ORCID Profile
0000-0001-5116-6308
Current Organisation
University of Wollongong
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Instruments And Techniques | Nuclear And Particle Physics | Atomic, Molecular, Nuclear, Particle and Plasma Physics | Medical Physics | Medical Physics | Other Physical Sciences | Medical Devices | Condensed Matter Physics | Biomedical Engineering | Synchrotrons; Accelerators; Instruments and Techniques | Medical physics | Particle physics | Characterisation of Biological Macromolecules | Space instrumentation | Medicinal and Biomolecular Chemistry | Radiation Therapy | Particle and high energy physics | Biological Physics | Electrical and Electronic Engineering not elsewhere classified | Medicinal and Biomolecular Chemistry not elsewhere classified | Central Nervous System | Biomedical Engineering not elsewhere classified | Surfaces and Structural Properties of Condensed Matter | Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Nanobiotechnology | Condensed Matter Characterisation Technique Development | Atomic and Molecular Physics
ANZSRC Socio-Economic Objective (SEO)
Physical sciences | Medical instrumentation | Scientific instrumentation | Expanding Knowledge in the Physical Sciences | Cancer and Related Disorders | Occupational health (excl. economic development aspects) | Scientific Instruments | Neurodegenerative Disorders Related to Ageing | Biological sciences | Chemical sciences | Expanding Knowledge in Technology | Medical Instruments | Expanding Knowledge in Engineering | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
BrachyView: Proof-of-principle of a novel in-body gamma camera for low dose-rate prostate brachytherapy
Publisher: Wiley
Date: 15-03-2013
DOI: 10.1118/1.4794487
Abstract: The conformity of the achieved dose distribution to the treatment plan strongly correlates with the accuracy of seed implantation in a prostate brachytherapy treatment procedure. Incorrect seed placement leads to both short and long term complications, including urethral and rectal toxicity. The authors present BrachyView, a novel concept of a fast intraoperative treatment planning system, to provide real-time seed placement information based on in-body gamma camera data. BrachyView combines the high spatial resolution of a pixellated silicon detector (Medipix2) with the volumetric information acquired by a transrectal ultrasound (TRUS). The two systems will be embedded in the same probe so as to provide anatomically correct seed positions for intraoperative planning and postimplant dosimetry. Dosimetric calculations are based on the TG-43 method using the real position of the seeds. The purpose of this paper is to demonstrate the feasibility of BrachyView using the Medipix2 pixel detector and a pinhole collimator to reconstruct the real-time 3D position of low dose-rate brachytherapy seeds in a phantom. BrachyView incorporates three Medipix2 detectors coupled to a multipinhole collimator. Three-dimensionally triangulated seed positions from multiple planar images are used to determine the seed placement in a PMMA prostate phantom in real time. MATLAB codes were used to test the reconstruction method and to optimize the device geometry. The results presented in this paper show a 3D position reconstruction accuracy of the seed in the range of 0.5-3 mm for a 10-60 mm seed-to-detector distance interval (Z direction), respectively. The BrachyView system also demonstrates a spatial resolution of 0.25 mm in the XY plane for sources at 10 mm distance from Medipix2 detector plane, comparable to the theoretical value calculated for an equivalent gamma camera arrangement. The authors successfully demonstrated the capability of BrachyView for real-time imaging (using a 3 s data acquisition time) of different brachytherapy seed configurations (with an activity of 0.05 U) throughout a 60 × 60 × 60 mm(3) Perspex prostate phantom. The newly developed miniature gamma camera component of BrachyView, with its high spatial resolution and real time capability, allows accurate 3D localization of seeds in a prostate phantom. Combination of the gamma camera with TRUS in a single probe will complete the BrachyView system.
Impurity spectra in germanium due to bulk stress from surface strain
Publisher: Elsevier BV
Date: 2001
Evaluation of a thin microstrip detector for high spatial resolution dosimetry
Publisher: Elsevier BV
Date: 12-2011
Fabrication and First Characterization of Silicon-Based Full 3-D Microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2020
Review of four novel dosimeters developed for use in radiotherapy
Publisher: IOP Publishing
Date: 26-06-2013
Microdosimetric investigation for multi-ion therapy by means of silicon on insulator (SOI) microdosimeter
Publisher: IOP Publishing
Date: 21-10-2022
Abstract: Objective. Ion radiotherapy with protons or carbon ions is one of the most advanced clinical methods for cancer treatment. To further improve the local tumor control, ion radiotherapy using multiple ion species has been investigated. Due to complexity of dose distributions delivered by multi-ion therapy in a tumor, a validation strategy for the planned treatment efficacy must be established that can be potentially used in the quality assurance (QA) protocol for the multi-ion treatment plans. In previous work, we demonstrated that the microdosimetric approach using the silicon on insulator (SOI) microdosimeter is practical for validating cell surviving fraction (SF) of MIA PaCa-2 cells in the independent fields of helium, carbon, oxygen, and neon ion beams. Approach. This paper extends the previous study, and we demonstrate a microdosimetry based approach as a pilot study to build the QA protocol in the multi-ion therapy predicting the cell SF along the spread-out Bragg peak obtained by combined irradiations of He+O and C+Ne ions. Across the study, the SOI microdosimeter system MicroPlus was used for measurement of the lineal energy in in idual ion fields followed by deriving the lineal energy of combined ion fields delivered by a pencil beam scanning system at HIMAC. Main results. The predicted cell SF based on derived lineal energy and dose in the combined fields was in good agreement with the planned cell SF by our in-house treatment planning system. Significance. The presented results indicated the potential benefit of the SOI microdosimeter system MicroPlus as the QA system in the multi-ion radiotherapy.
Introduction to Mini-Micro & Nano Dosimetry and Innovative Technologies in Radiation Oncology (MMNDITRO) 2018
Publisher: IOP Publishing
Date: 05-2025
Evaluation of the MOSkin dosimeter for diagnostic X-ray CT beams
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.EJMP.2019.03.030
Abstract: The aim of the present study was to evaluate the response of the MOSkin MOSFET dosimeter for X-ray diagnostic CT beams. Experiments were performed to investigate the sensitivity, energy dependence, reproducibility, fading and angular dependence of the dose response for the device. The dosimeter's performance was evaluated for the standard radiation qualities RQT 8, RQT 9 and RQT 10 in a metrology laboratory. In a CT scanner, the MOSkin was used to assess the air kerma profile and the dose profile in a phantom. The integral of the dose profile was compared to the C
A comparison of entrance skin dose delivered by clinical angiographic c-arms using the real-time dosimeter: the MOSkin
Publisher: Springer Science and Business Media LLC
Date: 20-04-2016
DOI: 10.1007/S13246-016-0435-0
Abstract: Coronary angiography is a procedure used in the diagnosis and intervention of coronary heart disease. The procedure is often considered one of the highest dose diagnostic procedures in clinical use. Despite this, there is minimal use of dosimeters within angiographic catheterisation laboratories due to challenges resulting from their implementation. The aim of this study was to compare entrance dose delivery across locally commissioned c-arms to assess the need for real-time dosimetry solutions during angiographic procedures. The secondary aim of this study was to establish a calibration method for the MOSkin dosimeter that accurately produces entrance dose values from the clinically s led beam qualities and energies. The MOSkin is a real-time dosimeter used to measure the skin dose delivered by external radiation beams. The suitability of the MOSkin for measurements in the angiographic catheterisation laboratory was assessed. Measurements were performed using a 30 × 30 × 30 cm(3) PMMA phantom positioned at the rotational isocenter of the c-arm gantry. The MOSkin calibration factor was established through comparison of the MOSkin response to EBT2 film response. Irradiation of the dosimeters was performed using several clinical beam qualities ranging in energy from 70 to 105 kVp. A total of four different interventional c-arm machines were surveyed and compared using the MOSkin dosimeter. The phantom was irradiated from a normal angle of incidence using clinically relevant protocols, field sizes and source to image detector distance values. The MOSkin was observed to be radiotranslucent to the c-arm beam in all clinical environments. The MOSkin response was reproducible to within 2 % of the average value across repeated measurements for each beam setting. There were large variations in entrance dose delivery to the phantom between the different c-arm machines with the highest observed cine-acquisition entrance dose rate measuring 326 % higher than the lowest measured cine-acquisition entrance dose rate and with the highest measured fluoroscopic entrance dose rate measuring 346 % higher than the lowest measured fluoroscopic entrance dose rate. This comparison of entrance dose delivery across local clinical c-arms demonstrated the disparity in entrance dose delivery across catheterisation laboratories and outlined a need for real-time dose monitoring systems for patients during angiographic procedures. Through use of our calibration method, an average MOSkin calibration of 7.37 mV/cGy was established. The calibration method allowed entrance dose to be measured across a range of beam energies and beam qualities without the input of the c-arm beam characteristics. This calibration factor was proven to reproduce entrance dose values to within 5 % value of the reference dosimeter's response, suggesting potential for further studies and utilisation of the dosimeter in this field.
“Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array”
Publisher: Wiley
Date: 22-05-2018
DOI: 10.1002/ACM2.12345
The effect of an air gap on a 2D monolithic silicon detector for relative dosimetry
Publisher: IOP Publishing
Date: 12-06-2019
In vitro investigation of the dose-rate effect on the biological effectiveness of megavoltage X-ray radiation doses
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.APRADISO.2017.07.008
Abstract: Radiation therapy is rapidly evolving toward the delivery of higher dose rates to improve cancer treatment. In vitro experiments were performed to investigate the response of 9L and MCF-7 cancer cell lines, exposed to 10MV X-ray radiations. Up to 8Gy was delivered at a dose-rate of 50cGy/min compared to 5Gy/min. The data obtained emphasizes the importance of taking into account not only the physical, but also the radiobiological parameters, when planning a particular cancer treatment.
Measurement of multi-slice computed tomography dose profile with the Dose Magnifying Glass and the MOSkin radiation dosimeter
Publisher: Elsevier BV
Date: 08-2013
An electron-impact cross section data set (10 eV–1 keV) of DNA constituents based on consistent experimental data: A requisite for Monte Carlo simulations
Publisher: Elsevier BV
Date: 2017
Characterisation and evaluation of a PNP strip detector for synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 21-06-2018
Out-of-Field Dose Equivalents Delivered by Passively Scattered Therapeutic Proton Beams for Clinically Relevant Field Configurations
Publisher: Elsevier BV
Date: 2009
DOI: 10.1016/J.IJROBP.2008.09.030
Abstract: Microdosimetric measurements were performed at Massachusetts General Hospital, Boston, MA, to assess the dose equivalent external to passively delivered proton fields for various clinical treatment scenarios. Treatment fields evaluated included a prostate cancer field, cranial and spinal medulloblastoma fields, ocular melanoma field, and a field for an intracranial stereotactic treatment. Measurements were completed with patient-specific configurations of clinically relevant treatment settings using a silicon-on-insulator microdosimeter placed on the surface of and at various depths within a homogeneous Lucite phantom. The dose equivalent and average quality factor were assessed as a function of both lateral displacement from the treatment field edge and distance downstream of the beam's distal edge. Dose-equivalent value range was 8.3-0.3 mSv/Gy (2.5-60-cm lateral displacement) for a typical prostate cancer field, 10.8-0.58 mSv/Gy (2.5-40-cm lateral displacement) for the cranial medulloblastoma field, 2.5-0.58 mSv/Gy (5-20-cm lateral displacement) for the spinal medulloblastoma field, and 0.5-0.08 mSv/Gy (2.5-10-cm lateral displacement) for the ocular melanoma field. Measurements of external field dose equivalent for the stereotactic field case showed differences as high as 50% depending on the modality of beam collimation. Average quality factors derived from this work ranged from 2-7, with the value dependent on the position within the phantom in relation to the primary beam. This work provides a valuable and clinically relevant comparison of the external field dose equivalents for various passively scattered proton treatment fields.
Evaluation of rectal dose discrepancies between planned and in vivo dosimetry using MOSkin detector and PTW 9112 semiconductor probe during 60Co HDR CT-based intracavitary cervix brachytherapy
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.EJMP.2019.11.025
Abstract: Dose to the rectum during brachytherapy treatment may differ from an approved treatment plan which can be quantified with in vivo dosimetry (IVD). This study compares the planned with in vivo doses measured with MOSkin and PTW 9112 rectal probe in patients undergoing CT based HDR cervical brachytherapy with Co-60 source. Dose measurement of a standard pear-shaped plan carried out in phantom to verify the MOSkin dose measurement accuracy. With MOSkin attached to the third diode, RP3 of the PTW 9112, both detectors were inserted into patients' rectum. The RP3 and MOSkin measured doses in 18 sessions as well as the maximum measured doses from PTW 9112, RP Percentage dose differences ΔD (%) in phantom study for two MOSkin found to be 2.22 ± 0.07% and 2.5 ± 0.07%. IVD of 18 sessions resulted in ΔD(%) of -16.3% to 14.9% with MOSkin and ΔD(%) of -35.7% to -2.1% with RP3. In 48 sessions, RP The delivered doses proven to deviate from planned doses due to unavoidable shift between imaging and treatment as measured with MOSkin and PTW 9112 detectors. The integration of MOSkin on commercial PTW 9112 surface found to be feasible for rectal dose IVD during cervical HDR ICBT.
Neutron shielding for a new projected proton therapy facility: A Geant4 simulation study
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.12.003
Abstract: In this work, we used the Monte Carlo-based Geant4 simulation toolkit to calculate the ambient dose equivalents due to the secondary neutron field produced in a new projected proton therapy facility. In particular the facility geometry was modeled in Geant4 based on the CAD design. Proton beams were originated with an energy of 250MeV in the gantry rooms with different angles with respect to the patient a fixed 250MeV proton beam was also modeled. The ambient dose equivalent was calculated in several locations of interest inside and outside the facility, for different scenarios. The simulation results were compared qualitatively to previous work on an existing facility bearing some similarities with the design under study, showing that the ambient dose equivalent ranges obtained are reasonable. The ambient dose equivalents, calculated by means of the Geant4 simulation, were compared to the Australian regulatory limits and showed that the new facility will not pose health risks for the public or staff, with a maximum equivalent dose rate equal to 7.9mSv/y in the control rooms and maze exit areas and 1.3·10
Design and fabrication of pulmonary embolism phantom for planar and SPECT V/Q imaging quality assurance
Publisher: Springer Science and Business Media LLC
Date: 20-07-2010
DOI: 10.1007/S13246-010-0025-5
Abstract: Planar and Single Photon Emission Computed Tomography (SPECT) scintigraphy are the two main modalities for pulmonary embolism (PE) diagnosis via lung ventilation erfusion (V/Q) scans. This study aims to develop an anatomical lung phantom for the quality assurance (QA) of V/Q scans using planar and SPECT imaging. The phantom consists of two hollow anatomical lung cavities and 20 solid anatomical bronchopulmonary segments. The phantom functions as a PE simulator by enabling an interchangeable perfusion defect, represented by a solid anatomical bronchopulmonary segment, to be introduced into each of the lung cavities. These cavities are filled with expanded polystyrene (EPS) beads immersed in a 99mTc solution, which simulates the alveoli. The anatomical 'dead space' due to the solid introduced segment represents a perfusion defect in lung V/Q scans. In this study, a s le anatomical PE event was simulated. The phantom was prepared with a perfusion defect within the posterior basal segment in the left lung. Images were acquired for subsequent qualitative analysis. This study has demonstrated promising results in the simulation of PE events in lungs. Further development is warranted for the phantom to be used as a viable QA tool in V/Q lung scanning using planar or SPECT imaging.
Dosimetry verification in eye brachytherapy using silicon pixelated detectors
Publisher: Elsevier BV
Date: 12-2011
Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
Publisher: Wiley
Date: 11-05-2020
DOI: 10.1002/MP.14177
Abstract: This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in‐beam whole‐body positron emission tomography scanner for range verification quality assurance. The energy deposited by monoenergetic beams of C at 350 MeV/u, O at 250 MeV/u, C at 350 MeV/u, and O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose‐mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon‐on‐insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron‐emitting nuclei were measured for each beam in a gelatin phantom using the in‐beam whole‐body positron emission tomography scanner at HIMAC. The depth of maximum positron‐annihilation density was compared with the depth of maximum dose deposition and the signal‐to‐background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom. In the entrance region, the was 1.2 ± 0.1 for both C and C beams, while for O and O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the was 2.7 ± 0.4 for C and 2.9 ± 0.4 for C, while for O and O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, could only be evaluated for carbon the was 1.6 ± 0.2 and 1.5 ± 0.1 for C and C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal‐to‐background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5‐fold and 11‐fold increases in the ratios calculated for the O and C images compared with the values obtained for O and C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for C, compared to −5.6 ± 0.8 mm for C and 0.9 ± 0.8 mm for O vs −6.6 ± 0.8 mm for O. The values for C and O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, C and O beams produce much better quality images for range verification compared with C and O, in particular with regard to estimating the location of the Bragg peak.
TU‐C‐204B‐04: Monte Carlo Characterization of Skin Doses in MRI‐Guided‐Radiotherapy
Publisher: Wiley
Date: 06-2010
DOI: 10.1118/1.3469227
Evaluation of organ doses following high dose rate (HDR) brachytherapy of breast cancer: A Geant4 Monte Carlo simulation study
Publisher: IOP Publishing
Date: 06-2019
DOI: 10.1088/1742-6596/1248/1/012048
Abstract: This study aimed to evaluate the absorbed doses received by the organs at risk (OARs) following Iridium-192 ( 192 Ir) high dose rate (HDR) brachytherapy of the left breast. The MIRD5 adult female anthropomorphic phantom, readily available in the Geant4 Monte Carlo package was used. However, the left breast was modified from 195 to 145 cm 3 , to represent a breast following lumpectomy. Left breast was chosen due to its higher cancer occurrence than the right breast. The HDR sources were constructed with an outer cylindrical dimension of 4.5 mm (length) × 0.9 mm (diameter). Various influencing parameters were studied, i.e. catheter arrangement (single versus dual plane), source inter-dwell distances (5 versus 10 mm), and different radionuclides, i.e. Cobalt-60 ( 60 Co) and 192 Ir, by delivering a total treatment dose of 32 Gy to the left breast. Absorbed doses to the OARs (e.g. left lung, heart, right breast, spleen, etc.) were then evaluated. A maximum left lung dose of 1.5 Gy was recorded, while doses to the other OARs were all below 1 Gy. The treatment using dual plane catheter arrangement contributed to a slightly higher dose to the OARs, despite equal dose to the breast. There was no dose difference between different inter-dwell distances used in this study. 60 Co resulted in a slightly higher left lung dose than that of 192 Ir, while the results were the opposite for the other OARs. HDR brachytherapy allows high dose to be delivered to the breast within a short period of time, with minimal absorbed doses to the OARs.
Evaluation of organ doses following prostate treatment with permanent brachytherapy seeds: A Geant4 Monte Carlo simulation study
Publisher: IOP Publishing
Date: 06-2019
DOI: 10.1088/1742-6596/1248/1/012049
Abstract: This study aimed to evaluate the absorbed doses received by the organs at risk (OARs) following prostate treatment with permanent Iodine-125 ( 125 I) brachytherapy seeds. In order to simulate an enlarged abnormal prostate due to malignancy, the MIRD5 adult male anthropomorphic phantom (readily available in the Geant4 Monte Carlo package) was modified by increasing the prostate volume to 35 cm 3 . The permanent seeds were constructed with an outer cylindrical dimension of 4.5 mm (length) × 0.8 mm (diameter). The effects of various activity per seed (0.5, 0.6 and 0.8 mCi), number of seeds (62, 78, 94 and 110 seeds) and radionuclides, i.e. Palladium-103 ( 103 Pd), 125 I and Cesium-131 ( 131 Cs), towards the absorbed dose to the OARs (i.e. rectum, urinary bladder and both testicles) were investigated. In this study, prostate dose of up to 237 Gy was simulated, which resulted in 11 Gy dose to rectum, 7 Gy to urinary bladder and 4 Gy to each testicle. The doses were considered as reasonable, given the low dose rate nature of the treatment, allowing tissue repair for the OARs. Optimal seeds arrangement was found to consist of 78 or fewer seeds, as it resulted in the lowest dose to the OARs. For similar prostate dose, 103 Pd resulted in the lowest dose to the OARs, followed by 125 I and 131 Cs. Permanent seed brachytherapy allows high dose to be delivered to the prostate, while ensuring minimal dose to the OARs.
Novel detectors for silicon based microdosimetry, their concepts and applications
Publisher: Elsevier BV
Date: 02-2016
Preclinical studies using a prototype high-resolution PET system with depth of interaction
Publisher: IEEE
Date: 10-2011
Charge Collection in SOI Microdosimeters and Their Radiation Hardness
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2023
Thin silicon strip detectors for beam monitoring in Micro-beam Radiation Therapy
Publisher: IOP Publishing
Date: 16-11-2015
Development of a Geant4 application to characterise a prototype neutron detector based on three orthogonal 3He tubes inside an HDPE sphere
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.EJMP.2016.12.016
Abstract: The Bonner Sphere Spectrometer (BSS) system is a well-established technique for neutron dosimetry that involves detection of thermal neutrons within a range of hydrogenous moderators. BSS detectors are often used to perform neutron field surveys in order to determine the ambient dose equivalent H*(10) and estimate health risk to personnel. There is a potential limitation of existing neutron survey techniques, since some detectors do not consider the direction of the neutron field, which can result in overly conservative estimates of dose in neutron fields. This paper shows the development of a Geant4 simulation application to characterise a prototype neutron detector based on three orthogonal
Characterization of prompt gamma-ray emission with respect to the Bragg peak for proton beam range verification: A Monte Carlo study
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.EJMP.2016.12.011
Abstract: In this paper we report a Geant4 simulation study to investigate the characteristic prompt gamma (PG) emission in a water phantom for real-time monitoring of the Bragg peak (BP) during proton beam irradiation. The PG production, emission spatial correlation with the BP, and position preference for detection with respect to the BP have been quantified in different PG energy windows as a function of proton pencil-beam energy from 100 to 200MeV. The PG response to small BP shifts was evaluated using a 2cm-thick slab with different human body materials embedded in a water phantom. Our results show that the prominent characteristic PG emissions of 4.44, 5.21 and 6.13MeV exhibit distinctive correlation with the dose deposition curve. The accuracy in BP position identification using these characteristic PG rays is highly consistent as the beam energy increases from 100 to 200MeV. There exists a position preference for PG detection with respect to the BP position, which has a strong dependence on the proton beam energy and PG energies. It was also observed that a submillimeter shift of the BP position can be realized by using PG signals. These results indicate that the characteristic PG signal is sensitive and reliable for BP tracking. Although the maximization of the PG measurement associated with the BP is difficult, it can be optimized with energy and detection position preferences.
Strip Detector For Short-Range Particles
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-1992
DOI: 10.1109/23.159680
Validation of Geant4 for silicon microdosimetry in heavy ion therapy
Publisher: IOP Publishing
Date: 13-02-2020
Abstract: Microdosimetry is a particularly powerful method to estimate the relative biological effectiveness (RBE) of any mixed radiation field. This is particularly convenient for therapeutic heavy ion therapy (HIT) beams, referring to ions larger than protons, where the RBE of the beam can vary significantly along the Bragg curve. Additionally, due to the sharp dose gradients at the end of the Bragg peak (BP), or spread out BP, to make accurate measurements and estimations of the biological properties of a beam a high spatial resolution is required, less than a millimetre. This requirement makes silicon microdosimetry particularly attractive due to the thicknesses of the sensitive volumes commonly being ∼10 [Formula: see text]m or less. Monte Carlo (MC) codes are widely used to study the complex mixed HIT radiation field as well as to model the response of novel microdosimeter detectors when irradiated with HIT beams. Therefore it is essential to validate MC codes against experimental measurements. This work compares measurements performed with a silicon microdosimeter in mono-energetic [Formula: see text], [Formula: see text] and [Formula: see text] ion beams of therapeutic energies, against simulation results calculated with the Geant4 toolkit. Experimental and simulation results were compared in terms of microdosimetric spectra (dose lineal energy, [Formula: see text]), the dose mean lineal energy, y
GMC ['gimik]: A one-variable Monte Carlo dose algorithm for proton therapy
Publisher: IOP Publishing
Date: 24-03-2014
Synthesis of potential theranostic system consisting of methotrexate-immobilized (3-aminopropyl)trimethoxysilane coated α-Bi 2 O3 nanoparticles for cancer treatment
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4RA02160F
Radiation Shielding Evaluation of Spacecraft Walls Against Heavy Ions Using Microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2021
Electronic dosimetry in radiation therapy
Publisher: Elsevier BV
Date: 12-2006
A new silicon detector for microdosimetry applications in proton therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2000
DOI: 10.1109/23.872983
Cylindrical silicon-on-insulator microdosimeter: Design, fabrication and TCAD modeling
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2009
Tissue equivalence of diamond for heavy charged particles
Publisher: Elsevier BV
Date: 03-2019
Thin Silicon Microdosimeter Utilizing 3-D MEMS Fabrication Technology: Charge Collection Study and Its Application in Mixed Radiation Fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2018
Particle tracking with a Timepix based triple GEM detector
Publisher: IOP Publishing
Date: 05-11-2015
A more accurate reconstruction system matrix for quantitative proton computed tomography
Publisher: Wiley
Date: 09-09-2009
DOI: 10.1118/1.3218759
Abstract: An accurate system matrix is required for quantitative proton CT (pCT) image reconstruction with iterative projection algorithms. The system matrix is composed of chord lengths of in idual proton path intersections with reconstruction pixels. In previous work, reconstructions were performed assuming constant intersection chord lengths, which led to systematic errors of the reconstructed proton stopping powers. The purpose of the present work was to introduce a computationally efficient variable intersection chord length in order to improve the accuracy of the system matrix. An analytical expression that takes into account the discrete stepping nature of the pCT most likely path (MLP) reconstruction procedure was created to describe an angle-dependent effective mean chord length function. A pCT dataset was simulated with GEANT4 using a parallel beam of 200 MeV protons intersecting a computerized head phantom consisting of tissue-equivalent materials with known relative stopping power. The phantom stopping powers were reconstructed with the constant chord length, exact chord length, and effective mean chord length approaches, in combination with the algebraic reconstruction technique. Relative stopping power errors were calculated for each anatomical phantom region and compared for the various methods. It was found that the error of approximately 10% in the mean reconstructed stopping power value for a given anatomical region, resulting from a system matrix with a constant chord length, could be reduced to less than 0.5% with either the effective mean chord length or exact chord length approaches. Reconstructions with the effective mean chord length were found to be approximately 20% faster than reconstructions with an exact chord length. The effective mean chord length method provides the possibility for more accurate, computationally efficient quantitative pCT reconstructions.
First in vitro evidence of modulated electro-hyperthermia treatment performance in combination with megavoltage radiation by clonogenic assay
Publisher: Springer Science and Business Media LLC
Date: 09-11-2018
DOI: 10.1038/S41598-018-34712-0
Abstract: Modulated electro-hyperthermia (mEHT) is a form of hyperthermia used in the treatment of cancer. It is a variation that relies on a particular form of enhanced selectivity to enable more effective cancerous cell death yet maintaining the integrity of healthy non-cancerous cells. It is yet to successfully make the major step into the wider medical community despite several encouraging trials. In this study, we investigate mEHT from an in vitro perspective. We demonstrate a supra-additive effect on 9 L gliosarcoma cells when exposed to mEHT in combination with MV X-ray radiation. The supra-additive effect is hypothesized to be induced by the mEHT mechanism that in turn causes apoptosis, membrane damage and an increase in rate of cell growth. This proves to be extremely advantageous in the case of the aggressive 9 L cell line as it is known to be radioresistant. However, the universal success of this multimodal treatment does not appear to be positive for all cell lines and requires further research. Due to the fundamental approach taken in this research, our results also provide a new prospect for mEHT to be a tool for sterilizing otherwise radioresistant cancers.
Editorial conference comments by the editors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
A comparison of temporal Cherenkov separation techniques in pulsed signal scintillator dosimetry
Publisher: IOP Publishing
Date: 07-2018
“Edge-on” MOSkin detector for stereotactic beam measurement and verification
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.EJMP.2016.12.020
Abstract: Dosimetry in small radiation field is challenging and complicated because of dose volume averaging and beam perturbations in a detector. We evaluated the suitability of the "Edge-on" MOSkin (MOSFET) detector in small radiation field measurement. We also tested the feasibility for dosimetric verification in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). "Edge-on" MOSkin detector was calibrated and the reproducibility and linearity were determined. Lateral dose profiles and output factors were measured using the "Edge-on" MOSkin detector, ionization chamber, SRS diode and EBT2 film. Dosimetric verification was carried out on two SRS and five SRT plans. In dose profile measurements, the "Edge-on" MOSkin measurements concurred with EBT2 film measurements. It showed full width at half maximum of the dose profile with average difference of 0.11mm and penumbral width with difference of ±0.2mm for all SRS cones as compared to EBT2 film measurement. For output factor measurements, a 1.1% difference was observed between the "Edge-on" MOSkin detector and EBT2 film for 4mm SRS cone. The "Edge-on" MOSkin detector provided reproducible measurements for dose verification in real-time. The measured doses concurred with the calculated dose for SRS (within 1%) and SRT (within 3%). A set of output correction factors for the "Edge-on" MOSkin detector for small radiation fields were derived from EBT2 film measurement and presented. This study showed that the "Edge-on" MOSkin detector is a suitable tool for dose verification in small radiation field.
SOI Thin Microdosimeters for High LET Single-Event Upset Studies in Fe, O, Xe, and Cocktail Ion Beam Fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Beam perturbation characteristics of a 2D transmission silicon diode array, Magic Plate
Publisher: Wiley
Date: 03-2016
Detection of rotational errors in single-isocenter multiple-target radiosurgery: Is a routine off-axis Winston–Lutz test necessary?
Publisher: Wiley
Date: 17-06-2022
DOI: 10.1002/ACM2.13665
Abstract: Recently the use of linear accelerator (linac)‐based stereotactic radiosurgery (SRS) has increased, including single‐isocenter multiple‐target SRS. The workload of medical physicists has grown as a result and so has the necessity of maximizing the efficiency of quality assurance (QA). This study aimed to determine if measurement‐based patient‐specific QA with a high‐spatial‐resolution dosimeter is sensitive to rotational errors, potentially reducing the need for routine off‐axis Winston–Lutz (WL) testing. The impact of rotational errors along gantry, couch, and collimator axes on dose coverage of the gross tumor volume (GTV) and planning target volume (PTV) was determined with a 1‐mm GTV/PTV expansion margin. Two techniques, the off‐axis WL test using the StereoPHAN MultiMet‐WL Cube (Sun Nuclear Corporation, Melbourne, Florida, USA) and patient‐specific QA using the SRS MapCHECK (Sun Nuclear Corporation, Melbourne, Florida, USA), were assessed on their ability to detect introduced errors before target coverage was compromised. These findings were also considered in the context of routine machine QA of rotational axis calibrations. Rotational errors significantly impacted PTV dose coverage, especially in the couch angle. GTV dose coverage remained unaffected except for with large couch angle errors (≥1.5°). The off‐axis WL test was shown to be sensitive to rotational errors with results consistently exceeding tolerance levels when or before coverage fell below departmentally accepted limits. Although patient‐specific QA using the SRS MapCHECK was previously validated for SRS, this study showed inconsistency in detection of rotational errors. It is recommended that off‐axis WL testing be conducted regularly to supplement routine monthly machine QA, as it is sensitive to errors that patient‐specific QA may not detect. This frequency should be determined by in idual departments, with consideration of GTV–PTV margins used, limitations on target off‐axis distances, and routine mechanical QA results for particular linacs.
Monte Carlo investigation of the characteristics of radioactive beams for heavy ion therapy
Publisher: Springer Science and Business Media LLC
Date: 25-04-1970
DOI: 10.1038/S41598-019-43073-1
Abstract: This work presents a simulation study evaluating relative biological effectiveness at 10% survival fraction (RBE10) of several different positron-emitting radionuclides in heavy ion treatment systems, and comparing these to the RBE10s of their non-radioactive counterparts. RBE10 is evaluated as a function of depth for three positron-emitting radioactive ion beams ( 10 C, 11 C and 15 O) and two stable ion beams ( 12 C and 16 O) using the modified microdosimetric kinetic model (MKM) in a heterogeneous skull phantom subject to a rectangular 50 mm × 50 mm × 60 mm spread out Bragg peak. We demonstrate that the RBE10 of the positron-emitting radioactive beams is almost identical to the corresponding stable isotopes. The potential improvement in PET quality assurance image quality which is obtained when using radioactive beams is evaluated by comparing the signal to background ratios of positron annihilations at different intra- and post-irradiation time points. Finally, the incidental dose to the patient resulting from the use of radioactive beams is also quantified and shown to be negligible.
A 3D lateral electrode structure for diamond based microdosimetry
Publisher: AIP Publishing
Date: 02-01-2017
DOI: 10.1063/1.4973628
Abstract: A diamond based microdosimeter prototype featuring a 3D lateral electrode structure was created using laser ablation and active brazing alloys and characterised by means of ion beam induced charge collection measurements and finite element analysis, using Synopsys TCAD simulation package.
Improved spatial resolution by MOSFET dosimetry of an x-ray microbeam
Publisher: Wiley
Date: 2000
DOI: 10.1118/1.598866
Abstract: Measurement of the lateral profile of the dose distribution across a narrow x-ray microbeam requires a dosimeter with a micron resolution. We investigated the use of a MOSFET dosimeter in an "edge-on" orientation with the gate insulating oxide layer parallel to the direction of the beam. We compared results using this technique to Gafchromic film measurements of a 200 micrometer wide planar x-ray microbeam. The microbeam was obtained by using a vernier micrometer-driven miniature collimator attached to a Therapax DXT300 x-ray machine operated at 100 kVp. The "edge-on" application allows utilization of the ultra thin sensitive volume of the MOSFET detector. Spatial resolution of both the MOSFET and Gafchromic film dosimeters appeared to be of about 1 micrometer. The MOSFET dosimeter appeared to provide more uniform dose profiles with the advantage of on-line measurements.
