factors contribute to such variations. However, variations due to operator dependent factors such as the choice of exposure factors, scanning protocol and positioning technique must also be considered. When such factors are taken into account the absorbed dose received by the patient can vary considerably, by as much as 16.2 for lens dose. Increased awareness of the factors influencing CT dose and the standardization of scanning protocols is recommended.
Publisher: Wiley
Date: 26-05-2005
DOI: 10.1118/1.1997978
Publisher: Wiley
Date: 13-02-2020
DOI: 10.1002/ACM2.12825
Publisher: Elsevier BV
Date: 12-2011
DOI: 10.1016/J.IJROBP.2010.09.017
Abstract: The quality assurance (QA) of image-guided radiation therapy (IGRT) within clinical trials is in its infancy, but its importance will continue to grow as IGRT becomes the standard of care. The purpose of this study was to demonstrate the feasibility of IGRT QA as part of the credentialing process for a clinical trial. As part of the accreditation process for a randomized trial in prostate cancer hypofraction, IGRT benchmarking across multiple sites was incorporated. Each participating site underwent IGRT credentialing via a site visit. In all centers, intraprostatic fiducials were used. A real-time assessment of analysis of IGRT was performed using Varian's Offline Review image analysis package. Two-dimensional (2D) kV and MV electronic portal imaging prostate patient datasets were used, consisting of 39 treatment verification images for 2D/2D comparison with the digitally reconstructed radiograph derived from the planning scan. The influence of differing sites, image modality, and observer experience on IGRT was then assessed. Statistical analysis of the mean mismatch errors showed that IGRT analysis was performed uniformly regardless of institution, therapist seniority, or imaging modality across the three orthogonal planes. The IGRT component of clinical trials that include sophisticated planning and treatment protocols must undergo stringent QA. The IGRT technique of intraprostatic fiducials has been shown in the context of this trial to be undertaken in a uniform manner across Australia. Extending this concept to many sites with different equipment and IGRT experience will require a robust remote credentialing process.
Publisher: IOP Publishing
Date: 31-07-2004
DOI: 10.1088/0031-9155/49/16/013
Abstract: A new technique for intensity modulated radiation therapy (IMRT) delivery is helical tomotherapy (HT). Like most IMRT delivery methods, HT utilizes many small fields as part of the treatment plan, which can be difficult to characterize. A novel technique for small field characterization, based on inter- and extrapolation of ion chamber readings, is presented in the context of HT. As a fan beam is characterized by its thickness and output factor, plane parallel chambers with different active volumes were used to scan the fan beam profiles. The fan beam thickness (FBT) can be determined from the thickness measured with the chamber by extrapolating to an infinitesimally small chamber size. The effective output was derived from the integral under the dose profile ided by the FBT. This was done for five FBTs and demonstrated a sharp fall off in dose when the FBT decreased below 8 mm. Similar techniques can be applied to other IMRT techniques to improve the characterization of various beam parameters.
Publisher: Elsevier BV
Date: 08-2009
Publisher: IOP Publishing
Date: 31-07-2004
DOI: 10.1088/0031-9155/49/16/014
Abstract: Lung cancer treatment is one of the most challenging fields in radiotherapy. The aim of the present study was to investigate what role helical tomotherapy (HT), a novel approach to the delivery of highly conformal dose distributions using intensity-modulated radiation fan beams, can play in difficult cases with large target volumes typical for many of these patients. Tomotherapy plans were developed for 15 patients with stage III inoperable non-small-cell lung cancer. While not necessarily clinically indicated, elective nodal irradiation was included for all cases to create the most challenging scenarios with large target volumes. A 2 cm margin was used around the gross tumour volume (GTV) to generate primary planning target volume (PTV2) and 1 cm margin around elective nodes for secondary planning target volume (PTV1) resulting in PTV1 volumes larger than 1000 cm3 in 13 of the 15 patients. Tomotherapy plans were created using an inverse treatment planning system (TomoTherapy Inc.) based on superposition/convolution dose calculation for a fan beam thickness of 25 mm and a pitch factor between 0.3 and 0.8. For comparison, plans were created using an intensity-modulated radiation therapy (IMRT) approach planned on a commercial treatment planning system (TheraplanPlus, Nucletron). Tomotherapy delivery times for the large target volumes were estimated to be between 4 and 19 min. Using a prescribed dose of 60 Gy to PTV2 and 46 Gy to PTV1, the mean lung dose was 23.8+/-4.6 Gy. A 'dose quality factor' was introduced to correlate the plan outcome with patient specific parameters. A good correlation was found between the quality of the HT plans and the IMRT plans with HT being slightly better in most cases. The overlap between lung and PTV was found to be a good indicator of plan quality for HT. The mean lung dose was found to increase by approximately 0.9 Gy per percent overlap volume. Helical tomotherapy planning resulted in highly conformal dose distributions. It allowed easy achievement of two different dose levels in the target simultaneously. As the overlap between PTV and lung volume is a major predictor of mean lung dose, future work will be directed to control of margins. Work is underway to investigate the possibility of breath-hold techniques for tomotherapy delivery to facilitate this aim.
Publisher: Elsevier BV
Date: 06-2007
DOI: 10.1016/J.IJROBP.2006.11.052
Abstract: To report results from two clinical trials evaluating helical tomotherapy (HT). Patients were enrolled in one of two prospective trials of HT (one for palliative and one for radical treatment). Both an HT plan and a companion three-dimensional conformal radiotherapy (3D-CRT) plan were generated. Pretreatment megavoltage computed tomography was used for daily image guidance. From September 2004 to January 2006, a total of 61 sites in 60 patients were treated. In all but one case, a clinically acceptable tomotherapy plan for treatment was generated. Helical tomotherapy plans were subjectively equivalent or superior to 3D-CRT in 95% of plans. Helical tomotherapy was deemed equivalent or superior in two thirds of dose-volume point comparisons. In cases of inferiority, differences were either clinically insignificant and/or reflected deliberate tradeoffs to optimize the HT plan. Overall imaging and treatment time (median) was 27 min (range, 16-91 min). According to a patient questionnaire, 78% of patients were satisfied to very satisfied with the treatment process. Helical tomotherapy demonstrated clear advantages over conventional 3D-CRT in this erse patient group. The prospective trials were helpful in deploying this technology in a busy clinical setting.
Publisher: Elsevier BV
Date: 11-2021
DOI: 10.1016/J.ZEMEDI.2021.04.003
Abstract: Dose to the contralateral breast (CLB) from radiotherapy treatment has the potential to induce secondary breast cancer. Electronic tissue compensation (eComp) for breast cancer patients is one of the alternative methods to conventional 3D-conformal radiotherapy that eliminates the use of wedges. Several studies have investigated dose to the CLB using tangential fields involving wedges, intensity-modulated radiation therapy and volumetric modulated arc radiation therapy and various other techniques via treatment planning system calculations, Monte Carlo methods and phantoms. However, there are limited data published in assessing the actual dose received by the CLB from treatment with eComp-based tangential fields. In this study, the CLB dose for patients undergoing tangential field radiotherapy with eComp and enhanced dynamic wedged (standard) tangential fields was measured and compared to assess the CLB dose between the two methods. Measurements were conducted on a randomised trial of 40 patients, 20 of them had undergone standard planning, and the remaining 20 were treated with eComp. The mean surface dose measured with TLDs at 3cm from the medial tangential border for eComp and standard techniques was 10.04±1.37% and 10.14±2.05%, respectively for a prescription dose of 2.65Gy/fraction. The estimated dose at 1cm depth in tissue, measured with the use of perspex domes placed over the TLD at the same location, was 5.12±0.87% and 6.29±2.01% for eComp and standard, respectively. The CLB dose is dependent on the proximity of the medial tangential field edge to the contralateral breast and is patient-specific. The results of this study show that at 1cm depth, eComp technique delivers significantly less dose (p<0.05) to the CLB as compared to standard tangential fields. Furthermore, the surface dose measured for both eComp and standard are comparable indicating that the eComp-based tangential field technique does not contribute any excess dose to CLB when compared to standard tangential fields. The excess relative risk (ERR) for radiation-induced cancers for eComp was found to be 0.08, compared to 0.11 for standard tangential fields.
Publisher: British Institute of Radiology
Date: 06-2005
DOI: 10.1259/BJR/53491625
Abstract: Helical tomotherapy (HT) plans for craniospinal radiation were generated for the case of a 4-year-old boy with disseminated ependymoma. The HT plans demonstrated excellent target coverage, homogeneity and organ sparing compared with a conventional linear accelerator based craniospinal radiation plan. On the basis of this case study, further evaluation of HT for craniospinal radiotherapy seems justified.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 09-2015
DOI: 10.1007/S13246-015-0373-2
Abstract: It was the aim of this work to assess and track the workload, working conditions and professional recognition of radiation oncology medical physicists (ROMPs) in the Asia Pacific region over time. In this third survey since 2008, a structured questionnaire was mailed in 2014 to 22 senior medical physicists representing 23 countries. As in previous surveys the questionnaire covered seven themes: 1 education, training and professional certification, 2 staffing, 3 typical tasks, 4 professional organisations, 5 resources, 6 research and teaching, and 7 job satisfaction. The response rate of 100% is a result of performing a survey through a network, which allows easy follow-up. The replies cover 4841 ROMPs in 23 countries. Compared to 2008, the number of medical physicists in many countries has doubled. However, the number of experienced ROMPs compared to the overall workforce is still small, especially in low and middle income countries. The increase in staff is matched by a similar increase in the number of treatment units over the years. Furthermore, the number of countries using complex techniques (IMRT, IGRT) or installing high end equipment (tomotherapy, robotic linear accelerators) is increasing. Overall, ROMPs still feel generally overworked and the professional recognition, while varying widely, appears to be improving only slightly. Radiation oncology medical physics practice has not changed significantly over the last 6 years in the Asia Pacific Region even if the number of physicists and the number and complexity of treatment techniques and technologies have increased dramatically.
Publisher: IOP Publishing
Date: 04-09-2009
DOI: 10.1088/0031-9155/54/19/004
Abstract: Tumor motion is a particular concern for a complex treatment modality such as helical tomotherapy, where couch position, gantry rotation and MLC leaf opening all change with time. In the present study, we have investigated the impact of tumor motion for helical tomotherapy, which could result in three distinct motion-induced dose artifacts, namely (1) dose rounding, (2) dose rippling and (3) IMRT leaf opening asynchronization effect. Dose rounding and dose rippling effects have been previously described, while the IMRT leaf opening asynchronization effect is a newly discovered motion-induced dose artifact. Dose rounding is the penumbral widening of a delivered dose distribution near the edges of a target volume along the direction of tumor motion. Dose rippling is a series of periodic dose peaks and valleys observed within the target region along the direction of couch motion, due to an asynchronous interplay between the couch motion and the longitudinal component of tumor motion. The IMRT leaf opening asynchronization effect is caused by an asynchronous interplay between the temporal patterns of leaf openings and tumor motion. The characteristics of each dose artifact were investigated in idually as functions of target motion litude and period for both non-IMRT and IMRT helical tomotherapy cases, through computer simulation modeling and experimental verification. The longitudinal dose profiles generated by the simulation program agreed with the experimental data within +/-0.5% and +/-1.5% inside the PTV region for the non-IMRT and IMRT cases, respectively. The dose rounding effect produced a penumbral increase up to 20.5 mm for peak-to-peak target motion litudes ranging from 1.0 cm to 5.0 cm. Maximum dose rippling magnitude of 25% was calculated, when the target motion period approached an unusually high value of 10 s. The IMRT leaf opening asynchronization effect produced dose differences ranging from -29% to 7% inside the PTV region. This information on the potential motion-induced dose artifacts will be important in defining the optimal motion mitigation strategies for lung tomotherapy.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Medknow
Date: 2017
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.IJROBP.2015.05.011
Abstract: Measuring changes in lung perfusion resulting from radiation therapy dose requires registration of the functional imaging to the radiation therapy treatment planning scan. This study investigates registration accuracy and utility for positron emission tomography (PET)/computed tomography (CT) perfusion imaging in radiation therapy for non-small cell lung cancer. (68)Ga 4-dimensional PET/CT ventilation-perfusion imaging was performed before, during, and after radiation therapy for 5 patients. Rigid registration and deformable image registration (DIR) using B-splines and Demons algorithms was performed with the CT data to obtain a deformation map between the functional images and planning CT. Contour propagation accuracy and correspondence of anatomic features were used to assess registration accuracy. Wilcoxon signed-rank test was used to determine statistical significance. Changes in lung perfusion resulting from radiation therapy dose were calculated for each registration method for each patient and averaged over all patients. With B-splines/Demons DIR, median distance to agreement between lung contours reduced modestly by 0.9/1.1 mm, 1.3/1.6 mm, and 1.3/1.6 mm for pretreatment, midtreatment, and posttreatment (P < .01 for all), and median Dice score between lung contours improved by 0.04/0.04, 0.05/0.05, and 0.05/0.05 for pretreatment, midtreatment, and posttreatment (P .2). Poorer posttreatment results were likely caused by posttreatment pneumonitis and tumor regression. Up to 80% standardized uptake value loss in perfusion scans was observed. There was limited change in the loss in lung perfusion between registration methods however, Demons resulted in larger interpatient variation compared with rigid and B-splines registration. DIR accuracy in the data sets studied was variable depending on anatomic changes resulting from radiation therapy caution must be exercised when using DIR in regions of low contrast or radiation pneumonitis. Lung perfusion reduces with increasing radiation therapy dose however, DIR did not translate into significant changes in dose-response assessment.
Publisher: American Physical Society (APS)
Date: 28-11-2005
Publisher: Springer Science and Business Media LLC
Date: 03-2009
DOI: 10.1007/BF03178620
Publisher: Elsevier BV
Date: 09-2005
Publisher: Elsevier BV
Date: 05-2015
Publisher: IOP Publishing
Date: 12-01-2015
Publisher: British Institute of Radiology
Date: 06-03-2018
DOI: 10.1259/BJR.20170737
Publisher: Springer Science and Business Media LLC
Date: 07-03-2021
DOI: 10.1186/S40658-021-00375-6
Abstract: Functional lung mapping from Ga 68 -ventilation erfusion (V/Q) PET/CT, which has been shown to correlate with pulmonary function tests (PFTs), may be beneficial in a number of clinical applications where sparing regions of high lung function is of interest. Regions of clumping in the proximal airways in patients with airways disease can result in areas of focal intense activity and artefact in ventilation imaging. These artefacts may even shine through to subsequent perfusion images and create a challenge for quantitative analysis of PET imaging. We aimed to develop an automated algorithm that interprets the uptake histogram of PET images to calculate a peak uptake value more representative of the global lung volume. Sixty-six patients recruited from a prospective clinical trial underwent both V/Q PET/CT imaging and PFT analysis before treatment. PET images were normalised using an iterative histogram analysis technique to account for tracer hotspots prior to the threshold-based delineation of varying values. Pearson’s correlation between fractional lung function and PFT score was calculated for ventilation, perfusion, and matched imaging volumes at varying threshold values. For all functional imaging thresholds, only FEV1/FVC PFT yielded reasonable correlations to image-based functional volume. For ventilation, a range of 10–30% of adapted peak uptake value provided a reasonable threshold to define a volume that correlated with FEV1/FVC ( r = 0.54–0.61). For perfusion imaging, a similar correlation was observed ( r = 0.51–0.56) in the range of 20–60% adapted peak threshold. Matched volumes were closely linked to ventilation with a threshold range of 15–35% yielding a similar correlation ( r = 0.55–0.58). Histogram normalisation may be implemented to determine the presence of tracer clumping hotspots in Ga-68 V/Q PET imaging allowing for automated delineation of functional lung and standardisation of functional volume reporting.
Publisher: Springer Science and Business Media LLC
Date: 25-01-2021
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.IJROBP.2009.01.054
Abstract: The objective of this investigation was to measure the agreement between in-room computed tomography (CT) on rails and electronic portal image (EPI) radiography. Agreement between the location of the center of gravity (COG) of fiducial markers (FMs) on CT and EPI images was determined in phantom studies and a patient cohort. A secondary analysis between the center of volume (COV) of the prostate on CT and the COG of FMs on CT and EPI was performed. Agreement was defined as the 95% probability of a difference of <or=3.0 mm between images. Systematic and random errors from CT and EPI are reported. From 8 patients, 254 CT and EPI pairs were analyzed. FMs were localized to within 3 mm on CT and EPI images 96.9% of the time in the left-right (LR) plane, 85.8% superior-inferior (SI), and 89% anterior-posterior (AP). The differences between the COV on CT and the COG on EPI were not within 3 mm in any plane: 87.8% (LR), 64.2% (SI), and 70.9% (AP). The systematic error varied from 1.2 to 2.9 mm (SI) and 1.8-2.9 mm (AP) between the COG on EPI and COV on CT. Considerable differences between in-room CT and EPI exist. The phantom measurements showed slice thickness affected the accuracy of localization in the SI plane, and couch sag that occurs at the CT on rails gantry could not be totally corrected for in the AP plane. Other confounding factors are the action of rotating the couch and associated time lag between image acquisitions (prostate motion), EPI image quality, and outlining uncertainties.
Publisher: Informa UK Limited
Date: 04-2019
DOI: 10.1111/AP.12375
Publisher: Wiley
Date: 09-1993
DOI: 10.1118/1.597157
Abstract: Data on the dose distribution in the penumbral region of megavoltage x rays are of importance for most radiotherapy planning systems. For medical linear accelerators the distance between the points representing 20% and 80% of the central axis dose (20/80) is typically only a few millimeters. To achieve good spatial resolution a radiation detector with small physical size has to be used for penumbra measurements. The penumbra in a 6-MV therapeutic x-ray beam was investigated for field sizes of 10 x 10 cm2 and 20 x 20 cm2 at depth of maximum dose (dmax = 1.5 cm) and at 10-cm depth in a solid water phantom. In addition, the field edge of an independent jaw driven to the center of the axis of the primary collimator was investigated. LiF thermoluminescent (TL) ribbons and rods were used embedded in solid water in different geometries resulting in relative detector sizes of 1, 3.1, and 6 mm. A forming function based on an inverse square root function was used to fit the experimental penumbra measurements. For the asymmetric field an amendment to the function is proposed to give a better fit for the experimental data. From the penumbra measured with the three different detector sizes, a penumbra can be extrapolated for an infinitesimal small detector. The extrapolated penumbral width (20/80) was found to be 2.3, 3.2, and 2.7 mm at dmax for the 10 x 10-cm2 symmetric, 10 x 10-cm2 asymmetric, and 20 x 20-cm2 field sizes, respectively. The 20/80 values at 10-cm depth in the solid water phantom for the same radiation fields were 4.2, 4.3, and 4.1 mm, respectively.
Publisher: Wiley
Date: 29-04-2019
DOI: 10.1002/CASP.2406
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-1995
DOI: 10.1097/00004032-199512000-00014
Abstract: An important factor in the design of primary protective barriers is the use factor. The present study was aimed at obtaining historical data on the use factor of two dual modality linear accelerators in a radiotherapy department. Gantry angle, field size, and beam modifiers were recorded for all radiation qualities in use at two medical linear accelerators with 6 MV and 18 MV x-rays and multiple electron energies ranging from 4 MeV to 20 MeV. The data for one year of clinical use was extracted from a record and verifying system and an estimate of the physics workload on the machines was obtained by going through the quality assurance records and machine log books. Of the total dose of approximately 37,000 Gy delivered in one year at isocenter on each unit 80% was given as 6 MV x-rays. As can be expected, most x-ray beams were directed at the four cardinal gantry angles with the angular distribution for 6 MV and 18 MV x-rays being very similar. Electron fields were broadly distributed around the gantry pointing down position. Less than 25% of all clinical x-ray treatment fields extended beyond a field size of 200 cm2.