Microdosimetry simulations of solar protons within a spacecraft
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2005
High spatial resolution microdosimetry with monolithic ΔE-E detector on 12C beam: Monte Carlo simulations and experiment
Publisher: Elsevier BV
Date: 04-2018
Edge-on Face-to-Face MOSFET for synchrotron microbeam dosimetry: MC modeling
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2005
Intensity modulated radiation therapy: Film verification of planar dose maps
Publisher: Springer Science and Business Media LLC
Date: 12-2003
DOI: 10.1007/BF03179181
A real-time in vivo dosimetric verification method for high-dose rate intracavitary brachytherapy of nasopharyngeal carcinoma
Publisher: Wiley
Date: 19-11-4201
DOI: 10.1118/1.4758067
Abstract: A real-time in vivo dosimetric verification method using metal-oxide-semiconductor field effect transistor (MOSFET) dosimeters has been developed for patient dosimetry in high-dose rate (HDR) intracavitary brachytherapy of nasopharyngeal carcinoma (NPC). The necessary calibration and correction factors for MOSFET measurements in (192)Iridium source were determined in a water phantom. With the detector placed inside a custom-made nasopharyngeal applicator, the actual dose delivered to the tumor was measured in vivo and compared to the calculated values using a commercial brachytherapy planning system. Five MOSFETs were independently calibrated with the HDR source, yielding calibration factors of 0.48 ± 0.007 cGy∕mV. The maximum sensitivity variation was no more than 7% in the clinically relevant distance range of 1-5 cm from the source. A total of 70 in vivo measurements in 11 NPC patients demonstrated good agreement with the treatment planning. The mean differences between the planned and the actually delivered dose within a single treatment fraction were -0.1% ± 3.8% and -0.1% ± 3.7%, respectively, for right and left side assessments. The maximum dose deviation was less than 8.5%. In vivo measurement using the real-time MOSFET dosimetry system is possible to evaluate the actual dose to the tumor received by the patient during a treatment fraction and thus can offer another line of security to detect and prevent large errors.
Feasibility study of online high-spatial-resolution MOSFET dosimetry in static and pulsed X-ray radiation fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2001
DOI: 10.1109/23.983173
Monte Carlo validation and optimisation of detector packaging for spectroscopic dosimetry for in vivo urethral dosimetry during low dose rate brachytherapy
Publisher: Springer Science and Business Media LLC
Date: 04-08-2015
DOI: 10.1007/S13246-015-0366-1
Abstract: The urethral mini-dosimeter, developed by the Centre for Medical Radiation Physics, University of Wollongong, uses spectroscopic dosimetry to provide real time point dose measurements along the urethra during low dose rate prostate brachytherapy. Spectroscopic dosimetry uses the measured spectrum of the treatment isotope to estimate the dose rate at the point of measurement, however, the silicon mini-detectors employed in the urethral mini-dosimeter require water proof encapsulation which must be capable of providing electromagnetic shielding without greatly increasing the size of the probe. The introduction of non-tissue equivalent materials within the encapsulation can change the spectrum of radiation incident on the detector, which may influence the application of spectroscopic dosimetry within the urethral dosimeter. The Monte Carlo code Geant4 was adopted to study the effect of encapsulation on the operation of the urethral mini-dosimeter, as well as to determine whether an appropriate thickness of aluminium shielding was possible for electromagnetic screening. The depth dose response and angular dependence of the urethral mini-dosimeter with three thicknesses of aluminium shielding (20, 50, 100 µm) was compared with the urethral mini-dosimeter without aluminium shielding. The aluminium shielding had the effect of increasing the depth dose response (up to 3% within 30 mm and up to 5% within 50 mm), slightly reduced the azimuth angular dependence and slightly increased the polar angular dependence. The 100 µm thick shielding provided the least azimuth angular dependence (±2 %) and provided a polar angular dependence of ±1.4 % within the angles of -45° to 45°.
BrachyView: Initial preclinical results for a real-time in-body HDR PBT source tracking system with simultaneous TRUS image fusion
Publisher: IOP Publishing
Date: 05-04-2019
Abstract: A prototype in-body gamma camera system with integrated trans-rectal ultrasound (TRUS) and associated real-time image acquisition and analysis software was developed for intraoperative source tracking in high dose rate (HDR) brachytherapy. The accuracy and temporal resolution of the system was validated experimentally using a deformable tissue-equivalent prostate gel phantom and a full clinical HDR treatment plan. The BrachyView system was able to measure 78% of the 200 source positions with an accuracy of better than 1 mm. A minimum acquisition time of 0.28 s/frame was required to achieve this accuracy, restricting dwell times to a minimum of 0.3 s. Additionally, the performance of the BrachyView-TRUS fusion probe for mapping the spatial location of the tracked source within the prostate volume was evaluated. A global coordinate system was defined by scanning the phantom with the probe in situ using a CT scanner, and was subsequently used for co-registration of the BrachyView and TRUS fields of view (FoVs). TRUS imaging was used to segment the prostate volume and reconstruct it into a three-dimensional (3D) image. Fusion of the estimated source locations with the 3D prostate image was performed using integrated 3D visualisation software. HDR BrachyView is demonstrated to be a valuable tool for intraoperative source tracking in HDR brachytherapy, capable of resolving source dwell locations relative to the prostate anatomy when combined with TRUS.
3D sensitive volume microdosimeter with improved tissue equivalency: Charge collection study and its application in 12C ion therapy
Publisher: IOP Publishing
Date: 2019
Parametric characterization of penumbra reduction for aperture-collimated pencil beam scanning (PBS) proton therapy
Publisher: IOP Publishing
Date: 12-06-2023
SiPM based detector module and digital data acquisition system for PET: Initial results
Publisher: IEEE
Date: 10-2009
Online in vivo dosimetry in high dose rate prostate brchytherapy with MOSkin detectors: In phantom feasibility study
Publisher: Elsevier BV
Date: 2014
DOI: 10.1016/J.APRADISO.2013.06.001
Abstract: MOSkin detectors were studied to perform real-time in vivo dose measurements in high dose rate prostate brachytherapy. Measurements were performed inside an urethral catheter in a gel phantom simulating a real prostate implant. Measured and expected doses were compared and the discrepancy was found to be within 8.9% and 3.8% for single MOSkin and dual-MOSkin configurations, respectively. Results show that dual-MOSkin detectors can be profitably adopted in prostate brachytherapy treatments to perform real-time in vivo dosimetry inside the urethra.
Local dose enhancement of proton therapy by ceramic oxide nanoparticles investigated with Geant4 simulations
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.11.112
Abstract: Nanoparticles (NPs) have been shown to enhance X-ray radiotherapy and proton therapy of cancer. The effectiveness of radiation damage is enhanced in the presence of high atomic number (high-Z) NPs due to increased production of low energy, higher linear energy transfer (LET) secondary electrons when NPs are selectively internalized by tumour cells. This work quantifies the local dose enhancement produced by the high-Z ceramic oxide NPs Ta
Clinical application of MOSkin dosimeters to rectal wall in vivo dosimetry in gynecological HDR brachytherapy
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.EJMP.2017.05.003
Abstract: Three MOSkins dosimeters were assembled over a rectal probe and used to perform in vivo dosimetry during HDR brachytherapy treatments of vaginal cancer. The purpose of this study was to verify the applicability of the developed tool to evaluate discrepancies between planned and measured doses to the rectal wall. MOSkin dosimeters from the Centre for Medical Radiation Physics are particularly suitable for brachytherapy procedures for their ability to be easily incorporated into treatment instrumentation. In this study, 26 treatment sessions of HDR vaginal brachytherapy were monitored using three MOSkin mounted on a rectal probe. A total of 78 measurements were collected and compared to doses determined by the treatment planning system. Mean dose discrepancy was determined as 2.2±6.9%, with 44.6% of the measurements within ±5%, 89.2% within ±10% and 10.8% higher than ±10%. When dose discrepancies were grouped according to the time elapsed between imaging and treatment (i.e., group 1: ≤90min group 2: >90min), mean discrepancies resulted in 4.7±3.6% and 7.1±5.0% for groups 1 and 2, respectively. Furthermore, the position of the dosimeter on the rectal catheter was found to affect uncertainty, where highest uncertainties were observed for the dosimeter furthest inside the rectum. This study has verified MOSkin applicability to in-patient dose monitoring in gynecological brachytherapy procedures, demonstrating the dosimetric rectal probe setup as an accurate and convenient IVD instrument for rectal wall dose verification. Furthermore, the study demonstrates that the delivered dose discrepancy may be affected by the duration of treatment planning.
MOSFET dosimetry for microbeam radiation therapy at the European Synchrotron Radiation Facility
Publisher: Wiley
Date: 25-03-2003
DOI: 10.1118/1.1562169
Abstract: Preclinical experiments are carried out with approximately 20-30 microm wide, approximately 10 mm high parallel microbeams of hard, broad-"white"-spectrum x rays (approximately 50-600 keV) to investigate microbeam radiation therapy (MRT) of brain tumors in infants for whom other kinds of radiotherapy are inadequate and/or unsafe. Novel physical microdosimetry (implemented with MOSFET chips in the "edge-on" mode) and Monte Carlo computer-simulated dosimetry are described here for selected points in the peak and valley regions of a microbeam-irradiated tissue-equivalent phantom. Such microbeam irradiation causes minimal damage to normal tissues, possible because of rapid repair of their microscopic lesions. Radiation damage from an array of parallel microbeams tends to correlate with the range of peak-valley dose ratios (PVDR). This paper summarizes comparisons of our dosimetric MOSFET measurements with Monte Carlo calculations. Peak doses at depths 22 mm and valley doses at all depths investigated (2 mm-62 mm) are within 2-13% of the Monte Carlo values. These results lend credence to the use of MOSFET detector systems in edge-on mode for microplanar irradiation dosimetry.
Evaluation of silicon strip detectors in transmission mode for online beam monitoring in microbeam radiation therapy at the Australian Synchrotron
Publisher: International Union of Crystallography (IUCr)
Date: 2022
DOI: 10.1107/S1600577521011140
Abstract: Successful transition of synchrotron-based microbeam radiation therapy (MRT) from pre-clinical animal studies to human trials is dependent upon ensuring that there are sufficient and adequate measures in place for quality assurance purposes. Transmission detectors provide researchers and clinicians with a real-time quality assurance and beam-monitoring instrument to ensure safe and accurate dose delivery. In this work, the effect of transmission detectors of different thicknesses (10 and 375 µm) upon the photon energy spectra and dose deposition of spatially fractionated synchrotron radiation is quantified experimentally and by means of a dedicated Geant4 simulation study. The simulation and experimental results confirm that the presence of the 375 µm thick transmission detector results in an approximately 1–6% decrease in broad-beam and microbeam peak dose. The capability to account for the reduction in dose and change to the peak-to-valley dose ratio justifies the use of transmission detectors as thick as 375 µm in MRT provided that treatment planning systems are able to account for their presence. The simulation and experimental results confirm that the presence of the 10 µm thick transmission detector shows a negligible impact ( .5%) on the photon energy spectra, dose delivery and microbeam structure for both broad-beam and microbeam cases. Whilst the use of 375 µm thick detectors would certainly be appropriate, based upon the idea of best practice the authors recommend that 10 µm thick transmission detectors of this sort be utilized as a real-time quality assurance and beam-monitoring tool during MRT.
TH‐D‐BRC‐09: A Status Update On the Development of Proton CT at Loma Linda University Medical Center
Publisher: Wiley
Date: 06-2009
DOI: 10.1118/1.3182682
A new virtual ring-based system matrix generator for iterative image reconstruction in high resolution small volume PET systems
Publisher: IOP Publishing
Date: 10-01-2022
DOI: 10.1088/0031-9155/60/17/6949
Abstract: A common approach to improving the spatial resolution of small animal PET scanners is to reduce the size of scintillation crystals and/or employ high resolution pixellated semiconductor detectors. The large number of detector elements results in the system matrix--an essential part of statistical iterative reconstruction algorithms--becoming impractically large. In this paper, we propose a methodology for system matrix modelling which utilises a virtual single-layer detector ring to greatly reduce the size of the system matrix without sacrificing precision. Two methods for populating the system matrix are compared the first utilises a geometrically-derived system matrix based on Siddon's ray tracer method with the addition of an accurate detector response function, while the second uses Monte Carlo simulation to populate the system matrix. The effectiveness of both variations of the proposed technique is demonstrated via simulations of PETiPIX, an ultra high spatial resolution small animal PET scanner featuring high-resolution DoI capabilities, which has previously been simulated and characterised using classical image reconstruction methods. Compression factors of 5 x 10(7) and 2.5 x 10(7)are achieved using this methodology for the system matrices produced using the geometric and Monte Carlo-based approaches, respectively, requiring a total of 0.5-1.2 GB of memory-resident storage. Images reconstructed from Monte Carlo simulations of various point source and phantom models, produced using system matrices generated via both geometric and simulation methods, are used to evaluate the quality of the resulting system matrix in terms of achievable spatial resolution and the CRC, CoV and CW-SSIM index image quality metrics. The Monte Carlo-based system matrix is shown to provide the best image quality at the cost of substantial one-off computational effort and a lower (but still practical) compression factor. Finally, a straightforward extension of the virtual ring method to a three dimensional virtual cylinder is demonstrated using a 3D DoI PET scanner.
A new radiotherapy surface dose detector: The MOSFET
Publisher: Wiley
Date: 05-1996
DOI: 10.1118/1.597702
Abstract: Radiotherapy x-ray and electron beam surface doses are accurately measurable by use of a MOS-FET detector system. The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is approximately 200-microns in diameter and consists of a 0.5-microns Al electrode on top of a 1-microns SiO2 and 300-microns Si substrate. Results for % surface dose were within +/- 2% compared to the Attix chamber and within +/- 3% of TLD extrapolation results for normally incident beams. Detectors were compared using different energies, field size, and beam modifying devices such as block trays and wedges. Percentage surface dose for 10 x 10-cm and 40 x 40-cm field size for 6-MV x rays at 100-cm SSD using the MOSFET were 16% and 42% of maximum, respectively. Factors such as its small size, immediate retrieval of results, high accuracy attainable from low applied doses, and as the MOSFET records its dose history make it a suitable in vivo dosimeter where surface and skin doses need to be determined. This can be achieved within part of the first fraction of dose (i.e., only 10 cGy is required.)
Characterization of 3-D-Mesa Silicon Single Strip Detectors for Use in Synchrotron Microbeam Radiation Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2020
Attenuation of UV absorption by poly(lactic acid)-iron oxide nanocomposite particles and their potential application in sunscreens
Publisher: Elsevier BV
Date: 02-2021
Characterizing magnetically focused contamination electrons by off-axis irradiation on an inline MRI-Linac
Publisher: Wiley
Date: 25-03-2022
DOI: 10.1002/ACM2.13591
Abstract: The aim of this study is to investigate off‐axis irradiation on the Australian MRI‐Linac using experiments and Monte Carlo simulations. Simulations are used to verify experimental measurements and to determine the minimum offset distance required to separate electron contamination from the photon field. Dosimetric measurements were performed using a microDiamond detector, Gafchromic ® EBT3 film, and MO Skin TM . Three field sizes were investigated including 1.9 × 1.9, 5.8 × 5.8, and 9.7 × 9.6 cm 2 . Each field was offset a maximum distance, approximately 10 cm, from the central magnetic axis (isocenter). Percentage depth doses (PDDs) were collected at a source‐to‐surface distance (SSD) of 1.8 m for fields collimated centrally and off‐axis. PDD measurements were also acquired at isocenter for each off‐axis field to measure electron contamination. Monte Carlo simulations were used to verify experimental measurements, determine the minimum field offset distance, and demonstrate the use of a spoiler to absorb electron contamination. Off‐axis irradiation separates the majority of electron contamination from an x‐ray beam and was found to significantly reduce in‐field surface dose. For the 1.9 × 1.9, 5.8 × 5.8, and 9.7 × 9.6 cm 2 field, surface dose was reduced from 120.9% to 24.9%, 229.7% to 39.2%, and 355.3% to 47.3%, respectively. Monte Carlo simulations generally were within experimental error to MO Skin TM and microDiamond, and used to determine the minimum offset distance, 2.1 cm, from the field edge to isocenter. A water spoiler 2 cm thick was shown to reduce electron contamination dose to near zero. Experimental and simulation data were acquired for a range of field sizes to investigate off‐axis irradiation on an inline MRI‐Linac. The skin sparing effect was observed with off‐axis irradiation, a feature that cannot be achieved to the same extent with other methods, such as bolusing, for beams at isocenter.
Surface dosimetry for breast radiotherapy in the presence of immobilization cast material
Publisher: IOP Publishing
Date: 21-01-2011
DOI: 10.1088/0031-9155/56/4/008
Abstract: Curative breast radiotherapy typically leaves patients with varying degrees of cosmetic damage. One problem interfering with cosmetically acceptable breast radiotherapy is the external contour for large pendulous breasts which often results in high doses to skin folds. Thermoplastic casts are often employed to secure the breasts to maintain setup reproducibility and limit the presence of skin folds. This paper aims to determine changes in surface dose that can be attributed to the use of thermoplastic immobilization casts. Skin dose for a clinical hybrid conformal/IMRT breast plan was measured using radiochromic film and MOSFET detectors at a range of water equivalent depths representative of the different skin layers. The radiochromic film was used as an integrating dosimeter, while the MOSFETs were used for real-time dosimetry to isolate the contribution of skin dose from in idual IMRT segments. Strips of film were placed at various locations on the breast and the MOSFETs were used to measure skin dose at 16 positions spaced along the film strips for comparison of data. The results showed an increase in skin dose in the presence of the immobilization cast of up to 45.7% and 62.3% of the skin dose without the immobilization cast present as measured with Gafchromic EBT film and MOSFETs, respectively. The increase in skin dose due to the immobilization cast varied with the angle of beam incidence and was greatest when the beam was normally incident on the phantom. The increase in surface dose with the immobilization cast was greater under entrance dose conditions compared to exit dose conditions.
P-channel MOS sensor for measurement of emergency gamma and neutron irradiation
Publisher: Oxford University Press (OUP)
Date: 07-1996
Fibre optic dosimetry in synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 2019
BrachyView: Verification of LDR patient plans - Hardware optimisation
Publisher: IOP Publishing
Date: 2019
Modelling the Biological Beamline at HIMAC using Geant4
Publisher: IOP Publishing
Date: 2019
Today's monolithic silicon array detector for small field dosimetry: The Octa
Publisher: IOP Publishing
Date: 2019
High spatial resolution scintillator dosimetry of synchrotron microbeams
Publisher: Springer Science and Business Media LLC
Date: 03-05-2019
DOI: 10.1038/S41598-019-43349-6
Abstract: Microbeam radiation therapy is a novel pre-clinical external beam therapy that uses high-brilliance synchrotron X-rays to deliver the necessary high dose rates. The unique conditions of high dose rate and high spatial fractionation demand a new class of detector to experimentally measure important beam quality parameters. Here we demonstrate the highest spatial resolution plastic scintillator fibre-optic dosimeter found in the literature to date and tested it on the Imaging and Medical Beam-Line at the Australian Synchrotron in a X-ray beam where the irradiation dose rate was 4435 Gy/s. With a one-dimensional spatial resolution of 10 μ m the detector is able to resolve the in idual microbeams (53.7 ± 0.4 μ m wide), and measure the peak-to-valley dose ratio to be 55 ± 17. We also investigate the role of radioluminescence in the optical fibre used to transport the scintillation photons, and conclude that it creates a significant contribution to the total light detected.
Evolution of Diamond based Microdosimetry
Publisher: IOP Publishing
Date: 2019
Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures
Publisher: Wiley
Date: 05-2015
DOI: 10.1118/1.4918576
Abstract: The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualities were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (± 1%), field size (± 1%), frame rate (± 3%), or beam energy (± 5%). The detector angular dependence was within ± 5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ± 3%. The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.
Characterization of a high spatiotemporal resolution monolithic silicon strip detector for MRI-linac dosimetry
Publisher: IOP Publishing
Date: 2019
Multi-strip silicon sensors for beam array monitoring in micro-beam radiation therapy
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.11.005
Abstract: We present here the latest results from tests performed at the ESRF ID17 and ID21 beamlines for the characterization of novel beam monitors for Microbeam Radiation Therapy (MRT), which is currently being implemented at ID17. MRT aims at treating solid tumors by exploiting an array of evenly spaced microbeams, having an energy spectrum distributed between 27 and 600keV and peaking at 100keV. Given the high instantaneous dose delivered (up to 20kGy/s), the position and the intensity of the microbeams has to be precisely and instantly monitored. For this purpose, we developed dedicated silicon microstrip beam monitors. We have successfully characterized them, both with a microbeam array at ID17, and a submicron scanning beam at ID21. We present here the latest results obtained in recent tests along with an outlook on future developments.
A monolithic 180 nm CMOS dosimeter for wireless in Vivo Dosimetry
Publisher: Elsevier BV
Date: 2016
Synthesis of methotrexate-loaded tantalum pentoxide–poly(acrylic acid) nanoparticles for controlled drug release applications
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.JCIS.2018.11.097
Abstract: Over the past decade, there has been increasing interest in the use of multifunctional nanoparticles (NPs) for cancer treatment. Of importance are systems that can deliver drugs at a sustained rate to target cancer cells, which can result in higher efficiency and reduced systemic toxicity. In this study, we present the route for the synthesis of tantalum pentoxide (Ta
The role of nonelastic reactions in absorbed dose distributions from therapeutic proton beams in different medium
Publisher: Wiley
Date: 14-12-2005
DOI: 10.1118/1.1824194
Abstract: Many new techniques for delivering radiation therapy are being developed for the treatment of cancer. One of these, proton therapy, is becoming increasingly popular because of the precise way in which protons deliver dose to the tumor volume. In order to achieve this level of precision, extensive treatment planning needs to be carried out to determine the optimum beam energies, energy spread (which determines the width of the spread-out Bragg peak), and angles for each patient's treatment. Due to the level of precision required and advancements in computer technology, there is increasing interest in the use of Monte Carlo calculations for treatment planning in proton therapy. However, in order to achieve optimum simulation times, nonelastic nuclear interactions between protons and the target nucleus within the patient's internal structure are often not accounted for or are simulated using less accurate models such as analytical or ray tracing. These interactions produce high LET particles such as neutrons, alpha particles, and recoil protons, which affect the dose distribution and biological effectiveness of the beam. This situation has prompted an investigation of the importance of nonelastic products on depth dose distributions within various materials including water, A-150 tissue equivalent plastic, ICRP (International Commission on Radiological Protection) muscle, ICRP bone, and ICRP adipose. This investigation was conducted utilizing the GEANT4.5.2 Monte Carlo hadron transport toolkit.
Toward personalized synchrotron microbeam radiation therapy
Publisher: Springer Science and Business Media LLC
Date: 06-2020
DOI: 10.1038/S41598-020-65729-Z
Abstract: Synchrotron facilities produce ultra-high dose rate X-rays that can be used for selective cancer treatment when combined with micron-sized beams. Synchrotron microbeam radiation therapy (MRT) has been shown to inhibit cancer growth in small animals, whilst preserving healthy tissue function. However, the underlying mechanisms that produce successful MRT outcomes are not well understood, either in vitro or in vivo . This study provides new insights into the relationships between dosimetry, radiation transport simulations, in vitro cell response, and pre-clinical brain cancer survival using intracerebral gliosarcoma (9LGS) bearing rats. As part of this ground-breaking research, a new image-guided MRT technique was implemented for accurate tumor targeting combined with a pioneering assessment of tumor dose-coverage an essential parameter for clinical radiotherapy. Based on the results of our study, we can now (for the first time) present clear and reproducible relationships between the in vitro cell response, tumor dose-volume coverage and survival post MRT irradiation of an aggressive and radioresistant brain cancer in a rodent model. Our innovative and interdisciplinary approach is illustrated by the results of the first long-term MRT pre-clinical trial in Australia. Implementing personalized synchrotron MRT for brain cancer treatment will advance this international research effort towards clinical trials.
Fibre-Optic Dosimetry for MRI-LINACs: A Mini-Review
Publisher: Frontiers Media SA
Date: 30-05-2022
Abstract: For the past few decades, fibre-optic dosimeters (FODs) have been a focus of research for dosimetry with LINACs, owing to a unique set of advantageous qualities: compact dosimeter sizes, an all optical composition ( i.e. no wires or electronics around their sensitive volume), real-time response proportional to the absorbed dose-rate in their sensitive volumes and direct water equivalence. Such a set of qualities makes FODs “near-correctionless” for dosimetry with LINACs, such that they have been recommended as in vivo dosimeters and small field dosimeters. Further, their scintillation and luminescence response mechanisms are not affected by magnetic fields. Given this set of qualities, FODs are attractive candidates for dosimetry with MRI-LINACs. This mini-review aims to provide an overview of FODs to the wider medical physics community, and present the current challenges and opportunities for FODs given previous investigations into MRI-LINAC dosimetry.
Monte Carlo simulation of dose distributions from a synchrotron-produced microplanar beam array using the EGS4 code system4
Publisher: IOP Publishing
Date: 25-08-2000
DOI: 10.1088/0031-9155/45/9/304
Abstract: Microbeam therapy is established as a general concept for brain tumour treatment. A synchrotron based x-ray source was chosen for experimental research into microbeam therapy, and therefore new simulations were essential for investigating the therapy parameters with a proper description of the synchrotron radiation characteristics. To design therapy parameters for tumour treatments, the newly upgraded LSCAT (Low energy SCATtering) package of the EGS4 Monte Carlo simulation code was adapted to develop an accurate self-written user code for calculating microbeam radiation dose profiles with a precision of 1 microm. LSCAT is highly suited to this purpose due to its ability to simulate low-energy x-ray transport with detailed photon interactions (including bound electron incoherent scattering functions, and linear polarized coherent scattering). The properties of the synchrotron x-ray microbeam, including its polarization, source spectrum and beam penumbra, were simulated by the new user codes. Two concentric spheres, an inner sphere, defined as a brain, and a surrounding sphere, defined as a skull, represented the phantom. The microbeam simulation was tested using a 3 x 3 cm array beam for small treatment areas and a 6 x 6 cm array for larger ones, with different therapy parameters, such as beam width and spacing. The results showed that the microbeam array retained an adequate peak-to-valley ratio, of five times at least, at tissue depths suitable for radiation therapy. Dose measurements taken at 1 microm resolution with an 'edge-on' MOSFET validated the basics of the user code for microplanar radiation therapy.
Measurement of magnetic fields produced by a Magnetic deflector for the removal of electron contamination in radiotherapy
Publisher: Springer Science and Business Media LLC
Date: 12-2006
DOI: 10.1007/BF03178398
LET Dependence of the Charge Collection Efficiency of Silicon Microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2003
Opportunities in space life sciences
Publisher: Springer Science and Business Media LLC
Date: 10-06-2019
Absolute depth-dose-rate measurements for an 192Ir HDR brachytherapy source in water using MOSFET detectors
Publisher: Wiley
Date: 09-05-2006
DOI: 10.1118/1.2198168
Abstract: Reported MOSFET measurements concern mostly external radiotherapy and in vivo dosimetry. In this paper, we apply the technique for absolute dosimetry in the context of HDR brachytherapy using an 192Ir source. Measured radial dose rate distributions in water for different planes perpendicular to the source axis are presented and special attention is paid to the calibration of the R and K type detectors, and to the determination of appropriate correction factors for the sensitivity variation with the increase of the threshold voltage and the energy dependence. The experimental results are compared with Monte Carlo simulated dose rate distributions. The experimental results show a good agreement with the Monte Carlo simulations: the discrepancy between experimental and Monte Carlo results being within 5% for 82% of the points and within 10% for 95% of the points. Moreover, all points except two are found to lie within the experimental uncertainties, confirming thereby the quality of the results obtained.
Application of an SOI Microdosimeter for Monitoring of Neutrons in Various Mixed Radiation Field Environments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2022
Microdosimetric applications in proton and heavy ion therapy using silicon microdosimeters
Publisher: Oxford University Press (OUP)
Date: 21-10-2018
DOI: 10.1093/RPD/NCX226
Abstract: Using the CMRP 'bridge' μ+ probe, microdosimetric measurements were undertaken out-of-field using a therapeutic scanning proton pencil beam and in-field using a 12C ion therapy field. These measurements were undertaken at Mayo Clinic, Rochester, USA and at HIMAC, Chiba, Japan, respectively. For a typical proton field used in the treatment of deep-seated tumors, we observed dose-equivalent values ranging from 0.62 to 0.99 mSv/Gy at locations downstream of the distal edge. Lateral measurements at depths close to the entrance and along the SOBP plateau were found to reach maximum values of 3.1 mSv/Gy and 5.3 mSv/Gy at 10 mm from the field edge, respectively, and decreased to ~0.04 mSv/Gy 120 mm from the field edge. The ability to measure the dose-equivalent with high spatial resolution is particularly relevant to healthy tissue dose calculations in hadron therapy treatments. We have also shown qualitatively and quantitively the effects critical organ motion would have in treatment using microdosimetric spectra. Large differences in spectra and RBE10 were observed for treatments where miscalculations of 12C ion range would result in critical structures being irradiated, showing the importance of motion management.
Total variation superiorization schemes in proton computed tomography image reconstruction
Publisher: Wiley
Date: 20-10-2010
DOI: 10.1118/1.3504603
Development of LEU-based targets for radiopharmaceutical manufacturing: A review
Publisher: Elsevier BV
Date: 06-2019
The feasibility study and characterization of a two-dimensional diode array in magic phantom for high dose rate brachytherapy quality assurance
Publisher: Wiley
Date: 02-10-2013
DOI: 10.1118/1.4822736
Abstract: High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly (192)Ir with an air KERMA strength range between 20,000 and 40,000 U, where 1 U = 1 μGy m(2)/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named "magic phantom." The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array "magic plate" (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the (192)Ir source, s led at 100 ms intervals by a fast data acquisition (DAQ) system. Using a (192)Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ. The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm the relative response of the epitaxial diodes used in the MP is in good agreement (within 8%) with radial dose function measurements found within the TG-43 protocol, with SDD of up to 70 mm showing a 40% over response. A method for four-dimensional localization of the HDR source was developed, allowing the source dwell position to be derived within 0.50 mm of the expected position. An estimation of the average transit speed for varying step sizes was determined and was found to increase from (12.8 ± 0.3) up to (38.6 ± 0.4) cm/s for a step size of 2.5 and 50 mm, respectively. Our characterization of the designed QA "magic phantom" with MP in realistic HDR photon fields demonstrates the promising performance for real-time source position tracking in four dimensions and measurements of transit times. Further development of this system will allow a full suite for QA in HDR brachytherapy and analysis, and for future in vivo tracking.
Real-time high spatial resolution dose verification in stereotactic motion adaptive arc radiotherapy
Publisher: Wiley
Date: 05-06-2018
DOI: 10.1002/ACM2.12364
Semiconductor Radiation Detectors in Modern Radiation Therapy
Publisher: Elsevier
Date: 2006
Initial testing of a pixelated silicon detector prototype in proton therapy
Publisher: Wiley
Date: 18-07-2017
DOI: 10.1002/ACM2.12120
Megavoltage cone beam CT near surface dose measurements: Potential implications for breast radiotherapy
Publisher: Wiley
Date: 27-10-2011
DOI: 10.1118/1.3641867
Abstract: Cone beam computed tomography (CBCT) is fast becoming standard on modern linear accelerators. CBCT increases the dose to regions within and outside the treatment field, potentially increasing secondary cancer induction and toxicity. This study quantified megavoltage (MV) CBCT skin dose and compared it to skin dose delivered during standard tangential breast radiotherapy. Dosimetry was performed both in- and out-of-field using thermoluminescent dosimeters (TLDs) and a metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector specifically designed for skin dosimetry these were placed superficially on a female anthropomorphic phantom. The skin dose from a single treatment fraction ranged from 0.5 to 1.4 Gy on the ipsilateral breast, 0.031-0.18 Gy on the contralateral breast, and 0-0.02 Gy in the head and pelvic region. An 8 MU MV CBCT delivered a skin dose that ranged from 0.02 to 0.05 Gy in the chest region and was less than 0.01 Gy in the head and pelvis regions. One MV CBCT per fraction was found to increase the out-of-field skin dose from both the CBCT and the treatment fields by approximately 20%. The imaging dose as a percentage of treatment doses in the ipsilateral breast region was 3% for both dosimeters. Imaging increases the skin dose to regions outside the treatment field particularly regions immediately adjacent the target volume. This small extra dose to the breasts should be considered when developing clinical protocols and assessing dose for clinical trials.
HDR brachytherapy in vivo source position verification using a 2D diode array: A Monte Carlo study
Publisher: Wiley
Date: 06-2018
DOI: 10.1002/ACM2.12360
Studies of the characteristics of a silicon neutron sensor
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2009
Charge collection imaging of a monolithic ΔE-E telescope for radiation protection applications
Publisher: Oxford University Press (OUP)
Date: 12-2006
DOI: 10.1093/RPD/NCL396
Abstract: The development of microdosimeters and particle telescopes is important for risk assessment in space and aviation applications. The charge collection properties of a monolithic particle telescope, suitable for both microdosimetry and fluence based approaches, were studied using an ion microprobe.
Teaching Monte Carlo codes at university: Development of a Geant4 course for students of schools of physics
Publisher: IEEE
Date: 08-2012
Simulation study of dose enhancement in a cell due to nearby carbon and oxygen in particle radiotherapy
Publisher: Korean Physical Society
Date: 07-2015
DOI: 10.3938/JKPS.67.209
Simulation of cosmic radiation spectra for personal microdosimetry at the International Space Station's altitude
Publisher: IOP Publishing
Date: 2019
Characterisations of a fibre optic dosimetry system for source tracking during HDR Brachytherapy
Publisher: IOP Publishing
Date: 2019
Preliminary epi-diode characterization for HDR brachytherapy quality assurance
Publisher: IOP Publishing
Date: 2019
A high resolution 2D array detector system for small-field MRI-linac applications
Publisher: IOP Publishing
Date: 25-04-2018
Dose build up characteristics with eXaSkin bolus during 6MV radiotherapy: MOSkin dosimetry results
Publisher: IOP Publishing
Date: 2019
BrachyView: Multiple seed position reconstruction and comparison with CT post-implant dosimetry
Publisher: IOP Publishing
Date: 03-05-2016
Verification of the plan dosimetry for high dose rate brachytherapy using metal-oxide-semiconductor field effect transistor detectors
Publisher: Wiley
Date: 11-05-2007
DOI: 10.1118/1.2736288
Abstract: The feasibility of a recently designed metal-oxide-semiconductor field effect transistor (MOSFET) dosimetry system for dose verification of high dose rate (HDR) brachytherapy treatment planning was investigated. MOSFET detectors were calibrated with a 0.6 cm3 NE-2571 Farmer-type ionization chamber in water. Key characteristics of the MOSFET detectors, such as the energy dependence, that will affect phantom measurements with HDR 192Ir sources were measured. The MOS-FET detector was then applied to verify the dosimetric accuracy of HDR brachytherapy treatments in a custom-made water phantom. Three MOSFET detectors were calibrated independently, with the calibration factors ranging from 0.187 to 0.215 cGy/mV. A distance dependent energy response was observed, significant within 2 cm from the source. The new MOSFET detector has a good reproducibility (<3%), small angular effect (<2%), and good dose linearity (R2=1). It was observed that the MOSFET detectors had a linear response to dose until the threshold voltage reached approximately 24 V for 192Ir source measurements. Further comparison of phantom measurements using MOSFET detectors with dose calculations by a commercial treatment planning system for computed tomography-based brachytherapy treatment plans showed that the mean relative deviation was 2.2 +/- 0.2% for dose points 1 cm away from the source and 2.0 +/- 0.1% for dose points located 2 cm away. The percentage deviations between the measured doses and the planned doses were below 5% for all the measurements. The MOSFET detector, with its advantages of small physical size and ease of use, is a reliable tool for quality assurance of HDR brachytherapy. The phantom verification method described here is universal and can be applied to other HDR brachytherapy treatments.
Time-of-flight spectrometry of ultra-short, polyenergetic proton bunches
Publisher: AIP Publishing
Date: 12-2018
DOI: 10.1063/1.5052059
Abstract: A common approach for spectrum determination of polyenergetic proton bunches from laser-ion acceleration experiments is based on the time-of-flight (TOF) method. However, spectra obtained using this method are typically given in relative units or are estimated based on some prior assumptions on the energy distribution of the accelerated ions. In this work, we present a new approach using the TOF method that allows for an absolute energy spectrum reconstruction from a current signal acquired with a sub-nanosecond fast and 10 µm thin silicon detector. The reconstruction is based on solving a linear least-squares problem, taking into account the response function of the detection system. The general principle of signal generation and spectrum reconstruction by setting up an appropriate system response matrix is presented. Proof-of-principle experiments at a 12 MV Tandem accelerator using different nanosecond-short (quasi-)monoenergetic and polyenergetic proton bunches at energies up to 20 MeV were successfully performed. Within the experimental uncertainties of 2.4% and 12.1% for energy and particle number, respectively, reconstructed energy distributions were found in excellent agreement with the spectra calculated using Monte Carlo simulations and measured by a magnetic spectrometer. This TOF method can hence be used for absolute online spectrometry of laser-accelerated particle bunches.
Characterization of an “Edgeless” Dosimeter for Angular Independent Measurements in Advanced Radiotherapy Treatments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2201
On Monolithic Silicon Array Detectors for Small-Field Photon Beam Dosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2018
Monte Carlo study of the potential reduction in out-of-field dose using a patient-specific aperture in pencil beam scanning proton therapy
Publisher: IOP Publishing
Date: 19-04-2012
A Large Area Pixelated Silicon Array Detector for Independent Transit In Vivo Dosimetry
Publisher: MDPI AG
Date: 06-01-2022
DOI: 10.3390/APP12020537
Abstract: A large area pixelated silicon array detector named “MP987” has been developed for in vivo dosimetry. The detector was developed to overcome the non-water equivalent response of EPID (Electronic Portal Imaging Device) dosimetry systems, due to the shortfalls of the extensive corrections required. The detector, readout system and software have all been custom designed to be operated independently from the linac with the array secured directly above the EPID, to be used in combination with the 6 MV imaging system. Dosimetry characterisation measurements of percentage depth dose (PDD), dose rate dependence, radiation damage, output factors (OF), profile measurements, linearity and uniformity were performed. Additionally, the first pre-clinical tests with this novel detector of a transit dosimetry characterization and a collapsed IMRT (intensity-modulated radiation therapy) study are presented. Both PDD and OF measurements had a percentage difference of less than 2.5% to the reference detector. A maximum change in sensitivity of 4.3 ± 0.3% was observed after 30 kGy of gamma accumulated dose. Transit dosimetry measurements through a homogeneous Solid Water phantom had a measured dose within error of the TPS calculations, for field sizes between 3 × 3 cm2 and 10 × 10 cm2. A four-fraction collapsed IMRT plan on a lung phantom had absolute dose pass fractions between the MP987 and TPS (treatment planning system) from 94.2% to 97.4%, with a 5%/5 mm criteria. The ability to accurately measure dose at a transit level, without the need for correction factors derived from extensive commissioning data collection procedures, makes the MP987 a viable alternative to the EPID for in vivo dosimetry. This MP987 is this first of its kind to be successfully developed specifically for a dual detector application.
Fission converter and metal-oxide-semiconductor field effect transistor study of thermal neutron flux distribution in an epithermal neutron therapy beam
Publisher: Wiley
Date: 09-1999
DOI: 10.1118/1.598703
Abstract: The depth distribution of the thermal neutron flux is a major factor in boron neutron capture therapy (BNCT) in determining the efficiency of cell sterilization. In this paper the fission detector method is developed and applied to measure the in‐phantom thermal neutron flux depth distribution. Advantages of the fission detector include small size, direct measurement of thermal neutron flux in a mixed radiation field of BNCT beam, self‐calibration, and the possibility of on‐line measurement. The measurements were performed at epithermal a BNCT facility. The experimental results were compared with the thermal neutron flux calculated by the Monte Carlo method and found to be in good agreement.
Small beams, fast predictions: a comparison of machine learning dose prediction models for proton minibeam therapy
Publisher: Wiley
Date: 10-11-2022
DOI: 10.1002/MP.16066
Abstract: Dose calculations for novel radiotherapy cancer treatments such as proton minibeam radiation therapy is often done using full Monte Carlo (MC) simulations. As MC simulations can be very time consuming for this kind of application, deep learning models have been considered to accelerate dose estimation in cancer patients. This work systematically evaluates the dose prediction accuracy, speed and generalization performance of three selected state‐of‐the‐art deep learning models for dose prediction applied to the proton minibeam therapy. The strengths and weaknesses of those models are thoroughly investigated, helping other researchers to decide on a viable algorithm for their own application. The following recently published models are compared: first, a 3D U‐Net model trained as a regression network, second, a 3D U‐Net trained as a generator of a generative adversarial network (GAN) and third, a dose transformer model which interprets the dose prediction as a sequence translation task. These models are trained to emulate the result of MC simulations. The dose depositions of a proton minibeam with a diameter of 800μm and an energy of 20–100 MeV inside a simple head phantom calculated by full Geant4 MC simulations are used as a case study for this comparison. The spatial resolution is 0.5 mm. Special attention is put on the evaluation of the generalization performance of the investigated models. Dose predictions with all models are produced in the order of a second on a GPU, the 3D U‐Net models being fastest with an average of 130 ms. An investigated 3D U‐Net regression model is found to show the strongest performance with overall 61.00.5% of all voxels exhibiting a deviation in energy deposition prediction of less than 3% compared to full MC simulations with no spatial deviation allowed. The 3D U‐Net models are observed to show better generalization performance for target geometry variations, while the transformer‐based model shows better generalization with regard to the proton energy. This paper reveals that (1) all studied deep learning models are significantly faster than non‐machine learning approaches predicting the dose in the order of seconds compared to hours for MC, (2) all models provide reasonable accuracy, and (3) the regression‐trained 3D U‐Net provides the most accurate predictions.
A Geant4 shielding design for the first US carbon multi-ion hybrid synchrotron facility
Publisher: IOP Publishing
Date: 28-02-2023
Abstract: The Mayo Clinic Florida Integrated Oncology Building will be the home of the first spot-scanning only carbon roton hybrid therapy system by Hitachi, Ltd. It will provide proton beams up to kinetic energies of 230 MeV and carbon beams up to 430 MeV n −1 for clinical deployment. To provide adequate radiation protection, the Geant4 (v10.6) Monte Carlo toolkit was utilized to quantify the ambient dose equivalent at a 10 mm depth ( H *(10)) for photons and neutrons. To perform accurate calculations of the ambient dose equivalent, three-dimensional computer-aided design files of the entire planned facility were imported into Geant4, as well as certain particle system components such as the bending magnets, fast Faraday cup, and gantry. Particle fluence was scored using 60 cm diameter spheres, which were strategically placed throughout areas of interests. Analytical calculations were performed as first-pass design checks. Major shielding slabs were optimized using Geant4 simulations iteratively, with more than 20 alternative designs evaluated within Geant4. The 430 MeV n −1 carbon beams played the most significant role in concrete thickness Requirements. The primary wall thickness for the carbon fixed beam room is 4 meters. The presence of the proton gantry structure in the simulation caused the ambient dose equivalent to increase by around 67% at the maze entrance, but a decrease in the high energy beam transport corridor. All shielding primary and secondary goals for clinical operations were met per state regulation and national guidelines.
Dose Reconstruction from PET Images in Carbon Ion Therapy: A Deconvolution Approach Using an Evolutionary Algorithm
Publisher: IEEE
Date: 10-2018
BrachyView: Reconstruction of seed positions and volume of an LDR prostate brachytherapy patient plan using a baseline subtraction algorithm
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.EJMP.2019.09.237
Abstract: BrachyView is a novel in-body imaging system developed with the objective to provide real-time intraoperative dosimetry for low dose rate (LDR) prostate brachytherapy treatments. The BrachyView coordinates combined with conventional transrectal ultrasound (TRUS) imaging, provides the possibility to localise the effective position of the implanted seeds inside the prostate volume, providing a unique tool for intra-operative verification of the quality of the implantation. This research presents the first complete LDR brachytherapy plan reconstructed by the BrachyView system and is used to evaluate the effectiveness of an imaging algorithm with baseline subtraction. A plan featuring 98 I-125 brachytherapy seeds, with an average activity of 0.248 mCi, were implanted into a prostate gel phantom under TRUS guidance. Images of implanted seeds were obtained by the BrachyView after the implantation of seeds. The baseline subtraction algorithm is applied as a pixel-to-pixel counts subtraction and is applied to every second projection obtained after the implantation of each needle. Seed positions and effectiveness of the baseline reconstruction in the identification of seeds were verified by a high-resolution post-implant CT scan. A complete brachytherapy plan has been reconstructed with a 100% detection rate. This is possible due to the effectiveness of the baseline subtraction, with its application an overall increase of 11.3% in position accuracy and 8.2% increase in detection rate was noted. It has been demonstrated that the BrachyView system shows the potential to be a solution to providing clinics with the means for intraoperative dosimetry for LDR prostate brachytherapy treatments.
4He dose- and track-averaged linear energy transfer: Monte Carlo algorithms and experimental verification
Publisher: IOP Publishing
Date: 05-08-2022
Abstract: Objective. In the present hadrontherapy scenario, there is a growing interest in exploring the capabilities of different ion species other than protons and carbons. The possibility of using different ions paves the way for new radiotherapy approaches, such as the multi-ions treatment, where radiation could vary according to target volume, shape, depth and histologic characteristics of the tumor. For these reasons, in this paper, the study and understanding of biological-relevant quantities was extended for the case of 4 He ion. Approach. Geant4 Monte Carlo based algorithms for dose- and track-averaged LET (Linear Energy Transfer) calculations, were validated for 4 He ions and for the case of a mixed field characterised by the presence of secondary ions from both target and projectile fragmentation. The simulated dose and track averaged LETs were compared with the corresponding dose and frequency mean values of the lineal energy, y D ¯ and y ¯ F , derived from experimental microdosimetric spectra. Two microdosimetric experimental c aigns were carried out at the Italian eye proton therapy facility of the Laboratori Nazionali del Sud of Istituto Nazionale di Fisica Nucleare (INFN-LNS, Catania, I) using two different microdosimeters: the MicroPlus probe and the nano-TEPC (Tissue Equivalent Proportional Counter). Main results. A good agreement of L ¯ d Total and L ¯ t Total with y ¯ D and y ¯ T experimentally measured with both microdosimetric detectors MicroPlus and nano-TEPC in two configurations: full energy and modulated 4 He ion beam, was found. Significance. The results of this study certify the use of a very effective tool for the precise calculation of LET, given by a Monte Carlo approach which has the advantage of allowing detailed simulation and tracking of nuclear interactions, even in complex clinical scenarios.
Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector
Publisher: Wiley
Date: 22-11-2019
DOI: 10.1002/ACM2.12496
Biocompatible Bi(OH)3 nanoparticles with reduced photocatalytic activity as possible ultraviolet filter in sunscreens
Publisher: Elsevier BV
Date: 12-2018
Study of a monolithic silicon telescope for solid state microdosimetry: Response to a 100 MeV proton beam
Publisher: Elsevier BV
Date: 12-2011
Evaluation of transmission methodology for the microPET focus 220 animal scanner
Publisher: IEEE
Date: 2005
In vivo dosimetry: Trends and prospects for brachytherapy
Publisher: British Institute of Radiology
Date: 09-2014
DOI: 10.1259/BJR.20140206
Simulations of silicon microdosimetry measurements in fast neutron therapy.
Publisher: Springer Science and Business Media LLC
Date: 12-2002
DOI: 10.1007/BF03178290
Characterization of prompt gamma rays for in-vivo range verification in hadron therapy: A Geant4 simulation study
Publisher: IOP Publishing
Date: 2019
Development and fabrication of cylindrical silicon-on-insulator microdosimeter arrays
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Electron emission from amorphous solid water after proton impact: Benchmarking PTra and Geant4 track structure Monte Carlo simulations
Publisher: Elsevier BV
Date: 12-2012
A monolithic 180 nm CMOS dosimeter for in vivo dosimetry medical application
Publisher: Elsevier BV
Date: 12-2014
Characterization of a novel two dimensional diode array the magic plate as a radiation detector for radiation therapy treatment
Publisher: Wiley
Date: 18-04-2012
DOI: 10.1118/1.3700234
Abstract: Intensity modulated radiation therapy (IMRT) utilizes the technology of multileaf collimators to deliver highly modulated and complex radiation treatment. Dosimetric verification of the IMRT treatment requires the verification of the delivered dose distribution. Two dimensional ion chamber or diode arrays are gaining popularity as a dosimeter of choice due to their real time feedback compared to film dosimetry. This paper describes the characterization of a novel 2D diode array, which has been named the "magic plate" (MP). It was designed to function as a 2D transmission detector as well as a planar detector for dose distribution measurements in a solid water phantom for the dosimetric verification of IMRT treatment delivery. The prototype MP is an 11 × 11 detector array based on thin (50 μm) epitaxial diode technology mounted on a 0.6 mm thick Kapton substrate using a proprietary "drop-in" technology developed by the Centre for Medical Radiation Physics, University of Wollongong. A full characterization of the detector was performed, including radiation damage study, dose per pulse effect, percent depth dose comparison with CC13 ion chamber and build up characteristics with a parallel plane ion chamber measurements, dose linearity, energy response and angular response. Postirradiated magic plate diodes showed a reproducibility of 2.1%. The MP dose per pulse response decreased at higher dose rates while at lower dose rates the MP appears to be dose rate independent. The depth dose measurement of the MP agrees with ion chamber depth dose measurements to within 0.7% while dose linearity was excellent. MP showed angular response dependency due to the anisotropy of the silicon diode with the maximum variation in angular response of 10.8% at gantry angle 180°. Angular dependence was within 3.5% for the gantry angles ± 75°. The field size dependence of the MP at isocenter agrees with ion chamber measurement to within 1.1%. In the beam perturbation study, the surface dose increased by 12.1% for a 30 × 30 cm(2) field size at the source to detector distance (SDD) of 80 cm whilst the transmission for the MP was 99%. The radiation response of the magic plate was successfully characterized. The array of epitaxial silicon based detectors with "drop-in" packaging showed properties suitable to be used as a simplified multipurpose and nonperturbing 2D radiation detector for radiation therapy dosimetric verification.
Imaging and radiation isocentre determination for inline MR-guided radiotherapy systems-proof of principle using MR-phantom with embedded monolithic silicon detector
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012008
Abstract: Multiple vendors are now offering real-time MRI-guided radiotherapy systems. Quality assurance of the imaging and radiation isocentre alignment is an essential component of the QA programme for any linear accelerator used for delivering image-guided radiotherapy. In this work, the authors describe the design and feasibility testing of a device that combines a high resolution monolithic silicon strip detector with an MRI visible phantom for characterisation of optical, MR imaging and radiation isocentre for inline MR-guided radiotherapy systems.
Comparative evaluation of modern dosimetry techniques near low- and high-density heterogeneities
Publisher: Wiley
Date: 09-2015
The use of a new 2D array of diodes for small-field dosimetry of a CyberKnife equipped with a novel multi-leaf collimator
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012007
Abstract: In the present work, we reported on the use of a new 2D array of diodes, the Duo, for dosimetry of small beams produced with a CyberKnife system, and shaped with a novel multi-leaf collimator, the InCise 2.
Microdosimetry at the 62 MeV Proton Beam of CATANA: Preliminary comparison of three detectors
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012006
Abstract: A microdosimetric characterization of the 62 MeV proton beam line of CATANA has been performed all along the Spread Out Bragg Peak with three different detectors. Two silicon detectors and a Tissue Equivalent Proportional Counter measured at approximately the same depths of the SOBP. The TEPC is a new miniaturized gas counter developed at the Legnaro National Laboratories of INFN, modified to work without gas flow. The first silicon detector has been developed at the Politecnico of Milano and it is a monolithic telescope composed by a matrix of 2 µm thick cylindrical diodes with a diameter 9 µm. that compose the ΔE layer. The E and ΔE layers are fabricated on a single substrate of silicon. The third detector is the MicroPlus probe developed at the CMRP - University of Wollongong, it is an array of 3D sensitive volumes each with dimension 30x30 µm and 10 µm thick fabricated on SOI. Measurements performed with the three detectors are presented and discussed.
Two-dimensional solid-state array detectors: A technique for in vivo dose verification in a variable effective area
Publisher: Wiley
Date: 14-10-2019
DOI: 10.1002/ACM2.12744
Quality assurance of VMAT on flattened and flattening filter-free accelerators using a high spatial resolution detector
Publisher: Wiley
Date: 11-04-2020
DOI: 10.1002/ACM2.12864
Microbeam radiation therapy: A Monte Carlo study of the influence of the source, multislit collimator, and beam divergence on microbeams
Publisher: Wiley
Date: 14-01-2009
DOI: 10.1118/1.3049786
Abstract: Microbeam radiation therapy (MRT) is a new oncology method currently under development for the treatment of inoperable pediatric brain tumors. Monte Carlo simulation, or the computational study of radiation transport in matter, is often used in radiotherapy to theoretically estimate the dose required for treatment. However, its potential use in MRT dose planning systems is currently hindered by the significant discrepancies that have been observed between measured and theoretical dose and the PVDR (peak to valley dose ratio). The need to resolve these discrepancies is driven by the desirability of making MRT available to humans in the next few years. This article aims to resolve some of the discrepancies by examining the simplifications adopted in previous MRT Monte Carlo studies, such as the common practice of commencing microbeam transport on the surface of the target which neglects the influence of the distributed synchrotron source, multislit collimator, and the beam ergence between them. This article uses PENELOPE Monte Carlo simulation to investigate the influence of these beamline components upstream of the target on the lateral dose profiles and PVDRs of an array of 25 microbeams. It also compares the dose profiles and PVDRs of a microbeam array produced from a single simulation (full array) to those produced from the superposition of a single microbeam profile (sup array). The effect of modeling the distributed source and the beam ergence was an increase in the absorbed dose in the penumbral and valley regions of the microbeam profiles. Inclusion of the multislit collimator resulted in differences of up to 5 microm in the FWHM of microbeam profiles across the array, which led to minor variations in the corresponding PVDR yields.
Study on the RBE estimation for carbon beam scanning irradiation using a solid-state microdosimeter
Publisher: Wiley
Date: 02-12-2020
DOI: 10.1002/MP.13924
Abstract: The purpose of this study was to study the field size effect on the estimated Relative Biological Effectiveness (RBE) for carbon scanning beam irradiation. A silicon-on-insulator (SOI) microdosimeter system developed by the Centre for Medical Radiation Physics, University of Wollongong, Australia, was used for lineal-energy measurements (microdosimetric quantity). The RBE values were derived based on the modified microdosimetric kinetic model (MKM) at different depths in a water phantom in the scanning carbon beam for various scanned areas. Our study shows that the difference in RBE values derived from the SOI microdosimeter measurements with the MKM model and from the Treatment Planning System (TPS). The difference of the RBE values is within 6.5 % at the peak point of the spread-out Bragg Peak (SOBP) region. Compared to the spot-beam, RBE values obtained in the scanned-beam with a larger scanned area of 1.0 × 1.0 cm This study shows the possibility of using the SOI microdosimeter system as a quality assurance (QA) tool for RBE evaluation in carbon-pencil beam scanning radiotherapy.
The microdosimetric extension in TOPAS: Development and comparison with published data
Publisher: IOP Publishing
Date: 11-07-2019
New 3D Silicon detectors for dosimetry in Microbeam Radiation Therapy
Publisher: IOP Publishing
Date: 2017
Introducing dynamic dosimaging: Potential applications for MRI-linac
Publisher: IOP Publishing
Date: 2017
History of International Workshop on Mini-Micro- and Nano- Dosimetry (MMND) and Innovation Technologies in Radiation Oncology (ITRO)
Publisher: IOP Publishing
Date: 2017
Design and development of PETiPIX: An ultra high spatial resolution small animal PET scanner
Publisher: IEEE
Date: 10-2013
INVESTIGATING VARIABLE RBE in A 12C MINIBEAM FIELD with MICRODOSIMETRY and GEANT4
Publisher: Oxford University Press (OUP)
Date: 21-01-2019
DOI: 10.1093/RPD/NCY234
Abstract: An experimental and simulation-based study was performed on a 12C ion minibeam radiation therapy (MBRT) field produced with a clinical broad beam and a brass multi-slit collimator (MSC). Silicon-on-insulator (SOI) microdosimeters developed at the Centre for Medical Radiation Physics (CMRP) with micron sized sensitive volumes were used to measure the microdosimetric spectra at varying positions throughout the MBRT field and the corresponding dose-mean lineal energies and RBE for 10% cell survival (RBE10) were calculated using the modified Microdosimetric Kinetic Model (MKM). An increase in the average RBE10 of ∼30% and 10% was observed in the plateau region compared to broad beam for experimental and simulation values, respectively. The experimental collimator misalignment was determined to be 0.7° by comparison between measured and simulated microdosimetric spectra at varying collimator angles. The simulated dose-mean lineal energies in the valley region between minibeams were found to be higher on average than in the minibeams due to higher LET particles being produced in these regions from the MSC. This work presents the first experimental microdosimetry measurements and characterisation of the local biological effectiveness in a MBRT field.
High-resolution entry and exit surface dosimetry in a 1.5 T MR-linac
Publisher: Springer Science and Business Media LLC
Date: 29-03-2023
DOI: 10.1007/S13246-023-01251-6
Abstract: The magnetic field of a transverse MR-linac alters electron trajectories as the photon beam transits through materials, causing lower doses at flat entry surfaces and increased doses at flat beam-exiting surfaces. This study investigated the response of a MOSFET detector, known as the MO Skin ™, for high-resolution surface and near-surface percentage depth dose measurements on an Elekta Unity. Simulations with Geant4 and the Monaco treatment planning system (TPS), and EBT-3 film measurements, were also performed for comparison. Measured MO Skin ™ entry surface doses, relative to D max , were (9.9 ± 0.2)%, (10.1 ± 0.3)%, (11.3 ± 0.6)%, (12.9 ± 1.0)%, and (13.4 ± 1.0)% for 1 × 1 cm 2 , 3 × 3 cm 2 , 5 × 5 cm 2 , 10 × 10 cm 2 , and 22 × 22 cm 2 fields, respectively. For the investigated fields, the maximum percent differences of Geant4, TPS, and film doses extrapolated and interpolated to a depth suitable for skin dose assessment at the beam entry, relative to MO Skin ™ measurements at an equivalent depth were 1.0%, 2.8%, and 14.3%, respectively, and at a WED of 199.67 mm at the beam exit, 3.2%, 3.7% and 5.7%, respectively. The largest measured increase in exit dose, due to the electron return effect, was 15.4% for the 10 × 10 cm 2 field size using the MO Skin ™ and 17.9% for the 22 × 22 cm 2 field size, using Geant4 calculations. The results presented in the study validate the suitability of the MO Skin ™ detector for transverse MR-linac surface dosimetry.
TH‐A‐137‐03: Application of the Dose Magnifying Glass to Proton Radiosurgery
Publisher: Wiley
Date: 06-2013
DOI: 10.1118/1.4815685
Editorial Conference Comments by the Editors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2017
Tissue equivalence study of a novel diamond-based microdosimeter for galactic cosmic rays and solar particle events
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
Deriving spatially resolved beta dose rates in sediment using the Timepix pixelated detector
Publisher: Elsevier BV
Date: 11-2017
New silicon microdosimetry probes for RBE and biological dose studies using stationary and movable targets in 12C ion therapy
Publisher: IOP Publishing
Date: 2017
In-silico calculations of DNA damage induced by α-particles in the 224Ra DaRT decay chain for a better understanding of the radiobiological effectiveness of this treatment
Publisher: Elsevier BV
Date: 08-2023
Monte Carlo study of the energy response and depth dose water equivalence of the MOSkin radiation dosimeter at clinical kilovoltage photon energies
Publisher: Springer Science and Business Media LLC
Date: 11-05-2011
DOI: 10.1007/S13246-011-0075-3
Abstract: Skin dose is often the quantity of interest for radiological protection, as the skin is the organ that receives maximum dose during kilovoltage X-ray irradiations. The purpose of this study was to simulate the energy response and the depth dose water equivalence of the MOSkin radiation detector (Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia), a MOSFET-based radiation sensor with a novel packaging design, at clinical kilovoltage photon energies typically used for superficial/orthovoltage therapy and X-ray CT imaging. Monte Carlo simulations by means of the Geant4 toolkit were employed to investigate the energy response of the CMRP MOSkin dosimeter on the surface of the phantom, and at various depths ranging from 0 to 6 cm in a 30 × 30 × 20 cm water phantom. By varying the thickness of the tissue-equivalent packaging, and by adding thin metallic foils to the existing design, the dose enhancement effect of the MOSkin dosimeter at low photon energies was successfully quantified. For a 5 mm diameter photon source, it was found that the MOSkin was water equivalent to within 3% at shallow depths less than 15 mm. It is recommended that for depths larger than 15 mm, the appropriate depth dose water equivalent correction factors be applied to the MOSkin at the relevant depths if this detector is to be used for depth dose assessments. This study has shown that the Geant4 Monte Carlo toolkit is useful for characterising the surface energy response and depth dose behaviour of the MOSkin.
Monte Carlo characterisation of the Dose Magnifying Glass for proton therapy quality assurance
Publisher: IOP Publishing
Date: 2017
Corrigendum: “Quality assurance of VMAT on flattened and flattening filter free accelerators using high spatial resolution detector” (Journal of Applied Clinical Medical Physics, (2020), 21, 6, (44-52), 10.1002/acm2.12864)
Publisher: Wiley
Date: 18-07-2020
DOI: 10.1002/ACM2.12967
Experimental studies with two novel silicon detectors for the development of time-of-flight spectrometry of laser-accelerated proton beams
Publisher: IOP Publishing
Date: 2017
Synchrotron activation radiotherapy: Effects of dose-rate and energy spectra to tantalum oxide nanoparticles selective tumour cell radiosentization enhancement
Publisher: IOP Publishing
Date: 02-2020
In-field and out-of-file application in 12C ion therapy using fully 3D silicon microdosimeters
Publisher: Elsevier BV
Date: 08-2018
Innovative detectors for quality assurance dosimetry in SBRT of stationary and movable targets
Publisher: IOP Publishing
Date: 2017
2D monolithic silicon-diode array detectors in megavoltage photon beams: does the fabrication technology matter? A medical physicist’s perspective
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.
Proton computed tomography: Update on current status
Publisher: IEEE
Date: 2007
The angular dependence of a two dimensional monolithic detector array for dosimetry in small radiation fields
Publisher: IOP Publishing
Date: 2017
The use of a silicon strip detector dose magnifying glass in stereotactic radiotherapy QA and dosimetry
Publisher: Wiley
Date: 14-02-2011
DOI: 10.1118/1.3549759
Abstract: Stereotactic radiosurgery/therapy (SRS/SRT) is the use of radiation ablation in place of conventional surgical excision to remove or create fibrous tissue in small target volumes. The target of the SRT/SRS treatment is often located in close proximity to critical organs, hence the requirement of high geometric precision including a tight margin on the planning target volume and a sharp dose fall off. One of the major problems with quality assurance (QA) of SRT/SRS is the availability of suitable detectors with the required spatial resolution. The authors present a novel detector that they refer to as the dose magnifying glass (DMG), which has a high spatial resolution (0.2 mm) and is capable of meeting the stringent requirements of QA and dosimetry in SRS/SRT therapy. The DMG is an array of 128 phosphor implanted n+ strips on a p-type Si wafer. The sensitive area defined by a single n+ strip is 20 x 2000 microm2. The Si wafer is 375 microm thick. It is mounted on a 0.12 mm thick Kapton substrate. The authors studied the dose per pulse (dpp) and angular response of the detector in a custom-made SRS phantom. The DMG was used to determine the centers of rotation and positioning errors for the linear accelerator's gantry, couch, and collimator rotations. They also used the DMG to measure the profiles and the total scatter factor (S(cp)) of the SRS cones. Comparisons were made with the EBT2 film and standard S(cp) values. The DMG was also used for dosimetric verification of a typical SRS treatment with various noncoplanar fields and arc treatments when applied to the phantom. The dose per pulse dependency of the DMG was found to be < 5% for a dpp change of 7.5 times. The angular response of the detector was investigated in the azimuthal and polar directions. The maximum polar angular response was 13.8% at the gantry angle of 320 degrees, which may be partly due to the phantom geometry. The maximum azimuthal angular response was 15.3% at gantry angles of 90 degrees and 270 degrees. The angular response at the gantry angle of 180 degrees was 6.3%. A correction function was derived to correct for the angular dependence of the detector, which takes into account the contribution of the azimuthal and polar angular response at different treatment couch positions. The maximum positioning errors due to collimator, gantry, and couch rotation were 0.2 +/- 0.1, 0.4 +/- 0.1, and 0.4 +/- 0.2 mm, respectively. The SRS cone S(cp) agrees very well with the standard data with an average difference of 1.2 +/- 1.1%. Comparison of the relative intensity profiles of the DMG and EBT2 measurements for a simulated SRS treatment shows a maximum difference of 2.5%. The DMG was investigated for dose per pulse and angular dependency. Its application to SRS/SRT delivery verification was demonstrated. The DMG with its high spatial resolution and real time capability allows measurement of dose profiles for cone applicators down to 5 mm in diameter, both accurately and rapidly as required in typical SRS/SRT deliveries.
Solid state microdosimetry with heavy ions for space applications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2007
A silicon strip detector dose magnifying glass for IMRT dosimetry
Publisher: Wiley
Date: 06-01-2010
DOI: 10.1118/1.3264176
Abstract: Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 microm) suitable for measuring the high dose gradients in an IMRT delivery. A full characterization of the detector was performed, including dose per pulse effect, percent depth dose comparison with Farmer ion chamber measurements, stem effect, dose linearity, uniformity, energy response, angular response, and penumbra measurements. They also present the application of the CMRP DMG in the dosimetric verification of a clinical IMRT plan. The detector response changed by 23% for a 390-fold change in the dose per pulse. A correction function is derived to correct for this effect. The strip detector depth dose curve agrees with the Farmer ion chamber within 0.8%. The stem effect was negligible (0.2%). The dose linearity was excellent for the dose range of 3-300 cGy. A uniformity correction method is described to correct for variations in the in idual detector pixel responses. The detector showed an over-response relative to tissue dose at lower photon energies with the maximum dose response at 75 kVp nominal photon energy. Penumbra studies using a Varian Clinac 21EX at 1.5 and 10.0 cm depths were measured to be 2.77 and 3.94 mm for the secondary collimators, 3.52 and 5.60 mm for the multileaf collimator rounded leaf ends, respectively. Point doses measured with the strip detector were compared to doses measured with EBT film and doses predicted by the Philips Pinnacle treatment planning system. The differences were 1.1% +/- 1.8% and 1.0% +/- 1.6%, respectively. They demonstrated the high temporal resolution capability of the detector readout system, which will allow one to investigate the temporal dose pattern of IMRT and volumetric modulated are therapy (VMAT) deliveries. The CMRP silicon strip detector dose magnifying glass interfaced to a TERA ASIC DAQ system has high spatial and temporal resolution. It is a novel and valuable tool for QA in IMRT dose delivery and for VMAT dose delivery.
Semiconductor microdosimetry in mixed radiation and photon fields: Present and future
Publisher: Oxford University Press (OUP)
Date: 09-1999
Temporal separation of Cerenkov radiation and scintillation using artificial neural networks in Clinical LINACs
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.EJMP.2018.10.007
Abstract: The irradiation of scintillator-fiber optic dosimeters by clinical LINACs results in the measurement of scintillation and Cerenkov radiation. In scintillator-fiber optic dosimetry, the scintillation and Cerenkov radiation responses are separated to determine the dose deposited in the scintillator volume. Artificial neural networks (ANNs) were trained and applied in a novel single probe method for the temporal separation of scintillation and Cerenkov radiation. Six dose profiles were measured using the ANN, with the dose profiles compared to those measured using background subtraction and an ionisation chamber. The average dose discrepancy of the ANN measured dose was 2.2% with respect to the ionisation chamber dose and 1.2% with respect to the background subtraction measured dose, while the average dose discrepancy of the background subtraction dose was 1.6% with respect to the ionisation chamber dose. The ANNs performance was degraded when compared with background subtraction, arising from an inaccurate model used to synthesise ANN training data.