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576167
Publisher: Wiley
Date: 07-2006
DOI: 10.1118/1.2244668
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 11-2023
Publisher: Frontiers Media SA
Date: 03-03-2022
Abstract: Delivering radiotherapy to patients in an upright position can allow for increased patient comfort, reduction in normal tissue irradiation, or reduction of machine size and complexity. This paper gives an overview of the requirements for the delivery of contemporary arc and modulated radiation therapy to upright patients. We explore i) patient positioning and immobilization, ii) simulation imaging, iii) treatment planning and iv) online setup and image guidance. Treatment chairs have been designed to reproducibly position seated patients for treatment and can be augmented by several existing immobilisation systems or promising emerging technologies such as soft robotics. There are few solutions for acquiring CT images for upright patients, however, cone beam computed tomography (CBCT) scans of upright patients can be produced using the imaging capabilities of standard Linacs combined with an additional patient rotation device. While these images will require corrections to make them appropriate for treatment planning, several methods indicate the viability of this approach. Treatment planning is largely unchanged apart from translating gantry rotation to patient rotation, allowing for a fixed beam with a patient rotating relative to it. Rotation can be provided by a turntable during treatment delivery. Imaging the patient with the same machinery as used in treatment could be advantageous for online plan adaption. While the current focus is using clinical linacs in existing facilities, developments in this area could also extend to lower-cost and mobile linacs and heavy ion therapy.
Publisher: Wiley
Date: 23-06-2005
DOI: 10.1118/1.2031059
Publisher: IOP Publishing
Date: 1998
DOI: 10.1088/0031-9155/43/1/014
Abstract: Parasites extracted from the lungs and the pterygoid sinus complex of 6 species of odontocetes stranded along the north-west Spanish coast (Northeast Atlantic) between 2009 and 2019 were morphologically identified. The s les belonged to 14 specimens, including 3 harbour porpoises,
Publisher: Wiley
Date: 10-01-2020
DOI: 10.1002/ACM2.12808
Publisher: IOP Publishing
Date: 28-10-2010
DOI: 10.1088/0031-9155/55/22/006
Abstract: Gated radiotherapy of lung lesions is particularly complex for helical tomotherapy, due to the simultaneous motions of its three subsystems (gantry, couch and collimator). We propose a new way to implement gating for helical tomotherapy, namely multi-pass respiratory gating. In this method, gating is achieved by delivering only the beam projections that occur within a respiratory gating window, while blocking the rest of the beam projections by fully closing all collimator leaves. Due to the continuous couch motion, the planned beam projections must be delivered over multiple passes of radiation deliveries. After each pass, the patient couch is reset to its starting position, and the treatment recommences at a different phase of tumour motion to 'fill in' the previously blocked beam projections. The gating process may be repeated until the plan dose is delivered (full gating), or halted after a certain number of passes, with the entire remaining dose delivered in a final pass without gating (partial gating). The feasibility of the full gating approach was first tested for sinusoidal target motion, through experimental measurements with film and computer simulation. The optimal gating parameters for full and partial gating methods were then determined for various fractionation schemes through computer simulation, using a patient respiratory waveform. For sinusoidal motion, the PTV dose deviations of -29 to 5% observed without gating were reduced to range from -1 to 3% for a single fraction, with a 4 pass full gating. For a patient waveform, partial gating required fewer passes than full gating for all fractionation schemes. For a single fraction, the maximum allowed residual motion was only 4 mm, requiring large numbers of passes for both full (12) and partial (7 + 1) gating methods. The number of required passes decreased significantly for 3 and 30 fractions, allowing residual motion up to 7 mm. Overall, the multi-pass gating technique was shown to be a promising way to reduce the impact of lung tumour motion during helical tomotherapy.
Publisher: Springer Science and Business Media LLC
Date: 28-10-2011
Publisher: Wiley
Date: 06-2015
DOI: 10.1118/1.4925786
Publisher: Springer Science and Business Media LLC
Date: 17-09-2021
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.RADONC.2018.07.014
Abstract: Advanced imaging techniques allow functional information to be derived and integrated into treatment planning. A systematic review was conducted with the primary objective to evaluate the ability of functional lung imaging to predict risk of radiation pneumonitis. Secondary objectives were to evaluate dose-response relationships on post treatment functional imaging and assess the utility in including functional lung information into treatment planning. A structured search for publications was performed following PRISMA guidelines and registered on PROSPERO. 814 articles were screened against review criteria and 114 publications met criteria. Methods of identifying functional lung included using CT, MRI, SPECT and PET to image ventilation or perfusion. Six studies compared differences between functional and anatomical lung imaging at predicting radiation pneumonitis. These found higher predictive values using functional lung imaging. Twenty-one studies identified a dose-response relationship on post-treatment functional lung imaging. Nineteen planning studies demonstrated the ability of functional lung optimised planning techniques to spare regions of functional lung. Meta-analysis of these studies found that mean (95% CI) functional volume receiving 20 Gy was reduced by 4.2% [95% CI: 2.3: 6.0] and mean lung dose by 2.2 Gy [95% CI: 1.2: 3.3] when plans were optimised to spare functional lung. There was significant variation between publications in the definition of functional lung. Functional lung imaging may have potential utility in radiation therapy planning and delivery, although significant heterogeneity was identified in approaches and reporting. Recommendations have been made based on the available evidence for future functional lung trials.
Publisher: Wiley
Date: 06-2015
DOI: 10.1118/1.4924451
Publisher: Wiley
Date: 23-06-2005
DOI: 10.1118/1.2031067
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.EJMP.2017.12.010
Abstract: Flattening filter free (FFF) beams are increasingly being considered for stereotactic radiotherapy (SRT). For the first time, the performance of a monolithic silicon array detector under 6 and 10 MV FFF beams was evaluated. The dosimeter, named "Octa" and designed by the Centre for Medical Radiation Physics (CMRP), was tested also under flattened beams for comparison. Output factors (OFs), percentage depth-dose (PDD), dose profiles (DPs) and dose per pulse (DPP) dependence were investigated. Results were benchmarked against commercially available detectors for small field dosimetry. The dosimeter was shown to be a 'correction-free' silicon array detector for OFs and PDD measurements for all the beam qualities investigated. Measured OFs were accurate within 3% and PDD values within 2% compared against the benchmarks. Cross-plane, in-plane and diagonal DPs were measured simultaneously with high spatial resolution (0.3 mm) and real time read-out. A DPP dependence (24% at 0.021 mGy ulse relative to 0.278 mGy ulse) was found and could be easily corrected for in the case of machine specific quality assurance applications. Results were consistent with those for monolithic silicon array detectors designed by the CMRP and previously characterized under flattened beams only, supporting the robustness of this technology for relative dosimetry for a wide range of beam qualities and dose per pulses. In contrast to its predecessors, the design of the Octa offers an exhaustive high-resolution 2D dose map characterization, making it a unique real-time radiation detector for small field dosimetry for field sizes up to 3 cm side.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Informa UK Limited
Date: 08-2020
DOI: 10.1111/AP.12465
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576160
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576162
Publisher: Cambridge University Press (CUP)
Date: 06-2011
Publisher: Wiley
Date: 25-06-2020
Abstract: Due to size and close proximity to skin, the sternum is a complicated target for stereotactic ablative body radiotherapy (SABR). This is a retrospective case series of single‐fraction SABR to sternal metastasis in patients with oligometastatic breast cancer. Between June 2014 and June 2018, ten breast cancer patients received 20 Gy in 1 fraction to a solitary sternal metastasis. Eligible patients had Eastern Cooperative Oncology Group performance status of 0–2, oligometastatic disease (defined as 1–5 metastases) and a controlled primary site. Patients were treated with 3‐dimensional conformal radiotherapy, each patient case comprising of 6 coplanar beams and 2–6 non‐coplanar beams. Local control, pain response and adverse events were retrospectively reviewed. The median planned target volumes were 84.75cc (range, 14.4–197.8cc). The median conformity index was 1.29 (range, 1.2–1.49). At a median follow‐up of 32 months, nine patients achieved in‐field control. Two patients had triple negative disease, one of them developed marginal recurrence, and the other had in‐field recurrence. Seven patients had sternal pain prior to SABR, and within 3 months after SABR treatment, the pain improved ( n = 3) or resolved ( n = 2). Four patients developed acute grade 1 and 2 skin reactions, and two patients had late grade 1 skin reactions. There were no grade 3 or 4 toxicities. Our case series demonstrates safety of SABR with associated disease control and analgesic benefit in selected patients with oligometastatic breast cancer. The marginal recurrence observed in this cohort suggests wider margins could be beneficial to account for microscopic disease.
Publisher: Emerald
Date: 13-12-2022
Abstract: Radiotherapy relies on the delivery of radiation to cancer cells with millimetre accuracy, and immobilisation of patients is essential to minimise unwanted damage to surrounding healthy cells due to patient movement. Traditional thermoformed face masks can be uncomfortable and stressful for patients and may not be accurately fitted. The purpose of this study was to use 3D scanning and additive manufacturing to digitise this workflow and improve patient comfort and treatment outcomes. The head of a volunteer was scanned using an Artec Leo optical scanner (Artec, Luxembourg) and ANSYS (Ansys, Canonsburg, USA) software was used to make two 3D models of the mask: one with a nose bridge and one open as would be used with optical surface guidance. Data based on measurements from ten pressure sensors around the face was used to perform topology optimisation, with the best designs 3D printed using fused deposition modelling (FDM) and tested on the volunteer with embedded pressure sensors. The two facemasks proved to be significantly different in terms of restricting head movement inside the masks. The optimised mask with a nose bridge effectively restricted head movement in roll and yaw orientations and exhibited minimal deformation as compared to the open mask design and the thermoformed mask. The proposed workflow allows customisation of masks for radiotherapy immobilisation using additive manufacturing and topology optimisation based on collected pressure sensor data. In the future, sensors could be embedded in masks to provide real-time feedback to clinicians during treatment.
Publisher: Springer Science and Business Media LLC
Date: 12-2005
DOI: 10.1007/BF03178723
Publisher: The American Association of Immunologists
Date: 11-2000
DOI: 10.4049/JIMMUNOL.165.9.5161
Abstract: Understanding the basic immunology of an infectious disease requires insight into the pattern of T cell reactivity and specificity. Although lymphatic filariasis is a major tropical disease, the predominant T cell Ags of filarial species such as Brugia malayi are still undefined. We have now identified a prominent T cell Ag from B. malayi microfilariae (Mf) as Bm-SPN-2, a serpin secreted exclusively by this stage. Mf-infected mice mounted strong, but short-lived, Bm-SPN-2-specific Th1 responses, measured by in vitro production of IFN-γ, but not IL-4 or IL-5, 14 days postinfection. By day 35, responsiveness to Bm-SPN-2 was lost despite enhanced reactivity to whole Mf extract. Single immunization with Mf extract also stimulated typical Th1 reactions to Bm-SPN-2, but IgG1 Ab responses dominated after repeated immunizations. Human patients displayed potent humoral responses to Bm-SPN-2 in both IgG1 and IgG4 subclasses. Thus, 100% (20 of 20) of the microfilaremic (MF+) patients bore IgG4 responses to Bm-SPN-2, while only 30% of endemic normal subjects were similarly positive. Following chemotherapy, Bm-SPN-2-specific Abs disappeared in 12 of 13 MF+ patients, although the majority remained seropositive for whole parasite extract. PBMC from most, but not all, endemic subjects were induced to secrete IFN-γ when stimulated with Bm-SPN-2. These findings demonstrate that Bm-SPN-2 is recognized by both murine and human T and B cells and indicate that their responses are under relatively stringent temporal control. This study also provides the first ex le of a stage-specific secreted molecule that acts as a major T cell Ag from filarial parasites and is a prime candidate for a serodiagnostic probe.
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012019
Abstract: Radiation dose is the therapeutic agent in radiotherapy where the objective is to maximise radiation dose to a target while minimising the dose to surrounding healthy tissues. Dose in this context is typically associated with the quantity “absorbed dose” as energy deposited per unit mass and measured in J/kg of tissue. However, even if high doses are delivered (no stochastic distribution considered) and photon or electron radiation is considered (no neutrons or heavy charged particles), there will be differences in the actual dose delivered to different tissue types as the stopping power for the electrons that deliver the vast majority of dose varies with elemental composition. Historically, radiation beam calibration and dose calculations were performed in water as a readily available, easily standardised material that closely matches the radiation properties of many human tissues. However, many superior dose calculation algorithms that have recently become available due to improved computer power (Monte Carlo Calculations, Acuros) calculate dose as deposited in the medium. The present paper examines arguments for both and proposes that based on the current scientific and political developments specification of dose as dose to medium would be the more robust and future proof choice.
Publisher: Springer Science and Business Media LLC
Date: 03-09-2021
DOI: 10.1038/S41598-021-96600-4
Abstract: Radiomics is a promising technique for discovering image based biomarkers of therapy response in cancer. Reproducibility of radiomics features is a known issue that is addressed by the image biomarker standardisation initiative (IBSI), but it remains challenging to interpret previously published radiomics signatures. This study investigates the reproducibility of radiomics features calculated with two widely used radiomics software packages (IBEX, MaZda) in comparison to an IBSI compliant software package (PyRadiomics). Intensity histogram, shape and textural features were extracted from 334 diffusion weighted magnetic resonance images of 59 head and neck cancer (HNC) patients from the PREDICT-HN observational radiotherapy study. Based on name and linear correlation, PyRadiomics shares 83 features with IBEX and 49 features with MaZda, a sub-set of well correlated features are considered reproducible (IBEX: 15 features, MaZda: 18 features). We explore the impact of including non-reproducible radiomics features in a HNC radiotherapy response model. It is possible to classify equivalent patient groups using radiomic features from either software, but only when restricting the model to reliable features using a correlation threshold method. This is relevant for clinical biomarker validation trials as it provides a framework to assess the reproducibility of reported radiomic signatures from existing trials.
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 08-1997
DOI: 10.1016/S0167-8140(97)00086-8
Abstract: Oligodeoxynucleotides (ODNs) are typically purified and analysed with HPLC equipped with a UV-Vis detector. Quantities of ODNs are usually determined using a UV-Vis spectrometer separately after HPLC, and are reported as optical density at 260 nm (OD
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012018
Abstract: Stereotactic ablative body radiotherapy (SABR) is demonstrating good local control for patients with inoperable primary renal cell carcinoma. In a previous pilot study we identified magnetic resonance imaging (MRI) early response biomarkers that correlate with later morphological changes in computed tomography (CT) images. These early functional changes in diffusion and perfusion following radiotherapy were observed on MRI and have the potential to identify non-responders who may benefit from adjuvant or salvage therapies. Here we detail the imaging protocol for an MRI sub-study of the Focal Ablative STereotactic Radiosurgery for Cancers of the Kidney (FASTRACK II) trial. A preliminary patient case demonstrates the high quality of the imaging data, with discussion of the improvements made from the pilot protocol for improved motion management and correction. We aim to validate the previously identified early response MRI biomarkers with this rich prospective multi-centre dataset.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Frontiers Media SA
Date: 25-02-2020
Publisher: Public Library of Science (PLoS)
Date: 16-08-2018
Publisher: Springer Science and Business Media LLC
Date: 25-01-2022
DOI: 10.1007/S13246-022-01105-7
Abstract: With the increased use of X-ray imaging for patient alignment in external beam radiation therapy, particularly with cone-beam computed tomography (CBCT), the additional dose received by patients has become of greater consideration. In this study, we analysed the radiation dose from CBCT for clinical lung radiotherapy and assessed its relative contribution when combined with radiation treatment planning for a variety of lung radiotherapy techniques. The Monte Carlo simulation program ImpactMC was used to calculate the 3D dose delivered by a Varian TrueBeam linear accelerator to patients undergoing thorax CBCT imaging. The concomitant dose was calculated by simulating the daily CBCT irradiation of ten lung cancer patients. Each case was planned with a total dose of 50-60 Gy to the target lesion in 25-30 fractions using the 3DCRT or IMRT plan and retrospectively planned using VMAT. For each clinical case, the calculated CBCT dose was summed with the planned dose, and the dose to lungs, heart, and spinal cord were analysed according to conventional dose conformity metrics. Our results indicate greater variations in dose to the heart, lungs, and spinal cord based on planning technique, (3DCRT, IMRT, VMAT) than from the inclusion of daily cone-beam imaging doses over 25-30 fractions. The average doses from CBCT imaging per fraction to the lungs, heart and spinal cord were 0.52 ± 0.10, 0.49 ± 0.15 and 0.39 ± 0.08 cGy, respectively. Lung dose variations were related to the patient's size and body composition. Over a treatment course, this may result in an additional mean absorbed dose of 0.15-0.2 Gy. For lung V5, the imaging dose resulted in an average increase of ~ 0.6% of the total volume receiving 5 Gy. The increase in V20 was more dependent on the planning technique, with 3DCRT increasing by 0.11 ± 0.09% with imaging and IMRT and VMAT increasing by 0.17 ± 0.05% and 0.2 ± 0.06%, respectively. In this study, we assessed the concomitant dose for daily CBCT lung cancer patients undergoing radiotherapy. The additional radiation dose to the normal lungs from daily CBCT was found to range from 0.15 to 0.2 Gy when the patient was treated with 25-30 fractions. Consideration of potential variation in relative biological effectiveness between kilovoltage imaging and megavoltage treatment dose was outside the scope of this study. Regardless of this, our results show that the assessment of imaging dose can be incorporated into the treatment planning process and the relative effect on overall dose distribution was small compared to the difference among planning techniques.
Publisher: Elsevier BV
Date: 11-2020
Publisher: IOP Publishing
Date: 06-02-2015
DOI: 10.1088/0031-9155/60/5/1793
Abstract: Collected real-life clinical target volume (CTV) displacement data show that some patients undergoing external beam radiotherapy (EBRT) demonstrate significantly more fraction-to-fraction variability in their displacement ('random error') than others. This contrasts with the common assumption made by historical recipes for margin estimation for EBRT, that the random error is constant across patients. In this work we present statistical models of CTV displacements in which random errors are characterised by an inverse gamma (IG) distribution in order to assess the impact of random error variability on CTV-to-PTV margin widths, for eight real world patient cohorts from four institutions, and for different sites of malignancy. We considered a variety of clinical treatment requirements and penumbral widths. The eight cohorts consisted of a total of 874 patients and 27 391 treatment sessions. Compared to a traditional margin recipe that assumes constant random errors across patients, for a typical 4 mm penumbral width, the IG based margin model mandates that in order to satisfy the common clinical requirement that 90% of patients receive at least 95% of prescribed RT dose to the entire CTV, margins be increased by a median of 10% (range over the eight cohorts -19% to +35%). This substantially reduces the proportion of patients for whom margins are too small to satisfy clinical requirements.
Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.JTHO.2016.04.016
Abstract: Stereotactic radiotherapy is a high-dose precision technique necessitating accurate target visualization through either cone beam computed tomography (CBCT) or planar imaging with implanted fiducial markers. We have investigated the properties for image guidance using fiducial markers implanted through minimally invasive bronchoscopy. Two fiducial marker types were implanted endobronchially in 10 patients undergoing radical radiation treatment for non-small cell lung cancer (eight using Visicoil linear fiducial markers [IBA Dosimetry GmbH, Schwarzenbruck Germany] and two using superDimension and superLock two-band markers [Covidien Inc., Minneapolis, MN]). Patients underwent four-dimensional computed tomography imaging for treatment planning and after completion of treatment to investigate marker movement. As part of the image guidance assessment, megavolt electronic portal images (EPIs) were acquired in addition to kilovolt planar and CBCT (Varian Medical Systems, Palo Alto, CA) images. In two of 10 patients (both receiving Visicoil markers), marker migration was observed before treatment. In patients with stable markers, both types were clearly visible in planar kilovolt imaging however, in EPIs the markers could be detected only in selected beam directions in which bony interference was minimal. Diagnostic computed tomography scanning was able to demonstrate the markers with clarity, but significant starring artifacts were observed in CBCT. This was particularly problematic in patients with some lateral component of tumor motion during breathing. The potential for fiducial migration must be considered and investigated if bronchoscopic implantation of fiducial markers is performed. The choice of marker is a compromise between trying to minimize CBCT artifacts while enabling visualization in EPI imaging, which is an ideal tool to verify gated radiotherapy delivery.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 04-2020
Publisher: Elsevier BV
Date: 07-2000
Publisher: Elsevier BV
Date: 04-2014
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576171
Publisher: Elsevier BV
Date: 04-2013
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576170
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576172
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.CLON.2014.12.001
Abstract: The delivery of radical radiotherapy in lung cancer is complicated by respiratory-induced tumour motion. The aim of the study was to correlate tumour motion characteristics with tumour and patient factors, particularly the anatomical lobe and pulmonary zone. Lung tumour volumes on four-dimensional computed tomography were delineated by a single observer at maximal expiration and propagated through all 10 phases of the breathing cycle. Movements were tracked in the superior-inferior (SI), anterior-posterior (AP) and medio-lateral (ML) directions by changes in the tumour centroid coordinates. Tumour motion characteristics were correlated with anatomical lobe, pulmonary zone, tumour volume, T-stage, smoking status and spirometry. In 101 consecutive patients, the median magnitude of tumour motion in the SI direction was significantly larger in tumours located in lower lobes compared with upper lobes and middle/lingular lobes (0.70 cm versus 0.09 cm versus 0.26 cm, P < 0.01). No significant difference was found in median tumour motion between lower, upper and middle/lingular lobes in the AP (0.16 cm versus 0.13 cm versus 0.16 cm, P = 0.45) and ML (0.08 cm versus 0.08 cm versus 0.13 cm, P = 0.32) directions, respectively. When assessed by zone, the median tumour displacement in the SI direction was significantly larger in the lower zones (0.81 cm) as compared with the middle zones (0.30 cm) and upper zones (0.11 cm), P < 0.01. No difference was observed in the AP (P = 0.45) and ML (P = 0.73) directions. Tumour volume, T-stage and forced expiratory ratio were not statistically significant predictors of respiratory-induced tumour motion. Respiratory-induced tumour motion in the SI direction was significantly greater in lower lobe and lower pulmonary zone tumours compared with apical tumours. Tumour volume, T-stage and spirometry did not correlate with the magnitude or direction of respiratory-induced tumour motion. During curative radiotherapy in lung cancer, attention should be paid to motion management, especially for lower lobe tumours.
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576174
Publisher: Informa UK Limited
Date: 04-1992
Publisher: MDPI AG
Date: 24-01-2023
DOI: 10.3390/APP13031533
Abstract: Dramatic improvements in radiotherapy equipment have allowed radiation fields to be conformed to tumours for more accurate treatment. Successful delivery often requires imaging at every treatment fraction, a method known as image guided radiation therapy (IGRT). But increased X-ray imaging exposes patients to doses that carry risks of inducing second cancers in normal tissues. Therefore, reductions in high-dose treatment margins achieved with IGRT must be balanced against detriments from greater imaging doses. ICRP Task Group 116 has been set up to prepare guidance on radiological protection aspects of IGRT. Factors affecting the optimization of radiological protection are the modalities used, the frequency of imaging, the image acquisition parameters influencing image quality and radiation dose, and the volume of normal tissue included in the images. The Task Group has undertaken two projects: (1) a snapshot survey of radiotherapy imaging practices across six continents, which has shown that use of kV cone beam CT (CBCT) increases with Human Development Index for the country and (2) a project looking at ways for measuring CBCT doses that could be applied more widely. The results highlight the need for raising awareness of imaging doses, and development of the dose quantities displayed on imaging equipment used in radiotherapy.
Publisher: Informa UK Limited
Date: 10-06-2015
Publisher: Elsevier BV
Date: 2014
DOI: 10.1016/J.MEDDOS.2013.09.003
Abstract: In this study, we analyzed planning organ at risk volume (PRV) for the rectum using a series of cone beam computed tomographies (CBCTs) acquired during the treatment of prostate cancer and evaluated the dosimetric effect of different PRV definitions. Overall, 21 patients with prostate cancer were treated radically with 78Gy in 39 fractions had in total 418 CBCTs, each acquired at the end of the first 5 fractions and then every alternate fraction. The PRV was generated from the Boolean sum volume of the rectum obtained from first 5 fractions (PRV-CBCT-5) and from all CBCTs (PRV-CBCT-All). The PRV margin was compared at the superior, middle, and inferior slices of the contoured rectum to compare PRV-CBCT-5 and PRV-CBCT-All. We also compared the dose received by the planned rectum (Rectum-computed tomography [CT]), PRV-CBCT-5, PRV-CBCT-All, and average rectum (CBCT-AV-dose-volume histogram [DVH]) at critical dose levels. The average measured rectal volume for all 21 patients for Rectum-CT, PRV-CBCT-5, and PRV-CBCT-All was 44.3 ± 15.0, 92.8 ± 40.40, and 121.5 ± 36.7cm(3), respectively. For PRV-CBCT-All, the mean ± standard deviation displacement in the anterior, posterior, right, and left lateral directions in centimeters was 2.1 ± 1.1, 0.9 ± 0.5, 0.9 ± 0.8, and 1.1 ± 0.7 for the superior rectum 0.8 ± 0.5, 1.1 ± 0.5, 1.0 ± 0.5, and 1.0 ± 0.5 for the middle rectum and 0.3 ± 0.3 0.9 ± 0.5 0.4 ± 0.2, and 0.5 ± 0.3 for the inferior rectum, respectively. The first 5 CBCTs did not predict the PRV for in idual patients. Our study shows that the PRV margin is different for superior, middle, and the inferior parts of the rectum, it is wider superiorly and narrower inferiorly. A uniform PRV margin does not represent the actual rectal variations during treatment for all treatment fractions. The large variation in interpatient rectal size implies a potential role for adaptive radiotherapy for prostate cancer.
Publisher: Wiley
Date: 16-09-2013
Abstract: The purpose of this study is to assess the impact of a vacuum immobilisation system on reproducibility of patient set-up, interfraction stability and tumour motion litude. From February 2010 to February 2012 as part of a prospective clinical trial 12 patients with solitary pulmonary metastases had consecutive four-dimensional computed tomography (4DCT) scans performed with and without vacuum immobilisation. The displacement of the tumour centroid position was recorded in each of the 10 phases of the 4DCT reconstruction. A further six patients with seven metastases underwent single fraction stereotactic ablative body radiotherapy (SABR) during this period (a total of 19 targets) and were included in an analysis of positional reproducibility and intrafraction immobilisation. Couch shifts recorded in the medio-lateral (X), cranio-caudal (Y) and ventero-dorsal (Z) planes. For the 19 treatments delivered, the median (0-90% range) shift required immediately pretreatment was 1 mm (0-3) in the X-plane, 2 mm (0-6) in the Y-plane and 4 mm (0-8) in the Z-plane, respectively. The mean (+/- standard deviation) of mid-treatment shifts were 0.3 mm (+/- 0.7), 1.1 mm (+/- 2) and 0.8 mm (+/- 1.5) in the X, Y and Z planes, respectively. Mid-treatment shifts were <2 mm in all directions (P = < 0.001). The length of treatment time correlated to the required shifts in the Z plane (r(2) = 0.377, P = 0.005), but not in the X or Y planes (P = 0.198 and P = 0.653, respectively). In the subset of 12 patients who had two 4DCTs, the median (range) litude of tumour displacements in the X, Y and Z planes when immobilised were 0.9 mm (0.3-2.9), 2.6 mm (0.2-10.6) and 1.6 mm (0.5-5.5), respectively. Immobilisation reduced the volume of tumour displacement during respiration by a median of 52.6% (P = 0.021). Vacuum immobilisation reduces total tumour excursion, facilitates reproducible positioning and provides robust intrafractional immobilisation during SABR treatments for pulmonary metastases.
Publisher: Elsevier BV
Date: 05-2015
DOI: 10.1016/J.RADONC.2015.04.013
Abstract: To assess the utility of functional lung avoidance using IMRT informed by four-dimensional (4D) ventilation erfusion (V/Q) PET/CT. In a prospective clinical trial, patients with non-small cell lung cancer (NSCLC) underwent 4D-V/Q PET/CT scanning before 60Gy of definitive chemoradiation. Both "highly perfused" (HPLung) and "highly ventilated" (HVLung) lung volumes were delineated using a 70th centile SUV threshold, and a "ventilated lung volume" (VLung) was created using a 50th centile SUV threshold. For each patient four IMRT plans were created, optimised to the anatomical lung, HPLung, HVLung and VLung volumes, respectively. Improvements in functional dose volumetrics when optimising to functional volumes were assessed using mean lung dose (MLD), V5, V10, V20, V30, V40, V50 and V60 parameters. The study cohort consisted of 20 patients with 80 IMRT plans. Plans optimised to HPLung resulted in a significant reduction of functional MLD by a mean of 13.0% (1.7Gy), p=0.02. Functional V5, V10 and V20 were improved by 13.2%, 7.3% and 3.8% respectively (p-values<0.04). There was no significant sparing of dose to functional lung when adapting to VLung or HVLung. Plan quality was highly consistent with a mean PTV D95 and D5 ranging from 60.8Gy to 61.0Gy and 63.4Gy to 64.5Gy, respectively, and mean conformity and heterogeneity index ranging from 1.11 to 1.17 and 0.94 to 0.95, respectively. IMRT plans adapted to perfused but not ventilated lung on 4D-V/Q PET/CT allowed for reduced dose to functional lung whilst maintaining consistent plan quality.
Publisher: Wiley
Date: 09-06-2016
Abstract: The RANZCR Faculty of Radiation Oncology Lung Interest Cooperative (FROLIC) surveyed patterns of lung cancer radiation therapy practice for non-small cell (NSCLC) and small cell lung cancer (SCLC) to evaluate current patterns of care and potential for improvement. In October 2014, Radiation Oncologists (ROs) from all 62 departments in Australia and New Zealand were invited to a web-based survey directed at those treating lung cancer. Questions covered current radiation therapy practice as well as quality measures. Fifty-eight per cent of respondents used 4D-CT simulation. For curative treatment, 98% employed 3D-CRT and 34% intensity modulated radiotherapy (IMRT) techniques. Treatment verification was primarily performed using cone-beam CT (86%). In NSCLC, the commonest curative dose-fractionation regime was 60 Gy/30# (96%) and for palliative intent, 30 Gy/10# (76%). Forty-four per cent treated patients with stereotactic ablative body radiotherapy (SABR) and half treated central tumours with this technique. In fit patients with synchronous solitary brain metastases, 80% would give radical treatment. For curative-intent SCLC, 45-50.4 Gy/25-28# (61%) and 45 Gy/30#/1.5 Gy b.d. (48%) were used. Ninety-four per cent discussed lung cancer patients at multidisciplinary meetings. Contours were peer-reviewed by 74% and 50% for conventional fractionation and SABR respectively. A significant proportion of ROs did not have access to 4D-CT. The majority used 3D image verification and consistently prescribed evidence based doses. A significant number did not participate in peer-review of contours. Practice in IMRT and synchronous oligo-metastatic disease is variable and should be an area of future research. Utilising survey findings, FROLIC is developing consensus recommendations to guide practice.
Publisher: Elsevier BV
Date: 03-2010
Publisher: Wiley
Date: 28-09-2009
Publisher: Elsevier BV
Date: 09-2008
DOI: 10.1016/J.MEDDOS.2007.12.002
Abstract: Many different methods of image guidance are available for radiotherapy treatment (IGRT). The aims of the study were (1) to determine the optimal diameter of gold markers for IGRT to the prostate (2) to compare, using the Siemens Primatom, the relative merits of in-room computerized tomography (CT) and electronic portal image (EPI) for locating the marker seeds. Gold markers of differing widths were embedded in 2 phantoms (perspex slabs and anthropomorphic). Images were acquired with an amorphous silicon flat panel detector (Siemens Optivue 500) and with the in-room CT scanner (Siemens Somatom Balance). The EPIs were reviewed independently by 6 operators to determine which diameter marker could be best visualized. The optimal marker technique was determined by comparing the investigators' observed marker co-ordinates with the known locations within the phantom. The visibility of all markers on anterior-posterior EPIs was 100%. On the lateral EPI, of a possible 180 visualizations of 1.2-, 1.0-, and 0.8-mm diameter markers, 176 (97.8%), 151 (83.9%), and 132 (73.3%), respectively, were successful. On EPI, the average deviation of fiducial markers from the known position was less than 0.5 mm in any direction. On CT, the largest deviation (2.17 mm) of markers from the known coordinate position was in the superior-inferior direction, reflecting the 3.0-mm slice thickness used. EPI accurately located internal markers in all dimensions. The availability of "gold standard" CT imagery at the treatment unit does not improve how accurately the position of markers in a phantom can be defined compared with EPI. However, CT imagery does provide important soft tissue information, the benefits of which are being investigated further.
Publisher: Elsevier BV
Date: 10-2019
Publisher: Wiley
Date: 09-1993
DOI: 10.1118/1.597107
Abstract: The measurement of x-ray beam dose profiles in the penumbral region, using silicon diode, ionization chamber, TLD, and film dosimetry, has been investigated for a 6-MV beam defined by independent collimators. Penumbral width (80%-20%) at dmax, as measured by diode, film, and TLD was found to be 3.6, 3.6, and 3.4 mm, respectively. These results reflect the relative sensitive widths of each of the measurement systems (2.5, 2.0, and 1.0 mm, respectively). An empirical forming function was used to relate the penumbral shape measured with a finite-sized detector to that which would be measured with a point detector, the width of the point detector penumbra calculated from the diode penumbra is 3.4 mm, indicating that the TLD rods are a good approximation to a point detector. An alternative method of determining the width of a point detector penumbra is to extrapolate the penumbral widths obtained using two or more detectors of sensitive width. With this method, using Farmer and RK ionization chambers, a point detector penumbra width of 3.1 mm is obtained. An EGS4 Monte Carlo simulation, where a point source was assumed, gave a penumbral width of 2.8 mm. Negligible differences between the penumbra of beams defined by symmetric and asymmetric collimators was observed.
Publisher: Elsevier BV
Date: 03-2012
DOI: 10.1016/J.MEDDOS.2010.12.011
Abstract: Partial-breast irradiation (PBI) aims to limit the target volume for radiotherapy in women with early breast cancer after partial mastectomy to the region at highest risk of local recurrence, the tumor bed. Multileaf collimators are used to achieve conformal radiation beam portals required for PBI. Narrower leaf widths are generally assumed to allow more conformal shaping of beam portals around irregularly shaped target volumes. The aim was to compare 5-mm and 10-mm leaf widths for patients previously treated using PBI and assess subsequent planning target volume (PTV) coverage and organ at risk (OAR) doses for 16 patients. Several plans (5-mm leaf width or 10-mm leaf width) were generated for each patient using the original treated plan as the basis for attempts at further optimization. Alternating between different leaf widths found no significant difference in terms of overall PTV coverage and OAR doses between treatment plans. Optimization of the original treated plan allowed a small decrease in ipsilateral breast dose, which was offset by a lower PTV minimum. No significant dosimetric difference was found to support an advantage of 5-mm over 10-mm leaf width in this setting.
Publisher: BMJ
Date: 12-2020
DOI: 10.1136/BMJOPEN-2020-042465
Abstract: In the curative-intent treatment of locally advanced lung cancer, significant morbidity and mortality can result from thoracic radiation therapy. Symptomatic radiation pneumonitis occurs in one in three patients and can lead to radiation-induced fibrosis. Local failure occurs in one in three patients due to the lungs being a dose-limiting organ, conventionally restricting tumour doses to around 60 Gy. Functional lung imaging using positron emission tomography (PET)/CT provides a geographic map of regional lung function and preclinical studies suggest this enables personalised lung radiotherapy. This map of lung function can be integrated into Volumetric Modulated Arc Therapy (VMAT) radiotherapy planning systems, enabling conformal avoidance of highly functioning regions of lung, thereby facilitating increased doses to tumour while reducing normal tissue doses. This prospective interventional study will investigate the use of ventilation and perfusion PET/CT to identify highly functioning lung volumes and avoidance of these using VMAT planning. This single-arm trial will be conducted across two large public teaching hospitals in Australia. Twenty patients with stage III non-small cell lung cancer will be recruited. All patients enrolled will receive dose-escalated (69 Gy) functional avoidance radiation therapy. The primary endpoint is feasibility with this achieved if ≥15 out of 20 patients meet pre-defined feasibility criteria. Patients will be followed for 12 months post-treatment with serial imaging, biomarkers, toxicity assessment and quality of life assessment. Using advanced techniques such as VMAT functionally adapted radiation therapy may enable safe moderate dose escalation with an aim of improving local control and concurrently decreasing treatment related toxicity. If this technique is proven feasible, it will inform the design of a prospective randomised trial to assess the clinical benefits of functional lung avoidance radiation therapy. This study was approved by the Peter MacCallum Human Research Ethics Committee. All participants will provide written informed consent. Results will be disseminated via publications. NCT03569072 Pre-results
Publisher: IOP Publishing
Date: 22-01-2001
DOI: 10.1088/0031-9155/46/2/312
Abstract: In polymer gel dosimetry using magnetic resonance imaging, the uncertainty in absorbed dose is dependent on the experimental determination of T2. The concept of dose resolution (Dpdelta) of polymer gel dosimeters is developed and applied to the uncertainty in dose related to the uncertainty in T2 from a range of T4 encountered in polymer gel dosimetry. Dpdelta is defined as the minimal separation between two absorbed doses such that they may be distinguished with a given level of confidence, p. The minimum detectable dose (MDD) is Dpdelta as the dose approaches zero. Dpdelta and the minimum detectable dose both give a quantifiable indication of the likely practical limitations and usefulness of the dosimeter. Dpdelta of a polyacrylamide polymer gel dosimeter is presented for customized 32-echo and standard multiple-spin-echo sequences on a clinical MRI scanner. In evaluating uncertainties in T2, a parameter of particular significance in the pulse sequence is the echo spacing (ES). For optimal results, ES should be selected to minimize Dpdelta over a range of doses of interest in polymer gel dosimetry.