Intraoperative solid-state based urethral dosimetry in low dose rate prostate brachytherapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2006
Application of p-i-n diodes and MOSFETS for dosimetry in gamma and neutron radiation fields
Publisher: Oxford University Press (OUP)
Date: 08-1999
A silicon strip detector array for energy verification and quality assurance in heavy ion therapy:
Publisher: Wiley
Date: 06-07-0016
DOI: 10.1002/MP.12736
Abstract: The measurement of depth dose profiles for range and energy verification of heavy ion beams is an important aspect of quality assurance procedures for heavy ion therapy facilities. The steep dose gradients in the Bragg peak region of these profiles require the use of detectors with high spatial resolution. The aim of this work is to characterize a one dimensional monolithic silicon detector array called the "serial Dose Magnifying Glass" (sDMG) as an independent ion beam energy and range verification system used for quality assurance conducted for ion beams used in heavy ion therapy. The sDMG detector consists of two linear arrays of 128 silicon sensitive volumes each with an effective size of 2mm × 50μm × 100μm fabricated on a p-type substrate at a pitch of 200 μm along a single axis of detection. The detector was characterized for beam energy and range verification by measuring the response of the detector when irradiated with a 290 MeV/u The relative response profiles along the single axis measured with the sDMG detector were found to have good agreement between experiment and simulation with the position of the Bragg peak determined to fall within 0.2 mm or 1.1% of the range in the detector for the two cases. The energy of the beam incident on the detector was found to vary less than 1% between experiment and simulation. The beam energy incident on the phantom was determined to be (280.9 ± 0.8) MeV/u from the experimental and (280.9 ± 0.2) MeV/u from the simulated profiles. These values coincide with the expected energy of 281 MeV/u. The sDMG detector response was studied experimentally and characterized using a Monte Carlo simulation. The sDMG detector was found to accurately determine the
Geometrical optimization of a particle tracking system for proton computed tomography
Publisher: Elsevier BV
Date: 12-2201
Improvement of SOI microdosimeter performance using pulse-shape discrimination techniques
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2002
Comparison of SOI microdosimeter and tissue equivalent proportional counter measurements at the CERF facility
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2012
An accurate method to quantify breathing-induced prostate motion for patients implanted with electromagnetic transponders
Publisher: SAGE Publications
Date: 03-2017
DOI: 10.5301/TJ.5000609
Abstract: To validate and apply a method for the quantification of breathing-induced prostate motion (BIPM) for patients treated with radiotherapy and implanted with electromagnetic transponders for prostate localization and tracking. For the analysis of electromagnetic transponder signal, dedicated software was developed and validated with a programmable breathing simulator phantom. The software was then applied to 1,132 radiotherapy fractions of 30 patients treated in supine position, and to a further 61 fractions of 2 patients treated in prone position. Application of the software in phantom demonstrated reliability of the developed method in determining simulated breathing frequencies and litudes. For supine patients, the in vivo analysis of BIPM resulted in median (maximum) litudes of 0.10 mm (0.35 mm), 0.24 mm (0.66 mm), and 0.17 mm (0.61 mm) in the left-right (LR), cranio-caudal (CC), and anterior-posterior (AP) directions, respectively. Breathing frequency ranged between 7.73 and 29.43 breaths per minute. For prone patients, the ranges of the BIPM litudes were 0.1-0.5 mm, 0.5-1.3 mm, and 0.7-1.7 mm in the LR, CC, and AP directions, respectively. The developed method was able to detect the BIPM with sub-millimeter accuracy. While for patients treated in supine position the BIPM represents a reduced source of treatment uncertainty, for patients treated in prone position, it can be higher than 3 mm.
Microdosemeter instrument (MIDN) for assessing risk in space
Publisher: Oxford University Press (OUP)
Date: 02-01-2011
DOI: 10.1093/RPD/NCQ525
Abstract: Radiation in space generally produces higher dose rates than that on the Earth's surface, and contributions from primary galactic and solar events increase with altitude within the magnetosphere. Presently, no personnel monitor is available to astronauts for real-time monitoring of dose, radiation quality and regulatory risk. This group is developing a prototypic instrument for use in an unknown, time-varying radiation field. This microdosemeter-dosemeter nucleon instrument is for use in a spacesuit, spacecraft, remote rover and other applications. It provides absorbed dose, dose rate and dose equivalent in real time so that action can be taken to reduce exposure. Such a system has applications in health physics, anti-terrorism and radiation-hardening of electronics as well. The space system is described and results of ground-based studies are presented and compared with predictions of transport codes. An early prototype in 2007 was successfully launched, the only solid-state microdosemeter to have flown in space.
Validation of linear energy transfer computed in a Monte Carlo dose engine of a commercial treatment planning system
Publisher: IOP Publishing
Date: 17-01-2020
Abstract: The relative biological effectiveness (RBE) of protons is highly variable and difficult to quantify. However, RBE is related to the local ionization density, which can be related to the physical measurable dose weighted linear energy transfer (LET
Optimisation of output factor measurements using the Magic Plate 512 silicon dosimeter array in small megavoltage photon fields
Publisher: IOP Publishing
Date: 2017
A feasibility study of PETiPIX: An ultra high resolution small animal PET scanner
Publisher: IOP Publishing
Date: 06-12-2013
Characterization of the mixed radiation field produced by carbon and oxygen ion beams of therapeutic energy: A Monte Carlo simulation study
Publisher: Medknow
Date: 2019
Independent quality assurance of a helical tomotherapy machine using the dose magnifying glass
Publisher: Wiley
Date: 30-03-2011
DOI: 10.1118/1.3566067
Abstract: Helical tomotherapy is a complex delivery technique, integrating CT image guidance and intensity modulated radiotherapy in a single system. The integration of the CT detector ring on the gantry not only allows patient position verification but is also often used to perform various QA procedures. This convenience lacks the rigor of a machine-independent QA process. In this article, a Si strip detector, known as the Dose Magnifying Glass (DMG), was used to perform machine-independent QA measurements of the multileaf collimator alignment, leaf open time threshold, and leaf fluence output factor (LFOF). The DMG measurements showed good agreements with EDR2 film for the MLC alignment test while the CT detector agrees well with DMG measurements for leaf open time threshold and LFOF measurements. The leaf open time threshold was found to be approximately 20 ms. The LFOF measured with the DMG agreed within error with the CT detector measured LFOF. The DMG with its 0.2 mm spatial resolution coupled to TERA ASIC allowed real-time high temporal resolution measurements of the tomotherapy leaf movement. In conclusion, DMG was shown to be a suitable tool for machine-independent QA of a tomotherapy unit.
A novel technique for compensation of space charge effects in the LUPIN-II detector
Publisher: Elsevier BV
Date: 12-2015
The effect of tissue inhomogeneities on the accuracy of proton path reconstruction for proton computed tomography
Publisher: AIP
Date: 2009
DOI: 10.1063/1.3120078
Development of a large-area silicon α-particle detector
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.APRADISO.2014.06.009
Abstract: Circular ion-implanted silicon detector of α-particles with a large, 5-cm(2), sensitive area has been developed. An advantage of the detector is that the detector surface is easily cleanable with chemicals. The hardened surface of the detector shows no signs of deterioration of the spectroscopic and electrical characteristics upon repeated cleaning. The energy resolution along the diameters of the detector was (1.0±0.1)% for the 5.486-MeV α-particles. Detailed tests of the charge collection efficiency and uniformity of the detector entrance window were also performed with a 5.5-MeV He(2+) microbeam.
Geant4 simulation model of electromagnetic processes in oriented crystals for accelerator physics
Publisher: Springer Science and Business Media LLC
Date: 29-06-2023
Nanoscale characterization of ion tracks: MC simulations versus analytical approach
Publisher: Springer Science and Business Media LLC
Date: 11-2012
Towards real time in-vivo rectal dosimetry during trans-rectal ultrasound based high dose rate prostate brachytherapy using MOSkin dosimeters
Publisher: Elsevier BV
Date: 10-2020
Comparison of phantom materials for use in quality assurance of microbeam radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 18-05-2017
DOI: 10.1107/S1600577517005641
Abstract: Microbeam radiation therapy (MRT) is a promising radiotherapy modality that uses arrays of spatially fractionated micrometre-sized beams of synchrotron radiation to irradiate tumours. Routine dosimetry quality assurance (QA) prior to treatment is necessary to identify any changes in beam condition from the treatment plan, and is undertaken using solid homogeneous phantoms. Solid phantoms are designed for, and routinely used in, megavoltage X-ray beam radiation therapy. These solid phantoms are not necessarily designed to be water-equivalent at low X-ray energies, and therefore may not be suitable for MRT QA. This work quantitatively determines the most appropriate solid phantom to use in dosimetric MRT QA. Simulated dose profiles of various phantom materials were compared with those calculated in water under the same conditions. The phantoms under consideration were RMI457 Solid Water (Gammex-RMI, Middleton, WI, USA), Plastic Water (CIRS, Norfolk, VA, USA), Plastic Water DT (CIRS, Norfolk, VA, USA), PAGAT (CIRS, Norfolk, VA, USA), RW3 Solid Phantom (PTW Freiburg, Freiburg, Germany), PMMA, Virtual Water (Med-Cal, Verona, WI, USA) and Perspex. RMI457 Solid Water and Virtual Water were found to be the best approximations for water in MRT dosimetry (within ±3% deviation in peak and 6% in valley). RW3 and Plastic Water DT approximate the relative dose distribution in water (within ±3% deviation in the peak and 5% in the valley). PAGAT, PMMA, Perspex and Plastic Water are not recommended to be used as phantoms for MRT QA, due to dosimetric discrepancies greater than 5%.
Neutron dosimeter development based on Medipix2
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2010
Characterization of angular detection dependence of prompt gamma-rays with respect to the Bragg peak in a water phantom using proton beam irradiations
Publisher: IEEE
Date: 10-2017
Small spot size versus large spot size: Effect on plan quality for lung cancer in pencil beam scanning proton therapy
Publisher: Wiley
Date: 06-01-2022
DOI: 10.1002/ACM2.13512
Abstract: The purpose of the current study was to evaluate the impact of spot size on the interplay effect, plan robustness, and dose to the organs at risk for lung cancer plans in pencil beam scanning (PBS) proton therapy The current retrospective study included 13 lung cancer patients. For each patient, small spot (∼3 mm) plans and large spot (∼8 mm) plans were generated. The Monte Carlo algorithm was used for both robust plan optimization and final dose calculations. Each plan was normalized, such that 99% of the clinical target volume (CTV) received 99% of the prescription dose. Interplay effect was evaluated for treatment delivery starting in two different breathing phases (T0 and T50). Plan robustness was investigated for 12 perturbed scenarios, which combined the isocenter shift and range uncertainty. The nominal and worst‐case scenario (WCS) results were recorded for each treatment plan. Equivalent uniform dose (EUD) and normal tissue complication probability (NTCP) were evaluated for the total lung, heart, and esophagus. In comparison to large spot plans, the WCS values of small spot plans at CTV D 95% , D 96% , D 97% , D 98% , and D 99% were higher with the average differences of 2.2% (range, 0.3%–3.7%), 2.3% (range, 0.5%–4.0%), 2.6% (range, 0.6%–4.4%), 2.7% (range, 0.9%–5.2%), and 2.7% (range, 0.3%–6.0%), respectively. The nominal and WCS mean dose and EUD for the esophagus, heart, and total lung were higher in large spot plans. The difference in NTCP between large spot and small spot plans was up to 1.9% for the total lung, up to 0.3% for the heart, and up to 32.8% for the esophagus. For robustness acceptance criteria of CTV D 95% ≥ 98% of the prescription dose, seven small spot plans had all 12 perturbed scenarios meeting the criteria, whereas, for 13 large spot plans, there were ≥2 scenarios failing to meet the criteria. Interplay results showed that, on average, the target coverage in large spot plans was higher by 1.5% and 0.4% in non‐volumetric and volumetric repainting plans, respectively. For robustly optimized PBS lung cancer plans in our study, a small spot machine resulted in a more robust CTV against the setup and range errors when compared to a large spot machine. In the absence of volumetric repainting, large spot PBS lung plans were more robust against the interplay effect. The use of a volumetric repainting technique in both small and large spot PBS lung plans led to comparable interplay target coverage.
Response of silicon diodes for synchrotron radiation
Publisher: IEEE
Date: 10-2012
Solid state diode - Ionization chamber method for measuring out-of-field neutron dose in proton therapy
Publisher: Elsevier BV
Date: 12-2011
Strip detector for short-range particles
Publisher: Elsevier BV
Date: 03-1993
Development of proton computed tomography for applications in proton therapy
Publisher: AIP
Date: 2009
DOI: 10.1063/1.3120073
Validation of the Geant4 PIXE component for incident carbon ions
Publisher: Elsevier BV
Date: 12-2022
Editorial conference comments by the editors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Cigarette Smoking, Diabetes, and Diabetes Complications: Call for Urgent Action
Publisher: Springer Science and Business Media LLC
Date: 08-2017
DOI: 10.1007/S11892-017-0903-2
Abstract: This review aimed to examine the latest evidence linking cigarette smoking and cessation to risk of incident diabetes and its complications. Abundant evidence has demonstrated that smoking is associated with increased risk of type 2 diabetes and cardiovascular disease among diabetic patients, while its relationship with microvascular complications is more limited to diabetic nephropathy and neuropathy in type 1 diabetes. In addition, diabetes risk remains high in the short term after smoking cessation, while it reduces gradually in the long term. Risk of cardiovascular complications also substantially decreases after quitting smoking, but results for microvascular complications are not consistent. Smoking is associated with increased risks of incident diabetes in the general population and cardiovascular complications among diabetic patients. Although the short-term post-cessation diabetes risk needs to be acknowledged, this review calls for urgent action to implement population-wide policies and in idual pharmaceutical and lifestyle interventions (if evidence accumulated in future) to aid smoking cessation and prevent diabetes and its complications.
Experimental characterization of magnetically focused electron contamination at the surface of a high-field inline MRI-linac
Publisher: Wiley
Date: 21-10-2019
DOI: 10.1002/MP.13847
Abstract: The fringe field of the Australian MRI-linac causes contaminant electrons to be focused along the central axis resulting in a high surface dose. This work aims to characterize this effect using Gafchromic film and high-resolution detectors, MOSkin The Australian MRI-linac has the unique feature that the linac is mounted on rails allowing for measurements to be performed at different magnetic field strengths while maintaining a constant source-to-surface distance (SSD). Percentage depth doses (PDD) were collected at SSD 1.82 m in a solid water phantom positioned in a low magnetic field region and then at isocenter of the MRI where the magnetic field is 1 T. Measurements for a range of field sizes were taken with the MOSkin Skin dose in the MRI, as measured with the MOSkin Experimental characterization of the high electron contamination at the surface was performed for a range of field sizes. The relative response of MOSkin
The relative biological effectiveness for carbon, nitrogen, and oxygen ion beams using passive and scanning techniques evaluated with fully 3D silicon microdosimeters
Publisher: Wiley
Date: 10-04-2018
DOI: 10.1002/MP.12874
Abstract: The aim of this study was to measure the microdosimetric distributions of a carbon pencil beam scanning (PBS) and passive scattering system as well as to evaluate the relative biological effectiveness (RBE) of different ions, namely Two different silicon microdosimeters with rectangular parallelepiped and cylindrical shaped SVs, both 10 μm in thickness were used in this study. The microdosimeters were connected to low noise electronics which allowed for the detection of lineal energies as low as 0.15 keV/μm in tissue. The silicon microdosimeters provide extremely high spatial resolution and can be used for in-field and out-of-field measurements in both passive scattering and PBS deliveries. The response of the microdosimeters was studied in 290 MeV/u For a 180 MeV/u These SOI microdosimeters with well-defined three-dimensional (3D) SVs have applicability in characterizing heavy ion radiation fields and measuring lineal energy deposition with sub-millimeter spatial resolution. It has been shown that the dose-mean lineal energy increased significantly at the distal part of the BP and SOBP due to very high LET particles. Good agreement was observed for the experimental and simulation results obtained with silicon microdosimeters in
Development of a new microdosimetric biological weighting function for the RBE10 assessment in case of the V79 cell line exposed to ions from 1H to 238U
Publisher: IOP Publishing
Date: 02-12-2020
Abstract: An improved biological weighting function (IBWF) is proposed to phenomenologically relate microdosimetric lineal energy probability density distributions with the relative biological effectiveness (RBE) for the in vitro clonogenic cell survival (surviving fraction = 10%) of the most commonly used mammalian cell line, i.e. the Chinese hamster lung fibroblasts (V79). The IBWF, intended as a simple and robust tool for a fast RBE assessment to compare different exposure conditions in particle therapy beams, was determined through an iterative global-fitting process aimed to minimize the average relative deviation between RBE calculations and literature in vitro data in case of exposure to various types of ions from 1 H to 238 U. By using a single particle- and energy- independent function, it was possible to establish an univocal correlation between lineal energy and clonogenic cell survival for particles spanning over an unrestricted linear energy transfer range of almost five orders of magnitude (0.2 keV µ m −1 to 15 000 keV µ m −1 in liquid water). The average deviation between IBWF-derived RBE values and the published in vitro data was ∼14%. The IBWF results were also compared with corresponding calculations ( in vitro RBE 10 for the V79 cell line) performed using the modified microdosimetric kinetic model (modified MKM). Furthermore, RBE values computed with the reference biological weighting function (BWF) for the in vivo early intestine tolerance in mice were included for comparison and to further explore potential correlations between the BWF results and the in vitro RBE as reported in previous studies. The results suggest that the modified MKM possess limitations in reproducing the experimental in vitro RBE 10 for the V79 cell line in case of ions heavier than 20 Ne. Furthermore, due to the different modelled endpoint, marked deviations were found between the RBE values assessed using the reference BWF and the IBWF for ions heavier than 2 H. Finally, the IBWF was unchangingly applied to calculate RBE values by processing lineal energy density distributions experimentally measured with eight different microdosimeters in 19 1 H and 12 C beams at ten different facilities (eight clinical and two research ones). Despite the differences between the detectors, irradiation facilities, beam profiles (pristine or spread out Bragg peak), maximum beam energy, beam delivery (passive or active scanning), energy degradation system (water, PMMA, polyamide or low-density polyethylene), the obtained IBWF-based RBE trends were found to be in good agreement with the corresponding ones in case of computer-simulated microdosimetric spectra (average relative deviation equal to 0.8% and 5.7% for 1 H and 12 C ions respectively).
Dose quantification in carbon ion therapy using in-beam positron emission tomography.
Publisher: IOP Publishing
Date: 12-2020
Abstract: This work presents an iterative method for the estimation of the absolute dose distribution in patients undergoing carbon ion therapy, via analysis of the distribution of positron annihilations resulting from the decay of positron-emitting fragments created in the target volume. The proposed method relies on the decomposition of the total positron-annihilation distributions into profiles of the three principal positron-emitting fragment species -
Response of a PIN diode and SOI microdosimeter to the TSL quasi-monoenergetic neutron field
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2011
The 16th solid state dosimetry conference (SSD16)
Publisher: Elsevier BV
Date: 12-2011
A validated Geant4 model of a whole-body PET scanner with four-layer DOI detectors.
Publisher: IOP Publishing
Date: 12-2020
Abstract: The purpose of this work is to develop a validated Geant4 simulation model of a whole-body prototype PET scanner constructed from the four-layer depth-of-interaction detectors developed at the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan. The simulation model emulates the behaviour of the unique depth of interaction sensing capability of the scanner without needing to directly simulate optical photon transport in the scintillator and photodetector modules. The model was validated by evaluating and comparing performance metrics from the NEMA NU 2-2012 protocol on both the simulated and physical scanner, including spatial resolution, sensitivity, scatter fraction, noise equivalent count rates and image quality. The results show that the average sensitivities of the scanner in the field-of-view were 5.9 cps kBq
Comparison of the new MOSkin detector and fiber optic dosimetry system for radiotherapy
Publisher: Informa UK Limited
Date: 06-2008
Temporal separation of Cerenkov radiation and scintillation using a clinical LINAC and artificial intelligence
Publisher: IOP Publishing
Date: 09-11-2018
Abstract: Convolutional neural network (CNN) type artificial intelligences were trained to estimate the Cerenkov radiation present in the temporal response of a LINAC irradiated scintillator-fiber optic dosimeter. The CNN estimate of Cerenkov radiation is subtracted from the combined scintillation and Cerenkov radiation temporal response of the irradiated scintillator-fiber optic dosimeter, giving the sole scintillation signal, which is proportional to the scintillator dose. The CNN measured scintillator dose was compared to the background subtraction measured scintillator dose and ionisation chamber measured dose. The dose discrepancy of the CNN measured dose was on average 1.4% with respect to the ionisation chamber measured dose, matching the 1.4% average dose discrepancy of the background subtraction measured dose with respect to the ionisation chamber measured dose. The developed CNNs had an average time of 3 ms to calculate scintillator dose, permitting the CNNs presented to be applicable for dosimetry in real time.
Ionization cross section data of nitrogen, methane, and propane for light ions and electrons and their suitability for use in track structure simulations
Publisher: American Physical Society (APS)
Date: 29-10-2013
Monte Carlo modelling of a silicon strip detector for microbeam radiation therapy
Publisher: Elsevier BV
Date: 12-2011
Real-time eye lens dose monitoring during cerebral angiography procedures
Publisher: Springer Science and Business Media LLC
Date: 23-05-2016
DOI: 10.1007/S00330-015-3818-9
Abstract: To develop a real-time dose-monitoring system to measure the patient's eye lens dose during neuro-interventional procedures. Radiation dose received at left outer canthus (LOC) and left eyelid (LE) were measured using Metal-Oxide-Semiconductor Field-Effect Transistor dosimeters on 35 patients who underwent diagnostic or cerebral embolization procedures. The radiation dose received at the LOC region was significantly higher than the dose received by the LE. The maximum eye lens dose of 1492 mGy was measured at LOC region for an AVM case, followed by 907 mGy for an aneurysm case and 665 mGy for a diagnostic angiography procedure. Strong correlations (shown as R(2)) were observed between kerma-area-product and measured eye doses (LOC: 0.78, LE: 0.68). Lateral and frontal air-kerma showed strong correlations with measured dose at LOC (AKL: 0.93, AKF: 0.78) and a weak correlation with measured dose at LE. A moderate correlation was observed between fluoroscopic time and dose measured at LE and LOC regions. The MOSkin dose-monitoring system represents a new tool enabling real-time monitoring of eye lens dose during neuro-interventional procedures. This system can provide interventionalists with information needed to adjust the clinical procedure to control the patient's dose. Real-time patient dose monitoring helps interventionalists to monitor doses. Strong correlation was observed between kerma-area-product and measured eye doses. Radiation dose at left outer canthus was higher than at left eyelid.
A Solid-State Microdosimeter for Dose and Radiation Quality Monitoring for Astronauts in Space
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Radiation dose enhancement at tissue-tungsten interfaces in HDR brachytherapy
Publisher: IOP Publishing
Date: 17-10-2014
DOI: 10.1088/0022-3727/59/21/6659
Abstract: HDR BrachyView is a novel in-body dosimetric imaging system for real-time monitoring and verification of the source position in high dose rate (HDR) prostate brachytherapy treatment. It is based on a high-resolution pixelated detector array with a semi-cylindrical multi-pinhole tungsten collimator and is designed to fit inside a compact rectal probe, and is able to resolve the 3D position of the source with a maximum error of 1.5 mm. This paper presents an evaluation of the additional dose that will be delivered to the patient as a result of backscatter radiation from the collimator. Monte Carlo simulations of planar and cylindrical collimators embedded in a tissue-equivalent phantom were performed using Geant4, with an (192)Ir source placed at two different source-collimator distances. The planar configuration was replicated experimentally to validate the simulations, with a MOSkin dosimetry probe used to measure dose at three distances from the collimator. For the cylindrical collimator simulation, backscatter dose enhancement was calculated as a function of axial and azimuthal displacement, and dose distribution maps were generated at three distances from the collimator surface. Although significant backscatter dose enhancement was observed for both geometries immediately adjacent to the collimator, simulations and experiments indicate that backscatter dose is negligible at distances beyond 1 mm from the collimator. Since HDR BrachyView is enclosed within a 1 mm thick tissue-equivalent plastic shell, all backscatter radiation resulting from its use will therefore be absorbed before reaching the rectal wall or other tissues. dosimetry, brachytherapy, HDR.
In vivo endorectal dosimetry of prostate tomotherapy using dual MOSkin detectors
Publisher: Wiley
Date: 05-2015
Abstract: Verification of dose to the anterior rectal wall in helical tomotherapy to the prostate is important due to the close proximity of the rectal wall to the treatment field. The steep dose gradient makes these measurements challenging. A phantom-based study was completed, aimed at developing a system for measurement of anterior rectal wall doses during hypofractionated prostate stereotactic body radiotherapy (SBRT) utilizing tomotherapy delivery. An array of four dual MOSkinTM dosimeters, spaced 1 cm apart, was placed on a replica Rectafix® immobilization spacer device. This Perspex probe is a more rigid alternative to rectal balloons, to improve geometric reproducibility. The doses at each point were measured in real time and compared to doses calculated by the treatment planning system (TPS). Additionally, distance-to-agreement (DTA) measurements were acquired to assist in the comparison of measured and predicted doses. All dual MOSkin detectors measured dose to within ± 5% of the TPS at the anterior rectal wall. Whilst several points were outside of experimental error, the largest deviation from the TPS predicted dose represented a DTA of only 1.3 mm, within the acceptable DTA tolerance of 3 mm. Larger deviations of up to -11.9% were observed for the posterior and side walls however, if acceptable DTA measurements are accounted for, then an agreement of 75% was observed. Although larger differences were observed at the other rectal wall locations, the overall effect of dose at these points was not as significant, given the lower doses. Despite the very high-dose gradient region, real-time measurements of the anterior rectal wall doses were within acceptable limits of TPS-predicted doses. The differences between measured and planned data were due to difficulties in precisely locating each detector on the TPS dose grid, which presented large variations in dose between CT voxels in regions of steep dose gradients. The dual MOSkin system would, therefore, be a useful device for detecting errors in real time, such as patient shifts or incorrect setup, during tomotherapy of the prostate.
Ten channel background alpha radiometer for nondestructive analysis of low activity samples
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-1992
DOI: 10.1109/23.173207
Retention and Recruitment of Oncology Pharmacists
Publisher: Wiley
Date: 06-2007
DOI: 10.1002/J.2055-2335.2007.TB00031.X
Abstract: A noticeable turnover of staff through the specialty of oncology pharmacy has been observed nationally. Literature searches failed to identify research directly relating to oncology pharmacist retention. Studies in pharmacists and non‐pharmacist oncology staff have determined that, while patient care and contact, personal accomplishment and satisfaction are important, stress levels and lack of professional support were factors considered when leaving the profession. To explore why pharmacists choose to remain in or leave the specialty of oncology pharmacy and identify strategies to ensure retention of current staff and aid recruitment of new oncology pharmacists. Electronic surveys designed to obtain retrospective quantitative and qualitative data were sent to: current oncology pharmacists former oncology pharmacists and directors of pharmacy at institutions with oncology services. Participants were identified through databases of the Society of Hospital Pharmacists of Australia, Clinical Oncological Society of Australia, and International Society of Oncology Pharmacy Practice. Reasons for pharmacists remaining in oncology generally related to job satisfaction issues (closely associated with clinical involvement). Reasons for leaving included stress levels, staffing issues, lack of recognition from hospital management and remuneration. Strategies for retaining staff should include improved pay structure, opportunities for professional development and continuing education, peer support, availability of suitably trained staff to cover periods of leave, positive feedback and support from hospital management, and devising methods for reducing work‐related stress. Implementation of information gained from this study will facilitate recruitment and retention of experienced, well‐trained oncology staff.
Alpha particle and proton relative thermoluminescence efficiencies in LIF:MG,CU,PIS track structure theory up to the task?
Publisher: Oxford University Press (OUP)
Date: 31-10-2012
DOI: 10.1093/RPD/NCR406
Abstract: Low-energy alpha particle and proton heavy charged particle (HCP) relative thermoluminescence (TL) efficiencies are calculated for the major dosimetric glow peak in LiF:Mg,Cu,P (MCP-N) in the framework of track structure theory (TST). The calculations employ previously published TRIPOS-E Monte Carlo track segment values of the radial dose in condensed phase LiF calculated at the Instituto National de Investigaciones Nucleares (Mexico) and experimentally measured normalised (60)Co gamma-induced TL dose-response functions, f(D), carried out at the Institute of Nuclear Physics (Poland). The motivation for the calculations is to test the validity of TST in a TL system in which f(D) is not supralinear (f(D) >1) and is not significantly dependent on photon energy contrary to the behaviour of the dose-response of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100). The calculated HCP relative efficiencies in LiF:MCP-N are 23-87% lower than the experimentally measured values, indicating a weakness in the major premise of TST which exclusively relates HCP effects to the radiation action of the secondary electrons liberated by the HCP slowing down. However, an analysis of the uncertainties involved in the TST calculations and experiments (i.e. experimental measurement of f(D) at high levels of dose, s le light self-absorption and accuracy in the estimation of D(r), especially towards the end of the HCP track) indicate that these may be too large to enable a definite conclusion. More accurate estimation of s le light self-absorption, improved measurements of f(D) and full-track Monte Carlo calculations of D(r) incorporating improvements of the low-energy electron transport are indicated in order to reduce uncertainties and enable a final conclusion.
Use of a megavoltage electronic portal imaging device to identify prosthetic materials
Publisher: Springer Science and Business Media LLC
Date: 10-01-2015
DOI: 10.1007/S13246-015-0327-8
Abstract: To achieve accurate dose calculations in radiation therapy the electron density of patient tissues must be known. This information is ordinarily gained from a computed tomography (CT) image that has been calibrated to allow relative electron density (RED) to be determined from CT number. When high density objects such as metallic prostheses are involved, direct use of the CT data can become problematic due to the artefacts introduced by high attenuation of the beam. This requires manual correction of the density values, however the properties of the implanted prosthetic are not always known. A method is introduced where the RED of such an object can be determined using the treatment beam of a linear accelerator with an electronic portal imaging device. The technique was tested using a metallic hip replacement that was placed within a container of water. Compared to the theoretical RED of 6.8 for cobalt-chromium alloy, these measurements calculated a value of 6.4 ± 0.7. This would allow the distinction of an implant as Co-Cr or steel, which have similar RED, or titanium, which is much less dense with an RED of 3.7.
Radiosensitisation enhancement effect of BrUdR and Ta2 O5 NSPs in combination with 5-Fluorouracil antimetabolite in kilovoltage and megavoltage radiation
Publisher: IOP Publishing
Date: 17-04-2018
The impact of sensitive volume thickness for silicon on insulator microdosimeters in hadron therapy
Publisher: IOP Publishing
Date: 24-01-2020
Abstract: Compact silicon on insulator (SOI) microdosimeters have been used to characterise the radiation field of many different hadron therapy beams. SOI devices are particularly attractive in hadron therapy fields due to their spatial resolution being well suited to the sharp dose gradients at the end of the primary beam's range. Due to the small size of SOI's sensitive volumes (SVs), which are usually ∼1-10 [Formula: see text]m thick, the fabrication of these devices can present challenges which are not as common for more conventional thickness silicon devices such as silicon spectroscopy detectors. Microdosimetry is the study of the energy deposition in micrometre sized volumes representing biological sites and is a powerful approach to estimate the biological effect of radiation on the micron-scale level, in a cell. However, cell sizes vary extensively translating in different energy deposition spectra. This work studies SV thicknesses between 1 and 100 [Formula: see text]m using Geant4 and examines the impact of SV dimensions on microdosimetric quantities. The quantities studied were the frequency mean lineal energy, [Formula: see text], and the dose mean lineal energy, [Formula: see text]. Additionally the relative biological effectiveness (RBE), estimated by the microdosimetric kinetic model (MKM), is also investigated. To study the impact of the SV thickness, SOI microdosimeters were irradiated with proton, [Formula: see text] and [Formula: see text] ion beams with ranges of ∼160 mm, with the microdosimeter being set at various positions along the Bragg curve. It was found that [Formula: see text] was influenced the least in proton beams and increased for heavier ion beams. Conversely, [Formula: see text] was impacted by the SV thickness the most in proton beams and [Formula: see text] was the least. Similar to [Formula: see text], protons were impacted the most by the SV thickness when estimating the RBE using the MKM. The cause of these differences was largely due to the different densities of the delta electron track structure for the case of [Formula: see text] and the energy transferred to the medium from the primary beam for [Formula: see text].
Evolution of alpha particle tracks in silicon strip detectors
Publisher: Elsevier BV
Date: 1991
Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates
Publisher: IOP Publishing
Date: 07-2016
Engineering of bismuth oxide nanoparticles to induce differential biochemical activity in malignant and nonmalignant cells
Publisher: Wiley
Date: 09-04-2014
From PET detectors to PET scanners
Publisher: Springer Science and Business Media LLC
Date: 02-10-2003
DOI: 10.1007/S00259-003-1266-2
Abstract: This review describes the properties of available and emerging radiation detector and read-out technologies and discusses how they may affect PET scanner performance. After a general introduction, there is a section in which the physical properties of several different detector scintillators are compared. This is followed by a discussion of recent advances in read-out electronics. Finally, the physical performance of the several commercial PET scanners is summarized.
BrachyView, a novel in-body imaging system for HDR prostate brachytherapy: Experimental evaluation
Publisher: Wiley
Date: 19-11-2015
DOI: 10.1118/1.4935866
Abstract: This paper presents initial experimental results from a prototype of high dose rate (HDR) BrachyView, a novel in-body source tracking system for HDR brachytherapy based on a multipinhole tungsten collimator and a high resolution pixellated silicon detector array. The probe and its associated position estimation algorithms are validated and a comprehensive evaluation of the accuracy of its position estimation capabilities is presented. The HDR brachytherapy source is moved through a sequence of positions in a prostate phantom, for various displacements in x, y, and z. For each position, multiple image acquisitions are performed, and source positions are reconstructed. Error estimates in each dimension are calculated at each source position and combined to calculate overall positioning errors. Gafchromic film is used to validate the accuracy of source placement within the phantom. More than 90% of evaluated source positions were estimated with an error of less than one millimeter, with the worst-case error being 1.3 mm. Experimental results were in close agreement with previously published Monte Carlo simulation results. The prototype of HDR BrachyView demonstrates a satisfactory level of accuracy in its source position estimation, and additional improvements are achievable with further refinement of HDR BrachyView's image processing algorithms.
Response of a SOI microdosimeter to a238PuBe neutron source
Publisher: IEEE
Date: 2005
IBIC microscopy – The powerful tool for testing micron – Sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies
Publisher: Elsevier BV
Date: 11-2019
SOI thin microdosimeter detectors for low-energy ions and radiation damage studies
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Synchrotron X-ray microbeam dosimetry with a 20 micrometre resolution scintillator fibre-optic dosimeter
Publisher: International Union of Crystallography (IUCr)
Date: 24-04-2018
DOI: 10.1107/S1600577518003016
Abstract: Cancer is one of the leading causes of death worldwide. External beam radiation therapy is one of the most important modalities for the treatment of cancers. Synchrotron microbeam radiation therapy (MRT) is a novel pre-clinical therapy that uses highly spatially fractionated X-ray beams to target tumours, allowing doses much higher than conventional radiotherapies to be delivered. A dosimeter with a high spatial resolution is required to provide the appropriate quality assurance for MRT. This work presents a plastic scintillator fibre optic dosimeter with a one-dimensional spatial resolution of 20 µm, an improvement on the dosimeter with a resolution of 50 µm that was demonstrated in previous work. The ability of this probe to resolve microbeams of width 50 µm has been demonstrated. The major limitations of this method were identified, most notably the low-light signal resulting from the small sensitive volume, which made valley dose measurements very challenging. A titanium-based reflective paint was used as a coating on the probe to improve the light collection, but a possible effect of the high- Z material on the probes water-equivalence has been identified. The effect of the reflective paint was a 28.5 ± 4.6% increase in the total light collected it did not affect the shape of the depth-dose profile, nor did it explain an over-response observed when used to probe at low depths, when compared with an ionization chamber. With improvements to the data acquisition, this probe design has the potential to provide a water-equivalent, inexpensive dosimetry tool for MRT.