Publisher: Medknow
Date: 2017
Publisher: CRC Press
Date: 08-03-2021
Publisher: Springer Science and Business Media LLC
Date: 13-08-2012
Publisher: Informa UK Limited
Date: 04-2018
DOI: 10.1111/AP.12325
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.EJMP.2016.06.001
Abstract: Our study aims to assess and track work load, working conditions and professional recognition of radiation oncology medical physicists (ROMPs) in the Asia Pacific Region over time. A structured questionnaire was mailed in 2008, 2011 and 2014 to senior medical physicists representing 23 countries. The questionnaire covers 7 themes: education and training including certification staffing typical tasks professional organisations resources research and teaching job satisfaction. Across all surveys the response rate was >85% with the replies representing practice affecting more than half of the world's population. The expectation of ROMP qualifications (MSc and between 1 and 3years of clinical experience) has not changed much over the years. However, compared to 2008, the number of medical physicists in many countries has doubled. Formal professional certification is only available in a small number of countries. The number of experienced ROMPs is small in particular in low and middle income countries. The increase in staff numbers from 2008 to 2014 is matched by a similar increase in the number of treatment units which is accompanied by an increase in treatment complexity. Many ROMPs are required to work overtime and not many find time for research. Resource availability has only improved marginally and ROMPs still feel generally overworked, but professional recognition, while varying widely, appears to be improving slowly. While number of physicists and complexity of treatment techniques and technologies have increased significantly, ROMP practice remains essentially unchanged over the last 6years in the Asia Pacific Region.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2007
Publisher: Elsevier BV
Date: 08-2009
Publisher: Springer Science and Business Media LLC
Date: 02-10-2014
Publisher: Elsevier BV
Date: 09-1991
Publisher: Wiley
Date: 21-06-2023
Abstract: Total body irradiation (TBI) practices vary considerably amongst centres, and the risk of treatment related toxicities remains unclear. We report lung doses for 142 TBI patients who underwent either standing TBI with lung shield blocks or lying TBI without blocks. Lung doses were calculated for 142 TBI patients treated between June 2016 and June 2021. Patients were planned using Eclipse (Varian Medical Systems) using AAA_15.6.06 for photon dose calculations and EMC_15.6.06 for electron chest wall boost fields. Mean and maximum lung doses were calculated. Thirty‐seven patients (26.2%) were treated standing using lung shielding blocks with 104 (73.8%) treated lying down. Lowest relative mean lung doses were achieved using lung shielding blocks in standing TBI, reducing the mean lung doses to 75.2% of prescription (9.9 Gy), ±4.1% (range 68.6–84.1%) for a prescribed dose of 13.2 Gy in 11 fractions, including contributions from electron chest wall boost fields, compared to 12 Gy in 6 fraction lying TBI receiving 101.6% mean lung dose (12.2 Gy) ±2.4% (range 95.2–109.5%) ( P ≪ 0.05). Patients treated lying down with 2 Gy single fraction received the highest relative mean lung dose on average, with 108.4% (2.2 Gy) ±2.6% of prescription (range 103.2–114.4%). Lung doses have been reported for 142 TBI patients using the lying and standing techniques described herein. Lung shielding blocks significantly reduced mean lung doses despite the addition of electron boost fields to the chest wall.
Publisher: Wiley
Date: 27-04-2016
Abstract: The development of technology such as intensity-modulated radiotherapy (IMRT), volumetric arc therapy (VMAT) and stereotactic ablative body radiotherapy (SABR) has resulted in highly conformal radiotherapy treatments. While such technology has allowed for improved dose delivery, it has also meant that improved accuracy in the treatment room is required. Image-guided radiotherapy (IGRT), the use of imaging prior to or during treatment delivery, has been shown to improve the accuracy of treatment delivery and in some circumstances, clinical outcomes. Allied with the adoption of highly conformal treatments, there is a need for stringent quality assurance processes in a multidisciplinary environment. In 2015, the Royal Australian and New Zealand College of Radiologist (RANZCR) updated its position paper on IGRT. The draft document was distributed through the membership of the Faculty of Radiation Oncology (FRO) for review and the final version was endorsed by the board of FRO. This article describes issues that radiotherapy departments throughout Australia and New Zealand should consider. It outlines the role of IGRT and reviews current clinical evidence supporting the benefit of IGRT in genitourinary, head and neck, and lung cancers. It also highlights important international publications which provide guidance on implementation and quality assurances for IGRT. A set of key recommendations are provided to guide safe and effective IGRT implementation and practice in the Australian and New Zealander context.
Publisher: Wiley
Date: 04-2008
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.IJROBP.2010.10.063
Abstract: A real-time dose verification method using a recently designed metal oxide semiconductor field effect transistor (MOSFET) dosimetry system was evaluated for quality assurance (QA) of intensity-modulated radiation therapy (IMRT). Following the investigation of key parameters that might affect the accuracy of MOSFET measurements (i.e., source surface distance [SSD], field size, beam incident angles and radiation energy spectrum), the feasibility of this detector in IMRT dose verification was demonstrated by comparison with ion chamber measurements taken in an IMRT QA phantom. Real-time in vivo measurements were also performed with the MOSFET system during serial tomotherapy treatments administered to 8 head and neck cancer patients. MOSFET sensitivity did not change with SSD. For field sizes smaller than 20 × 20 cm(2), MOFET sensitivity varied within 1.0%. The detector angular response was isotropic within 2% over 360°, and the observed sensitivity variation due to changes in the energy spectrum was negligible in 6-MV photons. MOSFET system measurements and ion chamber measurements agreed at all points in IMRT phantom plan verification, within 5%. The mean difference between 48 IMRT MOSFET-measured doses and calculated values in 8 patients was 3.33% and ranged from -2.20% to 7.89%. More than 90% of the total measurements had deviations of less than 5% from the planned doses. The MOSFET dosimetry system has been proven to be an effective tool in evaluating the actual dose within in idual patients during IMRT treatment.
Publisher: Cambridge University Press (CUP)
Date: 12-2009
DOI: 10.1017/S1460396909990045
Abstract: Accurate patient positioning is vitally important in intensity modulated radiation therapy (IMRT) for head and neck (H& N) cancer. The introduction of kilovoltage (kV) on-board imaging (OBI) at our centre was anticipated to improve the accuracy and efficiency of H& N IMRT patient position verification over traditional megavoltage (MV) electronic portal imaging (EPI). This study compares these imaging systems with a phantom accuracy study and retrospective analysis of imaging workload in H& N IMRT at our centre. Six therapists performed online evaluation of phantom images, and residual positional errors for each system were recorded. The largest residual error was 1 mm for OBI and 3 mm for EPI. The estimated improvement in residual error in OBI over EPI was 0.57 mm (95% confidence interval 0.33–0.81 mm), suggesting treatment staff would be better able to detect set-up deviations with OBI. Electronic treatment records of 20 H& N IMRT patients (10 verified daily with MV EPI and 10 with kV OBI) were analysed. Mean imaging session duration was 9.51 min for EPI and 9.76 min for OBI. Analysis found no evidence of an effect on duration due to the imaging system used for this subset of patients ( p = 0.664).
Publisher: Elsevier BV
Date: 03-1997
DOI: 10.1016/S0167-8140(97)01906-3
Abstract: In many radiotherapy centres where planning for external beam treatments is performed by radiation therapists, the treatment sheet and its calculations are independently checked by staff from a different educational background, typically a radiotherapy physicist. The benefits of this practice were evaluated in a radiotherapy department with two linear accelerators, one combined superficial-orthovoltage unit and one telecaesium unit. Within the 19 months of the investigation period, 2328 checks were performed on the treatment sheets of 1579 patients. In six cases, errors in excess of 5% were detected, which if uncorrected, could potentially have affected local tumour control or caused normal tissue complications. It was found that an independent check of treatment sheets assists in keeping these errors as low as can be achievable in clinical practice, and suggests that treatment sheet checking and in vivo dosimetry play a complementary role in this aim. Independent treatment sheet checking is an important quality assurance (QA) activity, with additional advantages such as improved communication in the department, education of staff and in vivo dosimetry targeting. Therefore the advantages of the procedure seem to outweigh the additional workload of approximately 0.3 full-time staff per 1000 patients per year.
Publisher: Medknow
Date: 2006
Publisher: Wiley
Date: 04-2009
DOI: 10.1111/J.1754-9485.2009.02066.X
Abstract: We investigated if an adaptive radiotherapy approach based on cone beam CT (CBCT) acquired during radical treatment was feasible and resulted in improved dosimetric outcomes for bladder cancer patients compared to conventional planning and treatment protocol. A secondary aim was to compare a conventional plan with a theoretical online process where positioning is based on soft tissue position on a daily basis and treatment plan choice is based on bladder size. A conventional treatment plan was derived from a planning CT scan in the radical radiotherapy of five patients with muscle invasive bladder cancer. In this offline adaptive protocol using CBCT, the patients had 10 CBCT: daily CBCT for the first five fractions and then CBCT scan on a weekly basis. The first five daily CBCT in each patient were used to create a single adaptive plan for treatment from fraction eight onwards. A different process using the planning CT and the first five daily CBCT was used to create small, average and large bladder volumes, giving rise to small, average and large adaptive bladder treatment plans, respectively. In a retrospective analysis using the CBCT scans, we compared the clinical target volume (CTV) coverage using three protocols: (i) conventional (ii) offline adaptive and (iii) online adaptive with choice of 'plan of the day'. Daily CBCT prolonged treatment time by an average of 7 min. Two of the five patients demonstrated such variation in CTV that an offline adaptive plan was used for treatment after the first five CBCT. Comparing the offline adaptive plan with the conventional plan, the CTV coverage improved from a minimum of 60.1 to 94.7% in subsequent weekly CBCT. Using the CBCT data, modelling an online adaptive protocol showed that coverage of the CTV by the 95% prescribed dose line by small, medium and large adaptive plans were 34.9, 67.4 and 90.7% of occasions, respectively. More normal tissue was irradiated using a conventional CTV to planning target volume margin (1.5 cm) compared to an online adaptive process (0.5 cm). An offline adaptive strategy improves dose coverage in certain patients to the CTV and results in a higher conformity index compared to conventional planning. Further research in online adaptive radiation therapy for bladder cancer is indicated.
Publisher: Wiley
Date: 08-2008
DOI: 10.1111/J.1440-1673.2008.01975.X
Abstract: The risk of breast cancer following radiotherapy for Hodgkin's lymphoma appears to be dose related. In this study we compared breast dose in an anthropomorphic phantom for conventional 'mantle' upper mediastinal/bilateral neck (minimantle) and unilateral neck fields, and evaluated the accuracy of computer planned dose estimates for out-of-field doses. For each field, computer-planned breast dose (CPD) estimates were compared with thermoluminescence dosimetry measurements in five locations within 'breast tissue'. CPD were also compared with ion chamber measurements in a slab phantom. Measured dose and CPD were within 20% of each other up to approximately 10 cm from the field edge. Beyond 10 cm, the CPD underestimated dose by a factor of 2 or more. The mini-mantle reduced the breast dose by a factor of approximately 10 compared with the mantle treatment. Treating the neck field lowered the breast dose by a further 50% or more. Modern involved-field radiotherapy for lymphoma substantially reduces breast dose compared with mantle fields. Computer dosimetery underestimated dose at larger distances from the field. This needs to be considered if computer dosimetery is used to estimate breast dose and, by extrapolation, breast cancer risk.
Publisher: Wiley
Date: 13-01-2021
DOI: 10.1002/ACM2.13160
Publisher: Elsevier BV
Date: 07-2015
DOI: 10.1016/J.EJMP.2015.04.002
Abstract: This work presents the Australian Clinical Dosimetry Service's (ACDS) findings of an investigation of systematic discrepancies between treatment planning system (TPS) calculated and measured audit doses. Specifically, a comparison between the Anisotropic Analytic Algorithm (AAA) and other common dose-calculation algorithms in regions downstream (≥2cm) from low-density material in anthropomorphic and slab phantom geometries is presented. Two measurement setups involving rectilinear slab-phantoms (ACDS Level II audit) and anthropomorphic geometries (ACDS Level III audit) were used in conjunction with ion chamber (planar 2D array and Farmer-type) measurements. Measured doses were compared to calculated doses for a variety of cases, with and without the presence of inhomogeneities and beam-modifiers in 71 audits. Results demonstrate a systematic AAA underdose with an average discrepancy of 2.9 ± 1.2% when the AAA algorithm is implemented in regions distal from lung-tissue interfaces, when lateral beams are used with anthropomorphic phantoms. This systemic discrepancy was found for all Level III audits of facilities using the AAA algorithm. This discrepancy is not seen when identical measurements are compared for other common dose-calculation algorithms (average discrepancy -0.4 ± 1.7%), including the Acuros XB algorithm also available with the Eclipse TPS. For slab phantom geometries (Level II audits), with similar measurement points downstream from inhomogeneities this discrepancy is also not seen.
Publisher: Frontiers Media SA
Date: 12-04-2022
Abstract: Biology-guided radiotherapy (BgRT) uses real-time functional imaging to guide radiation therapy treatment. Positron emission tomography (PET) tracers targeting prostate-specific membrane antigen (PSMA) are superior for prostate cancer detection than conventional imaging. This study aims at describing nodal and distant metastasis distribution from prostate cancer and at determining the proportion of metastatic lesions suitable for BgRT. A single-institution patient subset from the ProPSMA trial (ID ACTRN12617000005358) was analysed. Gross tumour volumes (GTV) were delineated on the CT component of a PSMA PET/CT scan. To determine the suitability of BgRT tracking zones, the normalized SUV (nSUV) was calculated as the ratio of SUVmax inside the GTV to the SUVmean of adjacent three-dimensional shells of thickness 5 mm/10 mm/20 mm as a measure of signal to background contrast. Targets were suitable for BgRT if (1) nSUV was larger than an nSUV threshold and (2) non-tumour tissue inside adjacent shell was free of PET-avid uptake. Of this cohort of 84 patients, 24 had at least one pelvic node or metastatic site disease, 1 to 13 lesions per patient, with a total of 98 lesions (60 pelvic nodes/38 extra-pelvic nodal diseases and haematogenous metastases). Target volumes ranged from 0.08 to 9.6 cm 3 while SUVmax ranged from 2.1 to 55.0. nSUV ranged from 1.9 to 15.7/2.4 to 25.7/2.5 to 34.5 for the 5 mm/10 mm/20 mm shell expansion. Furthermore, 74%/68%/34% of the lesions had nSUV ≥ 3 and were free of PSMA PET uptake inside the GTV outer shell margin expansion of 5 mm/10 mm/20 mm. Adjacent avid organs were another lesion, bladder, bowel, ureter, prostate, and liver. The majority of PSMA PET/CT-defined radiotherapy targets would be suitable for BgRT by using a 10-mm tracking zone in prostate cancer. A subset of lesions had adjacent non-tumour uptake, mainly due to the proximity of ureter or bladder, and may require exclusion from emission tracking during BgRT.
Publisher: Elsevier BV
Date: 09-2006
Publisher: Springer Science and Business Media LLC
Date: 12-2006
DOI: 10.1007/BF03178394
Publisher: Elsevier BV
Date: 11-2023
Publisher: Springer Science and Business Media LLC
Date: 12-2006
DOI: 10.1007/BF03178393
Publisher: Springer Berlin Heidelberg
Date: 1992
Publisher: Medknow
Date: 2008
Publisher: Medknow
Date: 2015
Publisher: Springer Science and Business Media LLC
Date: 04-04-2019
DOI: 10.1007/S13246-019-00751-8
Abstract: The implementation of stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) has greatly increased due to its convenience and advantages from perspectives ranging from radiobiology to radio physics. Because SBRT/SRS delivers high doses in few fractions, precise dose delivery to target volumes and sufficient sparing of adjacent organs at risk (OARs) are required. Achieving these conflicting objectives is challenging for all patients receiving SBRT/SRS and may be particularly challenging when SBRT/SRS is adopted for treating patients with cardiac implantable electronic devices (CIEDs) because cumulative doses in CIEDs must be limited. Published research considering the different aspects of stereotactic treatment in patients with CIEDs was reviewed to summarise their findings in the following sections: (I) conventional linear accelerator (linac)-based SBRT and SRS (II) CyberKnife, Gamma-Knife, VERO and helical tomotherapy SBRT and SRS and (III) proton therapy. A total of 65 patients who had CIEDs and underwent SRS, SBRT, or SABR treatments were identified in the reviewed studies. The functionality of the CIEDs was assessed for 58 patients. Of those, CIED malfunctions (such as data loss, mode change, and inappropriate shock) were reported in four patients (6.89%). This review highlights the available sparse information in the literature by posing questions for future research.
Publisher: Springer Science and Business Media LLC
Date: 23-07-2012
Publisher: Wiley
Date: 10-2014
DOI: 10.1118/1.4896097
Abstract: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%-8%. The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to facilities modifying clinical practice and changing planning protocols.
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.IJROBP.2017.07.035
Abstract: To investigate the associations between interim tumor responses on Patients with FDG-PET/computed tomography stage I-III NSCLC were prescribed concurrent chemotherapy and radiation therapy (60 Gy in 30 fractions). Scans were acquired at baseline (FDG-PET/computed tomography [FDG Between 2009 and 2013, 60 patients were recruited. Thirty-seven (62%) were male, and the median age was 66 years (range, 31-86 years). Two-year OS and PFS were 0.51 and 0.26, respectively. Unexpectedly, SD on FLT Stable uptake of
Publisher: Elsevier BV
Date: 07-2021
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.IJROBP.2013.07.036
Abstract: Partial breast irradiation (PBI) after lumpectomy may be an option for selected patients with early breast cancer. A feasibility study of accelerated PBI delivered using external beam 3-dimensional conformal radiation therapy (RT) was undertaken at 8 Australasian centers. The present study evaluated the impact of patient, tumor, and RT technique-related factors on the quality of RT plans as determined by the dose-volume parameters of organs at risk. Forty-eight patients were enrolled in the study. All RT plans were centrally reviewed using predefined dosimetric criteria before commencement and after completion of protocol therapy. The RT plans of 47 patients met the dose-volume constraints, and all 47 patients received PBI to a prescribed dose of 38.5 Gy in 10 fractions. The RT plan quality was determined by volumes of the ipsilateral whole breast, lung, and heart that received 50% and 95% 30% and 5% of the prescribed dose, respectively. Patient, tumor, and RT technique-related factors were investigated for association with the parameters of RT plan quality. The ratio of the planning target volume to the ipsilateral whole-breast volume was significantly associated with the ipsilateral breast doses on multiple variable analyses. The distance of the postlumpectomy surgical cavity from the heart and lung were predictive for heart and lung doses, respectively. A distance between surgical cavity and heart of >4 cm typically resulted in <1% of the heart volume receiving 5 Gy or less. It was more difficult to meet the heart dose constraint for left-sided and medially located tumors. Partial breast irradiation using 3-dimensional conformal RT was feasible within the study constraints. The ratio of planning target volume to ipsilateral whole-breast volume and the distance of surgical cavity from the heart were significant predictors of the quality of treatment plan for external beam PBI.
Publisher: Springer Science and Business Media LLC
Date: 21-09-2020
DOI: 10.1038/S41467-020-18151-Y
Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA s les, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological ergences between two reproducible somatic variant detection efforts.
Publisher: Routledge
Date: 17-04-2019
Publisher: IOP Publishing
Date: 22-08-2008
DOI: 10.1088/0031-9155/53/18/012
Abstract: Ion chamber dosimetry requires a high degree of precision, at all steps within the dosimetric process, in order to ensure accurate dose measurements. This work presents a novel technique for ion chamber volume determination and quality assurance, using micro-computed tomography (micro-CT). Four nominally identical Exradin A1SL chambers (0.056 cm(3)) (Standard Imaging, WI, USA) were imaged using a micro-CT system (GE Locus, GE Healthcare, London, Ontario) and irradiated in a 6 MV x-ray reference field. Air volumes were calculated from the CT datasets using 3D analysis software (Microview 2.1.1, General Electric Healthcare, London, Ontario). Differences in the volumes of each chamber determined using micro-CT images agreed with differences in the ionization response within 1% for each chamber. Calibration coefficients were then compared through cross-calibration with a calibrated ion chamber and from the CT-measured volumes. The average ratio of these values was found to be 0.958 +/- 0.009 indicating good correlation. The results demonstrate the promise of using micro-CT imaging for the absolute volumetric characterization of ion chambers. The images have the potential to be an important clinical tool for quality assurance of ion chamber construction and integrity after routine clinical usage.