Performance of silicon microdosimetry detectors in boron neutron capture therapy
Publisher: JSTOR
Date: 03-1999
DOI: 10.2307/3579934
The dose magnifying glass quality assurance system for daily proton therapy range verification
Publisher: IOP Publishing
Date: 23-04-2021
Abstract: Proton therapy has a distinct dosimetric advantage over conventional photon therapy due to its Bragg peak profile. This allows greater accuracy in dose delivery and dose conformation to the target, however it requires greater precision in setup, delivery and for quality assurance (QA) procedures. The AAPM TG 224 report recommends daily range and spot position checks with tolerance on the order of a millimetre. Daily QA systems must therefore be efficient for daily use and be capable of sub-millimetre precision however few suitable commercial systems are available. In this work, a compact, real-time daily QA system is optimised and characterised for proton range verification using an ad-hoc Geant4 simulation. The system is comprised of a monolithic silicon diode array detector embedded in a perspex phantom. The detector is orientated at an angular offset to the incident proton beam to allow range in perspex to be determined for flat proton fields. The accuracy of the system for proton range in perspex measurements was experimentally evaluated over the full range of clinical proton energies. The mean R 100 , R 90 and R 80 ranges measured with the system were accurate within ±0.6 mm of simulated ranges in a perspex phantom for all energies assessed. This system allows real-time read-out of in idual detector channels also making it appropriate for temporal beam delivery diagnostics and for spot position monitoring along one axis. The system presented provides a suitable, economical and efficient alternative for daily QA in proton therapy.
Evaluation of silicon based microdosimetry for Boron Neutron Capture Therapy Quality Assurance
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.EJMP.2019.09.072
Abstract: The shift from reactor to accelerator based neutron production has created a renewed interested in Boron Neutron Capture Therapy (BNCT). BNCT is reliant upon the favourable uptake of
2D mapping of the MV photon fluence and 3D dose reconstruction in real time for quality assurance during radiotherapy treatment
Publisher: IOP Publishing
Date: 17-09-2015
High-Z nanostructured ceramics in radiotherapy: First evidence of Ta 2 O5 -induced dose enhancement on radioresistant cancer cells in an MV photon field
Publisher: Wiley
Date: 16-10-2014
Modelling of reusable target materials for the production of fission produced 99Mo using MCNP6.2 and CINDER90
Publisher: Elsevier BV
Date: 10-2021
Characterization of a novel diamond-based microdosimeter prototype for radioprotection applications in space environments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
The investigation of prostatic calcifications using μ-PIXE analysis and their dosimetric effect in low dose rate brachytherapy treatments using Geant4
Publisher: IOP Publishing
Date: 18-05-2015
DOI: 10.1088/0031-9155/60/11/4335
Abstract: Low dose rate brachytherapy is a widely used modality for the treatment of prostate cancer. Most clinical treatment planning systems currently in use approximate all tissue to water, neglecting the existence of inhomogeneities, such as calcifications. The presence of prostatic calcifications may perturb the dose due to the higher photoelectric effect cross section in comparison to water. This study quantitatively evaluates the effect of prostatic calcifications on the dosimetric outcome of brachytherapy treatments by means of Monte Carlo simulations and its potential clinical consequences.Four pathological calcification s les were characterised with micro-particle induced x-ray emission (μ-PIXE) to determine their heavy elemental composition. Calcium, phosphorus and zinc were found to be the predominant heavy elements in the calcification composition. Four clinical patient brachytherapy treatments were modelled using Geant4 based Monte Carlo simulations, in terms of the distribution of brachytherapy seeds and calcifications in the prostate. Dose reductions were observed to be up to 30% locally to the calcification boundary, calcification size dependent. Single large calcifications and closely placed calculi caused local dose reductions of between 30-60%. In idual calculi smaller than 0.5 mm in diameter showed minimal dosimetric impact, however, the effects of small or diffuse calcifications within the prostatic tissue could not be determined using the methods employed in the study. The simulation study showed a varying reduction on common dosimetric parameters. D90 showed a reduction of 2-5%, regardless of calcification surface area and volume. The parameters V100, V150 and V200 were also reduced by as much as 3% and on average by 1%. These reductions were also found to relate to the surface area and volume of calcifications, which may have a significant dosimetric impact on brachytherapy treatment, however, such impacts depend strongly on specific factors in the patient's in idual treatment. These factors include the number, size, composition and spatial distribution of calcifications in the prostate as well as the distribution of brachytherapy seeds.
MIDN: A spacecraft microdosimeter mission
Publisher: Oxford University Press (OUP)
Date: 18-06-2006
DOI: 10.1093/RPD/NCI601
Abstract: MIDN (MIcroDosimetry iNstrument) is a payload on the MidSTAR-I spacecraft (Midshipman Space Technology Applications Research) under development at the United States Naval Academy. MIDN is a solid-state system being designed and constructed to measure microdosimetric spectra to determine radiation quality factors for space environments. Radiation is a critical threat to the health of astronauts and to the success of missions in low-Earth orbit and space exploration. The system will consist of three separate sensors, one external to the spacecraft, one internal and one embedded in polyethylene. Design goals are mass <3 kg and power <2 W. The MidSTAR-I mission in 2006 will provide an opportunity to evaluate a preliminary version of this system. Its low power and mass makes it useful for the International Space Station and manned and unmanned interplanetary missions as a real-time system to assess and alert astronauts to enhanced radiation environments.
CyberKnife® fixed cone and Iris™ defined small radiation fields: Assessment with a high-resolution solid-state detector array
Publisher: Wiley
Date: 12-07-2018
DOI: 10.1002/ACM2.12414
Validation of a Monte Carlo simulation for Microbeam Radiation Therapy on the Imaging and Medical Beamline at the Australian Synchrotron
Publisher: Springer Science and Business Media LLC
Date: 27-11-2019
DOI: 10.1038/S41598-019-53991-9
Abstract: Microbeam Radiation Therapy (MRT) is an emerging cancer treatment modality characterised by the use of high-intensity synchrotron-generated x-rays, spatially fractionated by a multi-slit collimator (MSC), to ablate target tumours. The implementation of an accurate treatment planning system, coupled with simulation tools that allow for independent verification of calculated dose distributions are required to ensure optimal treatment outcomes via reliable dose delivery. In this article we present data from the first Geant4 Monte Carlo radiation transport model of the Imaging and Medical Beamline at the Australian Synchrotron. We have developed the model for use as an independent verification tool for experiments in one of three MRT delivery rooms and therefore compare simulation results with equivalent experimental data. The normalised x-ray spectra produced by the Geant4 model and a previously validated analytical model, SPEC, showed very good agreement using wiggler magnetic field strengths of 2 and 3 T. However, the validity of absolute photon flux at the plane of the Phase Space File (PSF) for a fixed number of simulated electrons was unable to be established. This work shows a possible limitation of the G 4 SynchrotronRadiation process to model synchrotron radiation when using a variable magnetic field. To account for this limitation, experimentally derived normalisation factors for each wiggler field strength determined under reference conditions were implemented. Experimentally measured broadbeam and microbeam dose distributions within a Gammex RMI457 Solid Water ® phantom were compared to simulated distributions generated by the Geant4 model. Simulated and measured broadbeam dose distributions agreed within 3% for all investigated configurations and measured depths. Agreement between the simulated and measured microbeam dose distributions agreed within 5% for all investigated configurations and measured depths.
Feasibility study of solid-state microdosimetry for energetic protons and heavy ions with coincident particle identification
Publisher: Elsevier BV
Date: 12-2011
On the measurement uncertainty of microdosimetric quantities using diamond and silicon microdosimeters in carbon-ion beams
Publisher: Wiley
Date: 09-09-2022
DOI: 10.1002/MP.15929
Abstract: The purpose of this paper is to compare the response of two different types of solid‐state microdosimeters, that is, silicon and diamond, and their uncertainties. A study of the conversion of silicon microdosimetric spectra to the diamond equivalent for microdosimeters with different geometry of the sensitive volumes is performed, including the use of different stopping power databases. Diamond and silicon microdosimeters were irradiated under the same conditions, aligned at the same depth in a carbon‐ion beam at the MedAustron ion therapy center. In order to estimate the microdosimetric quantities, the readout electronic linearity was investigated with three different methods, that is, the first being a single linear regression, the second consisting of a double linear regression with a channel transition and last a multiple linear regression by splitting the data into odd and even groups. The uncertainty related to each of these methods was estimated as well. The edge calibration was performed using the intercept with the horizontal axis of the tangent through the inflection point of the Fermi function approximation multi‐channel analyzer spectrum. It was assumed that this point corresponds to the maximum energy difference of particle traversing the sensitive volume (SV) for which the residual range difference in the continuous slowing down approximation is equal to the thickness of the SV of the microdosimeter. Four material conversion methods were explored, the edge method, the density method, the maximum‐deposition energy method and the bin‐by‐bin transformation method. The uncertainties of the microdosimetric quantities resulting from the linearization, the edge calibration and the detectors thickness were also estimated. It was found that the double linear regression had the lowest uncertainty for both microdosimeters. The propagated standard ( k = 1) uncertainties on the frequency‐mean lineal energy and the dose‐mean lineal energy values from the marker point, in the spectra, in the plateau were 0.1% and 0.2%, respectively, for the diamond microdosimeter, whilst for the silicon microdosimeter data converted to diamond, the uncertainty was estimated to be 0.1%. In the range corresponding to the 90% of the litude of the Bragg Peak at the distal part of the Bragg curve (R 90 ) the uncertainty was found to be 0.1%. The uncertainty propagation from the stopping power tables was estimated to be between 5% and 7% depending on the method. The uncertainty on the and coming from the thickness of the detectors varied between 0.3% and 0.5%. This article demonstrate that the linearity of the readout electronics affects the microdosimetric spectra with a difference in values between the different linearization methods of up to 17.5%. The combined uncertainty was dominated by the uncertainty of stopping power on the edge.
Normal tissue dose and second cancer risk due to megavoltage fan-beam CT, static tomotherapy and helical tomotherapy in breast radiotherapy
Publisher: Elsevier BV
Date: 08-2013
DOI: 10.1016/J.RADONC.2013.05.019
Abstract: This study investigates the dose from the 1mm collimator width megavoltage fan-beam CT (fine, normal and coarse pitch) available on tomotherapy as well as for whole-breast tomotherapy treatments. The BEIR VII lifetime attributable risk model was utilised to assess the significance of the imaging dose relative to the treatment dose.
Impact of a monolithic silicon detector operating in transmission mode on clinical photon beams
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.EJMP.2017.10.017
Abstract: To investigate the effect on surface dose, as a function of different field sizes and distances from the solid water phantom to transmission detector (D The influence of operating the MP512T in transmission mode on the surface dose of a phantom for SSD 100cm was evaluated by using a Markus IC. The MP512T was fixed to an adjustable stand holder and was positioned at different D For all D The study demonstrated that positioning the MP512T in air between the Linac head and the phantom produced negligible perturbation of the surface dose for D
Effect of a magnetic field on the track structure of low-energy electrons: A Monte Carlo study
Publisher: Springer Science and Business Media LLC
Date: 26-05-2010
Temporal modelling of beryllium oxide ceramics’ real-time OSL for dosimetry with a superficial 140 kVp X-ray beam
Publisher: Elsevier BV
Date: 12-2020
Indirect radio-chemo-beta therapy: A targeted approach to increase biological efficiency of x-rays based on energy
Publisher: IOP Publishing
Date: 25-09-2015
DOI: 10.1088/0031-9155/60/20/7847
Abstract: Despite the use of multimodal treatments incorporating surgery, chemotherapy and radiotherapy, local control of gliomas remains a major challenge. The potential of a new treatment approach called indirect radio-chemo-beta therapy using the synergy created by combining methotrexate (MTX) with bromodeoxyuridine (BrUdR) under optimum energy x-ray irradiation is assessed. 9L rat gliosarcoma cells pre-treated with 0.01 μM MTX and/or 10 μM BrUdR were irradiated in vitro with 50 kVp, 125 kVp, 250 kVp, 6 MV and 10 MV x-rays. The cytotoxicity was assessed using clonogenic survival as the radiobiological endpoint. The photon energy with maximum effect was determined using radiation sensitization enhancement factors at 10% clonogenic survival (SER10%). The cell cycle distribution was investigated using flow cytometric analysis with propidium iodide staining. Incorporation of BrUdR in the DNA was detected by the fluorescence of labelled anti-BrUdR antibodies. The radiation sensitization enhancement exhibits energy dependence with a maximum of 2.3 at 125 kVp for the combined drug treated cells. At this energy, the shape of the clonogenic survival curve of the pharmacological agents treated cells changes substantially. This change is interpreted as an increased lethality of the local radiation environment and is attributed to supplemented inhibition of DNA repair. Radiation induced chemo-beta therapy was demonstrated in vitro by the targeted activation of combined pharmacological agents with optimized energy tuning of x-ray beams on 9 L cells. Our results show that this is a highly effective form of chemo-radiation therapy.
On the Combined Effect of Silicon Oxide Thickness and Boron Implantation under the Gate in MOSFET Dosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2020
First application of a high-resolution silicon detector for proton beam Bragg peak detection in a 0.95 T magnetic field
Publisher: Wiley
Date: 04-11-2020
DOI: 10.1002/MP.13871
Abstract: To report on experimental results of a high spatial resolution silicon-based detector exposed to therapeutic quality proton beams in a 0.95 T transverse magnetic field. These experimental results are important for the development of accurate and novel dosimetry methods in future potential real-time MRI-guided proton therapy systems. A permanent magnet device was utilized to generate a 0.95 T magnetic field over a 4 × 20 × 15 cm The nominal Bragg peak for each proton energy was successfully observed with a 0.2 mm spatial resolution in the 0.95 T transverse magnetic field in both a depth and lateral profiles. The proton beam deflection (at 0.95 T) was a consistent 2 ±0.5 mm at the center of the magnetic volume for each beam energy. However, a pristine Bragg peak was not observed for each energy. This was caused by the detector packaging having small air gaps between layers of the phantom material surrounding the diode array. These air gaps act to degrade the shape of the Bragg peak, and further to this, the nonwater equivalent silicon chip acts to separate the Bragg peak into multiple peaks depending on the proton path taken. Overall, a promising performance of the silicon detector array was observed, however, with a qualitative assessment rather than a robust quantitative dosimetric evaluation at this stage of development. For the first time, a high-resolution silicon-based radiation detector has been used to measure proton beam Bragg peak deflections in a phantom due to a strong magnetic field. Future efforts are required to optimize the detector packaging to strengthen the robustness of the dosimetric quantities obtained from the detector. Such high-resolution silicon diode arrays may be useful in future efforts in MRI-guided proton therapy research.
In vivo real-time rectal wall dosimetry for prostate radiotherapy
Publisher: IOP Publishing
Date: 22-06-2010
Evaluation of the PTW microDiamond in edge-on orientation for dosimetry in small fields
Publisher: Wiley
Date: 22-05-2020
DOI: 10.1002/ACM2.12906
Editorial conference comments by the general chairman
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2007
Method of Monte Carlo simulation verification in hadron therapy with non-tissue equivalent detectors
Publisher: Oxford University Press (OUP)
Date: 27-04-2006
DOI: 10.1093/RPD/NCI618
Abstract: In hadron therapy the spectra of secondary particles can be very broad in type and energy. The most accurate calculations of tissue equivalent (TE) absorbed dose and biological effect can be achieved using Monte Carlo (MC) simulations followed by the application of an appropriate radiobiological model. The verification of MC simulations is therefore an important quality assurance (QA) issue in dose planning. We propose a method of verification for MC dose calculations based on measurements of either the integral absorbed dose or the spectra of deposited energies from single secondary particles in non-TE material detectors embedded in a target of interest (phantom). This method was tested in boron neutron capture therapy and fast neutron therapy beams.
Functional characterisation of novel silicon beam monitors for the micro-beam radiation therapy
Publisher: IEEE
Date: 10-2016
X-Tream quality assurance in synchrotron X-ray microbeam radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 26-07-2016
DOI: 10.1107/S1600577516009322
Abstract: Microbeam radiation therapy (MRT) is a novel irradiation technique for brain tumours treatment currently under development at the European Synchrotron Radiation Facility in Grenoble, France. The technique is based on the spatial fractionation of a highly brilliant synchrotron X-ray beam into an array of microbeams using a multi-slit collimator (MSC). After promising pre-clinical results, veterinary trials have recently commenced requiring the need for dedicated quality assurance (QA) procedures. The quality of MRT treatment demands reproducible and precise spatial fractionation of the incoming synchrotron beam. The intensity profile of the microbeams must also be quickly and quantitatively characterized prior to each treatment for comparison with that used for input to the dose-planning calculations. The Centre for Medical Radiation Physics (University of Wollongong, Australia) has developed an X-ray treatment monitoring system (X-Tream) which incorporates a high-spatial-resolution silicon strip detector (SSD) specifically designed for MRT. In-air measurements of the horizontal profile of the intrinsic microbeam X-ray field in order to determine the relative intensity of each microbeam are presented, and the alignment of the MSC is also assessed. The results show that the SSD is able to resolve in idual microbeams which therefore provides invaluable QA of the horizontal field size and microbeam number and shape. They also demonstrate that the SSD used in the X-Tream system is very sensitive to any small misalignment of the MSC. In order to allow as rapid QA as possible, a fast alignment procedure of the SSD based on X-ray imaging with a low-intensity low-energy beam has been developed and is presented in this publication.
Microdosimetry of a therapeutic proton beam with a mini-TEPC and a MicroPlus-Bridge detector for RBE assessment
Publisher: IOP Publishing
Date: 09-12-2020
Abstract: Proton beams are widely used worldwide to treat localized tumours, the lower entrance dose and no exit dose, thus sparing surrounding normal tissues, being the main advantage of this treatment modality compared to conventional photon techniques. Clinical proton beam therapy treatment planning is based on the use of a general relative biological effectiveness (RBE) of 1.1 along the whole beam penetration depth, without taking into account the documented increase in RBE at the end of the depth dose profile, in the Bragg peak and beyond. However, an inaccurate estimation of the RBE can cause both underdose or overdose, in particular it can cause the unfavourable situation of underdosing the tumour and overdosing the normal tissue just beyond the tumour, which limits the treatment success and increases the risk of complications. In view of a more precise dose delivery that takes into account the variation of RBE, experimental microdosimetry offers valuable tools for the quality assurance of LET or RBE-based treatment planning systems. The purpose of this work is to compare the response of two different microdosimetry systems: the mini-TEPC and the MicroPlus-Bridge detector. Microdosimetric spectra were measured across the 62 MeV spread out Bragg peak of CATANA with the mini-TEPC and with the Bridge microdosimeter. The frequency and dose distributions of lineal energy were compared and the different contributions to the spectra were analysed, discussing the effects of different site sizes and chord length distributions. The shape of the lineal energy distributions measured with the two detectors are markedly different, due to the different water-equivalent sizes of the sensitive volumes: 0.85 μm for the TEPC and 17.3 μm for the silicon detector. When the Loncol’s biological weighting function is applied to calculate the microdosimetric assessment of the RBE, both detectors lead to results that are consistent with biological survival data for glioma U87 cells. Both the mini-TEPC and the MicroPlus-Bridge detector can be used to assess the RBE variation of a 62 MeV modulated proton beam along its penetration depth. The microdosimetric assessment of the RBE based on the Loncol’s weighting function is in good agreement with radiobiological results when the 10% biological uncertainty is taken into account.
Investigation of in vivo source tracking error thresholds for interstitial and intra-cavitary high-dose-rate cervical brachytherapy
Publisher: Termedia Sp. z.o.o.
Date: 2022
A cylindrical silicon-on-insulator microdosimeter: Charge collection characteristics
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2008
RBE estimation of proton radiation fields using a Δe-E telescope
Publisher: Wiley
Date: 09-09-2202
DOI: 10.1118/1.3215927
Abstract: A new monolithic silicon DeltaE-E telescope was evaluated in unmodulated and modulated 100 MeV proton beams used for hadron therapy. Compared to a classical microdosimetry detector, which provides one-dimensional information on lineal energy of charged particles, this detector system provides two-dimensional information on lineal energy and particle energy based on energy depositions, collected in coincidence, within the DeltaE and E stages of the detector. The authors investigated the possibility to use the information obtained with the DeltaE-E telescope to determine the relative biological effectiveness (RBE) at defined locations within the proton Bragg peak and spread-out Bragg peak (SOBP). An RBE matrix based on the established in vitro V79 cell survival data was developed to link the output of the device directly to RBE(alpha), the RBE in the low-dose limit, at various depths in a homogeneous polystyrene phantom. In the SOBP of a 100 MeV proton beam, the RBE(alpha) increased from 4.04 proximal to the SOBP to a maximum value of 5.4 at the distal edge. The DeltaE-E telescope, with its high spatial resolution, has potential applications to biologically weighted hadron treatment planning as it provides a compact and portable means for estimating the RBE in rapidly changing hadron radiation fields within phantoms.
Potential high resolution dosimeters for MRT
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3478205
Oxi-Redox Selective Breast Cancer Treatment: An in Vitro Study of Theranostic In-Based Oxide Nanoparticles for Controlled Generation or Prevention of Oxidative Stress
Publisher: American Chemical Society (ACS)
Date: 05-01-2021
X-tream: A novel dosimetry system for synchrotron microbeam radiation therapy
Publisher: IOP Publishing
Date: 31-07-2012
High spatial resolution microdosimetry with Δe-E detector on C-12 beam: Monte Carlo simulations
Publisher: IEEE
Date: 10-2013
Mysteries of LiF TLD response following high ionization density irradiation: Glow curve shapes, dose response, the unified interaction model and modified track structure theory
Publisher: Elsevier BV
Date: 12-2011
Real-time in vivo rectal wall dosimetry using MOSkin detectors during linac based stereotactic radiotherapy with rectal displacement
Publisher: Springer Science and Business Media LLC
Date: 27-02-2017
Tissue equivalence correction in silicon microdosimetry for protons characteristic of the LEO space environment
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2008
Silicon 3d microdosimeters for advanced quality assurance in particle therapy
Publisher: MDPI AG
Date: 30-12-2022
DOI: 10.3390/APP12010328
Abstract: The Centre for Medical Radiation Physics introduced the concept of Silicon On Insulator (SOI) microdosimeters with 3-Dimensional (3D) cylindrical sensitive volumes (SVs) mimicking the dimensions of cells in an array. Several designs of high-definition 3D SVs fabricated using 3D MEMS technology were implemented. 3D SVs were fabricated in different sizes and configurations with diameters between 18 and 30 µm, thicknesses of 2–50 µm and at a pitch of 50 µm in matrices with volumes of 20 × 20 and 50 × 50. SVs were segmented into sub-arrays to reduce capacitance and avoid pile up in high-dose rate pencil beam scanning applications. Detailed TCAD simulations and charge collection studies in in idual SVs have been performed. The microdosimetry probe (MicroPlus) is composed of the silicon microdosimeter and low-noise front–end readout electronics housed in a PMMA waterproof sheath that allows measurements of lineal energies as low as 0.4 keV/µm in water or PMMA. Microdosimetric quantities measured with SOI microdosimeters and the MicroPlus probe were used to evaluate the relative biological effectiveness (RBE) of heavy ions and protons delivered by pencil-beam scanning and passive scattering systems in different particle therapy centres. The 3D detectors and MicroPlus probe developed for microdosimetry have the potential to provide confidence in the delivery of RBE optimized particle therapy when introduced into routine clinical practice.
Thermoluminescence solid-state nanodosimetry-the peak 5a/5 dosemeter
Publisher: Oxford University Press (OUP)
Date: 13-12-2011
DOI: 10.1093/RPD/NCQ479
High-resolution fiber-optic dosimeters for microbeam radiation therapy
Publisher: Wiley
Date: 17-04-2017
DOI: 10.1002/MP.12209
Abstract: A high resolution, water equivalent, optical and passive x-ray dosimeter has been constructed using plastic scintillator and optical fiber. This dosimeter has a peak edge-on spatial resolution of 100 μm in one dimension, with a 10 μm resolution dosimeter under investigation. The dosimeter design has a potential application in synchrotron x-ray microbeam radiation therapy where a high resolution is vital for accurate dose measurements and quality assurance. BC-400 plastic scintillator, of thickness 100 μm, was optically coupled to an optical fiber with core diameter 1 mm. The end was coated in optical paint to improve sensitivity. An identical fiber was made without the scintillator to measure the background Cherenkov radiation induced in the fiber, to allow background signal subtraction. The light captured by the fibers was measured by PMTs. The probe system was exposed to a 6 MV, 10 × 10 cm The measured profiles matched well with ionisation chamber data. Important beam parameters such as penumbra width and percent depth dose at various depths matched the ionisation chamber data, within uncertainty. This work demonstrates that high resolutions can be achieved with a scintillation and optical fiber system. The probe is water-equivalent, passive, energy independent, radiation hard and inexpensive, making it ideal for further improvements for use with microbeam radiation therapy.
Radiation monitoring in mixed environments at CERN: From the IRRAD6 facility to the LHC experiments
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2007
Comparison of nanodosimetric parameters of track structure calculated by the Monte Carlo codes Geant4-DNA and PTra
Publisher: IOP Publishing
Date: 14-02-2012
DOI: 10.1088/0031-9155/57/5/1231
Abstract: The concept of nanodosimetry is based on the assumption that initial damage to cells is related to the number of ionizations (the ionization cluster size) directly produced by single particles within, or in the close vicinity of, short segments of DNA. The ionization cluster-size distribution and other nanodosimetric quantities, however, are not directly measurable in biological targets and our current knowledge is mostly based on numerical simulations of particle tracks in water, calculating track structure parameters for nanometric target volumes. The assessment of nanodosimetric quantities derived from particle-track calculations using different Monte Carlo codes plays, therefore, an important role for a more accurate evaluation of the initial damage to cells and, as a consequence, of the biological effectiveness of ionizing radiation. The aim of this work is to assess the differences in the calculated nanodosimetric quantities obtained with Geant4-DNA as compared to those of the ad hoc particle-track Monte Carlo code 'PTra' developed at Physikalisch-Technische Bundesanstalt (PTB), Germany. The comparison of the two codes was made for incident electrons of energy in the range between 50 eV and 10 keV, for protons of energy between 300 keV and 10 MeV, and for alpha particles of energy between 1 and 10 MeV as these were the energy ranges available in both codes at the time this investigation was carried out. Good agreement was found for nanodosimetric characteristics of track structure calculated in the high-energy range of each particle type. For lower energies, significant differences were observed, most notably in the estimates of the biological effectiveness. The largest relative differences obtained were over 50% however, generally the order of magnitude was between 10% and 20%.
Charge collection in n-SOI planar microdosimeters
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2013
First experimental measurement of the effect of cardio-synchronous brain motion on the dose distribution during microbeam radiation therapy
Publisher: Wiley
Date: 19-11-2020
DOI: 10.1002/MP.13899
Abstract: Microbeam radiation therapy (MRT) is an emerging radiation oncology modality ideal for treating inoperable brain tumors. MRT employs quasi-parallel beams of low-energy x rays produced from modern synchrotrons. A tungsten carbide multislit collimator (MSC) spatially fractionates the broad beam into rectangular beams. In this study, the MSC creates beams 50 μm wide ("peaks") separated by a center-to-center distance of 400 μm ("valleys"). The peak to valley dose ratio (PVDR) is of critical importance to the efficacy of MRT. The underlying radiobiological advantage of MRT relies on high peak dose for tumor control and low valley dose for healthy tissue sparing. Cardio synchronous brain motion of the order 100-200 μm is comparable to microbeam width and spacing. The motion can have a detrimental effect on the PVDR, full width at half maximum (FWHM) of the microbeams, and ultimately the dose distribution. We present the first experimental measurement of the effect of brain motion on MRT dose distribution. Dosimetry in MRT is difficult due to the high dose rate (up to 15-20 kGy/s) and small field sizes. A real-time dosimetry system based on a single silicon strip detector (SSSD) has been developed with spatial resolution ~10 μm. The SSSD was placed in a water-equivalent phantom and scanned through the microbeam distribution. A monodirectional positioning stage reproduced brain motion during the acquisition. Microbeam profiles were reconstructed from the SSSD and compared with Geant4 simulation and radiochromic HD-V2 film. The SSSD is able to reconstruct dose profiles within 2 μm compared to film. When brain motion is applied the SSSD shows a two time increase in FWHM of profiles and 50% reduction in PVDR. This is confirmed by Geant4 and film data. Motion-induced misalignment and distortion of microbeams at treatment delivery will result in a reduced PVDR and increased irradiation of additional healthy tissue compromising the radiobiological effectiveness of MRT. The SSSD was able to reconstruct dose profiles under motion conditions and predict similar effects on FWHM and PVDR as by the simulation. The SSSD is a simple to setup, real-time detector which can provide time-resolved high spatial resolution dosimetry of microbeams in MRT.
Estimating the biological effects of helium, carbon, oxygen, and neon ion beams using 3D silicon microdosimeters
Publisher: IOP Publishing
Date: 08-02-2021
Abstract: In this study, the survival fraction (SF) and relative biological effectiveness (RBE) of pancreatic cancer cells exposed to spread-out Bragg peak helium, carbon, oxygen, and neon ion beams are estimated from the measured microdosimetric spectra using a microdosimeter and the application of the microdosimetric kinetic (MK) model. To measure the microdosimetric spectra, a 3D mushroom silicon-on-insulator microdosimeter connected to low noise readout electronics (MicroPlus probe) was used. The parameters of the MK model were determined for pancreatic cancer cells such that the calculated SFs reproduced previously reported in vitro SF data. For a cuboid target of 10 × 10 × 6 cm 3 , treatment plans of helium, carbon, oxygen, and neon ion beams were designed using in-house treatment planning software (TPS) to achieve a 10% SF of pancreatic cancer cells throughout the target. The physical doses and microdosimetric spectra of the planned fields were measured at different depths in polymethyl methacrylate phantoms. The biological effects, such as SF, RBE, and RBE-weighted dose at different depths along the fields were predicted from the measurements. The predicted SFs at the target region were generally in good agreement with the planned SF from the TPS in most cases.
Characterization of proton pencil beam scanning and passive beam using a high spatial resolution solid-state microdosimeter
Publisher: Wiley
Date: 09-10-2017
DOI: 10.1002/MP.12563
Abstract: This work aims to characterize a proton pencil beam scanning (PBS) and passive double scattering (DS) systems as well as to measure parameters relevant to the relative biological effectiveness (RBE) of the beam using a silicon on insulator (SOI) microdosimeter with well-defined 3D sensitive volumes (SV). The dose equivalent downstream and laterally outside of a clinical PBS treatment field was assessed and compared to that of a DS beam. A novel silicon microdosimeter with well-defined 3D SVs was used in this study. It was connected to low noise electronics, allowing for detection of lineal energies as low as 0.15 keV/μm. The microdosimeter was placed at various depths in a water phantom along the central axis of the proton beam, and at the distal part of the spread-out Bragg peak (SOBP) in 0.5 mm increments. The RBE values of the pristine Bragg peak (BP) and SOBP were derived using the measured microdosimetric lineal energy spectra as inputs to the modified microdosimetric kinetic model (MKM). Geant4 simulations were performed in order to verify the calculated depth-dose distribution from the treatment planning system (TPS) and to compare the simulated dose-mean lineal energy to the experimental results. For a 131 MeV PBS spot (124.6 mm R The SOI microdosimeter with its well-defined 3D SV has applicability in characterizing proton radiation fields and can measure relevant physical parameters to model the RBE with submillimeter spatial resolution. It has been shown that for a physical dose of 1.82 Gy at the BP, the derived RBE based on the MKM model increased from 1.14 to 1.6 in the BP and its distal part. Good agreement was observed between the experimental and simulation results, confirming the potential application of SOI microdosimeter with 3D SV for quality assurance in proton therapy.
Polo-like kinase 1 inhibitor BI6727 sensitizes 9L gliosarcoma cells to ionizing irradiation
Publisher: IOP Publishing
Date: 24-10-2019
Systematic investigation on the validity of partition model dosimetry for 90Y radioembolization using Monte Carlo simulation
Publisher: IOP Publishing
Date: 22-08-2017
Abstract: We aimed to investigate the validity of the partition model (PM) in estimating the absorbed doses to liver tumour ([Formula: see text]), normal liver tissue ([Formula: see text]) and lungs ([Formula: see text]), when cross-fire irradiations between these compartments are being considered. MIRD-5 phantom incorporated with various treatment parameters, i.e. tumour involvement (TI), tumour-to-normal liver uptake ratio (T/N) and lung shunting (LS), were simulated using the Geant4 Monte Carlo (MC) toolkit. 10
A Monte Carlo study to evaluate and optimise the angular dependence of the Octa – A 2D silicon array detector used for dosimetry in stereotactic radiotherapy
Publisher: Elsevier BV
Date: 08-2023
MO‐F‐213AB‐03: Potential Reduction in Out‐Of‐Field Dose in Pencil Beam Scanning Proton Therapy Through Use of a Patient‐Specific Aperture
Publisher: Wiley
Date: 06-2012
DOI: 10.1118/1.4735808
Abstract: Patient specific apertures are commonly employed in passive double scattering (DS) proton therapy (PT). This study was aimed at identifying the potential benefits of using such an aperture in pencil beam scanning (PBS). An accurate Geant4 Monte Carlo model of the PBS PT treatment head at Massachusetts General Hospital (MGH) was developed based on an existing model of the passive double-scattering (DS) system. The Monte Carlo code specifies the treatment head at MGH with sub-millimeter accuracy and was configured based on the results of experimental measurements performed at MGH. This model was then used to compare out-of-field doses in simulated DS treatments and PBS treatments. The PBS treatments were simulated both with and without the patient-specific aperture used in the DS treatment. For the conditions explored, a typical prostate field, the lateral penumbra in PBS is wider than in DS, leading to higher absorbed doses and equivalent doses adjacent to the primary field edge. For lateral distances greater than 10cm from the field edge, the doses in PBS appear to be lower than those observed for DS. Including an aperture at nozzle exit reduces the penumbral width by preventing wide-angle scatter from reaching the patient. This can reduce the dose in PBS for lateral distances of less than 10cm from the field edge by over an order of magnitude and allow better dose conformity. Placing a patient-specific aperture at nozzle exit during PBS treatments can potentially reduce doses lateral to the primary radiation field by over an order of magnitude. This has the potential to further improve the normal tissue sparing capabilities of PBS. The magnitude of this effect depends on the beam spot size of the scanning system and is thus facility dependent.
Semiconductor dosimetry in modern external-beam radiation therapy
Publisher: IOP Publishing
Date: 31-08-2020
Influence of exposure and geometric parameters on absorbed doses associated with common neuro-interventional procedures
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.EJMP.2017.02.002
Abstract: The purpose of this study was to investigate the effects of routine exposure parameters on patient's dose during neuro-interventional radiology procedures. We scrutinized the routine radiological exposure parameters during 58 clinical neuro-interventional procedures such as, exposure direction, magnification, frame rate, and distance between image receptor to patient's body and evaluate their effects on patient's dose using an anthropomorphic phantom. Radiation dose received by the occipital region, ears and eyes of the phantom were measured using MOSkin detectors. DSA imaging technique is a major contributor to patient's dose (80.9%) even though they are used sparingly (5.3% of total frame number). The occipital region of the brain received high dose largely from the frontal tube constantly placed under couch (73.7% of the total KAP). When rotating the frontal tube away from under the couch, the radiation dose to the occipital reduced by 40%. The use of magnification modes could increase radiation dose by 94%. Changing the image receptor to the phantom surface distance from 10 to 40cm doubled the radiation dose received by the patient's skin at the occipital region. Our findings provided important insights into the contribution of selected fluoroscopic exposure parameters and their impact on patient's dose during neuro-interventional radiology procedures. This study showed that the DSA imaging technique contributed to the highest patient's dose and judicial use of exposure parameters might assist interventional radiologists in effective skin and eye lens dose reduction for patients undergoing neuro-interventional procedures.
Dose response of various radiation detectors to synchrotron radiation
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.
BrachyView: Development of an algorithm for real-time automatic LDR brachytherapy seed detection
Publisher: IOP Publishing
Date: 25-02-0033
Simulation of low dose positron emission mammography scanner for global breast health applications
Publisher: SPIE
Date: 04-03-2010
DOI: 10.1117/12.844017
Beta dose heterogeneity in sediment samples measured using a Timepix pixelated detector and its implications for optical dating of individual mineral grains
Publisher: Elsevier BV
Date: 03-2022
Characterisation of a ΔE-E particle telescope using the ANSTO heavy ion microprobe
Publisher: Elsevier BV
Date: 07-2007
Ion beam induced charge characterisation of a silicon microdosimeter using a heavy ion microprobe
Publisher: Elsevier BV
Date: 05-2002
A novel silicon microdosimeter using 3D sensitive volumes: Modeling the response in neutron fields typical of aviation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
X-TREAM protocol for in vitro microbeam radiation therapy at the Australian Synchrotron
Publisher: AIP Publishing
Date: 28-06-2021
DOI: 10.1063/5.0040013
Abstract: Recommendations for an experimental protocol for beam alignment/optimization and dosimetry relating to in vitro studies at the Imaging and Medical Beam Line of the Australian Synchrotron are presented. An evaluation of the protocol, based upon the consistency and reproducibility of in vitro experiments performed over several years at the Australian Synchrotron, is provided for the community.
eXaSkin: A novel high-density bolus for 6MV X-rays radiotherapy
Publisher: Elsevier BV
Date: 12-2020
A machine learning-based framework for delivery error prediction in proton pencil beam scanning using irradiation log-files
Publisher: Elsevier BV
Date: 10-2020
Characterization of a plastic dosimeter based on organic semiconductor photodiodes and scintillator
Publisher: Elsevier BV
Date: 04-2020
Derivation of in vivo source tracking error thresholds for TRUS-based HDR prostate brachytherapy through simulation of source positioning errors
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.BRACHY.2019.05.001
Abstract: The purpose of this study was to simulate treatment planning source positioning errors in transrectal ultrasound-based real-time high-dose-rate prostate brachytherapy treatments and determine appropriate in vivo source tracking error thresholds. Treatment planning source positioning errors were simulated for 20 patient plans in the brachytherapy treatment planning system by manually adjusting the dwell position coordinates within selected catheters without plan reoptimization. The change in dose-volume histogram (DVH) indices was calculated as a function of the source positioning error. The magnitude of the change in the DVH indices was then used to derive appropriate in vivo source tracking error thresholds. Source positioning error thresholds to prevent potentially significant changes in prostate (target) DVH metrics ranged from 2 to 5 mm, dependent on the direction of the source positioning error, as well as the relative weight of the dwell position within the plan, and its position relative to the patient anatomy. Source positioning error thresholds to prevent potentially clinically significant changes in organ at risk DVH metrics were found to be complex and patient-dependent. In vivo source tracking error thresholds for transrectal ultrasound-based real-time high-dose-rate prostate brachytherapy were investigated via the simulation of treatment planning source positioning errors. These error thresholds were found to be dependent not only on the direction of the error, but also on the endpoint. There is still the potential for larger changes in DVH indices to occur for catheter shifts smaller than the proposed threshold levels in this study.
Proton and iron ion observations from a solid-state microdosimeter
Publisher: Oxford University Press (OUP)
Date: 07-12-2012
DOI: 10.1093/RPD/NCR452
Abstract: The tissue equivalent proportional counter (TEPC) that utilises a gas cavity has been the standard to obtain microdosimetric observations. An alternative is the solid-state microdosimeter that replaces the gas with a solid-state detector with microscopic sensitive volumes. Here, we describe the development of two versions of a personal solid-state microdosimeter for space exploration applications and give test results for iron and proton beams with comparisons to TEPC measurements and Geant4 radiation transport code simulations. In addition, we describe and provide test results of an optical technique to carry out an end-to-end system test and calibration of a silicon solid-state microdosimeter. This technique eliminates the need for an ionising radiation source with its attendant issues on use and transportation and provides an advantage over the TEPC.
Experimental investigation of the 100 keV X-ray dose response of the high-temperature thermoluminescence in LiF:Mg,Ti (TLD-100): Theoretical interpretation using the unified interaction model
Publisher: Oxford University Press (OUP)
Date: 24-11-2009
DOI: 10.1093/RPD/NCP272
Abstract: The dose response of LiF:Mg,Ti (TLD-100) chips was measured from 1 to 50,000 Gy using 100 keV X rays at the European Synchroton Radiation Facility. Glow curves were deconvoluted into component glow peaks using a computerised glow curve deconvolution (CGCD) code based on first-order kinetics. The normalised dose response, f(D), of glow peaks 4 and 5 and 5b (the major components of composite peak 5), as well as peaks 7 and 8 (two of the major components of the high-temperature thermoluminescence (HTTL) at high levels of dose) was separately determined and theoretically interpreted using the unified interaction model (UNIM). The UNIM is a nine-parameter model encompassing both the irradiation/absorption stage and the thermally induced relaxation/recombination stage with an admixture of both localised and delocalised recombination mechanisms. The effects of radiation damage are included in the present modelling via the exponential removal of luminescent centres (LCs) at high dose levels. The main features of the experimentally measured dose response are: (i) increase in f(D)(max) with glow peak temperature, (ii) increase in D(max) (the dose level at which f(D)(max) occurs) with increasing glow peak temperature, and (iii) decreased effects of radiation damage with increasing glow peak temperature. The UNIM interpretation of this behaviour requires both strongly decreasing values of ks (the relative contribution of localised recombination) as a function of glow peak temperature and, as well, significantly different values of the dose-filling constants of the trapping centre (TC) and LC for peaks 7 and 8 than those used for peaks 4 and 5. This suggests that different TC/LC configurations are responsible for HTTL. The relative intensity of peak 5a (a low-temperature satellite of peak 5 arising from localised recombination) was found to significantly increase at higher dose levels due to preferential electron and hole population of the trapping/recombination complex giving rise to composite glow peak 5. It is also demonstrated that possible changes in the trapping cross section of the LC and the competitive centres due to increasing s le/glow peak temperature do not significantly influence these observations/conclusions.
Quality Assurance/Quality Control Issues for Intraoperative Planning and Adaptive Repeat Planning of Image-Guided Prostate Implants
Publisher: Elsevier BV
Date: 05-2008
DOI: 10.1016/J.IJROBP.2007.04.097
Abstract: The quality assurance/quality control purpose is this. We design a treatment plan, and we wish to be as certain as reasonably possible that the treatment is delivered as planned. In the case of conventionally planned prostate brachytherapy, implementing to the letter the implantation plan is rarely attainable and therefore can require adaptive replanning (a quality control issue). The reasons for this state of affairs include changes in the prostate shape and volume during implantation and treatment delivery (e.g., edema resolution) and unavoidable inaccuracy in the placement of the seeds in the prostate. As a result, quality-control activities (e.g., the need to monitor-ideally, on the fly-the target and urethral and rectal dosage) must be also addressed.
Thermoluminescence dose response of photon irradiated NaCl: Unified interaction model analysis of the dependence of the supralinearity on photon energy
Publisher: Elsevier BV
Date: 11-2017
Extrapolated surface dose measurements using a NdFeB magnetic deflector for 6 MV x-ray beams
Publisher: Springer Science and Business Media LLC
Date: 03-2007
DOI: 10.1007/BF03178409
An inception network for positron emission tomography based dose estimation in carbon ion therapy.
Publisher: IOP Publishing
Date: 23-09-2202
Abstract: Objective . We aim to evaluate a method for estimating 1D physical dose deposition profiles in carbon ion therapy via analysis of dynamic PET images using a deep residual learning convolutional neural network (CNN). The method is validated using Monte Carlo simulations of 12 C ion spread-out Bragg peak (SOBP) profiles, and demonstrated with an experimental PET image. Approach . A set of dose deposition and positron annihilation profiles for monoenergetic 12 C ion pencil beams in PMMA are first generated using Monte Carlo simulations. From these, a set of random polyenergetic dose and positron annihilation profiles are synthesised and used to train the CNN. Performance is evaluated by generating a second set of simulated 12 C ion SOBP profiles (one 116 mm SOBP profile and ten 60 mm SOBP profiles), and using the trained neural network to estimate the dose profile deposited by each beam and the position of the distal edge of the SOBP. Next, the same methods are used to evaluate the network using an experimental PET image, obtained after irradiating a PMMA phantom with a 12 C ion beam at QST’s Heavy Ion Medical Accelerator in Chiba facility in Chiba, Japan. The performance of the CNN is compared to that of a recently published iterative technique using the same simulated and experimental 12 C SOBP profiles. Main results . The CNN estimated the simulated dose profiles with a mean relative error (MRE) of 0.7% ± 1.0% and the distal edge position with an accuracy of 0.1 mm ± 0.2 mm, and estimate the dose delivered by the experimental 12 C ion beam with a MRE of 3.7%, and the distal edge with an accuracy of 1.7 mm. Significance . The CNN was able to produce estimates of the dose distribution with comparable or improved accuracy and computational efficiency compared to the iterative method and other similar PET-based direct dose quantification techniques.
Cell-shaped silicon-on-insulator microdosimeters: characterization and response to 239PuBe irradiations
Publisher: Springer Science and Business Media LLC
Date: 09-2017
DOI: 10.1007/S13246-017-0576-9
Abstract: This work tested the feasibility of a silicon-on-insulator microdosimeter, which mimics the size and shape of specific cells within the human body, to determine dose equivalent from neutron irradiation. The microdosimeters were analyzed in terms of their basic diode characteristics, i.e., leakage current as a function of bias voltage. Lineal energy spectra were acquired using two different converter layers placed atop the microdosimeter: a tissue-substitute converter made from high-density polyethylene, and a boron converter consisting of epoxy coated with boron powder. The spectra were then converted into absorbed dose and dose equivalent. Experimental results were compared to Monte Carlo simulations of the neutron irradiations, revealing good agreement. Uncertainty in the dose equivalent determinations was 7.5% when using the cell-shaped microdosimeter with the tissue-substitute converter and 13.1% when using the boron converter. This work confirmed that the SOI approach to cell-mimicking microdosimetry is feasible.
Microdosimeter instrument (MIDN) on MidSTAR-I
Publisher: SAE International
Date: 17-07-2006
DOI: 10.4271/2006-01-2146
Measurements in radiotherapy beams using on-line MOSFET detectors
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.
Response of a SOI microdosimeter to the CERF reference facility for aviation dosimetry
Publisher: IEEE
Date: 2007
A comparison of X-ray and proton beam low energy secondary electron track structures using the low energy models of Geant4
Publisher: Informa UK Limited
Date: 31-10-2012
DOI: 10.3109/09553002.2011.627975
Abstract: Lethal cell damage by ionising radiation is generally initiated by the formation of complex strand breaks, resulting from ionisation clusters in the DNA molecule. A better understanding of the effect of the distribution of ionisation clusters within the cell and particularly in regard to DNA segments could be beneficial to radiation therapy treatment planning. Low energy X-rays generate an abundance of low energy electrons similar to that associated with MeV protons. The study and comparison of the track structure of photon and proton beams could permit the substitution of photon microbeams for single cell ion irradiations at proton facilities used to predict the relative biological effectiveness (RBE) of charged particle fields. The track structure of X-ray photons is compared with proton pencil beams in voxels of approximate DNA strand size (2 × 2 × 5 nm). The Very Low Energy extension models of the Monte Carlo simulation toolkit GEometry ANd Tracking 4 (Geant4) is used. Simulations were performed in a water phantom for an X-ray and proton beam of energies 100 keV and 20 MeV, respectively. The track structure of the photon and proton beams are evaluated using the ionisation cluster size distribution as well as the radial dose deposition of the beam. A comparative analysis of the ionisation cluster distribution and radial dose deposition obtained is presented, which suggest that low energy X-rays could produce similar ionisation cluster distributions to MeV protons on the DNA scale of size at depths greater than ∼10 μm and at distances greater than ∼1 μm from the beam centre. Here the ionisation cluster size for each beam is less than ∼100. The radial dose deposition is also approximately equal at large depths and at distances greater than 10 μm from the beam centre.
Cylindrical silicon-on-insulator microdosimeter: Design, fabrication and TCAD modeling
Publisher: IEEE
Date: 2007
Small-sized UV radiometer on the basis of schottky diodes
Publisher: Elsevier BV
Date: 12-2011
From HEP to medical radiation dosimetry - The silicon strip detector dose magnifying glass
Publisher: Elsevier BV
Date: 12-2011
2D photon dosimetry with a scintillation fibre optic dosimeter
Publisher: Elsevier BV
Date: 2020
Miniature semiconductor detectors for in vivo dosimetry
Publisher: Oxford University Press (OUP)
Date: 27-04-2006
DOI: 10.1093/RPD/NCI645
Abstract: Silicon mini-semiconductor detectors are found in wide applications for in vivo personal dosimetry and dosimetry and microdosimetry of different radiation oncology modalities. These applications are based on integral and spectroscopy modes of metal oxide semiconductor field effect transistor and silicon p-n junction detectors. The advantages and limitations of each are discussed.
Measurement of radiotherapy x-ray skin dose on a chest wall phantom
Publisher: Wiley
Date: 07-2000
DOI: 10.1118/1.599035
Abstract: Sufficient skin dose needs to be delivered by a radiotherapy chest wall treatment regimen to ensure the probability of a near surface tumor recurrence is minimized. To simulate a chest wall treatment a hemicylindrical solid water phantom of 7.5 cm radius was irradiated with 6 MV x-rays using 20x20 cm2 and 10x20 cm2 fields at 100 cm source surface distance (SSD) to the base of the phantom. A surface dose profile was obtained from 0 to 180 degrees, in 10 degrees increments around the circumference of the phantom. Dosimetry results obtained from radiochromic film (effective depth of 0.17 mm) were used in the investigation, the superficial doses were found to be 28% (of Dmax) at the 0 degrees beam entry position and 58% at the 90 degrees oblique beam position. Superficial dose results were also obtained using extra thin thermoluminescent dosimeters (TLD) (effective depth 0.14 mm) of 30% at 0 degrees, 57% at 90 degrees, and a metal oxide semiconductor field effect transistor (MOSFET) detector (effective depth 0.5 mm) of 43% at 0 degrees, 62% at 90 degrees. Because the differences in measured superficial doses were significant and beyond those related to experimental error, these differences are assumed to be mostly attributable to the effective depth of measurement of each detector. We numerically simulated a bolus on/bolus off technique and found we could increase the coverage to the skin. Using an alternate "bolus on," "bolus off" regimen, the skin would receive 36.8 Gy at 0 degrees incidence and 46.4 Gy at 90 degrees incidence for a prescribed midpoint dose of 50 Gy. From this work it is evident that, as the circumference of the phantom is traversed the SSD increases and hence there is an inverse square fluence fall-off, this is more than offset by the increase in skin dose due to surface curvature to a plateau at about 90 degrees. Beyond this angle it is assumed that beam attenuation through the phantom and inverse square fall-off is causing the surface dose to reduce.
SU‐GG‐T‐289: Out‐Of‐Field Dose Equivalents Delivered by Passively Scattered Therapeutic Proton Beams for Clinically Relevant Field Configurations
Publisher: Wiley
Date: 06-2008
DOI: 10.1118/1.2962041
Development of a silicon diode detector for skin dosimetry in radiotherapy
Publisher: Wiley
Date: 12-08-2017
DOI: 10.1002/MP.12469
Abstract: The aim of in vivo skin dosimetry was to measure the absorbed dose to the skin during radiotherapy, when treatment planning calculations cannot be relied on. It is of particularly importance in hypo-fractionated stereotactic modalities, where excessive dose can lead to severe skin toxicity. Currently, commercial diodes for such applications are with water equivalent depths ranging from 0.5 to 0.8 mm. In this study, we investigate a new detector for skin dosimetry based on a silicon epitaxial diode, referred to as the skin diode. The skin diode is manufactured on a thin epitaxial layer and packaged using the "drop-in" technology. It was characterized in terms of percentage depth dose, dose linearity, and dose rate dependence, and benchmarked against the Attix ionization chamber. The response of the skin diode in the build-up region of the percentage depth dose (PDD) curve of a 6 MV clinical photon beam was investigated. Geant4 radiation transport simulations were used to model the PDD in order to estimate the water equivalent measurement depth (WED) of the skin diode. Measured output factors using the skin diode were compared with the MOSkin detector and EBT3 film at 10 cm depth and at surface at isocenter of a water equivalent phantom. The intrinsic angular response of the skin diode was also quantified in charge particle equilibrium conditions (CPE) and at the surface of a solid water phantom. Finally, the radiation hardness of the skin diode up to an accumulated dose of 80 kGy using photons from a Co-60 gamma source was evaluated. The PDD curve measured with the skin diode was within 0.5% agreement of the equivalent Geant4 simulated curve. When placed at the phantom surface, the WED of the skin diode was estimated to be 0.075 ± 0.005 mm from Geant4 simulations and was confirmed using the response of a corrected Attix ionization chamber placed at water equivalent depth of 0.075 mm, with the measurement agreement to within 0.3%. The output factor measurements at 10 cm depth were within 2% of those measured with film and the MOSkin detector down to a field size of 2 × 2 cm This work characterizes an innovative detector for in vivo and real-time skin dose measurements that is based on an epitaxial silicon diode combined with the Centre for Medical Radiation Physics (CMRP) "drop-in" packaging technology. The skin diode proved to have a water equivalent depth of measurement of 0.075 ± 0.005 mm and the ability to measure doses accurately relative to reference detectors.
Software platform for simulation of a prototype proton CT scanner
Publisher: Wiley
Date: 03-2017
DOI: 10.1002/MP.12107
Highly porous hematite nanorods prepared via direct spray precipitation method
Publisher: Elsevier BV
Date: 02-2014
SU‐GG‐T‐295: Determination of the Dose Equivalent Near Proton Pencil Beams
Publisher: Wiley
Date: 06-2008
DOI: 10.1118/1.2962047
Microdosimetric measurements of a clinical proton beam with micrometer-sized solid-state detector
Publisher: Wiley
Date: 13-10-2017
DOI: 10.1002/MP.12583
Abstract: Microdosimetry is a vital tool for assessing the microscopic patterns of energy deposition by radiation, which ultimately govern biological effect. Solid-state, silicon-on-insulator microdosimeters offer an approach for making microdosimetric measurements with high spatial resolution (on the order of tens of micrometers). These high-resolution, solid-state microdosimeters may therefore play a useful role in characterizing proton radiotherapy fields, particularly for making highly resolved measurements within the Bragg peak region. In this work, we obtain microdosimetric measurements with a solid-state microdosimeter (MicroPlus probe) in a clinical, spot-scanning proton beam of small spot size. The MicroPlus probe had a 3D single sensitive volume on top of silicon oxide. The sensitive volume had an active cross-sectional area of 250 μm × 10 μm and thickness of 10 μm. The proton facility was a synchrotron-based, spot-scanning system with small spot size (σ ≈ 2 mm). We performed measurements with the clinical beam current (≈1 nA) and had no detected pulse pile-up. Measurements were made in a water-equivalent phantom in water-equivalent depth (WED) increments of 0.25 mm or 1.0 mm along pristine Bragg peaks of energies 71.3 MeV and 159.9 MeV, respectively. For each depth, we measured lineal energy distributions and then calculated the dose-weighted mean lineal energy, y¯D. The measurements were repeated for two field sizes: 4 × 4 cm For both 71.3 MeV and 159.9 MeV and for both field sizes, y¯D increased with depth toward the distal edge of the Bragg peak, a result consistent with Monte Carlo calculations and measurements performed elsewhere. For the 71.3 MeV, 4 × 4 cm We performed microdosimetric measurements with a novel solid-state, silicon-on-insulator microdosimeter in a clinical spot-scanning proton beam of small spot size and unmodified beam current. For all of the proton field sizes and energies considered, the measurements of y¯D were in agreement with expected trends. Furthermore, we obtained measurements with a spatial resolution of 10 μm in the beam direction. This spatial resolution greatly exceeded that possible with a conventional gaseous tissue-equivalent proportional counter and allowed us to perform a high-resolution investigation within the Bragg peak region. The MicroPlus probe is therefore suitable for applications in proton radiotherapy.
Corrigendum: The impact of sensitive volume thickness for silicon on insulator microdosimeters in hadron therapy (2020 Phys. Med. Biol. 65 035004)
Publisher: IOP Publishing
Date: 25-02-2021
In vivo skin dose measurement using MOSkin detectors in tangential breast radiotherapy
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.EJMP.2016.10.022
Abstract: The purpose of this study is to measure patient skin dose in tangential breast radiotherapy. Treatment planning dose calculation algorithm such as Pencil Beam Convolution (PBC) and in vivo dosimetry techniques such as radiochromic film can be used to accurately monitor radiation doses at tissue depths, but they are inaccurate for skin dose measurement. A MOSFET-based (MOSkin) detector was used to measure skin dose in this study. Tangential breast radiotherapies ("bolus" and "no bolus") were simulated on an anthropomorphic phantom and the skin doses were measured. Skin doses were also measured in 13 patients undergoing each of the techniques. In the patient study, the EBT2 measurements and PBC calculation tended to over-estimate the skin dose compared with the MOSkin detector (p 0.05). The results from patients were similar to that of the phantom study. This shows that the EBT2 measurement and PBC calculation, while able to predict accurate doses at tissue depths, are inaccurate in predicting doses at build-up regions. The clinical application of the MOSkin detectors showed that the average total skin doses received by patients were 1662±129cGy (medial) and 1893±199cGy (lateral) during "no bolus radiotherapy". The average total skin doses were 4030±72cGy (medial) and 4004±91cGy (lateral) for "bolus radiotherapy". In some cases, patient skin doses were shown to exceed the dose toxicity level for skin erythema. Hence, a suitable device for in vivo dosimetry is necessary to accurately determine skin dose.
In vivo verification of superficial dose for head and neck treatments using intensity-modulated techniques
Publisher: Wiley
Date: 05-12-2009
DOI: 10.1118/1.3030951
Abstract: Skin dose is one of the key issues for clinical dosimetry in radiation therapy. Currently planning computer systems are unable to accurately predict dose in the buildup region, leaving ambiguity as to the dose levels actually received by the patient's skin during radiotherapy. This is one of the prime reasons why in vivo measurements are necessary to estimate the dose in the buildup region. A newly developed metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector designed specifically for dose measurements in rapidly changing dose gradients was introduced for accurate in vivo skin dosimetry. The feasibility of this detector for skin dose measurements was verified in comparison with plane parallel ionization chamber and radiochromic films. The accuracy of a commercial treatment planning system (TPS) in skin dose calculations for intensity-modulated radiation therapy treatment of nasopharyngeal carcinoma was evaluated using MOSFET detectors in an anthropomorphic phantom as well as on the patients. Results show that this newly developed MOSFET detector can provide a minimal but highly reproducible intrinsic buildup of 7 mg cm(-2) corresponding to the requirements of personal surface dose equivalent Hp (0.07). The reproducibility of the MOSFET response, in high sensitivity mode, is found to be better than 2% at the phantom surface for the doses normally delivered to the patients. The MOSFET detector agrees well with the Attix chamber and the EBT Gafchromic film in terms of surface and buildup region dose measurements, even for oblique incident beams. While the dose difference between MOSFET measurements and TPS calculations is within measurement uncertainty for the depths equal to or greater than 0.5 cm, an overestimation of up to 8.5% was found for the surface dose calculations in the anthropomorphic phantom study. In vivo skin dose measurements reveal that the dose difference between the MOSFET results and the TPS calculations was on average -7.2%, ranging from -4.3% to -9.2%. The newly designed MOSFET detector encapsulated into a thin water protective film has a minimal reproducible intrinsic buildup recommended for skin dosimetry. This feature makes it very suitable for routine IMRT QA and accurate in vivo skin dosimetry.
In-line MRI-LINAC depth dose measurements using an in-house plastic scintillation dosimeter
Publisher: IOP Publishing
Date: 11-02-2021
Abstract: Plastic scintillation dosimeters (PSDs) have many properties that make them desirable for relative dosimetry with MRI-LINACs. An in-house PSD, Farmer ionisation chamber and Gafchromic EBT3 film were used to measure central axis percentage depth dose distributions (PDDs) at the Australian MRI-LINAC Mean errors were calculated between each detector’s responses, where the in-house PSD was on average within 0.7% of the Farmer chamber and 1.4% of film, while the Farmer chamber and film were on average within 1.1% of each other. However, the PSD systematically over-estimated the dose as depth increased, approaching a maximum overestimation of the order of 3.5% for the smallest field size measured. This trend was statistically insignificant for all other field sizes measured further investigation is required to determine the source of this effect. The calculated values of mean absolute error are comparable to the those of trusted dosimeters reported in the literature. These mean absolute errors, and the ubiquity of desirable dosimetric qualities inherent to PSDs suggest that PSDs in general are accurate for relative dosimetry with the MRI-LINAC. Further investigation is required into the source of the reported systematic trends dependent on field-size and depth of measurement.
A novel approach to postmastectomy radiation therapy using scanned proton beams
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.IJROBP.2014.10.039
Abstract: Postmastectomy radiation therapy (PMRT), currently offered at Massachusetts General Hospital, uses proton pencil beam scanning (PBS) with intensity modulation, achieving complete target coverage of the chest wall and all nodal regions and reduced dose to the cardiac structures. This work presents the current methodology for such treatment and the ongoing effort for its improvements. A single PBS field is optimized to ensure appropriate target coverage and heart/lung sparing, using an in-house-developed proton planning system with the capability of multicriteria optimization. The dose to the chest wall skin is controlled as a separate objective in the optimization. Surface imaging is used for setup because it is a suitable surrogate for superficial target volumes. In order to minimize the effect of beam range uncertainties, the relative proton stopping power ratio of the material in breast implants was determined through separate measurements. Phantom measurements were also made to validate the accuracy of skin dose calculation in the treatment planning system. Additionally, the treatment planning robustness was evaluated relative to setup perturbations and patient breathing motion. PBS PMRT planning resulted in appropriate target coverage and organ sparing, comparable to treatments by passive scattering (PS) beams but much improved in nodal coverage and cardiac sparing compared to conventional treatments by photon/electron beams. The overall treatment time was much shorter than PS and also shorter than conventional photon/electron treatment. The accuracy of the skin dose calculation by the planning system was within ±2%. The treatment was shown to be adequately robust relative to both setup uncertainties and patient breathing motion, resulting in clinically satisfying dose distributions. More than 25 PMRT patients have been successfully treated at Massachusetts General Hospital by using single-PBS fields. The methodology and robustness of both the setup and the treatment have been discussed.
Characterization of an alternative diamond based microdosimeter prototype
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2014
Performance uniformity evaluation of two SensL's SiPM modules
Publisher: IEEE
Date: 10-2013
On the Instantaneous Dose Rate and Angular Dependence of Monolithic Silicon Array Detectors
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Study of the correlation between rectal wall in vivo dosimetry performed with MOSkins and implant modification during TRUS-guided HDR prostate brachytherapy
Publisher: Elsevier BV
Date: 11-2017
Feasibility study of a novel multi-strip silicon detector for use in proton therapy range verification quality assurance
Publisher: Elsevier BV
Date: 11-2017
Optimizing dose enhancement with Ta2 O5 nanoparticles for synchrotron microbeam activated radiation therapy
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.EJMP.2016.10.024
Abstract: Microbeam Radiation Therapy (MRT) exploits tumour selectivity and normal tissue sparing with spatially fractionated kilovoltage X-ray microbeams through the dose volume effect. Experimental measurements with Ta
Synthesis-Dependent Surface Defects and Morphology of Hematite Nanoparticles and Their Effect on Cytotoxicity in Vitro
Publisher: American Chemical Society (ACS)
Date: 24-02-2016
Abstract: In this study, we investigate the toxicity of hematite (α-Fe2O3) nanoparticles on the Madin-Darby Canine Kidney (MDCK) cell line. The oxide particles have been synthesized through two different methods and annealing conditions. These two methods, spray precipitation and precipitation, resulted in particles with rod-like and spherical morphology and feature different particle sizes, surface features, and magnetic properties. Through flow cytometry it was found that particle morphology heavily influences the degree to which the nanomaterials are internalized into the cells. It was also found that the ability of the nanoparticles to generate free radicals species is hindered by the formation of tetrahedrally coordinated maghemite-like (γ-Fe2O3) spinel defects on the surfaces of the particles. The combination of these two factors resulted in variable cytotoxic effects of the hematite nanoparticles synthesized with different conditions. This article highlights the importance on the fabrication method, materials properties, and surface characteristics on the cytotoxicity of hematite nanomaterials.
Tissue equivalency of phantom materials for neutron dosimetry in proton therapy
Publisher: Wiley
Date: 05-11-2009
DOI: 10.1118/1.3250857
Abstract: Previous Monte Carlo and experimental studies involving secondary neutrons in proton therapy have employed a number of phantom materials that are designed to represent human tissue. In this study, the authors determined the suitability of common phantom materials for dosimetry of secondary neutrons, specifically for pediatric and intracranial proton therapy treatments. This was achieved through comparison of the absorbed dose and dose equivalent from neutrons generated within the phantom materials and various ICRP tissues. The phantom materials chosen for comparison were Lucite, liquid water, solid water, and A150 tissue equivalent plastic, These phantom materials were compared to brain, muscle, and adipose tissues. The magnitude of the doses observed were smaller than those reported in previous experimental and Monte Carlo studies, which incorporated neutrons generated in the treatment head. The results show that for both neutron absorbed dose and dose equivalent, no single phantom material gives agreement with tissue within 5% at all the points considered. Solid water gave the smallest mean variation with the tissues out of field where neutrons are the primary contributor to the total dose. Of the phantom materials considered, solid water shows best agreement with tissues out of field.
Accurate and Fast Deep Learning Dose Prediction for a Preclinical Microbeam Radiation Therapy Study Using Low-Statistics Monte Carlo Simulations
Publisher: MDPI AG
Date: 04-04-2023
Abstract: Microbeam radiation therapy (MRT) utilizes coplanar synchrotron radiation beamlets and is a proposed treatment approach for several tumor diagnoses that currently have poor clinical treatment outcomes, such as gliosarcomas. Monte Carlo (MC) simulations are one of the most used methods at the Imaging and Medical Beamline, Australian Synchrotron to calculate the dose in MRT preclinical studies. The steep dose gradients associated with the 50μm-wide coplanar beamlets present a significant challenge for precise MC simulation of the dose deposition of an MRT irradiation treatment field in a short time frame. The long computation times inhibit the ability to perform dose optimization in treatment planning or apply online image-adaptive radiotherapy techniques to MRT. Much research has been conducted on fast dose estimation methods for clinically available treatments. However, such methods, including GPU Monte Carlo implementations and machine learning (ML) models, are unavailable for novel and emerging cancer radiotherapy options such as MRT. In this work, the successful application of a fast and accurate ML dose prediction model for a preclinical MRT rodent study is presented for the first time. The ML model predicts the peak doses in the path of the microbeams and the valley doses between them, delivered to the tumor target in rat patients. A CT imaging dataset is used to generate digital phantoms for each patient. Augmented variations of the digital phantoms are used to simulate with Geant4 the energy depositions of an MRT beam inside the phantoms with 15% (high-noise) and 2% (low-noise) statistical uncertainty. The high-noise MC simulation data are used to train the ML model to predict the energy depositions in the digital phantoms. The low-noise MC simulations data are used to test the predictive power of the ML model. The predictions of the ML model show an agreement within 3% with low-noise MC simulations for at least 77.6% of all predicted voxels (at least 95.9% of voxels containing tumor) in the case of the valley dose prediction and for at least 93.9% of all predicted voxels (100.0% of voxels containing tumor) in the case of the peak dose prediction. The successful use of high-noise MC simulations for the training, which are much faster to produce, accelerates the production of the training data of the ML model and encourages transfer of the ML model to different treatment modalities for other future applications in novel radiation cancer therapies.