Publisher: Wiley
Date: 05-10-2023
DOI: 10.1002/MP.16761
Publisher: IOP Publishing
Date: 26-06-2013
Publisher: Wiley
Date: 12-09-2012
DOI: 10.1111/J.1754-9485.2012.02436.X
Abstract: Plan-of-the-day adaptive radiotherapy (ART) that has not been optimally designed may result in inefficient plan sizes. This can lead to unused plans, which may potentially reduce overall conformality. We compared two methods of in idualising ART plan sizes for muscle-invasive bladder cancer to determine which provides a more balanced distribution of plan selections. Twenty-seven previously treated patients had small, medium and large ART plans generated from CTV contours on the simulation CT and initial cone beam CTs (CBCT). In the original clinical method, the smallest plan was based on the smallest CTV, while the experimental method used the Boolean summation of the two smallest CTVs. The large plan was identical in both methods. The medium plans were created midway between small and large CTVs. Credentialed treatment staff performed plan selection clinically for the original plans and retrospectively for the experimental plans. A total of 646 CBCTs from 26 patients were included. The small, medium and large adaptive CTVs, and the conventional CTV, were used 29.7%, 45.4%, 22.0% and 2.9% of the time, respectively, compared to the previous 9.8%, 49.2%, 39.5% and 1.5%. The differences were significant between previous and new CTV (small), and CTV (large). The new design method resulted in the three adaptive CTV choices being selected more evenly, however, a reduction in a surrogate for normal tissue irradiation was not observed.
Publisher: Medknow
Date: 2011
Publisher: American Astronomical Society
Date: 20-04-2007
DOI: 10.1086/511329
Publisher: Wiley
Date: 03-1998
DOI: 10.1118/1.598213
Publisher: IOP Publishing
Date: 22-09-1999
Publisher: Elsevier BV
Date: 05-2011
Publisher: Informa UK Limited
Date: 27-02-2021
Publisher: Elsevier BV
Date: 08-2000
Publisher: Cambridge University Press (CUP)
Date: 14-05-2021
Publisher: Elsevier BV
Date: 12-2012
DOI: 10.1016/J.CLON.2012.06.012
Abstract: To determine the clinical target volume (CTV) to planning target volume (PTV) margins required for bladder coverage when using skin or bony or soft tissue matching on a daily basis. Twenty-seven patients with T2-T4 transitional cell carcinoma of the bladder were treated with daily online adaptive image-guided radiotherapy using cone beam computed tomography. All daily CTVs were contoured by a single observer. A retrospective comparison of coverage of the bladder CTV using skin, bone and soft tissue matching was conducted. With the skin set-up, bladder CTV coverage with a margin of 0.5, 1.0, 1.5, 2.0 and 2.5 cm was 0, 19, 56, 93 and 96%, respectively. For the daily set-up based on bone, the respective coverage was 0, 41, 63, 89 and 96%. For soft tissue set-up based on the geometric centre of the bladder, coverage was 52, 89, 96, 100 and 100%, respectively. Based on coverage of the CTV, the required CTV to PTV margins are smaller for the daily online soft tissue set-up compared with skin or bone.
Publisher: Wiley
Date: 12-2019
DOI: 10.1002/JMRS.365
Publisher: Elsevier BV
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 08-01-2014
DOI: 10.1007/S13246-013-0239-4
Abstract: Hypofractionated image guided radiotherapy of extracranial targets has become increasingly popular as a treatment modality for inoperable patients with one or more small lesions, often referred to as stereotactic ablative body radiotherapy (SABR). This report details the results of the physical quality assurance (QA) program used for the first 33 lung cancer SABR radiotherapy 3D conformal treatment plans in our centre. SABR involves one or few fractions of high radiation dose delivered in many small fields or arcs with tight margins to mobile targets often delivered through heterogeneous media with non-coplanar beams. We have conducted patient-specific QA similar to the more common intensity modulated radiotherapy QA with particular reference to motion management. In idual patient QA was performed in a Perspex phantom using point dose verification with an ionisation chamber and radiochromic film for verification of the dose distribution both with static and moving detectors to verify motion management strategies. While in idual beams could vary by up to 7%, the total dose in the target was found to be within ±2% of the prescribed dose for all 33 plans. Film measurements showed qualitative and quantitative agreement between planned and measured isodose line shapes and dimensions. The QA process highlighted the need to account for couch transmission and demonstrated that the ITV construction was appropriate for the treatment technique used. QA is essential for complex radiotherapy deliveries such as SABR. We found in idual patient QA helpful in setting up the technique and understanding potential weaknesses in SABR workflow, thus providing confidence in SABR delivery.
Publisher: IOP Publishing
Date: 10-1996
DOI: 10.1088/0031-9155/41/10/015
Abstract: Effective source-surface distances (ESSD) are assessed at the depth of maximum dose in electron beams. This study investigated the variation of the ESSD with the depth of measurement. The dose was measured with the range of SSDs 100-130 cm, using a water-equivalent parallel-plate ion chamber in solid water. ESSDs were calculated for electron beams in the energy range 4-20 MeV and were found to vary with depth. The surface ESSD varied from 68 cm for 4 MeV to 82 cm for 16 MeV, but increased with depth to a maximum value, which was found at approximately half the practical range (Rp), at 0.3Rp for 4 MeV and at 0.6Rp for 20 MeV. Beyond this depth the ESSD decreased towards the end of the practical range. Without an electron applicator, the ESSD was higher at the surface. For smaller field sizes, the depth of the maximum ESSD increased towards Rp, and ESSD values increased. The 20 MeV beam in the 6 cm x 6 cm2 field showed a difference of 31 cm between the surface ESSD and the maximum ESSD. The ESSD calculated at the maximum dose depth (Dmax) may be used with reasonable accuracy for calculation of the dose in the therapeutic range, except at larger SSDs or when high-energy beams are used in small fields Depth-dose distributions under these conditions should be compared with measured results.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.CLON.2011.04.004
Abstract: The target volume for breast radiotherapy after conservative surgery for breast cancer may be affected by breathing motion. We investigated differences between conventional and four-dimensional computed tomography-based treatment planning and whether gating could improve dose volume parameters. Ten patients with left-sided breast cancer and surgical clips at the excision site had conventional treatment planning computed tomography and four-dimensional computed tomography. Treatment plans using two tangential beams (6 MV X-rays) were optimised for target coverage and homogeneity using a field in field technique for the three-dimensional scan. This plan was applied directly to four-dimensional datasets representing in idual phases of the breathing cycle and combinations thereof (average and maximum intensity projection). Optimised plans were generated for the maximum inhalation scan to study what could potentially be achieved in gated radiotherapy. Four-dimensional computed tomography with effective doses of around 10 mSv proved to be adequate for treatment planning in all patients. The average motion of the surgical clips was 3.7 mm (range 1.7-6.5mm), which was similar to the movement of the chest wall. With a margin of 7 mm for the whole breast to planning target volume, conventional three-dimensional computed tomography-based planning was found to adequately cover the target as seen on four-dimensional computed tomography without significant differences in normal tissue sparing. Improved sparing of the heart and lung could only be achieved by reducing the posterior margin of the target volume, which may be justified if four-dimensional computed tomography is used to determine the target and its motion. No significant benefit has been shown for the use of four-dimensional computed tomography-based planning if motion management is not implemented concurrently with a reduced posterior margin between clinical and planning target volumes.
Publisher: Wiley
Date: 27-02-2017
DOI: 10.1002/ACM2.12058
Abstract: High energy radiotherapy can produce contaminant neutrons through the photonuclear effect. Patients receiving external beam radiation therapy to the pelvis may have high‐density hip prostheses. Metallic materials such as those in hip prostheses, often have high cross‐sections for neutron interaction. In this study, Thackray ( UK ) prosthetic hips have been irradiated by 18 MV radiotherapy beams to evaluate the additional dose to patients from the activation products. Hips were irradiated in‐ and out‐of field at various distances from the beam isocenter to assess activation caused in‐field by photo‐activation, and neutron activation which occurs both in and out‐of‐field. NaI(Tl) scintillator detectors were used to measure the subsequent gamma‐ray emissions and their half‐lives. High sensitivity Mg, Cu, P doped LiF thermoluminescence dosimeter chips ( TLD ‐100H) were used to measure the subsequent dose at the surface of a prosthesis over the 12 h following an in‐field irradiation of 10,000 MU to a hip prosthesis located at the beam isocenter in a water phantom. 53 Fe, 56 Mn, and 52 V were identified within the hip following irradiation by radiotherapy beams. The dose measured at the surface of a prosthesis following irradiation in a water phantom was 0.20 mG y over 12 h. The dose at the surface of prostheses irradiated to 200 MU was below the limit of detection (0.05 mG y) of the TLD 100H. Prosthetic hips are activated by incident photons and neutrons in high energy radiotherapy, however, the dose resulting from activation is very small.
Publisher: Springer Science and Business Media LLC
Date: 09-2012
DOI: 10.1007/S13246-012-0138-0
Abstract: Accuracy of dwell position and reproducibility of dwell time are critical in high dose rate (HDR) brachytherapy. A phantom was designed to verify dwell position and dwell time reproducibility for an Ir-192 HDR stepping source using Computed Radiography (CR). The central part of the phantom, incorporating thin alternating strips of lead and acrylic, was used to measure dwell positions. The outer part of the phantom features recesses containing different absorber materials (lead, aluminium, acrylic and polystyrene foam), and was used for determining reproducibility of dwell times. Dwell position errors of < 1 mm were easily detectable using the phantom. The effect of bending a transfer tube was studied with this phantom and no change of clinical significance was observed when varying the curvature of the transfer tube in typical clinical scenarios. Changes of dwell time as low as 0.1 s, the minimum dwell time of the treatment unit, could be detected by choosing dwell times over the four materials that produce identical exposure at the CR detector.
Publisher: Wiley
Date: 05-1993
DOI: 10.1118/1.597019
Abstract: Surface dose measurements in therapeutic x-ray beams are of importance in determining the dose to the skin of patients undergoing radiotherapy. Measurements were performed in the 6-MV beam of a medical linear accelerator with LiF thermoluminescence dosimeters (TLD) using a solid water phantom. TLD chips (surface area 3.17 x 3.17 cm2) of three different thicknesses (0.230, 0.099, and 0.038 g/cm2) were used to extrapolate dose readings to an infinitesimally thin layer of LiF. This surface dose was measured for field sizes ranging from 1 x 1 cm2 to 40 x 40 cm2. The surface dose relative to maximum dose was found to be 10.0% for a field size of 5 x 5 cm2, 16.3% for 10 x 10 cm2, and 26.9% for 20 x 20 cm2. Using a 6-mm Perspex block tray in the beam increased the surface dose in these fields to 10.7%, 17.7%, and 34.2% respectively. Due to the small size of the TLD chips, TLD extrapolation is applicable also for intracavity and exit dose determinations. The technique used for in vivo dosimetry could provide clinicians information about the build up of dose up to 1-mm depth in addition to an extrapolated surface dose measurement.
Publisher: Wiley
Date: 29-05-2014
DOI: 10.1118/1.4889315
Publisher: Wiley
Date: 12-09-2011
DOI: 10.1118/1.3626573
Abstract: An anthropomorphic pelvic phantom was designed and constructed to meet specific criteria for multicenter radiotherapy dosimetric intercomparison. Three dimensional external and organ outlines were generated from a computed tomography image set of a male pelvis, forming the basis of design for an anatomically realistic phantom. Clinically relevant points of interest were selected throughout the dataset where point-dose values could be measured with thermoluminescence dosimeters and a small-volume ionization chamber. Following testing, three materials were selected and the phantom was manufactured using modern prototyping techniques into five separate coronal slices. Time lines and resource requirements for the phantom design and manufacture were recorded. The ability of the phantom to mimic the entire treatment chain was tested. The phantom CT images indicated that organ densities and geometries were comparable to those of the original patient. The phantom proved simple to load for dosimetry and rapid to assemble. Due to heat release during manufacture, small air gaps and density heterogeneities were present throughout the phantom. The overall cost for production of the prototype phantom was comparable to other commercial anthropomorphic phantoms. The phantom was shown to be suitable for use as a "patient" to mimic the entire treatment chain for typical external beam radiotherapy for prostate and rectal cancer. The phantom constructed for the present study incorporates all characteristics necessary for accurate Level III intercomparison studies. Following use in an extensive Level III dosimetric comparison over a large time scale and geographic area, the phantom retained mechanical stability and did not show signs of radiation-induced degradation.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Cambridge University Press (CUP)
Date: 21-11-2011
DOI: 10.1017/S1460396911000422
Abstract: Aims: To obtain an estimate of dietary fibre and fluid intake in Australian men undergoing prostate radiotherapy and to establish feasibility and patient compliance with recording normal diet without intervention during the radical course of radiotherapy. Methods: Eleven participants were enrolled and treated with 74–78 Gray (Gy) to the prostate over 8 weeks. Participants were instructed to record a diary of their food and fluid intake and bowel motions for the duration of treatment. Treating radiation therapists were instructed to initial the diet diary daily. Diet diaries were assessed for compliance by analysing the number of days over the treatment period and the number of diary pages submitted. The diet diaries were analysed for nutrient intake of fibre and fluids. Results: A total of 10 of 11 participants submitted a diet record for the full duration of treatment with a median compliance of 100% (range 90.4–100%) of days recorded. The mean (standard deviation) of fibre and fluids recorded in the diets were 21.5 g (5.5) and 2227.1 g (733.1), respectively. Conclusions: It is feasible for patients to record a diet diary over a radical course of prostate radiotherapy. In this study, most patients were highly compliant with submitting a diet record for each day during treatment.
Publisher: Springer Science and Business Media LLC
Date: 14-07-2022
DOI: 10.1007/S13246-022-01160-0
Abstract: Healthcare relies upon the accurate and safe delivery of patient care. This is only achievable when systems are developed to ensure high quality, robust outcomes, for instance quality management systems. The concept of quality management can take on a different meaning depending on the context in which it is found. To add complication, the amount of education required for quality management will vary depending on one's exposure to the implementation of quality systems. In part to address these issues, the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) Queensland Branch held a quality management webinar for members and non-members across Australia and New Zealand. The purpose of the webinar was to educate and facilitate discussion regarding the application of quality management principles for the ACPSEM profession. In conjunction, a pre- and post-webinar survey was conducted to gain an insight into existing knowledge and attitudes within the professions governed by the ACPSEM and students undertaking related studies. This paper authored by the webinar speakers reintroduces the quality management principles that were discussed in webinar, exemplifies the importance of quality management skills within the ACPSEM professions and presents the results of the surveys, promoting the need for more educational resources on quality management tools.
Publisher: Wiley
Date: 09-02-2000
DOI: 10.1046/J.1440-1673.2000.00775.X
Abstract: Portal films continue to play an important role in the verification of radiotherapy treatment. There is still some discussion, however, as to what action should be taken after a port film has shown a radiation field deviation from the prescribed volume. It was the aim of the present pilot study to investigate the performance of three decision-making models ('Amsterdam', 'Quebec' and 'Newcastle') and an expert panel basing their decision on intuition rather than formal rules after portal film acquisition in a clinical setting. Portal films were acquired on every day during the first week of treatment for five head and neck and five prostate cancer patients (diagnostic phase). If required, the field position was modified according to our normal practice following the recommendation of the expert panel. In order to analyse the results of the models, however, additional port films were taken in the following 3 treatment weeks with the patient moved as required by the different models (intervention phase). The portal films were taken over 4 consecutive days, positioning the patient according to each of the different models on one day each. None of the models diagnosed a field misplacement in the head and neck patients, while the 'Amsterdam' and 'Quebec' models predicted a move in one prostate patient. The 'Newcastle' model, which is based on Hotelling's T2 statistic, proved to be more sensitive and diagnosed a systematic displacement for three prostate patients. The intervention phase confirmed the diagnosis of the model, even if the three portal films taken with the patient position adjusted as required by the model proved to be insufficient to demonstrate an improvement. The 'Newcastle' model does not rely on assumptions about the random movement of patients and requires five portal films before a decision can be reached. This approach lends itself well to incorporation into electronic portal imaging 'packages', where repeated image acquisitions present no logistical difficulty.
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.RADONC.2006.07.005
Abstract: The purpose of this study was to assess a variety of potential IMRT class solutions as compared to a helical tomotherapy (HT) class solution for localized prostate cancer. Target and critical structures were contoured on 10 prostate cancer patient CT datasets. HT treatment plans were compared to four different IMRT approaches by paired t-tests. HT prostate planning generally provided treatment plans with excellent target homogeneity and favorable critical structure sparing when compared to conventional IMRT.
Publisher: Elsevier BV
Date: 2021
Publisher: American Psychological Association (APA)
Date: 11-2021
DOI: 10.1037/PAG0000638
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.CLON.2017.11.010
Abstract: Stereotactic ablative body radiotherapy (SABR) is currently used to treat oligometastases, but the optimum dose/fractionation schedule is unknown. In this study, we evaluated outcomes after single fraction SABR in patients with oligometastatic disease. Single institutional retrospective review of patients treated with single fraction SABR for one to three oligometastases between 2010 and 2015. The primary outcome was freedom from widespread disease defined as distant recurrence not amenable to surgery or SABR or recurrence with four or more metastases. In total, 186 treatments were delivered in 132 patients. The two most common target sites were lung (51%) and bone (40%). The most frequent single fraction prescription dose was 26 Gy (47%). The most common primary malignancy was genitourinary (n = 46 patients). Freedom from widespread disease was 75% at 1 year (95% confidence interval 67-83%) and 52% at 2 years (95% confidence interval 42-63%). Freedom from local progression at 1 year was 90% (95% confidence interval 85-95%) and at 2 years was 84% (95% confidence interval 77-91%). A compression fracture of the lumbar vertebra was the only grade 3+ treatment-related toxicity. Single fraction SABR is associated with a high rate of freedom from widespread disease, favourable local control and low toxicity comparable with historic multi-fraction SABR reports.
Publisher: Wiley
Date: 05-1995
DOI: 10.1118/1.597544
Abstract: In women undergoing cesarean delivery under spinal anesthesia with intrathecal morphine, transversus abdominis plane (TAP) block with bupivacaine hydrochloride (HCl) may not improve postsurgical analgesia. This lack of benefit could be related to the short duration of action of bupivacaine HCl. A retrospective study reported that TAP block with long-acting liposomal bupivacaine (LB) reduced opioid consumption and improved analgesia following cesarean delivery. Therefore, we performed a prospective multicenter, randomized, double-blind trial examining efficacy and safety of TAP block with LB plus bupivacaine HCl versus bupivacaine HCl alone. Women (n = 186) with term pregnancies undergoing elective cesarean delivery under spinal anesthesia were randomized (1:1) to TAP block with LB 266 mg plus bupivacaine HCl 50 mg or bupivacaine HCl 50 mg alone. Efficacy was evaluated in a protocol-compliant analysis (PCA) set that was defined a priori. The primary end point was total postsurgical opioid consumption (oral morphine equivalent dosing [MED]) through 72 hours. Pain intensity was measured using a visual analog scale. Adverse events (AEs) after treatment were recorded through day 14. Total opioid consumption through 72 hours was reduced with LB plus bupivacaine HCl versus bupivacaine HCl alone (least squares mean [LSM] [standard error (SE)] MED, 15.5 mg [6.67 mg] vs 32.0 mg [6.25 mg]). This corresponded to an LSM treatment difference of -16.5 mg (95% confidence interval [CI], -30.8 to -2.2 mg P = .012). The area under the curve of imputed pain intensity scores through 72 hours supported noninferiority of LB plus bupivacaine HCl versus bupivacaine HCl alone (LSM [SE], 147.9 [21.13] vs 178.5 [19.78] LSM treatment difference, -30.6 95% CI, -75.9 to 14.7), with a prespecified noninferiority margin of 36 (P = .002). In an analysis of all treated patients, including those not meeting criteria for inclusion in the PCA, there was no difference in postsurgical opioid consumption between groups. In the LB plus bupivacaine HCl group, 63.6% of patients experienced an AE after treatment versus 56.2% in the bupivacaine HCl-alone group. Serious AEs after treatment were rare (≈3% in both groups). TAP block using LB plus bupivacaine HCl as part of a multimodal analgesia protocol incorporating intrathecal morphine resulted in reduced opioid consumption after cesarean delivery in the PCA set. Results suggest that with correct TAP block placement and adherence to a multimodal postsurgical analgesic regimen, there is an opioid-reducing benefit of adding LB to bupivacaine TAP blocks after cesarean delivery (ClinicalTrials.gov identifier: NCT03176459).