Matchline dosimetry in step and shoot IMRT fields: A film study
Publisher: IOP Publishing
Date: 20-08-2004
DOI: 10.1088/0031-9155/49/17/N03
Abstract: The Varian millennium 120 multileaf collimator has curved leaf ends. Transmission through the leaf ends generates a small asymmetric penumbral dose effect. This design can lead to hot spots between neighbouring beam segments during step and shoot IMRT dose delivery. We have observed some matchlines with film for clinical beams optimized using the pinnacle radiotherapy treatment planning system hence we sought to verify the optimum leaf offset required to minimize the matchline effect. An in-house program was created to control the MLC leaf banks in 2 cm steps with a 2 cm gap. The gap was varied by the following offset values from 0.0 to 0.1 cm. Two types of radiographic films (Kodak EDR and XV films) and a radiochromic film (Gafchromic MD-55-2) were used to measure the optical density maps. The films were positioned in a solid water phantom perpendicular to the beam axis and irradiated at d(max) using a 6 MV photon beam. An ion chamber (IC4) was used to measure point doses for normalization in a beam umbral minima position. The relative mean peak to valley dose ratios measured with no leaf offset were 1.31, 1.30 and 1.31 for the XV, EDR2 and Gafchromic films, respectively. For a 0.07 cm gap per leaf and a performance of end leaf repeatability of 0.01 cm, the central matchline was reduced to about 1.0 for all dosimeters, with two mini-peaks measured as 1.05, 1.05 and 1.08 each side of the matchline, for XV, EDR2 and Gafchromic, respectively. The average relative dose across the umbra for this offset was XO-mat V = 1.01, EDR = 1.01 and radiochromic film = 1.02, respectively. While we expected the beam penumbral tails from segment neighbours to cause overprediction of the dose in the central valley regions due to the energy response of radiographic films, by normalizing all dosimeters to an ion chamber reading in the minimum we could not observe any major shape distortion between the radiographic film and radiochromic film results. In conclusion, relative doses measured by radiographic and radiochromic films agree well with IC4 within +/-2%.
Angular independent silicon detector for dosimetry in external beam radiotherapy
Publisher: Wiley
Date: 17-07-2015
DOI: 10.1118/1.4926778
Abstract: In this work, the "edgeless" silicon detector technology is investigated, in combination with an innovative packaging solution, to manufacture silicon detectors with negligible angular response. The new diode is also characterized as a dosimeter for radiotherapy with the aim to verify its suitability as a single detector for in vivo dosimetry as well as large area 2D array that does not require angular correction to their response. For the characterisation of the "edgeless-drop-in" detector technology, a set of s les have been manufactured with different sensitive areas (1 × 1 and 0.5 × 0.5 mm(2)) and different thicknesses (0.1 and 0.5 mm) in four different combinations of top and peripheral p-n junction fabricated on p-type and n-type silicon substrates. The diode probes were tested in terms of percentage depth dose (PDD), dose rate, and linearity and compared to ion chambers. Measurements of the output factor have been compared to film. The angular response of the diodes probes has been tested in a cylindrical PMMA phantom, rotated with bidirectional accuracy of 0.25° under 10 × 10 cm(2) 6 MV Linac photon beam. The radiation hardness has been investigated as well as the effect of radiation damage on the angular and dose rate response of the diode probes when irradiated with photons from a Co-60 gamma source up to dose of 40 kGy. The PDDs measured by the edgeless detectors show an agreement with the data obtained using ion chambers within ±2%. The output factor measured with the smallest area edgeless diodes (0.5 × 0.5 mm(2)-0.1 and 0.5 mm thick) matches EBT3 film to within 2% for square field size from 10 to 0.5 cm side equivalent distance. The dose rate dependence in a dose per pulse range of 0.9 × 10(-5)-2.7 × 10(-4) Gy ulse was less than -7% and +300% for diodes fabricated on p-type and n-type substrates, respectively. The edgeless diodes fabricated on the p-type substrate demonstrated degradation of the response as a function of the irradiation dose within 5%-15%, while diodes on the n-type substrate show a variation of approximately 30% after 40 kGy. The angular response of all probes is minimal (within 2%) but the N on N and P on P configurations show the best performances with an angular dependence of ±1.0% between 0° and 180° in the transversal direction. In this configuration, the space charge region of the passive diode extends from the behind and sidewall toward the anode on the top providing beneficial electric field distribution in the peripheral area of the diode. Such performance has also been tested after irradiation by Co-60 up to 40 kGy with no measurable change in angular response. A new edgeless-drop-in silicon diode fabrication and packaging technology has been used to develop detectors that show no significant angular dependence in their response for dosimetry in radiation therapy. From the characterisation of the diodes, proposed in a wide range of different geometries and configurations, the authors recommend the P-on-P detectors in conjunction with "drop in" packaging technology as the candidate for further development as single diode probe or 2D diode array for dosimetry in radiotherapy.
SOI microdosemetry for mixed field radiation protection
Publisher: Elsevier BV
Date: 02-2008
Characterisation of Silicon Diode Arrays for Dosimetry in External Beam Radiation Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2016
BrachyView: Tomographic reconstruction using Timepix detectors in post-implant dosimetry checks for permanent prostate brachytherapy implants
Publisher: IEEE
Date: 09-2025
Latest Geant4 developments for PIXE applications
Publisher: Elsevier BV
Date: 12-2018
The next step in cylindrical silicon-on insulator microdosimetry: Charge collection results
Publisher: IEEE
Date: 10-2008
Monte Carlo implementation of new algorithms for the evaluation of averaged-dose and -track linear energy transfers in 62 MeV clinical proton beams
Publisher: IOP Publishing
Date: 30-11-2020
Abstract: We exploited the power of the Geant4 Monte Carlo toolkit to study and validate new approaches for the averaged linear energy transfer (LET) calculation in 62 MeV clinical proton beams. The definitions of the averaged LET dose and LET track were extended, so as to fully account for the contribution of secondary particles generated by target fragmentation, thereby leading to a more general formulation of the LET total. Moreover, in the proposed new strategies for the LET calculation, we minimised the dependencies in respect to the transport parameters adopted during the Monte Carlo simulations (such as the production cut of secondary particles, voxel size and the maximum steplength). The new proposed approach was compared against microdosimetric experimental spectra of clinical proton beams, acquired at the Italian eye proton therapy facility of the Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare (INFN-LNS, Catania, I) from two different detectors: a mini-tissue equivalent proportional chamber (TEPC), developed at the Legnaro National Laboratories of the National Institute for Nuclear Physics (LNL-INFN) and a silicon-on-insulator (SOI) microdosimeter with 3D sensitive volumes developed by the Centre for Medical Radiation Physics of Wollongong University (CMRP-UoW). A significant increase of the LET in the entrance region of the spread out Bragg peak (SOBP) was observed, when the contribution of the generated secondary particles was included in the calculation. This was consistent with the experimental results obtained.
Evaluation of silicon detectors with integrated JFET for biomedical applications
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Study of the effect of ceramic Ta2 O5 nanoparticle distribution on cellular dose enhancement in a kilovoltage photon field
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.EJMP.2016.09.006
Abstract: The application of nanoparticles (NPs) in radiotherapy is an increasingly attractive technique to improve clinical outcomes. The internalisation of NPs within the tumour cells enables an increased radiation dose to critical cellular structures. The purpose of this study is to investigate, by means of Geant4 simulations, the dose enhancement within a cell population irradiated with a 150kVp photon field in the presence of a varying concentration of tantalum pentoxide (Ta
Mysteries of LiF TLD response following high ionisation density irradiation: Nanodosimetry and track structure theory, dose response and glow curve shapes
Publisher: Oxford University Press (OUP)
Date: 24-11-2011
DOI: 10.1093/RPD/NCQ381
A feasibility study for high-resolution silicon array detector performance in the magnetic field of a permanent magnet system
Publisher: Wiley
Date: 12-07-2019
DOI: 10.1002/MP.13686
Abstract: Magnetic field effects on dose distribution and detector functionality must be well understood. The detector utilized to investigate these magnetic field effects was the DUO silicon array detector the performance of this high spatial resolution detector was assessed under these conditions. The results were compared to Gafchromic EBT3 film to highlight any intrinsic magnetic field effects in the silicon. The results were also compared to previously published MagicPlate-512 (M512) data. The DUO has an improved spatial resolution (200 µm) over the M512 (2 mm). A permanent magnet named Magnetic Apparatus for RaDiation Oncology Studies (MARDOS) paired with a standard linear accelerator (linac) enables either transverse (1.2 T) or inline (0.95 T) orientations of the magnetic field with respect to the radiation beam. A 6 MV Varian 2100C Linac provided the radiation component for the measurements. The DUO detector has 505 sensitive volumes (each volume measuring 800 × 40 × 100 µm The penumbral widths measured by the DUO detector demonstrated good agreement with film and the M512 to within an average of 0.5 mm (within uncertainty: ±1 mm). The static inline magnetic field had minimal effect on the profiles in solid water. As expected, the lower density of solid lung meant that this material was more susceptible to demonstrating magnetic field effects in the dose deposited. The greatest penumbral narrowing due to the inline field (0.7 mm) occurred in lung. Central axis dose increase was greatest in lung (maximum: 9%). The transverse field widened penumbra, most notably in the solid lung phantom, by a maximum of 2.3 mm. The largest asymmetry due to the transverse field (4.6%) was also in solid lung. When the air gap above the DUO was filled with bolus, the dose maximum measured by the DUO was within 1.4% of film. The DUO detector has been shown to be successful in accurately describing the dose changes for small field sizes to within a 200-µm resolution in an environment resembling that of an MRI-linac. The DUO measurements were in agreement with both film and the M512 measurements, and therefore the DUO was found to be an appropriate alternative to the M512, with improvement in terms of its higher spatial resolution. MARDOS provided a suitable environment for these preliminary tests before progressing to the MRI-linac.
SU‐E‐T‐679: Electron Contamination Modeling in Longitudinal Field MRI‐Linac Systems
Publisher: Wiley
Date: 06-2011
DOI: 10.1118/1.3612641
Detection and discrimination of neutron capture events for NCEPT dose quantification
Publisher: Springer Science and Business Media LLC
Date: 07-04-2022
DOI: 10.1038/S41598-022-09676-X
Abstract: Neutron Capture Enhanced Particle Therapy (NCEPT) boosts the effectiveness of particle therapy by capturing thermal neutrons produced by beam-target nuclear interactions in and around the treatment site, using tumour-specific $$^{10}$$ 10 B or $$^{157}$$ 157 Gd-based neutron capture agents. Neutron captures release high-LET secondary particles together with gamma photons with energies of 478 keV or one of several energies up to 7.94 MeV, for $$^{10}$$ 10 B and $$^{157}$$ 157 Gd, respectively. A key requirement for NCEPT’s translation is the development of in vivo dosimetry techniques which can measure both the direct ion dose and the dose due to neutron capture. In this work, we report signatures which can be used to discriminate between photons resulting from neutron capture and those originating from other processes. A Geant4 Monte Carlo simulation study into timing and energy thresholds for discrimination of prompt gamma photons resulting from thermal neutron capture during NCEPT was conducted. Three simulated $$300\\times 300\\times 300$$ 300 × 300 × 300 mm $$^3$$ 3 cubic PMMA targets were irradiated by $$^4$$ 4 He or $$^{12}$$ 12 C ion beams with a spread out Bragg peak (SOBP) depth range of 60 mm one target is homogeneous while the others include $$10\\times 10\\times 10$$ 10 × 10 × 10 mm $$^3$$ 3 neutron capture inserts (NCIs) of pure $$^{10}$$ 10 B or $$^{157}$$ 157 Gd located at the distal edge of the SOBP. The arrival times of photons and neutrons entering a simulated $$50\\times 50\\times 50$$ 50 × 50 × 50 mm $$^3$$ 3 ideal detector were recorded. A temporal mask of 50–60 ns was found to be optimal for maximising the discrimination of the photons resulting from the neutron capture by boron and gadolinium. A range of candidate detector and thermal neutron shielding materials were simulated, and detections meeting the proposed acceptance criteria (i.e. falling within the target energy window and arriving 60 ns post beam-off) were classified as true or false positives, depending on their origin. The ratio of true/false positives ( $$R_{TF}$$ R TF ) was calculated for targets with $$^{10}$$ 10 B and $$^{157}$$ 157 Gd NCIs, the detector materials which resulted in the highest $$R_{TF}$$ R TF were cadmium-shielded CdTe and boron-shielded LSO, respectively. The optimal irradiation period for both carbon and helium ions was 1 µs for the $$^{10}$$ 10 B NCI and 1 ms for the $$^{157}$$ 157 Gd NCI.
Silicon microdosimetry in heterogeneous materials: Simulation and experiment
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2006
Monte Carlo study of mosfet packaging, optimised for improved energy response: Single mosfet filtration
Publisher: Oxford University Press (OUP)
Date: 11-01-2021
DOI: 10.1093/RPD/NCQ144
Abstract: Monte Carlo simulations of the energy response of a conventionally packaged single metal-oxide field effect transistors (MOSFET) detector were performed with the goal of improving MOSFET energy dependence for personal accident or military dosimetry. The MOSFET detector packaging was optimised. Two different 'drop-in' design packages for a single MOSFET detector were modelled and optimised using the GEANT4 Monte Carlo toolkit. Absorbed photon dose simulations of the MOSFET dosemeter placed in free-air response, corresponding to the absorbed doses at depths of 0.07 mm (D(w)(0.07)) and 10 mm (D(w)(10)) in a water equivalent phantom of size 30 x 30 x 30 cm(3) for photon energies of 0.015-2 MeV were performed. Energy dependence was reduced to within + or - 60 % for photon energies 0.06-2 MeV for both D(w)(0.07) and D(w)(10). Variations in the response for photon energies of 15-60 keV were 200 and 330 % for D(w)(0.07) and D(w)(10), respectively. The obtained energy dependence was reduced compared with that for conventionally packaged MOSFET detectors, which usually exhibit a 500-700 % over-response when used in free-air geometry.
Simulation and testing of thin microstrip silicon dosimeters for the microbeam radiation therapy
Publisher: IEEE
Date: 11-2016
A two dimensional silicon detectors array for quality assurance in stereotactic radiotherapy: MagicPlate-512
Publisher: Wiley
Date: 30-08-2020
DOI: 10.1118/1.4892384
Abstract: Silicon diode arrays are commonly implemented in radiation therapy quality assurance applications as they have a number of advantages including: real time operation (compared to the film) and high spatial resolution, large dynamic range and small size (compared to ionizing chambers). Most diode arrays have detector pitch that is too coarse for routine use in small field applications. The goal of this work is to characterize the two-dimensional monolithic silicon diode array named "MagicPlate-512" (MP512) designed for QA in stereotactic body radiation therapy (SBRT) and stereotactic radio surgery (SRS). MP512 is a silicon monolithic detector manufactured on ap-type substrate. An array contains of 512 pixels with size 0.5×0.5 mm2 and pitch 2 mm with an overall dimension of 52×52 mm2. The MP512 monolithic detector is wire bonded on a printed circuit board 0.5 mm thick and covered by a thin layer of raisin to preserve the silicon detector from moisture and chemical contamination and to protect the bonding wires. Characterization of the silicon monolithic diode array response was performed, and included pixels response uniformity, dose linearity, percent depth dose, output factor, and beam profiling for beam sizes relevant to SBRT and SRS and depth dose response in comparison with ionization chamber. MP512 shows a good dose linearity (R2=0.998) and repeatability within 0.2%. The measured depth dose response for field size of 10×10 cm2 agreed to within 1.3%, when compared to a CC13 ionization chamber for depths in PMMA up to 30 cm. The output factor of a 6 MV Varian 2100EX medical linac beam measured by MP512 at the isocenter agrees to within 2% when compared to PTW diamond, Scanditronix point EDD-2 diode and MOSkin detectors for field sizes down to 1×1 cm2. An over response of 4% was observed for square beam size smaller than 1 cm when compared to EBT3 films, while the beam profiles (FWHM) of MP512 match to within 2% the data measured by radiochromic film. The response of the 2D detector array, MP512, has been evaluated. The properties of the array demonstrated suitability for use as in phantom dosimeter for QA in SRS and SBRT. Although MP512 matches film measurements down to 1×1 cm2 well, it showed a discrepancy of 4% in the determination of output factors of beams smaller than 0.5×0.5 cm2 due to the field perturbation generated by the large amount of silicon surrounding the central diode. MP512 is highly capable of measuring beam size (FWHM) and has a discrepancy of less than 1.3% when compared to EBT3 film. A reduction in the detector pitch to less than 2 mm would improve the penumbra reconstruction accuracy at the cost readout electronics complexity.
A novel methodology to assess linear energy transfer and relative biological effectiveness in proton therapy using pairs of differently doped thermoluminescent detectors
Publisher: IOP Publishing
Date: 05-04-2019
Abstract: A new methodology for assessing linear energy transfer (LET) and relative biological effectiveness (RBE) in proton therapy beams using thermoluminescent detectors is presented. The method is based on the different LET response of two different lithium fluoride thermoluminescent detectors (LiF:Mg,Ti and LiF:Mg,Cu,P) for measuring charged particles. The relative efficiency of the two detector types was predicted using the recently developed Microdosimetric d(z) Model in combination with the Monte Carlo code PHITS. Afterwards, the calculated ratio of the expected response of the two detector types was correlated with the fluence- and dose- mean values of the unrestricted proton LET. Using the obtained proton dose mean LET as input, the RBE was assessed using a phenomenological biophysical model of cell survival. The aforementioned methodology was benchmarked by exposing the detectors at different depths within the spread out Bragg peak (SOBP) of a clinical proton beam at iThemba LABS. The assessed LET values were found to be in good agreement with the results of radiation transport computer simulations performed using the Monte Carlo code GEANT4. Furthermore, the estimated RBE values were compared with the RBE values experimentally determined by performing colony survival measurements with Chinese Hamster Ovary (CHO) cells during the same experimental run. A very good agreement was found between the results of the proposed methodology and the results of the in vitro study.
Characteristics of proton CT images reconstructed with filtered backprojection and iterative projection algorithms
Publisher: IEEE
Date: 10-2009
Characterisation of a well-type NaI(Tl) detector by means of a Monte Carlo simulation for radionuclide metrology application
Publisher: Elsevier BV
Date: 10-2021
3D probability driven random walk segmentation with automated seed selection for the delineation of PET volumes
Publisher: IEEE
Date: 11-2018
Medipix detectors in radiation therapy for advanced quality-assurance
Publisher: Elsevier BV
Date: 2020
First proof of bismuth oxide nanoparticles as efficient radiosensitisers on highly radioresistant cancer cells
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.EJMP.2016.10.015
Abstract: This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50μg.mL
BrachyView, A novel inbody imaging system for HDR prostate brachytherapy: Design and Monte Carlo feasibility study
Publisher: Wiley
Date: 17-06-2013
DOI: 10.1118/1.4808360
Abstract: High dose rate (HDR) brachytherapy is a form of radiation therapy for treating prostate cancer whereby a high activity radiation source is moved between predefined positions inside applicators inserted within the treatment volume. Accurate positioning of the source is essential in delivering the desired dose to the target area while avoiding radiation injury to the surrounding tissue. In this paper, HDR BrachyView, a novel inbody dosimetric imaging system for real time monitoring and verification of the radioactive seed position in HDR prostate brachytherapy treatment is introduced. The current prototype consists of a 15 × 60 mm(2) silicon pixel detector with a multipinhole tungsten collimator placed 6.5 mm above the detector. Seven identical pinholes allow full imaging coverage of the entire treatment volume. The combined pinhole and pixel sensor arrangement is geometrically designed to be able to resolve the three-dimensional location of the source. The probe may be rotated to keep the whole prostate within the transverse plane. The purpose of this paper is to demonstrate the efficacy of the design through computer simulation, and to estimate the accuracy in resolving the source position (in detector plane and in 3D space) as part of the feasibility study for the BrachyView project. Monte Carlo simulations were performed using the GEANT4 radiation transport model, with a (192)Ir source placed in different locations within a prostate phantom. A geometrically accurate model of the detector and collimator were constructed. Simulations were conducted with a single pinhole to evaluate the pinhole design and the signal to background ratio obtained. Second, a pair of adjacent pinholes were simulated to evaluate the error in calculated source location. Simulation results show that accurate determination of the true source position is easily obtainable within the typical one second source dwell time. The maximum error in the estimated projection position was found to be 0.95 mm in the imaging (detector) plane, resulting in a maximum source positioning estimation error of 1.48 mm. HDR BrachyView is a feasible design for real-time source tracking in HDR prostate brachytherapy. It is capable of resolving the source position within a subsecond dwell time. In combination with anatomical information obtained from transrectal ultrasound imaging, HDR BrachyView adds a significant quality assurance capability to HDR brachytherapy treatment systems.
BrachyView: Feasibility study into the application of Timepix detectors for soft tissue thickness imaging in prostate brachytherapy treatment
Publisher: Elsevier BV
Date: 12-2014
Development and fabrication of cylindrical siliconon- insulator microdosimeter arrays
Publisher: IEEE
Date: 10-2008
Development of a high resolution voxelised head phantom for medical physics applications
Publisher: Elsevier BV
Date: 2017
Electron track structure simulations in a gold nanoparticle using Geant4-DNA
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.EJMP.2019.05.023
Abstract: Gold Nanoparticles (GNPs) have recently gained a lot of attention due to their potential benefit to improve the efficacy of X-ray radiotherapy. Owing to their high atomic number, GNPs are able to absorb higher quantities of incident radiation with respect to the surrounding tissue, producing, in particular, photoelectrons and low energy Auger electrons. These additional low energy electrons increase the local energy deposition in the region surrounding the GNP. Monte Carlo simulations play a key role in the investigation of GNP radio-enhancement and it is widely recognised that track structure physics models are the state-of-the-art for nano-scale studies. In 2016, we have developed track structure physics models for the Geant4-DNA toolkit allowing electron transport for microscopic bulk gold (Geant4_DNA_AU_2016) and we have recently improved them in the low energy domain (Geant4_DNA_AU_2018). In this paper, we report the benchmarking of these newly developed physics models when calculating the physical dose and the Dose Enhancement Factor (DEF) around a GNP. We demonstrate that Geant4_DNA_AU_2018 models give similar azimuthal distribution of two dimensional absorbed dose around a single GNP, but result in larger absorbed dose and DEF than Geant4_DNA_AU_2016 models. In parallel, we investigated the performance of a newly developed multiple scattering model in Geant4 based on the Goudsmit-Saunderson (GS) model, when used together with the electromagnetic physics models with the Geant4 Livermore condensed-history approach. Our results show that the GS model does not affect the results of the simulations when studying GNP radio-enhancement with a condensed-history approach.
Out-of-field dose equivalents delivered by proton therapy of prostate cancer
Publisher: Wiley
Date: 07-08-2007
DOI: 10.1118/1.2759839
Abstract: Measurements were performed to assess the dose equivalent outside a primary proton treatment field, using a silicon-on-insulator (SOI) microdosimeter. The SOI microdosimeter was placed on the surface of an anthropomorphic phantom and dose equivalents were determined as a function of lateral distance from a typical passively scattered and modulated prostate treatment field. Measurements were also completed within a polystyrene plate phantom as a function of depth for a distance of 5 cm from the field edge, as function of lateral distance from field edge at two different depths, and as a function of distance from the distal edge on the central beam axis. The dose equivalent at the surface of the anthropomorphic phantom decreases from 3.9 to 0.18 mSv/Gy when the lateral distance from the proton field edge increases from 2.5 to 60 cm. Measurements along the proton depth dose distribution at a constant distance of 5 cm from the primary field edge indicate a decrease in dose equivalent as a function of depth, with a 38% decrease relative to the surface dose at a depth of 5 cm in polystyrene. Measurements completed as a function of lateral distance from the primary field at two separate depths within polystyrene illustrate a convergence of the dose equivalent at approximately 20 cm from the primary field edge. Past the distal edge of the spread-out Bragg peak dose equivalents decrease exponentially for increasing distance, with an initial value of 1.6 mSv/Gy at 0.6 cm from the distal edge. Silicon microdosimetry measurements were also compared with published results obtained utilizing different measurement techniques. This study demonstrates the applicability of SOI microdosimetry in determining the dose equivalent outside proton treatment fields, and provides valuable information on the dose equivalent both at the surface and at depth experienced by prostate cancer patients treated with protons.
Semiconductor detectors in radiation medicine: Radiotherapy and related applications
Publisher: Springer Netherlands
Date: 2006
Evaluation of spot size using volumetric repainting technique on a ProteusPLUS PBS Proton Therapy System
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012027
Abstract: Volumetric repainting is considered as one of the techniques for motion mitigation in proton therapy. Faster layer switching time to deliver a volumetric repainting proton plan is very critical to reduce the overall treatment time. Recently, IBA (proton therapy vendor at the Miami Cancer Institute) has implemented a “field regulation” – a new feature to reduce the switching time between layers by applying a magnetic field setpoint to specific groups of magnets. In order to investigate the impact of field regulation and volumetric repainting technique on the spot size, several spot maps were generated. The spot sizes were measured at the isocenter and four off-axis points using the Lynx 2D scintillation detector. The average difference in spot size between two delivery sequences (“down” vs. “up” directions) for given energy at all five locations was 0.6±0.5%. The measurement results from the current study demonstrated that the impact of field regulation on the spot size was very minimal, and this was true for both the volumetric and non-volumetric techniques on a ProteusPLUS proton system with a PBS dedicated nozzle.
GEANT4 simulation of the CERN-EU high-energy reference field (CERF) facility
Publisher: Oxford University Press (OUP)
Date: 28-05-2010
DOI: 10.1093/RPD/NCQ152
Abstract: The CERN-EU high-energy reference field facility is used for testing and calibrating both active and passive radiation dosemeters for radiation protection applications in space and aviation. Through a combination of a primary particle beam, target and a suitable designed shielding configuration, the facility is able to reproduce the neutron component of the high altitude radiation field relevant to the jet aviation industry. Simulations of the facility using the GEANT4 (GEometry ANd Tracking) toolkit provide an improved understanding of the neutron particle fluence as well as the particle fluence of other radiation components present. The secondary particle fluence as a function of the primary particle fluence incident on the target and the associated dose equivalent rates were determined at the 20 designated irradiation positions available at the facility. Comparisons of the simulated results with previously published simulations obtained using the FLUKA Monte Carlo code, as well as with experimental results of the neutron fluence obtained with a Bonner sphere spectrometer, are made.
Erratum: Out-of-field dose equivalents delivered by proton therapy of prostate cancer (Medical Physics (2007) 34, (3449-3456))
Publisher: Wiley
Date: 26-06-2008
DOI: 10.1118/1.2940156
Initial experiments with gel-water: towards MRI-linac dosimetry and imaging
Publisher: Springer Science and Business Media LLC
Date: 04-11-2016
DOI: 10.1007/S13246-016-0495-1
Abstract: Tracking the position of a moving radiation detector in time and space during data acquisition can replicate 4D image-guided radiotherapy (4DIGRT). Magnetic resonance imaging (MRI)-linacs need MRI-visible detectors to achieve this, however, imaging solid phantoms is an issue. Hence, gel-water, a material that provides signal for MRI-visibility, and which will in future work, replace solid water for an MRI-linac 4DIGRT quality assurance tool, is discussed. MR and CT images of gel-water were acquired for visualisation and electron density verification. Characterisation of gel-water at 0 T was compared to Gammex-RMI solid water, using MagicPlate-512 (M512) and RMI Attix chamber this included percentage depth dose, tissue-phantom ratio (TPR
Neutron Dosimetry with Planar Silicon p-i-n Diodes
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2003
Advances in modelling gold nanoparticle radiosensitization using new Geant4-DNA physics models
Publisher: IOP Publishing
Date: 13-11-2020
Abstract: Gold nanoparticles have demonstrated significant radiosensitization of cancer treatment with x-ray radiotherapy. To understand the mechanisms at the basis of nanoparticle radiosensitization, Monte Carlo simulations are used to investigate the dose enhancement, given a certain nanoparticle concentration and distribution in the biological medium. Earlier studies have ordinarily used condensed history physics models to predict nanoscale dose enhancement with nanoparticles. This study uses Geant4-DNA complemented with novel track structure physics models to accurately describe electron interactions in gold and to calculate the dose surrounding gold nanoparticle structures at nanoscale level. The computed dose in silico due to a clinical kilovoltage beam and the presence of gold nanoparticles was related to in vitro brain cancer cell survival using the local effect model. The comparison of the simulation results with radiobiological experimental measurements shows that Geant4-DNA and local effect model can be used to predict cell survival in silico in the case of x-ray kilovoltage beams.
Microdosimetric study for helium-ion beam using fully 3D silicon microdosimeters
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012022
Abstract: In this study, the survival fraction of pancreatic cancer cells exposed to a spread-out Bragg peak (SOBP) helium-ion beam are estimated using the microdosimetric method with the microdosimetric kinetic (MK) model, by measuring the specific energy with a microdosimeter. To measure the microdosimetric spectra, a 3D mushroom microdosimeter was used by mounting it on silicon-on-insulator (SOI) substrates. At different positions of the Bragg curve of a pristine helium-ion beam of 166 MeV/u, microdosimetric spectra were measured via a scanning beam port in the National Institute of Radiological Sciences. The MK parameters were determined such that the survival fraction (SF) calculated by the MK model predicts the previously reported in vitro data. For a cuboid target of 10×10×6 cm3, a treatment plan that utilised helium-ion beam was designed from the in-house treatment planning software (TPS) to achieve a 10% SF of pancreatic cancer cells throughout the target. The physical doses and microdosimetric spectra were measured for different depths by irradiating the scanning-SOBP helium-ion beam consequently, the SF at each position of the SOBP was predicted. The predicted SFs from measured physical dose and microdosimetric spectra were in good agreement with the planned SF from TPS.
Verification of Monte Carlo calculations in Fast Neutron Therapy using silicon microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2004
Transient conductance technique for characterization of deep-level defects in highly irradiated detector-grade silicon
Publisher: Elsevier BV
Date: 09-1999
Assessing small-field output factors using a 2D monolithic diode array on a beam-matched Elekta linear accelerator
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012024
Abstract: The goal of this work was to assess small-field output factors (OPF) on a newly commissioned linear accelerator (linac) using a ‘correction-less’ 2D monolithic array of diodes, the Duo, which has a spatial resolution of 0.2 mm. The results would validate a set of OPF extracted from the golden beam data (GBD) used to represent the dosimetric characteristics of that linac, an Elekta Versa HD (Elekta, Crawley), fit with an Agility multileaf collimator (MLC). The Duo acquired relative OPF in real time for square fields of nominal side 1, 2, 3 and 4 cm, for 6 MV with flattening filter (WFF) and 6 MV flattening filter free (FFF) photon energies. Results revealed at most a 1.0% difference in OPF when compared to baseline, and bolstered confidence in the acceptance and commissioning of the linac using local GBD as a baseline match.
Sci—Thur AM: Planning ‐ 01: Experimental and Monte Carlo verification of Acuros XB calculations near low and high density heterogeneities
Publisher: Wiley
Date: 07-2012
DOI: 10.1118/1.4740086
Abstract: The purpose of this study was to examine the accuracy of AcurosXB and AAA algorithms near low and high density heterogeneities of different densities using EBT2 film, MOSFET detector "MOSkin" and Monte Carlo calculations using BEAMnrc/DOSXYZnrc. Three different interfaces were used that included a solid water phantom with 2×2×30cm
Dosimetric evaluation of proton CT using a prototype proton CT scanner
Publisher: IEEE
Date: 10-2017
Feasibility study on the use of 3D silicon microdosimeter detectors for microdosimetric analysis in boron neutron capture therapy
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.APRADISO.2018.06.022
Abstract: This paper presents the feasibility study of a novel 3D mesa bridge microdosimeter and its use for BNCT dosimetry. The performance of the microdosimeter was studied using Monte Carlo simulation. The clinical BNCT field at Kyoto University Reactor (KUR) using both thermal and epithermal irradiation modes were used in this study. Results show that this microdosimeter can be utilised as an effective tool to measure microdosimetric spectrum in the BNCT field and experimental validation will follow once KUR is operational.
Real-Time in-vivo dosimetry for DaRT
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012031
Abstract: Diffusing alpha-emitters radiation therapy (DaRT) is a revolutionary brachytherapy technique used to treat solid tumours. Implant seeds are coated with 224 Ra which, along its shortlived daughter atoms, emits alpha particles of high linear energy transfer (LET) and of high relative biological efficiency (RBE), creating a tumour-killing dose distribution a few mm wide. Those alpha particles are of energy between 5.67 and 8.78 MeV. DaRT is under investigation in clinical trials, but there currently is no obvious solution for dosimetry aimed at quality assurance of treatment. This study introduces alpha-RAD, a dosimeter based on a metal-oxide-semiconductor (MOS) sensor technology. Alpha-RAD was characterized with 241 Am, which emits alpha particles of energy 5.49 MeV. The results showed that alpha-RAD had good linearity with dose, with the signal increasing linearly in the range from 0 to 6.84 Gy. Also, an external bias in the range between 15 and 60 V, applied on the gate of alpha-RAD during irradiation, would optimize sensitivity to alpha particles of energies typical of DaRT. Alpha-RAD, owing to its compactness, can fit into a brachytherapy needle, to be placed next to 224 Ra seed implants in the tumour, for real-time in vivo dosimetry.
Characterization of MOSFET Dosimeters for Alpha Particle Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2022
Performance comparison of two compact multiplexed readouts with SensL's SPMArray4 for high-resolution detector module
Publisher: IEEE
Date: 10-2012
A novel high-resolution 2D silicon array detector for small field dosimetry with FFF photon beams
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.
Application of semiconductors for dosimetry of fast-neutron therapy beam
Publisher: Oxford University Press (OUP)
Date: 08-2004
DOI: 10.1093/RPD/NCH223
3D radiation detectors: Charge collection characterisation and applicability of technology for microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2004
A comparison of proton therapy and IMRT treatment plans for prostate radiotherapy
Publisher: Springer Science and Business Media LLC
Date: 12-2008
DOI: 10.1007/BF03178602
Skin dosimetry with new MOSFET detectors
Publisher: Elsevier BV
Date: 02-2008
Dosimetric verification of helical tomotherapy for total scalp irradiation
Publisher: Wiley
Date: 17-10-2008
DOI: 10.1118/1.2996288
Abstract: Total scalp irradiation is a treatment technique used for a variety of superficial malignancies. Helical tomotherapy is an effective technique used for total scalp irradiation. Recent published work has shown the TomoTherapy planning system to overestimate the superficial dose. In this study, the superficial doses for a helical tomotherapy total scalp irradiation have been measured on an anthropomorphic phantom using radiochromic and radiographic film as well as a new skin dosimeter, the MOSkin. The superficial dose was found to be accurately calculated by the Tomo-Therapy planning system. This is in contrast to recent reports, probably due to a combination of the smaller dose grid resolution used in planning and this particular treatment primarily consisting of beamlets tangential to the scalp. The superficial dose was found to increase from 33.6 to 41.2 Gy and 36.0 to 42.0 Gy over the first 2 mm depth in the phantom in selected regions of the PTV, measured with radiochromic film. The prescription dose was 40 Gy. The superficial dose was at the prescription dose or higher in some regions due to the bolus effect of the thermoplastic head mask and the head rest used to aid treatment setup. It is suggested that to achieve the prescription dose at the surface (< or =2 mm depth) bolus or a custom thermoplastic helmet is used.