Publisher: American Physical Society (APS)
Date: 10-08-2015
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.PRRO.2012.12.007
Abstract: The thyroid is not routinely considered an organ at risk in supraclavicular (SC) nodal radiation therapy (RT) for breast cancer. We compared the dosimetric impact of the following 2 RT planning techniques on the thyroid: (1) conventional single anterior field to encompass the SC nodal volume defined clinically and (2) 3-dimensional conformal radiation therapy (3DCRT) planning to encompass the computed tomography (CT)-contoured SC nodal volume. The thyroid, SC nodal volumes, and organs at risk were contoured on the planning CT of 20 patients who received 50 Gy in 2-Gy daily fractions to the breast or chest wall, and SC nodes. Comparisons of dosimetric parameters between the techniques were performed: thyroid, mean and maximum dose, V5, V30, and V50 (percentage of thyroid receiving ≥5 Gy, ≥30 Gy, and ≥50 Gy, respectively) SC nodal volume, homogeneity index (HI, percentage volume receiving 95%-107% of prescribed dose) and maximum doses of spinal cord and brachial plexus. Anatomic characteristics that influenced the dose distributions were investigated. The 3DCRT planning technique significantly increased all thyroid dosimetric measures (mean dose 17.2 Gy vs 26.7 Gy maximum dose 48.5 Gy vs 51.9 Gy V5 45.7% vs 64.9% V30 33.7% vs 48% and V50 0.6% vs 26.7% P < .001). It improved HI for the SC nodal volumes (P < .001) but resulted in higher maximum doses to the spinal cord (6.1 Gy vs 30 Gy) and brachial plexus (43.2 Gy vs 51.4 Gy). The thyroid volume and depth of SC nodes did not influence the thyroid dose distribution. The depth of SC nodes impacted on the HI of SC nodal volumes in the conventional technique (P = .004). The 3DCRT planning improved dosimetric coverage of the SC nodal volume but increased thyroid radiation doses. The potential adverse effects of incidental thyroid irradiation should be considered while improving dosimetric coverage in SC nodal irradiation for breast cancer.
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.CLON.2015.01.004
Abstract: To compare outcomes of single-fraction and multi-fraction stereotactic ablative body radiotherapy (SABR) for pulmonary metastases. A retrospective review from two academic institutions of patients with one to three pulmonary metastases staged with (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans. For single-fraction SABR, 26 Gy was prescribed for peripheral targets and 18 Gy for central targets. In the multi-fraction cohort, 48 Gy/4 or 50 Gy/5 was prescribed for peripheral targets and 50 Gy/5 was prescribed for central targets. Three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans were delivered using heterogeneity corrections. Conformity indices at an intermediate dose (R50%) and at a high dose (R100%) were used to assess a relationship with the planning target volume (PTV). Overall survival, local and distant progression and toxicity rates were analysed from the date of treatment completion. Between February 2010 and June 2013, 65 patients with 85 pulmonary metastases were reviewed. The median follow-up was 2.1 years. Metastases most commonly originated from colorectal cancer (31%), followed by non-small cell lung cancer (25%). 3D-CRT was used in 52 targets, IMRT in 21 and VMAT in 12. 3D-CRT showed a lower median R50% (P=0.01), but a higher median R100% than IMRT/VMAT (P=0.04). The R50% index was inversely correlated to the PTV with all techniques (P=0.01). Overall survival at 1 and 2 years in all patients was 93% (95% confidence interval 87-100%) and 71% (95% confidence interval 58-86%), respectively. The 2 year freedom from local and distant progression was 93% (95% confidence interval 86-100%) and 38% (95% confidence interval 27-55%), respectively. There were no significant differences between overall survival (P=0 .14), time to distant progression (P=0.06) or toxicity rates (P=0.75) between single- and multi-fraction cohorts. We report comparable local control, overall survival and toxicity rates between single-fraction and multi-fraction SABR treatments in patients with FDG-PET-staged pulmonary oligometastases. We propose a guideline for R50% conformity incorporating 3D-CRT/IMRT/VMAT techniques with heterogeneity corrected planning algorithms.
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.CLON.2015.01.005
Abstract: In many areas of health care, practice standards have become an accepted method for professions to assess and improve the quality of care delivery. The aim of this work is to present the development of practice standards for radiation oncology in Australia, highlighting critical points and lessons learned. Following a review of radiotherapy services in Australia, a multidisciplinary group with support from the Australian Government developed practice standards for radiation oncology in Australia. The standards were produced in a multistep process including a nationwide survey of radiotherapy centres and piloting of the standards in a representative subset of all Australian radiotherapy centres. The standards are grouped into three sections: Facility management (covering staffing, data management, equipment and processes) Treatment planning and delivery (providing more detailed guidance on prescription, planning and delivery) Safety and quality management (including radiation safety, incident monitoring and clinical trials participation). Each of the 16 standards contains specific criteria, a commentary and suggestions for the evidence required to demonstrate compliance. The development of the standards was challenging and time consuming, but the collaborative efforts of the professions resulted in standards applicable throughout Australia and possibly further afield.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Wiley
Date: 03-11-2020
DOI: 10.1002/ACM2.13076
Publisher: Wiley
Date: 02-03-2015
Abstract: To review the dose delivered to patients in time-resolved computed tomography (4D CT) used for radiotherapy treatment planning. 4D CT is used at Peter MacCallum Cancer Centre since July 2007 for radiotherapy treatment planning using a Philips Brilliance Wide Bore CT scanner (16 slice, helical 4D CT acquisition). All scans are performed at 140 kVp and reconstructed in 10 datasets for different phases of the breathing cycle. Dose records were analysed retrospectively for 387 patients who underwent 4D CT procedures between 2007 and 2013. A total of 444 4D CT scans were acquired with the majority of them (342) being for lung cancer radiotherapy. Volume CT dose index (CTDIvol) as recorded over this period was fairly constant at approximately 20 mGy for adults. The CTDI for 4D CT for lung cancers of 19.6 ± 9.3 mGy (n = 168, mean ± 1SD) was found to be 63% higher than CTDIs for conventional CT scans for lung patients that were acquired in the same period (CTDIvol 12 ± 4 mGy, s le of n = 25). CTDI and dose length product (DLP) increased with increasing field of view however, no significant difference between DLPs for different indications (breast, kidney, liver and lung) could be found. Breathing parameters such as breathing rate or pattern did not affect dose. 4D CT scans can be acquired for radiotherapy treatment planning with a dose less than twice the one required for conventional CT scanning.
Publisher: Wiley
Date: 20-02-2013
Abstract: We present the results of a pilot study to test the feasibility of a brachytherapy dosimetry audit. The feasibility study was conducted at seven sites from four Australian states in both public and private centres. A purpose-built cylindrical water phantom was imaged using the local imaging protocol and a treatment plan was generated to deliver 1 Gy to the central (1 of 3) thermoluminescent dosimeter (TLD) from six dwell positions. All centres completed the audit, consisting of three consecutive irradiations, within a 2-h time period, with the exception of one centre that uses a pulsed dose rate brachytherapy unit. All TLD results were within 4.5% of the predicted value, with the exception of one subset where the dwell position step size was incorrectly applied. While the limited data collected in the study demonstrated considerable heterogeneity in clinical practice, the study proved a brachytherapy dosimetry audit to be feasible. Future studies should include verification of source strength using a Standard Dosimetry Laboratory calibrated chamber, a phantom that more closely mimics the clinical situation, a more comprehensive review of safety and quality assurance (QA) procedures including source dwell time and position accuracy, and a review of patient treatment QA procedures such as applicator position verification.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Springer Science and Business Media LLC
Date: 05-06-2014
Publisher: Wiley
Date: 22-05-2003
DOI: 10.1111/1465-5922.T01-3-00003
Abstract: This study examines therapists' dreams about their patients from the Jungian and the relational perspectives. Few clinical and empirical references to this subject are to be found in the literature. In the present study 31 dreams were collected from 22 therapists. Dreams were collected using anonymous self-report inventory. The research focused on three theoretical research questions: 1. What themes appear in the manifest content of therapists' dreams about their patients? 2. What contributions are made by Jungian interpretation of therapists' dreams about their patients? 3. To what extent are masochistic contents present in the manifest content of therapists' dreams about their patients? The first question was addressed using categorical content analysis of a) themes common to different dreams and b) pre-determined themes for all dreams. The third research question was addressed using Beck's (1967) 'Masochistic Dream' measure. Among the themes common to different dreams were: therapist-patient role reversal therapist and/or patient attends and remains in meeting, departs/doesn't depart cancellation of therapy session sexuality between therapist and patient aggression presence vs. absence non-verbal relationship and communication time driving vs. stopping. With regard to pre-determined themes it was found that in 20 of the 31 dreams, the therapist had a negative experience and was characterized as vulnerable. Likewise it was found that 26 out of 31 dreams took place in either a) a street, a road, a route, a corridor b) en route to somewhere c) a therapy room and/or building d) a house. With regard to the contribution of Jungian interpretations of the dreams it was found that 17 of the dreams had diagnostic and prognostic elements, 4 of which were initial dreams, 9 of them were compensatory dreams and in 14 it was found that the patient represents the shadow of the therapist. With regard to the third question it was found that 18 of the 31 dreams met Beck's (1967) criteria for masochistic dreams. The theoretical discussion examines the findings from a Jungian perspective, with an emphasis on also understanding the dream in terms of its expression of relational aspects of the therapist-patient relationship. The findings affirm the presence of the 'wounded healer' archetypes in therapists' dreams about their patients. The results of the study indicate that therapists' dreams about their patients can be a valuable tool for deepening understanding of the therapeutic relationship and process.
Publisher: Wiley
Date: 2013
Publisher: CRC Press
Date: 31-10-2017
Publisher: Oxford University Press (OUP)
Date: 17-04-2012
DOI: 10.1093/RPD/NCS049
Abstract: Out-of-field doses to untargeted organs may have long-term detrimental health effects for patients treated with radiotherapy. It has been observed that equivalent treatments delivered to patients with different accelerators may result in significant differences in the out-of-field dose. In this work, the points of leakage dose are identified about the gantry of several treatment units. The origin of the observed higher doses is investigated. LiF:Mg,Cu,P thermoluminescent dosimetry has been employed to quantify the dose at a several points around the linac head of various linear accelerators (linacs): a Varian 600C, Varian 21-iX, Siemens Primus and Elekta Synergy-II. Comparisons are also made between different energy modes, collimator rotations and field sizes. Significant differences in leaked photon doses were identified when comparing the various linac models. The isocentric-waveguide 600C generally exhibits the lowest leakage directed towards the patient. The Siemens and Elekta models generally produce a greater leakage than the Varian models. The leakage 'hotspots' are evident on the gantry section housing the waveguide on the 21-iX. For all machines, there are significant differences in the x and y directions. Larger field sizes result in a greater leakage at the interface plate. There is a greater leakage around the waveguide when operating in a low-energy mode, but a greater leakage for the high-energy mode at the linac face. Of the vendors investigated, the Varian 600C showed the lowest average leakage dose. The Varian 21-iX showed double the dose of the 600C. The Elekta Synergy-II had on average four times the dose leakage than the 600C, and the Siemens Primus showed an average of five times that of the 600C. All vendors show strong differences in the x and y directions. The results offer the potential for patient-positioning strategies, linac choice and shielding strategies to reduce the leakage dose to patients.
Publisher: IOP Publishing
Date: 26-06-2013
Publisher: Elsevier BV
Date: 09-2006
Publisher: Elsevier BV
Date: 2022
DOI: 10.2139/SSRN.4212264
Publisher: Springer Science and Business Media LLC
Date: 08-08-2014
Publisher: Elsevier BV
Date: 12-2015
Publisher: CRC Press
Date: 31-10-2017
Publisher: Springer Science and Business Media LLC
Date: 18-08-2015
DOI: 10.1007/S13246-015-0342-9
Abstract: The history of medical physics in Asia-Oceania goes back to the late nineteenth century when X-ray imaging was introduced, although medical physicists were not appointed until much later. Medical physics developed very quickly in some countries, but in others the socio-economic situation as such prevented it being established for many years. In others, the political situation and war has impeded its development. In many countries their medical physics history has not been well recorded and there is a danger that it will be lost to future generations. In this paper, brief histories of the development of medical physics in most countries in Asia-Oceania are presented by a large number of authors to serve as a record. The histories are necessarily brief otherwise the paper would quickly turn into a book of hundreds of pages. The emphasis in each history as recorded here varies as the focus and culture of the countries as well as the length of their histories varies considerably.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 04-2020
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.MEDDOS.2010.03.002
Abstract: Fiducial markers (FMs) are commonly used as a correction technique for interfraction translations of the prostate. The aim of this investigation was to determine the magnitude of prostate rotations using 2 methods: FM coordinates and the anatomical border of the prostate and rectum. Daily computed tomography (CT) scans (n = 346) of 10 prostate cancer patients with 3 implanted FMs were acquired using the CT on rails. FM coordinates were used to determine rotation in the sagittal, transverse, and coronal planes, and CT contours of the prostate and rectum were used to determine rotation along the sagittal plane. An adaptive technique based on a subset of images (n = 6 planning and first 5 treatment CTs) to reduce systematic rotation errors in the sagittal plane was tested. The standard deviation (SD) of systematic rotation from FM coordinates was 7.6°, 7.7°, and 5.0° in the sagittal, transverse and coronal planes. The corresponding SD of random error was 10.2°, 15.8°, and 6.5°. Errors in the sagittal plane, determined from prostate and rectal contours, were 10.1° (systematic) and 7.7° (random). These results did not correlate with rotation computed from FM coordinates (r = -0.017 p = 0.753, n = 337). The systematic error could be reduced by 43% to 5.6° when the mean prostate position was estimated from 6 CT scans. Prostate rotation is a significant source of error that appears to be more accurately determined using the anatomical border of the prostate and rectum rather than FMs, thus highlighting the utility of CT image guidance.
Publisher: Informa UK Limited
Date: 06-2020
DOI: 10.1111/AP.12419
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-1999
DOI: 10.1109/23.819153
Publisher: Elsevier BV
Date: 07-2004
Publisher: Elsevier BV
Date: 04-2016
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.CLON.2011.01.511
Abstract: To analyse the relationship between body mass index (BMI) and intrafraction displacement in patients undergoing prostate cancer image-guided radiotherapy. An analysis was carried out on 151 prostate cancer patients treated with radical dose radiotherapy between January 2007 and March 2009. Patients had their height, weight and daily intrafraction prostate displacement data collected prospectively during fiducial marker image-guided radiotherapy with orthogonal imaging. For each of anterior-posterior, left-right and superior-inferior axes, a univariable linear regression analysis was carried out with the in idual patient standard deviation of shift as the response variable and BMI as a continuous explanatory variable. Displacement measurements were recorded from 4764 pre- and post-treatment image sets. Patients were grouped according to BMI as normal weight (24%), overweight (52%), obese (18%), severely obese (3%) or morbidly obese (3%). For intrafraction displacement, a one unit increase in BMI affected the standard deviation of shift by: anterior-posterior -0.02 (95% confidence interval -0.040 to 0.000), left-right -0.006 (95% confidence interval -0.020 to 0.008) and superior-inferior -0.020 (95% confidence interval -0.037 to -0.003). Our data indicate that patients with a higher BMI have less intrafraction displacement of the prostate in the superior-inferior dimension compared with patients with a lower BMI. This has implications for in idualised treatment margins for future prostate cancer patients undergoing image-guided radiotherapy. Further study is recommended.
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.CLON.2016.03.005
Abstract: In technically advanced multicentre clinical trials, participating centres can benefit from a credentialing programme before participating in the trial. Education of staff in participating centres is an important aspect of a successful clinical trial. In the multicentre study of fractionated versus single fraction stereotactic ablative body radiotherapy in lung oligometastases (TROG 13.01), knowledge transfer of stereotactic ablative body radiotherapy techniques to the local multidisciplinary team is intended as part of the credentialing process. In this study, a web-based learning platform was developed to provide education and training for the multidisciplinary trial teams at geographically distinct sites. A web-based platform using eLearning software consisting of seven training modules was developed. These modules were based on extracranial stereotactic theory covering the following discrete modules: Clinical background Planning technique and evaluation Planning optimisation Four-dimensional computed tomography simulation Patient-specific quality assurance Cone beam computed tomography and image guidance Contouring organs at risk. Radiation oncologists, medical physicists and radiation therapists from hospitals in Australia and New Zealand were invited to participate in this study. Each discipline was enrolled into a subset of modules (core modules) and was evaluated before and after completing each module. The effectiveness of the eLearning training will be evaluated based on (i) knowledge retention after participation in the web-based training and (ii) confidence evaluation after participation in the training. Evaluation consisted of a knowledge test and confidence evaluation using a Likert scale. In total, 130 participants were enrolled into the eLearning programme: 81 radiation therapists (62.3%), 27 medical physicists (20.8%) and 22 radiation oncologists (16.9%). There was an average absolute improvement of 14% in test score (P 4 weeks) after completing the modules (P < 0.001). For most there was significant increase in confidence (P < 0.001) after completing all the modules.
Publisher: Wiley
Date: 20-01-2015
Abstract: Stereotactic ablative body radiotherapy (SABR) is an emerging treatment technique for pulmonary metastases in which conventional Response Evaluation Criteria in Solid Tumours (RECIST) may be inadequate. This study aims to assess the utility of CT perfusion imaging in response assessment of pulmonary metastases after SABR. In this ethics board-approved prospective study, 11 patients underwent a 26-Gy single fraction of SABR to pulmonary metastases. CT perfusion imaging occurred prior to and at 14 and 70 days post-SABR. Blood flow (mL/100 mL/min), blood volume (mL/100 mL), time to peak (seconds) and surface permeability (mL/100 mL/min), perfusion parameters of pulmonary metastases undergoing SABR, were independently assessed by two radiologists. Inter-observer variability was analysed. CT perfusion results were analysed for early response assessment comparing day 14 with baseline scans and for late response by comparing day 70 with baseline scans. The largest diameter of the pulmonary metastases undergoing SABR was recorded. Ten patients completed all three scans and one patient had baseline and early response assessment CT perfusion scans only. There was strong level of inter-observer agreement of CT perfusion interpretation with a median intraclass coefficient of 0.87 (range 0.20-0.98). Changes in all four perfusion parameters and tumour sizes were not statistically significant. CT perfusion imaging of pulmonary metastases is a highly reproducible imaging technique that may provide additional response assessment information above that of conventional RECIST, and it warrants further study in a larger cohort of patients undergoing SABR.
Publisher: American Chemical Society (ACS)
Date: 15-11-1991
DOI: 10.1021/AC00022A013
Abstract: We have compared the use of stable and radioactive isotopes for determining the concentration of tellurium in body fluids of animals and man, specifically in the blood plasma of rabbits. Particular effort has been devoted to developing a s le-processing technique that allows the total amount of tellurium and isotope ratios to be measured by graphite furnace atomic absorption spectrometry (GFAAS) and secondary ion mass spectrometry (SIMS), respectively. The procedure employed in the SIMS analysis is discussed in detail. Investigations on the plasma clearance and the fractional intestinal absorption were carried out on four rabbits. Tracer solutions containing stable tellurium enriched in 124Te or 126Te and radioactive tellurium (121mTe or 123mTe) were administered by gavage and/or intravenously. Blood s les were drawn during the first 2 days after application. The activity of the separated plasma was measured by standard gamma ray spectrometry. After wet ashing and solvent extraction with MIBK the s les were analyzed for stable tellurium. A detection limit of 1 ng/mL of plasma could be achieved with GFAAS. For SIMS analysis the processed s les were deposited on high-purity graphite backings. Reliable isotope ratios could be determined with s le fractions containing 1 ng of tellurium or even less. The results obtained by applying stable isotopes were found to be in good agreement with the data achieved by using radioactive tracers. Studies on the intestinal absorption and the metabolic behavior of tellurium in human volunteers may thus be performed with stable isotopes.
Publisher: Science Publications
Date: 12-2017
Publisher: Elsevier BV
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 09-2007
DOI: 10.1007/BF03178430
Publisher: Wiley
Date: 27-10-2015
Abstract: The study aim was to develop a generic framework to derive the parameters to populate health-economic models for the rapid evaluation of new techniques and technologies in radiation oncology. A draft framework was developed through horizon scanning for relevant technologies, literature review to identify framework models, and a workshop program with radiation oncology professionals, biostatisticians, health economists and consumers to establish the Framework's structure. It was tested using four clinical protocols, comparing intensity modulated with 3D conformal therapy (post-prostatectomy, anal canal and nasopharynx) and image-guided radiation therapy techniques with off-line review of portal imaging (in the intact prostate). The draft generic research framework consisted of five sequential stages, each with a number of components, and was assessed as to its suitability for deriving the evidence needed to populate the decision-analytic models required for the health-economic evaluations. A final Framework was established from this experience for use by future researchers to provide evidence of clinical efficacy and cost-utility for other novel techniques. The four clinical treatment sites tested during the project were considered suitable to use in future evaluations. Development of a generic research framework to predict early and long-term clinical outcomes, combined with health-economic data, produced a generally applicable method for the rapid evaluation of new techniques and technologies in radiation oncology. Its application to further health technology assessments in the radiation oncology sector will allow further refinement and support its generalisability.
Publisher: Springer Science and Business Media LLC
Date: 03-08-2021
DOI: 10.1186/S13014-021-01820-7
Abstract: Quality assurance (QA) of treatment plans in clinical trials improves protocol compliance and patient outcomes. Retrospective use of knowledge-based-planning (KBP) in clinical trials has demonstrated improved treatment plan quality and consistency. We report the results of prospective use of KBP for real-time QA of treatment plan quality in the TROG 15.03 FASTRACK II trial, which evaluates efficacy of stereotactic ablative body radiotherapy (SABR) for kidney cancer. A KBP model was generated based on single institution data. For each patient in the KBP phase (open to the last 31 patients in the trial), the treating centre submitted treatment plans 7 days prior to treatment. A treatment plan was created by using the KBP model, which was compared with the submitted plan for each organ-at-risk (OAR) dose constraint. A report comparing each plan for each OAR constraint was provided to the submitting centre within 24 h of receiving the plan. The centre could then modify the plan based on the KBP report, or continue with the existing plan. Real-time feedback using KBP was provided in 24/31 cases. Consistent plan quality was in general achieved between KBP and the submitted plan. KBP review resulted in replan and improvement of OAR dosimetry in two patients. All centres indicated that the feedback was a useful QA check of their treatment plan. KBP for real-time treatment plan review was feasible for 24/31 cases, and demonstrated ability to improve treatment plan quality in two cases. Challenges include integration of KBP feedback into clinical timelines, interpretation of KBP results with respect to clinical trade-offs, and determination of appropriate plan quality improvement criteria.
Publisher: Cambridge University Press (CUP)
Date: 09-2008
DOI: 10.1017/S1460396908006365
Abstract: Purpose: To compare the Combifix ® immobilization device with a conventional double-leg cushion in terms of patient comfort, therapist feedback and systematic/random error outcomes. Materials and Methods: This prospective block-randomised crossover study enrolled 18 high-risk prostate cancer patients who received whole pelvic plus prostate radiotherapy. Treatment consisted of a prostate boost with one immobilization device followed by whole pelvic radiation using the other device. Our primary endpoints were device ease-of-use and patient comfort. Secondary endpoints included treatment time and systematic/random error assessments. Results: While our patients found both devices equally comfortable and easy to use, the therapists preferred the leg cushion for ease of set-up ( p = 0.04). Patient treatment time was similar for the two devices. In terms of electronic portal imaging (EPID)-based isocentre shifts, statistically, but not clinically, significant differences in systematic and random errors between the two devices exist in the superior–inferior directions ( p ≤ 0.05). Conclusions: No clinically important advantage was seen with the Combifix ® device versus our standard double-leg cushion in terms of patient/therapist preference, patient comfort, and bony pelvic immobilization. However, this research project confirmed the feasibility of mounting a small single-institution randomised crossover technology assessment related to a practical radiotherapy issue.
Publisher: Elsevier BV
Date: 09-2005
Publisher: American Society of Clinical Oncology (ASCO)
Date: 20-05-2018
Publisher: Elsevier BV
Date: 07-2003
Publisher: Springer Science and Business Media LLC
Date: 05-02-2020
DOI: 10.1038/S41586-020-1969-6
Abstract: Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale 1–3 . Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4–5 driver mutations when combining coding and non-coding genomic elements however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution in acral melanoma, for ex le, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter 4 identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation 5,6 analyses timings and patterns of tumour evolution 7 describes the erse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity 8,9 and evaluates a range of more-specialized features of cancer genomes 8,10–18 .
Publisher: Wiley
Date: 03-2022
Abstract: Radiation Oncology continues to rely on accurate delivery of radiation, in particular where patients can benefit from more modulated and hypofractioned treatments that can deliver higher dose to the target while optimising dose to normal structures. These deliveries are more complex, and the treatment units are more computerised, leading to a re‐evaluation of quality assurance (QA) to test a larger range of options with more stringent criteria without becoming too time and resource consuming. This review explores how modern approaches of risk management and automation can be used to develop and maintain an effective and efficient QA programme. It considers various tools to control and guide radiation delivery including image guidance and motion management. Links with typical maintenance and repair activities are discussed, as well as patient‐specific quality control activities. It is demonstrated that a quality management programme applied to treatment delivery can have an impact on in idual patients but also on the quality of treatment techniques and future planning. Developing and customising a QA programme for treatment delivery is an important part of radiotherapy. Using modern multidisciplinary approaches can make this also a useful tool for department management.
Publisher: American Physical Society (APS)
Date: 22-11-2005
Publisher: Elsevier BV
Date: 12-2009
DOI: 10.1016/J.CLON.2009.09.001
Abstract: It has been suggested that large rectal filling is associated with an increased risk of prostate motion in radiotherapy. The aim of the present study was to determine if there is a correlation between rectal distension on planning computed tomography and the intrafraction and interfraction stability of the prostate gland during a course of radical radiotherapy for prostate cancer if a protocol was used to rescan patients with excessive rectal diameter during planning. The computed tomography planning scans of 89 patients with adenocarcinoma of the prostate treated with conformal radiotherapy were reviewed. All patients had three gold seed fiducial markers implanted into the prostate before planning computed tomography. About one in five patients had repeat computed tomography because their rectum was judged to be too large at the time of the first planning computed tomography. Rectal distension was assessed on planning computed tomography using outlines following European Organization for Research and Treatment of Cancer guidelines by measuring the rectal volume, the average cross-sectional area and the mean anterior-posterior diameter of the rectum. Daily kV images were obtained before and after treatment delivery to determine positional matching of the fiducial markers in the superior-inferior, anterior-posterior and right-left dimensions. In total, 2860 pre- and post-treatment daily kV image pairs were obtained of 89 patients (average 32.1 image pairs per patient). The median rectal cross-sectional area was 7.3cm(2) (range 2.8-17.1), the median rectal volume was 54.8cm(3) (range 20.9-128.2), and the median anterior-posterior rectal diameter was 3.03cm (range 1.58-8.30). Unifactor linear regression models showed no statistically significant relationship between intra- and interfraction prostate stability and rectal volume on planning computed tomography. No statistically significant relationship between rectal distension on planning computed tomography and the intra- and interfraction stability of the prostate gland was identified if patients with a large rectal volume were rescanned for planning.
Publisher: Springer Science and Business Media LLC
Date: 29-04-2022
Publisher: Springer Science and Business Media LLC
Date: 10-09-2021
DOI: 10.1007/S13246-021-01056-5
Abstract: Volumetric medical imaging lacks a standardised coordinate geometry which links image frame-of-reference to specific anatomical regions. This results in an inability to locate anatomy in medical images without visual assessment and precludes a variety of image analysis tasks which could benefit from a standardised, machine-readable coordinate system. In this work, a proposed geometric system that scales based on patient size is described and applied to a variety of cases in computed tomography imaging. Subsequently, a convolutional neural network is trained to associate axial slice CT image appearance with the standardised coordinate value along the patient superior-inferior axis. The trained neural network showed an accuracy of ± 12 mm in the ability to predict per-slice reference location and was relatively stable across all annotated regions ranging from brain to thighs. A version of the trained model along with scripts to perform network training in other applications are made available. Finally, a selection of potential use applications are illustrated including organ localisation, image registration initialisation, and scan length determination for auditing diagnostic reference levels.
Publisher: SAGE Publications
Date: 23-09-2019
Publisher: Wiley
Date: 06-2011
DOI: 10.1111/J.1754-9485.2011.02273.X
Abstract: The purpose of the study was to determine if multi-field inverse-planned intensity-modulated radiation therapy (IMRT) improves on the sparing of organs at risk (heart, lungs and contralateral breast) when compared with field-in-field forward-planned RT (FiF). The planning CT scans of 10 women with left-sided breast cancer previously treated with whole-breast RT on an inclined breast board with both arms supported above the head were retrieved. The whole breast planning target volume (PTV) was defined by clinical mark-up and contoured on all relevant CT slices as were the organs at risk. For each patient, three plans were generated using FiF, five- and nine-field inverse-planned IMRT, all to a total dose of 50 Gy to the whole breast. Mean and maximum doses to the organs at risk and the homogeneity index (HI) of the whole-breast PTV were compared. The mean heart dose for the FiF plans was 2.63 Gy compared with 4.04 Gy for the five-field and 4.30 Gy for the nine-field IMRT plans, with no significant differences in the HI of the whole-breast PTV in all plans. The FiF plans resulted in a mean contralateral breast dose of 0.58 Gy compared with 0.70 and 2.08 Gy for the five- and nine-field IMRT plans, respectively. FiF resulted in a lower mean heart and contralateral breast dose with comparable HI of the whole-breast PTV in comparison with inverse-planned IMRT using five or nine fields.
Publisher: Elsevier BV
Date: 08-1995
DOI: 10.1016/0167-8140(95)01599-C
Abstract: Dose-response relationships have been studied using an ordinal visual scale and reflectance spectrophotometry data from 123 treatment sites on 110 patients treated with 10 dose fractions over 12-14 days. Dose rates varied between 3 and 240 Gy/h and total doses of between 25 and 41 Gy were given using teletherapy apparatus. We found qualitative scoring of erythematous skin reactions to be subject to considerable inter- and intra-observer variation. Reflectance spectrophotometry provided more reproducible information, some of which was undetectable by naked eye. Baseline erythema readings were significantly higher in male patients and at anatomical sites of previous heavy UV exposure. In addition, a pronounced decline in erythema readings during the second week of therapy and 'reciprocal vicinity' (abscopal) effects adjacent to the field, undetected by the eye, were observed in a subset of patients. Meaningful dose-response relationships could be derived only from reflectance data with peak change from the pretreatment baseline measure providing the best discrimination. Peak erythema measures following treatment were found to depend on the age and gender of the patient as well as the treatment site and its baseline erythema measurement. This was independent of the total dose administered or the instantaneous dose rate at which it was delivered. The rate of erythema development was also dose rate dependent but only weakly dependent on the biological dose intensity (Gy equiv./day) of the treatment course. The data raise the question of whether irradiation-induced erythema is exclusively a secondary phenomenon occurring as a result of basal cell killing. The short repair half time value of 0.06 h obtained by direct analysis is perplexing and may reflect a dose rate-dependent physiological vasodilatory response to irradiation and/or a multi-component cellular repair process.
Publisher: Wiley
Date: 04-2009
DOI: 10.1111/J.1754-9485.2009.02057.X
Abstract: We present the results of a pilot study designed to investigate methods that may be applied to develop a patient position correction protocol for the post-prostatectomy patient receiving radiotherapy. Imaging was carried out with cone beam CT (CBCT) to investigate its suitability for detecting changes in rectal and bladder volumes and movements of these organs relative to the treatment planning CT. Eligible patients were imaged daily during the first week of treatment and weekly thereafter. Surrogate explanatory variables, including distance from the isocentre to the anterior rectum and bladder length, were tested for their potential to substitute for contouring entire organs and predict for changes in coverage of the planning treatment volume (PTV) by the 95% isodose (PTV95) and the maximum dose delivered to 50% of the rectal volume (RECTD50). The PTV defined on the CBCT images was larger than that defined on the planning CT and resulted in a decrease in the PTV95. Bladder length correlated with bladder volume and changes in bladder volume were associated with a decrease in PTV95. Rectal volumes changed randomly during treatment. There was a trend for the rectum to move anteriorly as treatment progressed. CBCT may be used to define the PTV, rectum and bladder though the reason for an apparent increase in PTV on CBCT requires further investigation. The bladder length and distance to the anterior rectal wall are potential surrogate explanatory variables. Further studies will be designed to test values of these surrogates that predict the need for a change in isocentre position.
Publisher: Elsevier BV
Date: 06-2021
Publisher: IOP Publishing
Date: 20-10-1999
DOI: 10.1088/0031-9155/44/11/402
Abstract: Verification of advanced radiotherapy treatment modalities requires measurement of three-dimensional absorbed dose distributions with high spatial resolution and precision. Polymer gel dosimeters combined with magnetic resonance imaging may be able to fulfil this requirement. However, verification requires that the uncertainty in the dosimeter is well known. One method of estimating the overall uncertainty in polymer gel dosimeters involves the propagation of the uncertainty in the R2 (nuclear magnetic resonance relaxation rate) map and the uncertainties in the calibration data. This work shows that using this method with current data suggests that the lowest uncertainty currently obtainable is about 3% at 8 Gy and 7% at 2 Gy. Furthermore, the most significant reductions in overall uncertainty will be achieved by reducing the noise in the R2 map.
Publisher: Informa UK Limited
Date: 16-07-2020
Publisher: Wiley
Date: 08-1994
DOI: 10.1118/1.597208
Abstract: The COVID-19 pandemic required instructors to rapidly redesign subject delivery for the online environment. In dealing with this emergency situation, instructors may have focused their energies primarily on transitioning learning and assessment activities to the online context rather than working to support the socioemotional aspects of learning, such as belonging and motivation. As a result, online classes may have lacked social presence, leaving students feeling unvalued and demotivated. Research findings by Borup, West, and Thomas (Educ Technol Res Dev 63(2):161-184, 2015) indicate that instructors may be able to support positive socioemotional outcomes for online students through the provision of video feedback comments. The purpose of this short response is to briefly review the work of Borup et al. (2015) and, in doing so, highlight three key design considerations relating to the creation and provision of video feedback comments in order to bolster socioemotional outcomes for online students. Limitations and implications for future research are also discussed, including cultural and inclusivity issues.
Publisher: Elsevier BV
Date: 03-2011
DOI: 10.1016/J.IJROBP.2010.04.064
Abstract: To characterize the out-of-field doses in pediatric radiotherapy and to identify simple methods by which out-of-field dose might be minimized, with a view to reducing the risk of secondary cancers. With the aim of characterizing the peripheral doses under different treatment conditions, the dose measurements in an anthropomorphic child phantom were taken in various organs and critical structures outside the primary field using thermoluminescent dosimetry. The doses from a Varian 600C and Varian Trilogy linear accelerator, both at 6 MV, were investigated. Larger field sizes have been shown to result in greater peripheral doses close to the primary beam, with the difference becoming less significant at large distances, indicating that most of out-of-field doses result from head leakage and collimator scatter>40 cm from the primary field. The use of lead shields has been shown to reduce the absorbed dose resulting from leakage. Aligning the craniocaudal axis of the patient with the x-plane of the collimator resulted in a dose reduction of 40%, for both machines. Out-of-field doses from the Varian Trilogy were shown to be approximately 40% greater than those from the 600C linear accelerator, despite being operated at the same energy. Out-of-field doses to pediatric patients can be minimized by using simple treatment options, such as using the single-energy mode linear accelerator rather than the multimode, orienting the couch and collimator such that the patient lies along the x-plane and avoiding fields directed along the trunk of the body.
Publisher: Springer Science and Business Media LLC
Date: 12-2014
Publisher: Elsevier BV
Date: 06-2023
Publisher: Wiley
Date: 09-07-2010
DOI: 10.1002/CNCR.25392
Abstract: The authors studied growth and progression of untreated nonsmall cell lung cancer (NSCLC) by comparing diagnostic and radiotherapy (RT) planning fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) scans before proposed radical chemo-RT. Patients enrolled on a prospective clinical trial were eligible for this analysis if they underwent 2 pretreatment whole body FDG-PET/CT scans, >7 days apart. Scan 1 was performed for diagnosis/disease staging and scan 2 for RT planning. Interscan comparisons included disease stage, metabolic characteristics, tumor doubling times, and change in treatment intent. Eighty-two patients underwent planning PET/CT scans between October 2004 and February 2007. Of these, 28 patients (61% stage III, 18% stage II) had undergone prior staging PET/CT scans. The median interscan period was 24 days (range, 8-176 days). Interscan disease progression (TNM stage) was detected in 11 (39%) patients. The probability of upstaging within 24 days was calculated to be 32% (95% confidence interval [CI], 18%-49%). Treatment intent changed from curative to palliative in 8 (29%) cases, in 7 because of PET. For 17 patients who underwent serial PET/CT scans under standardized conditions, there was a mean relative interscan increase of 19% in tumor maximum standardized uptake value (SUV) (P=.022), 16% in average SUV (P=.004), and 116% in percentage injected dose (P=.002). Estimated doubling time of FDG avid tumor was 66 days (95% CI, 51-95 days). Rapid tumor progression was detected in patients with untreated, predominantly stage III, NSCLC on serial FDG-PET/CT imaging, highlighting the need for prompt diagnosis, staging, and initiation of therapy in patients who are candidates for potentially curative therapy.
Publisher: Wiley
Date: 19-08-2004
DOI: 10.1118/1.1776671
Abstract: Helical tomotherapy (HT) is a novel radiotherapy technique that utilizes intensity modulated fan beams that deliver highly conformal dose distributions in a helical beam trajectory. The most significant limitation in dose delivery with a constant fan beam thickness (FBT) is the penumbra width of the dose distribution in the craniocaudal direction, which is equivalent to the FBT. We propose to employ a half-blocked fan beam at start and stop location to reduce the penumbra width by half. By opening the jaw slowly during the helical delivery until the desired FBT is achieved it is possible to create a sharper edge in the superior and inferior direction from the target. The technique was studied using a tomotherapy beam model implemented on a commercial treatment planning system (Theraplan Plus V3.0). It was demonstrated that the dose distribution delivered using a 25 mm fan beam can be improved significantly, to reduce the dose to normal structures located superiorly and inferiorly of the target. Dosimetry for this technique is straightforward down to a FBT of 15 mm and implementation should be simple as no changes in couch movement are required compared to a standard HT delivery. We conclude that the use of asymmetric collimated fan beams for the start and stop of the helical tomotherapeutic dose delivery has the potential of significantly improving the dose distribution in helical tomotherapy.
Publisher: Springer Science and Business Media LLC
Date: 03-2008
DOI: 10.1007/BF03178446
Publisher: Springer Science and Business Media LLC
Date: 26-10-2013
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.CLON.2019.09.056
Abstract: To assess the intrafraction motion of the urinary bladder and delineate the appropriate margin size for radiotherapy planning, for both the full and empty bladder. This was a single-site, single-arm study of 20 patients planned to undergo radical cystectomy for histologically confirmed muscle-invasive bladder cancer. Patients underwent magnetic resonance imaging (cineMRI) of the entire pelvis using a 3-Tesla system, prior to cystectomy. Patients first underwent a cineMRI with a full bladder, then voided and underwent a second MRI with an empty bladder. All MRI sequences were acquired over 18 min. We assessed the differences in bladder filling and subsequent bladder wall displacement, between the empty and full bladder, during a time period consistent with radiotherapy treatment delivery. Twenty patients underwent cineMRI of the entire pelvis. The maximum mean directional displacements of the bladder walls over the 18 min duration of the scan for the empty bladders were 9.8 mm superiorly, 1.1 mm inferiorly, 2.39 mm anteriorly, 3.73 mm posteriorly, 2.74 mm to the left and 2.48 mm to the right. The maximal mean displacements for the full bladders were 9.2 mm superiorly, 1.1 mm inferiorly, 2.28 mm anteriorly, 1.08 mm posteriorly, 1.85 mm to the left and 1.73 mm to the right. Statistically significant differences were seen in the posterior, left and right displacements but were quantitatively small. Intrafractional motion secondary to bladder filling showed minimal variation between the full and empty bladder. Similar clinical target volume to planning target volume margins can be applied for the delivery of radiotherapy for a full and empty bladder.
Publisher: IOP Publishing
Date: 26-06-2013
Publisher: Elsevier BV
Date: 05-2023
Publisher: Wiley
Date: 18-08-2021
DOI: 10.1002/MP.15123
Abstract: The aim of this study is to investigate overdose to organs at risk (OARs) observed in dosimetry audits in Monte Carlo (MC) algorithms and Linear Boltzmann Transport Equation (LBTE) algorithms. The impact of penumbra modeling on OAR dose was assessed with the adjustment of MC modeling parameters and the clinical relevance of the audit cases was explored with a planning study of spine and head and neck (H& N) patient cases. Dosimetric audits performed by the Australian Clinical Dosimetry Service (ACDS) of 43 anthropomorphic spine plans and 1318 C‐shaped target plans compared the planned dose to doses measured with ion chamber, microdiamond, film, and ion chamber array. An MC EGSnrc model was created to simulate the C‐shape target case. The electron cut‐off energy E cut(kinetic) was set at 500, 200, and 10 keV, and differences between 1 and 3 mm voxel were calculated. A planning study with 10 patient stereotactic body radiotherapy (SBRT) spine plans and 10 patient H& N plans was calculated in both Acuros XB (AXB) v15.6.06 and Anisotropic Analytical Algorithm (AAA) v15.6.06. The patient contour was overridden to water as only the penumbral differences between the two different algorithms were under investigation. The dosimetry audit results show that for the SBRT spine case, plans calculated in AXB are colder than what is measured in the spinal cord by 5%–10%. This was also observed for other audit cases where a C‐shape target is wrapped around an OAR where the plans were colder by 3%–10%. Plans calculated with Monaco MC were colder than measurements by approximately 7% with the OAR surround by a C‐shape target, but these differences were not noted in the SBRT spine case. Results from the clinical patient plans showed that the AXB was on average 7.4% colder than AAA when comparing the minimum dose in the spinal cord OAR. This average difference between AXB and AAA reduced to 4.5% when using the more clinically relevant metric of maximum dose in the spinal cord. For the H& N plans, AXB was cooler on average than AAA in the spinal cord OAR (1.1%), left parotid (1.7%), and right parotid (2.3%). The EGSnrc investigation also noted similar, but smaller differences. The beam penumbra modeled by E cut(kinetic) = 500 keV was steeper than the beam penumbra modeled by E cut(kinetic) = 10 keV as the full scatter is not accounted for, which resulted in less dose being calculated in a central OAR region where the penumbra contributes much of the dose. The dose difference when using 2.5 mm voxels of the center of the OAR between 500 and 10 keV was 3%, reducing to 1% between 200 and 10 keV. Lack of full penumbral modeling due to approximations in the algorithms in MC based or LBTE algorithms are a contributing factor as to why these algorithms under‐predict the dose to OAR when the treatment volume is wrapped around the OAR. The penumbra modeling approximations also contribute to AXB plans predicting colder doses than AAA in areas that are in the vicinity of beam penumbra. This effect is magnified in regions where there are many beam penumbras, for ex le in the spinal cord for spine SBRT cases.
Publisher: British Institute of Radiology
Date: 02-2012
DOI: 10.1259/BJR/13553326
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.IJROBP.2022.05.034
Abstract: Medical operability is prognostic for survival after SABR in primary malignancies. This study investigated the prognostic significance of medical operability and total versus subtotal ablation of all oligometastatic disease sites. Consecutive patients with 1 to 5 sites of active extracranial oligometastases had medical operability status and presence of subtotal versus total metastatic ablation recorded prospectively in an institutional database. We retrospectively compared overall survival (OS) and progression-free survival (PFS) for medically operable or inoperable patients and patients undergoing total or subtotal metastatic ablation. Secondary endpoints were patterns of failure, high-grade treatment toxic effects (Common Terminology Criteria for Adverse Events version 4.0), and freedom from systemic therapy. The threshold dose per fraction considered ablative was 8 Gy. A total of 401 patients with 530 treated oligometastases were included, with a median follow-up of 3 years. Three hundred and two and 99 patients had metachronous and synchronous presentations of oligometastatic disease, respectively. Common histologies included prostate (24%), lung (18%), gastrointestinal (19%), and breast (11%). More than 90% of doses delivered were Biologically Effective Dose [BED Medical operability was not prognostic in patients with oligometastatic disease treated with SABR. Total metastatic ablation was associated with superior OS and PFS compared with subtotal metastatic ablation. Our data support ablation of all sites of oligometastases wherever feasible.
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.RADONC.2014.02.015
Abstract: To assess whether online adaptive radiotherapy for bladder cancer is feasible across multiple Radiation Oncology departments using different imaging, delivery and recording technology. A multi-centre feasibility study of online adaptive radiotherapy, using a choice of three "plan of the day", was conducted at 12 departments. Patients with muscle-invasive bladder cancer were included. Departments were activated if part of the pilot study or after a site-credentialing visit. There was real time review of the first two cases from each department. 54 patients were recruited, with 50 proceeding to radiotherapy. There were 43 males and 7 females with a mean age of 78 years. The tumour stages treated included T1 (1 patient), T2 (35), T3 (10) and T4 (4). One patient died of an unrelated cause during radiotherapy. The three adaptive plans were created before the 10th fraction in all cases. In 8 (16%) of the patients, a conventional plan using a 'standard' CTV to PTV margin of 1.5cm was used for one or more fractions where the pre-treatment bladder CTV was larger than any of the three adaptive plans. The bladder CTV extended beyond the PTV on post treatment imaging in 9 (18%) of the 49 patients. From a technical perspective an online adaptive radiotherapy technique can be instituted in a multi-centre setting. However, without further bladder filling control or imaging, a CTV to PTV margin of 7mm is insufficient.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Wiley
Date: 02-12-2022
DOI: 10.1002/MP.15364
Abstract: To design and manufacture a customized thoracic phantom slab utilizing the 3D printing process, also known as additive manufacturing, consisting of different tissue density materials. Here, we demonstrate the 3D‐printed phantom's clinical feasibility for imaging and dosimetric verification of volumetric modulated arc radiotherapy (VMAT) plans for lung and spine stereotactic ablative body radiotherapy (SABR) through end‐to‐end dosimetric verification. A customizable anthropomorphic phantom slab was designed using the CT dataset of a commercial phantom (adult female ATOM dosimetry phantom, CIRS Inc.). Material extrusion 3D printing was utilized to manufacture the phantom slab consisting of acrylonitrile butadiene styrene material for the lung and the associated lesion, polylactic acid (PLA) material for soft tissue and spinal cord, and both PLA and iron‐reinforced PLA materials for bone. CT images were acquired for both the commercial phantom and 3D‐printed phantom for HU comparison. VMAT plans were generated for spine and lung SABR scenarios and were delivered as per departmental SABR protocols using a Varian TrueBeam STx linear accelerator. End‐to‐end dosimetry was implemented with radiochromic films, analyzed with gamma criteria of 5% dose difference, and a distance‐to‐agreement of 1 mm, at a 10% low‐dose threshold by comparing with calculated dose using the Acuros algorithm of the Eclipse treatment planning system (v15.6). 3D‐printed phantom inserts were observed to produce HU ranging from –750 to 2100. The 3D‐printed phantom slab was observed to achieve a similar range of HU from the commercial phantom including a mean HU of –760 for lung tissue, a mean HU of 50 for soft tissue, and a mean HU of 220 and 630 for low‐ and high‐density bone, respectively. Film dosimetry results show 2D‐gamma passing rates for lung SABR (internal and superior) and spine SABR (inferior and superior) over 98% and 90%, respectively. The end‐to‐end testing of VMAT plans for spine and lung SABR suggests the clinical feasibility of the 3D‐printed phantom, consisting of different tissue density materials that emulate lung, soft tissue, and bone in kV imaging and megavoltage photon dosimetry. Further investigation of the proposed 3D printing techniques for manufacturability and reproducibility will enable the development of clinical 3D‐printed phantoms in radiotherapy.
Publisher: Elsevier BV
Date: 12-2022
Publisher: SAGE Publications
Date: 10-01-2018
Publisher: SAGE Publications
Date: 10-2004
DOI: 10.1177/153303460400300505
Abstract: Breast irradiation is one of the most challenging problems in radiotherapy due to the complex shape of the target volume, proximity of radiation sensitive normal structures and breathing motion. It was the aim of the present study to use electronic portal imaging (EPI) during treatment to determine intra- and inter-fraction motion in patients undergoing radiotherapy and to correlate the magnitude of motion with patient specific parameters. EPI cine images were acquired from the medial tangential fields of twenty radiotherapy patients on a minimum of 5 days each over the course of their treatment. The treatments were administered using 10 MV X-rays and dynamic wedges on a Varian Clinac 2100CD linear accelerator. Depending on the incident dose and the angle of the wedge, between 4 and 16 images could be acquired in one session using an EPI device based on liquid ionization chambers (Varian). The border between lung and chest-wall could be easily detected in all images and quantitative measurements were taken for the amount of lung in the field and the distance of the breast tissue from the field edges. Inter-fraction variability was found to be about twice as large as intra-fraction variability. The largest variability was detected in cranio/caudal direction (intra-fraction: 1.3 +/- 0.4 mm inter-fraction: 2.6 +/- 1.3 mm) while the lung involvement varied by 1.1 +/- 0.2 mm and 1.8 +/- 0.6 mm intra- and inter-fraction, respectively. This indicates that the effect of breathing motion on the amount of radiated lung was not of major concern in the patients studied. Of other patient specific parameters such as body weight, breast separation, field size and location of the target, only increasing age was significantly correlated with larger inter-fraction motion. Acquisition of EPI cine loops proved to be a quick and easy technique to establish the amount of patient movement during breast radiotherapy. The relatively small variability found in the present pilot study justifies considerations for more conformal dose delivery.
Publisher: Wiley
Date: 21-11-2011
DOI: 10.1118/1.3660773
Abstract: Measurement of actual dose delivered during radiotherapy treatment aids in checking the accuracy of dose delivered to the patient. In this study, a couch-based real time dosimetric device has been proposed to measure the exit or entrance dose to a patient during external beam radiotherapy. The utility and feasibility of such a device using a 2D array of diodes has been demonstrated. Two MAPCHECK devices: MAPCHECK (1175) and MAPCHECK 2 (both SunNuclear) were embedded in a foam block in the treatment couch of a Varian 21iX linear accelerator. The angular dependence of the detector response for both devices was studied before implementing the MAPCHECKs for experimental purposes. An Alderson Rando head phantom was scanned with the MAPCHECK and MAPCHECK 2 devices separately and four different treatment plans were generated with target volumes at three different positions simulating typical clinical situations. The analytical anisotropic algorithm (AAA) was used to compute the doses in an Eclipse treatment planning system (Varian Medical Systems). The Rando phantom with the MAPCHECK device was exposed in Clinac 21iX linear accelerator. The measured dose distribution was compared with the calculated dose distribution to check for the accuracy in dose delivery. Measured and computed dose distribution were found to agree with more than 93% of pixels passing at 3% and 3 mm gamma criteria for all the treatment plans. The couch-based real time dosimetry system may also be applied for noncoplanar beams where electronic portal imaging device (EPID) is not practical to measure the dose. Other advantages include checking the beam stability during the patient treatment, performing routine morning quality assurance (QA) tests in the linear accelerator, and to perform pretreatment verification of intensity modulated radiation therapy (IMRT). One of the drawbacks of this system is that it cannot be used for measuring the dose at 90° or 270° gantry angles. This preliminary study shows that a 2D array of detectors may be used as part of the treatment couch for real time patient dosimetry in studying the dose delivered to the patient in real time and also for performing routine quality assurance.
Publisher: Elsevier BV
Date: 2005
DOI: 10.1016/J.RADONC.2004.10.017
Abstract: Helical tomotherapy (HT) combines a rotating intensity modulated fan beam with integrated CT imaging for high precision radiotherapy. HT plans for 12 patients with small brain tumours were compared with five other radiotherapy techniques. Proton techniques gave overall the best results, while HT was shown to produce better target dose uniformity (average SD=1.3%) and kept irradiation of organs at risk as good as other photon methods.
Publisher: Elsevier BV
Date: 07-2019
Publisher: IOP Publishing
Date: 19-02-2009
Publisher: Elsevier BV
Date: 10-2005
DOI: 10.1016/J.RADONC.2005.06.035
Abstract: Improved radiotherapy techniques in pediatric craniospinal therapy (CSRT) strive to reduce risks of late morbidity. Using a pediatric anthropomorphic phantom, this research correlated measured target and normal tissue dose to that predicted from a 3D planning system (3D-RTP). A pediatric anthropomorphic phantom was planned following French Society of Pediatric Oncology (SFOP) protocols. Thermoluminescent detectors (TLDs) were used to perform dosimetric measurements during treatment. 4 and 6MV photon fields with multi leaf collimation (MLC) or custom blocks were compared to 3D-RTP computer (ADAC Pinnacle) predictions for cranial fields. Spinal dosimetry was studied using photons (4 and 6MV) and electrons (9 and 12MeV). 3D-RTP predictions generally concurred with dose received in cranial and spinal sites. The measured dose was over-predicted significantly by the 3D-RTP in the anterior cranial fossa. Normal tissue doses were reduced when treating the spine using megavoltage electron beams instead of photons. Treating the spinal field with electrons minimises the risk of pulmonary sequelae, however electron energy selection is critical to achieve adequate spinal field coverage. Despite adhering to a major trial protocol guideline, dose at the floor of the anterior cranial fossa remains a potential clinical problem and 3D-RTP do not predict this well.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Springer Science and Business Media LLC
Date: 09-2006
DOI: 10.1007/BF03178570
Publisher: Wiley
Date: 10-03-2017
DOI: 10.1111/BJU.13811
Abstract: To assess the feasibility and safety of stereotactic ablative body radiotherapy (SABR) for renal cell carcinoma (RCC) in patients unsuitable for surgery. Secondary objectives were to assess oncological and functional outcomes. This was a prospective interventional clinical trial with institutional ethics board approval. Inoperable patients were enrolled, after multidisciplinary consensus, for intervention with informed consent. Tumour response was defined using Response Evaluation Criteria In Solid Tumors v1.1. Toxicities were recorded using Common Terminology Criteria for Adverse Events v4.0. Time-to-event outcomes were described using the Kaplan-Meier method, and associations of baseline variables with tumour shrinkage was assessed using linear regression. Patients received either single fraction of 26 Gy or three fractions of 14 Gy, dependent on tumour size. Of 37 patients (median age 78 years), 62% had T1b, 35% had T1a and 3% had T2a disease. One patient presented with bilateral primaries. Histology was confirmed in 92%. In total, 33 patients and 34 kidneys received all prescribed SABR fractions (89% feasibility). The median follow-up was 24 months. Treatment-related grade 1-2 toxicities occurred in 26 patients (78%) and grade 3 toxicity in one patient (3%). No grade 4-5 toxicities were recorded and six patients (18%) reported no toxicity. Freedom from local progression, distant progression and overall survival rates at 2 years were 100%, 89% and 92%, respectively. The mean baseline glomerular filtration rate was 55 mL/min, which decreased to 44 mL/min at 1 and 2 years (P < 0.001). Neutrophil:lymphocyte ratio correlated to % change in tumour size at 1 year, r The study results show that SABR for primary RCC was feasible and well tolerated. We observed encouraging cancer control, functional preservation and early survival outcomes in an inoperable cohort. Baseline neutrophil:lymphocyte ratio may be predictive of immune-mediated response and warrants further investigation.
Publisher: Elsevier BV
Date: 05-2011
Publisher: Springer Science and Business Media LLC
Date: 26-11-2011
DOI: 10.1007/S13246-011-0114-0
Abstract: A commercially available motion phantom (QUASAR, Modus Medical) was modified for programmable motion control with the aim of reproducing patient respiratory motion in one dimension in both the anterior-posterior and superior-inferior directions, as well as, providing controllable breath-hold and sinusoidal patterns for the testing of radiotherapy gating systems. In order to simulate realistic patient motion, the DC motor was replaced by a stepper motor. A separate 'chest-wall' motion platform was also designed to accommodate a variety of surrogate marker systems. The platform employs a second stepper motor that allows for the decoupling of the chest-wall and insert motion. The platform's accuracy was tested by replicating patient traces recorded with the Varian real-time position management (RPM) system and comparing the motion platform's recorded motion trace with the original patient data. Six lung cancer patient traces recorded with the RPM system were uploaded to the motion platform's in-house control software and subsequently replicated through the phantom motion platform. The phantom's motion profile was recorded with the RPM system and compared to the original patient data. Sinusoidal and breath-hold patterns were simulated with the motion platform and recorded with the RPM system to verify the systems potential for routine quality assurance of commercial radiotherapy gating systems. There was good correlation between replicated and actual patient data (P 0.003). Mean differences between the location of maxima in replicated and patient data-sets for six patients amounted to 0.034 cm with the corresponding minima mean equal to 0.010 cm. The upgraded motion phantom was found to replicate patient motion accurately as well as provide useful test patterns to aid in the quality assurance of motion management methods and technologies.
Start Date: 03-2017
End Date: 12-2022
Amount: $372,500.00
Funder: Australian Research Council
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