Proton-impact ionisation cross sections for nanodosimetric track structure simulations
Publisher: Oxford University Press (OUP)
Date: 08-12-2014
DOI: 10.1093/RPD/NCT317
Abstract: Monte Carlo simulations of the particle track structure require accurate ion- and electron-impact cross-section data of the medium. These data are scarce and often inconsistent when measured by different groups. In this work, literature data on ionisation cross sections (CSs) of nitrogen and propane for protons with energies 0.1-10 MeV are reviewed and implemented in the code PTra. Methane data were used to obtain proton-impact CSs of propane due to their absence in the literature. PTra is benchmarked by comparing simulated particle-track parameters to experimental results, measured with an ion-counting nanodosemeter.
Analysis of inelastic interactions for therapeutic proton beams using Monte Carlo simulation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2004
Urethral alarm probe for permanent prostate implants
Publisher: Informa UK Limited
Date: 06-2008
Technical Note: Angular dependence of a 2D monolithic silicon diode array for small field dosimetry: Angular
Publisher: Wiley
Date: 10-07-2017
DOI: 10.1002/MP.12377
Abstract: This study aims to investigate the 2D monolithic silicon diode array size of 52 × 52 mm The MP512 was placed at the center of a cylindrical phantom, irradiated using 6 MV and 10 MV photons and incrementing the incidence of the beam angle in 15° steps from 0° to 180°, and then in 1° steps between 85° and 95°. The MP512 response was characterized for square field sizes varying between 1 × 1 cm The intrinsic angular dependence of the MP512 shows maximum relative deviation from the response normalized to 0° of 18.5 ± 0.5% and 15.5 ± 0.5% for 6 MV and 10 MV, respectively, demonstrating that the angular response is sensitive to the energy. In contrast, the variation of angular response is less affected by field size. Comparison of cross-plane profiles measured by the corrected MP512 and EBT3 shows an agreement within ±2% for all field sizes when the beams irradiated the array at 0°, 45°, 135°, and 180° angles of incidence from the normal to the detector plane. At 90° incidence, corresponding to a depth dose measurement, up to a 6% discrepancy was observed for a 1 × 1 cm An angular correction factor can be adopted for small field sizes. Measurements discrepancies could be encountered when irradiating with very small fields parallel to the detector plane. Using this approach, the MP512 is shown to be a suitable detector for 2D dose mapping of small field size photon beams.
A proteomic characterization shows differences in the milk fat globule membrane of buffalo and bovine milk
Publisher: Elsevier BV
Date: 09-2017
A dual scintillator - Dual silicon photodiode detector module for intraoperative gamma\beta probe and portable anti-compton spectrometer
Publisher: Informa UK Limited
Date: 06-2008
Response of a PIN diode and SOI microdosimeter to the TSL quasimonoenergetic neutron field
Publisher: IEEE
Date: 10-2008
Modelling ICRP110 Adult Reference Voxel Phantoms for dosimetric applications: Development of a new Geant4 Advanced Example
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1662/1/012021
Abstract: The reference adult male and female voxel phantoms described in the International Commission on Radiological Protection (ICRP) publication 110 have been successfully implemented in a Geant4 application named ICRP110Phantoms . The application allows users to simulate either the whole or a partial phantom, including as little as a single cross-sectional slice. The Geant4 application allows users to estimate the absorbed dose in in idual voxels and in entire organs. As ex le of application, the ICRP110Phantoms was used to estimate the dose deposited by a mono-energetic 125 MeV proton pencil beam, incident on the left breast and passing through the lungs and heart, modelled in partial chest phantoms of both male and female ICRP110 phantoms. The ICRP110Phantoms will be released in Geant4 as an Advanced Ex le to allow its use in the wider scientific community. This Geant4 Advanced Ex le application can be utilised for dosimetric studies in radiotherapy, nuclear medicine and radiation protection.
From imaging to dosimetry: GEANT4-based study on the application of Medipix to neutron dosimetry
Publisher: Elsevier BV
Date: 12-2010
Monte carlo characterization of skin doses in 6 MV transverse field MRI-linac systems: Effect of field size, surface orientation, magnetic field strength, and exit bolus
Publisher: Wiley
Date: 14-09-2010
DOI: 10.1118/1.3488980
Abstract: The main focus of this work is to continue investigations into the Monte Carlo predicted skin doses seen in MRI-guided radiotherapy. In particular, the authors aim to characterize the 70 microm skin doses over a larger range of magnetic field strength and x-ray field size than in the current literature. The effect of surface orientation on both the entry and exit sides is also studied. Finally, the use of exit bolus is also investigated for minimizing the negative effects of the electron return effect (ERE) on the exit skin dose. High resolution GEANT4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam (Varian 2100C) have been performed. Transverse magnetic fields of strengths between 0 and 3 T have been applied to a 30 x 30 x 20 cm3 phantom. This phantom is also altered to have variable entry and exit surfaces with respect to the beam central axis and they range from -75 degrees to +75 degrees. The exit bolus simulated is a 1 cm thick (water equivalent) slab located on the beam exit side. On the entry side, significant skin doses at the beam central axis are reported for large positive surface angles and strong magnetic fields. However, over the entry surface angle range of -30 degrees to -60 degrees, the entry skin dose is comparable to or less than the zero magnetic field skin dose, regardless of magnetic field strength and field size. On the exit side, moderate to high central axis skin dose increases are expected except at large positive surface angles. For exit bolus of 1 cm thickness, the central axis exit skin dose becomes an almost consistent value regardless of magnetic field strength or exit surface angle. This is due to the almost complete absorption of the ERE electrons by the bolus. There is an ideal entry angle range of -30 degrees to -60 degrees where entry skin dose is comparable to or less than the zero magnetic field skin dose. Other than this, the entry skin dose increases are significant, especially at higher magnetic fields. On the exit side there is mostly moderate to high skin dose increases for 0.2-3 T with the only exception being large positive angles. Exit bolus of 1 cm thickness will have a significant impact on lowering such exit skin dose increases that occur as a result of the ERE.
Measurement of rectal dose during HDR brachytherapy using the new MOSkin dosimeter
Publisher: Informa UK Limited
Date: 06-2008
Improvements in dose calculation accuracy for small off-axis targets in high dose per fraction tomotherapy
Publisher: Wiley
Date: 19-07-2012
DOI: 10.1118/1.4736811
Abstract: A recent field safety notice from TomoTherapy detailed the underdosing of small, off-axis targets when receiving high doses per fraction. This is due to angular unders ling in the dose calculation gantry angles. This study evaluates a correction method to reduce the underdosing, to be implemented in the current version (v4.1) of the TomoTherapy treatment planning software. The correction method, termed "Super S ling" involved the tripling of the number of gantry angles from which the dose is calculated during optimization and dose calculation. Radiochromic film was used to measure the dose to small targets at various off-axis distances receiving a minimum of 21 Gy in one fraction. Measurements were also performed for single small targets at the center of the Lucy phantom, using radiochromic film and the dose magnifying glass (DMG). Without super s ling, the peak dose deficit increased from 0% to 18% for a 10 mm target and 0% to 30% for a 5 mm target as off-axis target distances increased from 0 to 16.5 cm. When super s ling was turned on, the dose deficit trend was removed and all peak doses were within 5% of the planned dose. For measurements in the Lucy phantom at 9.7 cm off-axis, the positional and dose magnitude accuracy using super s ling was verified using radiochromic film and the DMG. A correction method implemented in the TomoTherapy treatment planning system which triples the angular s ling of the gantry angles used during optimization and dose calculation removes the underdosing for targets as small as 5 mm diameter, up to 16.5 cm off-axis receiving up to 21 Gy.
Validation of Geant4 fragmentation for Heavy Ion Therapy
Publisher: Elsevier BV
Date: 10-2017
Panoptes: Calibration of a dosimetry system for eye brachytherapy
Publisher: Elsevier BV
Date: 12-2014
Spectral characterization of a blue-enhanced silicon photodetector
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2001
DOI: 10.1109/23.958754
Introduction to the geant4 simulation toolkit
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3576174
Large area silicon microdosimeter for dosimetry in high LET space radiation fields: Charge collection study
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
MRI-LINAC beam profile measurements using a plastic scintillation dosimeter.
Publisher: Elsevier BV
Date: 05-2020
The planar silicon p-i-n diodes as sensors of fast neutrons
Publisher: IEEE
Date: 10-2008
Characterization of a Large Area Thinned Silicon Microdosimeter for Space and Particle Therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
HDR prostate brachytherapy plan robustness and its effect on in-vivo source tracking error thresholds: A multi-institutional study
Publisher: Wiley
Date: 19-04-2022
DOI: 10.1002/MP.15658
Abstract: The purpose of this study was to examine the effect of departmental planning techniques on appropriate in‐vivo source tracking error thresholds for high dose rate (HDR) prostate brachytherapy (BT) treatments, and to determine if a single in‐vivo source tracking error threshold would be appropriate for the same patient anatomy. The prostate, rectum, and urethra were contoured on a single patient transrectal ultrasound (TRUS) dataset. Anonymized DICOM files were disseminated to 16 departments who created an HDR prostate BT treatment plan on the dataset with a prescription dose of 15 Gy in a single fraction. Departments were asked to follow their own local treatment planning guidelines. Source positioning errors were then simulated in the 16 treatment plans and the effect on dose–volume histogram (DVH) indices calculated. Change in DVH indices were used to determine appropriate in‐vivo source tracking error thresholds. Plans were considered to require intervention if the following DVH conditions occurred: prostate V100% 90%, urethra D0.1cc 118%, and rectumtt D max 80%. There was wide variation in appropriate in‐vivo source tracking error thresholds among the 16 participating departments, ranging from 1 to 6 mm. Appropriate in‐vivo source tracking error thresholds were also found to depend on the direction of the source positioning error and the endpoint. A robustness parameter was derived, and found to correlate with the sensitivity of plans to source positioning errors. A single HDR prostate BT in‐vivo source tracking error threshold cannot be applied across multiple departments, even for the same patient anatomy. The burden on in‐vivo source tracking devices may be eased through improving HDR prostate BT plan robustness during the plan optimisation phase.
SOI microdosimetry and modified MKM for evaluation of relative biological effectiveness for a passive proton therapy radiation field
Publisher: IOP Publishing
Date: 23-11-2018
Abstract: With more patients receiving external beam radiation therapy with protons, it becomes increasingly important to refine the clinical understanding of the relative biological effectiveness (RBE) for dose delivered during treatment. Treatment planning systems used in clinics typically implement a constant RBE of 1.1 for proton fields irrespective of their highly heterogeneous linear energy transfer (LET). Quality assurance tools that can measure beam characteristics and quantify or be indicative of biological outcomes become necessary in the transition towards more sophisticated RBE weighted treatment planning and for verification of the Monte Carlo and analytical based models they use. In this study the RBE for the CHO-K1 cell line in a passively delivered clinical proton spread out Bragg peak (SOBP) is determined both in vitro and using a silicon-on-insulator (SOI) microdosimetry method paired with the modified microdosimetric kinetic model. The RBE along the central axis of a SOBP with 2 Gy delivered at the middle of the treatment field was found to vary between 1.11-1.98 and the RBE for 10% cell survival between 1.07-1.58 with a 250 kVp x-ray reference radiation and between 1.19-2.34 and 0.95-1.41, respectively, for a Co60 reference. Good agreement was found between RBE values calculated from the SOI-microdosimetry-MKM approach and in vitro. A strong correlation between proton lineal energy and RBE was observed particularly in the distal end and falloff of the SOBP.
Comparative analysis of the secondary electron yield from carbon nanoparticles and pure water medium Topical Issue: COST Action Nano-IBCT: Nano-scale Processes behind Ion-Beam Cancer Therapy Andrey Solov'yovNigel Mason, Gustavo García and Eugene Surdutovich
Publisher: Springer Science and Business Media LLC
Date: 04-2015
The evaluation of a 2D diode array in magic phantom for use in high dose rate brachytherapy pretreatment quality assurance
Publisher: Wiley
Date: 12-01-2015
DOI: 10.1118/1.4905233
Abstract: High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The development of a sound quality assurance program for the verification of treatment deliveries can be challenging due to the high source activity utilized and the need for precise measurements of dwell positions and times. This paper describes the application of a novel phantom, based on a 2D 11 × 11 diode array detection system, named “magic phantom” (MPh), to accurately measure plan dwell positions and times, compare them directly to the treatment plan, determine errors in treatment delivery, and calculate absorbed dose. The magic phantom system was CT scanned and a 20 catheter plan was generated to simulate a nonspecific treatment scenario. This plan was delivered to the MPh and, using a custom developed software suite, the dwell positions and times were measured and compared to the plan. The original plan was also modified, with changes not disclosed to the primary authors, and measured again using the device and software to determine the modifications. A new metric, the “position–time gamma index,” was developed to quantify the quality of a treatment delivery when compared to the treatment plan. The MPh was evaluated to determine the minimum measurable dwell time and step size. The incorporation of the TG-43U1 formalism directly into the software allows for dose calculations to be made based on the measured plan. The estimated dose distributions calculated by the software were compared to the treatment plan and to calibrated EBT3 film, using the 2D gamma analysis method. For the original plan, the magic phantom system was capable of measuring all dwell points and dwell times and the majority were found to be within 0.93 mm and 0.25 s, respectively, from the plan. By measuring the altered plan and comparing it to the unmodified treatment plan, the use of the position–time gamma index showed that all modifications made could be readily detected. The MPh was able to measure dwell times down to 0.067 ± 0.001 s and planned dwell positions separated by 1 mm. The dose calculation carried out by the MPh software was found to be in agreement with values calculated by the treatment planning system within 0.75%. Using the 2D gamma index, the dose map of the MPh plane and measured EBT3 were found to have a pass rate of over 95% when compared to the original plan. The application of this magic phantom quality assurance system to HDR brachytherapy has demonstrated promising ability to perform the verification of treatment plans, based upon the measured dwell positions and times. The introduction of the quantitative position–time gamma index allows for direct comparison of measured parameters against the plan and could be used prior to patient treatment to ensure accurate delivery.
Predicting the Biological Effects of Human Salivary Gland Tumour Cells for Scanned4He‐,12C‐,16O‐, and20Ne‐Ion Beams Using an SOI Microdosimeter
Publisher: MDPI AG
Date: 16-06-2022
DOI: 10.3390/APP12126148
Abstract: Experimental microdosimetry along with the microdosimetric kinetic (MK) model can be utilized to predict the biological effects of ions. To predict the relative biological effectiveness (RBE) of ions and the survival fraction (SF) of human salivary gland tumour (HSGc-C5) cells, microdosimetric quantities measured by a silicon-on-insulator (SOI) MicroPlus-mushroom microdosimeter along the spread-out Bragg peak (SOBP) delivered by pencil beam scanning of 4He, 12C, 16O, and 20Ne ions were used. The MK model parameters of HSGc-C5 cells were obtained from the best fit of the calculated SF for the different linear energy transfer (LET) of these ions and the formerly reported in vitro SF for the same LET and ions used for calculations. For a cube-shaped target of 10 × 10 × 6 cm3, treatment plans for 4He, 12C, 16O, and 20Ne ions were produced with proprietary treatment planning software (TPS) aiming for 10% SF of HSGc-C5 cells over the target volume and were delivered to a polymethyl methacrylate (PMMA) phantom. Afterwards, the saturation-corrected dose-mean lineal energy derived based on the measured microdosimetry spectra, along with the physical dose at various depths in PMMA phantoms, was used for the estimation of the SF, RBE, and RBE-weighted dose using the MK model. The predicted SF, RBE, and the RBE-weighted dose agreed with what was planned by the TPS within 3% at most depths for these ions.
Dosimetric evaluation near lung and soft tissue interface region during respiratory-gated and non-gated radiotherapy: A moving phantom study
Publisher: Elsevier BV
Date: 10-2200
DOI: 10.1016/J.EJMP.2017.08.011
Abstract: Challenges in treating lung tumours are related to the respiratory-induced tumour motion and the accuracy of dose calculation in charged particle disequilibrium condition. The dosimetric characteristics near the interface of lung and Perspex media in a moving phantom during respiratory-gated and non-gated radiotherapy were investigated using Gafchromic EBT2 and the MOSkin detector. The MOSkin detectors showed good agreement with the EBT2 films during static and gated radiotherapy. In static radiotherapy, the penumbral widths were found to be 3.66mm and 7.22mm in Perspex and lung media, respectively. In non-gated (moving) radiotherapy with 40mm respiratory litude, dose smearing effect was observed and the penumbral widths were increased to 28.81mm and 26.40mm, respectively. This has been reduced to 6.85mm and 9.81mm, respectively, in gated radiotherapy with 25% gating window. There were still some dose discrepancies as compared to static radiotherapy due to the residual motion. This should be taken into account in the margin generation for the target tumour.
Dose reconstruction from PET images in carbon ion therapy: A deconvolution approach
Publisher: IOP Publishing
Date: 10-01-2019
Abstract: Dose and range verification have become important tools to bring carbon ion therapy to a higher level of confidence in clinical applications. Positron emission tomography is among the most commonly used approaches for this purpose and relies on the creation of positron emitting nuclei in nuclear interactions of the primary ions with tissue. Predictions of these positron emitter distributions are usually obtained from time-consuming Monte Carlo simulations or measurements from previous treatment fractions, and their comparison to the current, measured image allows for treatment verification. Still, a direct comparison of planned and delivered dose would be highly desirable, since the dose is the quantity of interest in radiation therapy and its confirmation improves quality assurance in carbon ion therapy. In this work, we present a deconvolution approach to predict dose distributions from PET images in carbon ion therapy. Under the assumption that the one-dimensional PET distribution is described by a convolution of the depth dose distribution and a filter kernel, an evolutionary algorithm is introduced to perform the reverse step and predict the depth dose distribution from a measured PET distribution. Filter kernels are obtained from either a library or are created for any given situation on-the-fly, using predictions of the [Formula: see text]-decay and depth dose distributions, and the very same evolutionary algorithm. The applicability of this approach is demonstrated for monoenergetic and polyenergetic carbon ion irradiation of homogeneous and heterogeneous solid phantoms as well as a patient computed tomography image, using Monte Carlo simulated distributions and measured in-beam PET data. Carbon ion ranges are predicted within less than 0.5 mm and 1 mm deviation for simulated and measured distributions, respectively.
Submicron position-sensitive detector
Publisher: Elsevier BV
Date: 08-1992
Evaluation of pixellated, back-sided planar photodetectors for high-resolution imaging instrumentation
Publisher: Elsevier BV
Date: 05-2008
BrachyView: Combining LDR seed positions with transrectal ultrasound imaging in a prostate gel phantom
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.EJMP.2017.01.012
Abstract: BrachyView is a novel in-body imaging system which aims to provide LDR brachytherapy seeds position reconstruction within the prostate in real-time. The first prototype is presented in this study: the probe consists of a gamma camera featuring three single cone pinhole collimators embedded in a tungsten tube, above three, high resolution pixelated detectors (Timepix). The prostate was imaged with a TRUS system using a sagittal crystal with a 2.5mm slice thickness. Eleven needles containing a total of thirty 0.508U The reconstructed seed positions determined by the BrachyView probe showed a maximum discrepancy of 1.78mm, with 75% of the seeds reconstructed within 1mm of their nominal location. An accurate co-registration between the BrachyView and TRUS coordinate system was established. The BrachyView system has shown its ability to reconstruct all implanted LDR seeds within a tissue equivalent prostate gel phantom, providing both anatomical and seed position information in a single interface.
Multifunctional Fe2 O3 /CeO2 nanocomposites for free radical scavenging ultraviolet protection
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA10951A
Abstract: In this study we synthesized Fe 2 O 3 /CeO 2 composite nanoparticles with high ultraviolet absorption and free radical scavenging properties for application as multifunctional ultraviolet (UV) filters.
Correction factors to convert microdosimetry measurements in silicon to tissue in 12C ion therapy
Publisher: IOP Publishing
Date: 17-02-2017
Abstract: Silicon microdosimetry is a promising technology for heavy ion therapy (HIT) quality assurance, because of its sub-mm spatial resolution and capability to determine radiation effects at a cellular level in a mixed radiation field. A drawback of silicon is not being tissue-equivalent, thus the need to convert the detector response obtained in silicon to tissue. This paper presents a method for converting silicon microdosimetric spectra to tissue for a therapeutic
Real-time in vivo dosimetry with MOSFET detectors in serial tomotherapy for head and neck cancer patients
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.
Towards high spatial resolution tissue-equivalent dosimetry for microbeam radiation therapy using organic semiconductors
Publisher: International Union of Crystallography (IUCr)
Date: 08-07-2021
DOI: 10.1107/S1600577521006044
Abstract: Spatially fractionated ultra-high-dose-rate beams used during microbeam radiation therapy (MRT) have been shown to increase the differential response between normal and tumour tissue. Quality assurance of MRT requires a dosimeter that possesses tissue equivalence, high radiation tolerance and spatial resolution. This is currently an unsolved challenge. This work explored the use of a 500 nm thick organic semiconductor for MRT dosimetry on the Imaging and Medical Beamline at the Australian Synchrotron. Three beam filters were used to irradiate the device with peak energies of 48, 76 and 88 keV with respective dose rates of 3668, 500 and 209 Gy s −1 . The response of the device stabilized to 30% efficiency after an irradiation dose of 30 kGy, with a 0.5% variation at doses of 35 kGy and higher. The calibration factor after pre-irradiation was determined to be 1.02 ± 0.005 µGy per count across all three X-ray energy spectra, demonstrating the unique advantage of using tissue-equivalent materials for dosimetry. The percentage depth dose curve was within ±5% of the PTW microDiamond detector. The broad beam was fractionated into 50 microbeams (50 µm FHWM and 400 µm centre-to-centre distance). For each beam filter, the FWHMs of all 50 microbeams were measured to be 51 ± 1.4, 53 ± 1.4 and 69 ± 1.9 µm, for the highest to lowest dose rate, respectively. The variation in response suggested the photodetector possessed dose-rate dependence. However, its ability to reconstruct the microbeam profile was affected by the presence of additional dose peaks adjacent to the one generated by the X-ray microbeam. Geant4 simulations proved that the additional peaks were due to optical photons generated in the barrier film coupled to the sensitive volume. The simulations also confirmed that the litude of the additional peak in comparison with the microbeam decreased for spectra with lower peak energies, as observed in the experimental data. The material packaging can be optimized during fabrication by solution processing onto a flexible substrate with a non-fluorescent barrier film. With these improvements, organic photodetectors show promising prospects as a cost-effective high spatial resolution tissue-equivalent flexible dosimeter for synchrotron radiation fields.
A simulation study of BrachyShade, a shadow-based internal source tracking system for HDR prostate brachytherapy
Publisher: IOP Publishing
Date: 18-10-2018
Abstract: This paper presents a simulation study of BrachyShade, a proposed internal source-tracking system for real time quality assurance in high dose rate prostate brachytherapy. BrachyShade consists of a set of spherical tungsten occluders located above a pixellated silicon photodetector. The source location is estimated by minimising the mean squared error between a parametric model of the shadow image and acquired images of the shadows projected on the detector plane. A novel algorithm is finally employed to correct the systemic error resulting from Compton scattering in the medium. The worst-case error obtained with BrachyShade for a 13.5 ms image acquisition is less than 1.3 mm in the most distant part of the treatment volume, while for 75% of source locations an error of less than 0.42 mm was achieved.
Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI-LINAC systems
Publisher: Wiley
Date: 26-01-2015
DOI: 10.1118/1.4905108
Abstract: MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named "magic plate," for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. geant4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-line and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm(3)) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm(2) area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm(2) photon field size. The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI-linear accelerator systems. In the in-line orientation, the silicon dose is directly proportional to the water dose. In the perpendicular orientation, there is a shift in dose response relative to water in the highest dose gradient regions, at the edge of jaw-defined and single-segment MLC fields. The trend was not observed in-field for an IMRT beam. The array is expected to be a valuable tool in MRIgRT dosimetry.
Nanodosimetry-based quality factors for radiation protection in space
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.ZEMEDI.2008.06.011
Abstract: Evaluation and monitoring of the cancer risk from space radiation exposure is a crucial requirement for the success of long-term space missions. One important task in the risk calculation is to properly weigh the various components of space radiation dose according to their assumed contribution to the cancer risk relative to the risk associated with radiation of low ionization density. Currently, quality factors of radiation both on the ground and in space are defined by national and international commissions based on existing radiobiological data and presumed knowledge of the ionization density distribution of the radiation field at a given point of interest. This approach makes the determination of the average quality factor ofa given radiation field a rather complex task. In this contribution, we investigate the possibility to define quality factors of space radiation exposure based on nanodosimetric data. The underlying formalism of the determination of quality factors on the basis of nanodosimetric data is described, and quality factors for protons and ions (helium and carbon) of different energies based on simulated nanodosimetric data are presented. The value and limitations of this approach are discussed.
Characterization of MOSkin detector for in vivo dose verification during Cobalt-60 high dose-rate intracavitary brachytherapy
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.EJMP.2019.01.010
Abstract: In vivo dosimetry in high dose-rate (HDR) intracavitary brachytherapy (ICBT) is important for assessing the true dose received by surrounding organs at risk during treatment. It also serves as part of the treatment delivery quality assurance and verification program with the use of a suitable dosimeter. Such a dosimeter should be characterized under brachytherapy conditions before clinical application to ensure the accuracy of in vivo measurement. In this study, a MOSFET-based detector, MOSkin, was calibrated and characterized under HDR Cobalt-60 (Co-60) brachytherapy source. MOSkin possessed the major advantages of having small physical and dosimetric sizes of 4.8 × 10
MOSFET dosimeters: The Role of Encapsulation on Dosimetric Characteristics in Mixed Gamma-Neutron and Megavoltage X-ray Fields
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-1995
DOI: 10.1109/23.489229
Consistency of small-field dosimetry, on and off axis, in beam-matched linacs used for stereotactic radiosurgery
Publisher: Wiley
Date: 13-01-2021
DOI: 10.1002/ACM2.13160
Benchmarking and validation of a Geant4-SHADOW Monte Carlo simulation for dose calculations in microbeam radiation therapy
Publisher: International Union of Crystallography (IUCr)
Date: 03-04-2014
DOI: 10.1107/S1600577514004640
Abstract: Microbeam radiation therapy (MRT) is a synchrotron-based radiotherapy modality that uses high-intensity beams of spatially fractionated radiation to treat tumours. The rapid evolution of MRT towards clinical trials demands accurate treatment planning systems (TPS), as well as independent tools for the verification of TPS calculated dose distributions in order to ensure patient safety and treatment efficacy. Monte Carlo computer simulation represents the most accurate method of dose calculation in patient geometries and is best suited for the purpose of TPS verification. A Monte Carlo model of the ID17 biomedical beamline at the European Synchrotron Radiation Facility has been developed, including recent modifications, using the Geant4 Monte Carlo toolkit interfaced with the SHADOW X-ray optics and ray-tracing libraries. The code was benchmarked by simulating dose profiles in water-equivalent phantoms subject to irradiation by broad-beam (without spatial fractionation) and microbeam (with spatial fractionation) fields, and comparing against those calculated with a previous model of the beamline developed using the PENELOPE code. Validation against additional experimental dose profiles in water-equivalent phantoms subject to broad-beam irradiation was also performed. Good agreement between codes was observed, with the exception of out-of-field doses and toward the field edge for larger field sizes. Microbeam results showed good agreement between both codes and experimental results within uncertainties. Results of the experimental validation showed agreement for different beamline configurations. The asymmetry in the out-of-field dose profiles due to polarization effects was also investigated, yielding important information for the treatment planning process in MRT. This work represents an important step in the development of a Monte Carlo-based independent verification tool for treatment planning in MRT.
High resolution entry and exit Monte Carlo dose calculations from a linear accelerator 6 MV beam under the influence of transverse magnetic fields
Publisher: Wiley
Date: 02-07-2009
DOI: 10.1118/1.3157203
Abstract: A current concern with 6 MV transverse field MRI-linac hybrid systems is the predicted increases in skin dose (both the entry and exit sides) caused by the effects of the magnetic field on secondary electrons. In this work high resolution GEANT4 Monte Carlo simulations have been performed at the beam central axis in the entry and exit regions of a water phantom to predict surface (0 microm depth) and skin (70 microm depth) doses when placed in such a hybrid system. A 30 x 30 x 20 cm3 water phantom with 10 microm thick voxels has been simulated by being irradiated perpendicularly with a 6 MV photon beam (Varian 2100C) of sizes of 5 x 5, 10 x 10, 15 x 15, and 20 x 20 cm2. Uniform transverse magnetic fields of 0.2, 0.75, 1.5, and 3 T with varying thickness above the phantom have been investigated. Simulations with and without lepton contamination have been performed. In the entry region the high resolution scoring has yielded unexpected surface and skin doses. There is a small amount of nonpurged air-generated lepton contamination that originates immediately above the phantom surface and delivers its dose over very short longitudinal distances in the entry region. At 0.2 T the surface and skin doses are not accurately predicted using lepton-contamination-free simulations and extrapolated lower resolution scoring. Lepton-free simulations are up to 7% of Dmax lower than simulations with leptons. However, compared to 0 T, entry skin dose is reduced at 0.2 and 0.75 T but increases to 28%-31% of Dmax at 3 T. For skin doses at the central axis in the exit region, high resolution scoring shows relative increases of 38%-106%, depending on the magnetic field strength and field size. These values are also up to 20% higher than lower resolution results. The shape of the exit dose profiles varies unpredictably and so extrapolation of low resolution data is insufficient. In order to achieve accurate Monte Carlo skin dosimetry in a transverse field MRI-linac system, the authors recommend using high resolution scoring. In systems of 0.2 T the inclusion of air-generated lepton contamination is also recommended.
Impact of magnetic field regulation in conjunction with the volumetric repainting technique on the spot positions and beam range in pencil beam scanning proton therapy
Publisher: Wiley
Date: 15-10-2020
DOI: 10.1002/ACM2.13045
A prototype coded aperture detector for small animal SPECT
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2002
Optical dating in archaeology: Thirty years in retrospect and grand challenges for the future
Publisher: Elsevier BV
Date: 04-2015
Medical physics aspects of the synchrotron radiation therapies: Microbeam radiation therapy (MRT) and synchrotron stereotactic radiotherapy (SSRT)
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.EJMP.2015.04.016
Abstract: Stereotactic Synchrotron Radiotherapy (SSRT) and Microbeam Radiation Therapy (MRT) are both novel approaches to treat brain tumor and potentially other tumors using synchrotron radiation. Although the techniques differ by their principles, SSRT and MRT share certain common aspects with the possibility of combining their advantages in the future. For MRT, the technique uses highly collimated, quasi-parallel arrays of X-ray microbeams between 50 and 600 keV. Important features of highly brilliant Synchrotron sources are a very small beam ergence and an extremely high dose rate. The minimal beam ergence allows the insertion of so called Multi Slit Collimators (MSC) to produce spatially fractionated beams of typically ∼25-75 micron-wide microplanar beams separated by wider (100-400 microns center-to-center(ctc)) spaces with a very sharp penumbra. Peak entrance doses of several hundreds of Gy are extremely well tolerated by normal tissues and at the same time provide a higher therapeutic index for various tumor models in rodents. The hypothesis of a selective radio-vulnerability of the tumor vasculature versus normal blood vessels by MRT was recently more solidified. SSRT (Synchrotron Stereotactic Radiotherapy) is based on a local drug uptake of high-Z elements in tumors followed by stereotactic irradiation with 80 keV photons to enhance the dose deposition only within the tumor. With SSRT already in its clinical trial stage at the ESRF, most medical physics problems are already solved and the implemented solutions are briefly described, while the medical physics aspects in MRT will be discussed in more detail in this paper.
Characterization of an organic semiconductor diode for dosimetry in radiotherapy
Publisher: Wiley
Date: 03-06-2020
DOI: 10.1002/MP.14229
Abstract: The development of novel detectors for dosimetry in advanced radiotherapy modalities requires materials that have a water equivalent response to ionizing radiation such that characterization of radiation beams can be performed without the need for complex calibration procedures and correction factors. Organic semiconductors are potentially an ideal technology in fabricating devices for dosimetry due to tissue equivalence, mechanical flexibility, and relatively cheap manufacturing cost. The response of a commercial organic photodetector (OPD), coupled to a plastic scintillator, to ionizing radiation from a linear accelerator and orthovoltage x‐ray tube has been characterized to assess its potential as a dosimeter for radiotherapy. The radiation hardness of the OPD has also been investigated to demonstrate its longevity for such applications. Radiation hardness measurements were achieved by observing the response of the OPD to the visible spectrum and 70 keV x rays after pre‐exposure to 40 kGy of ionizing radiation. The response of a preirradiated OPD to 6‐MV photons from a linear accelerator in reference conditions was compared to a nonirradiated OPD with respect to direct and indirect (RP400 plastic scintillator) detection mechanisms. Dose rate dependence of the OPD was measured by varying the surface‐to‐source distance between 90 and 300 cm. Energy dependence was characterized from 29.5 to 129 keV with an x‐ray tube. The percentage depth dose (PDD) curves were measured from 0.5 to 20 cm and compared to an ionization chamber. The OPD sensitivity to visible light showed substantial degradation of the broad 450 to 600 nm peak from the donor after irradiation to 40 kGy. After irradiation, the spectral shape has a dominant absorbance peak at 370 nm, as the acceptor better withstood radiation damage. Its response to x rays stabilized to 30% after 35 kGy, with a 0.5% difference between 770 Gy increments. The OPD exhibited reproducible detection of ionizing radiation when coupled with a scintillator. Indirect detection showed a linear response from 25 to 500 cGy and constant response to dose rates from 0.31 Gy ulse to 3.4 × 10 −4 Gy ulse. However, without the scintillator, response increased by 100% at low dose rates. Energy independence between 100 keV and 1.2 MeV advocates their use as a dosimeter without beam correction factors. A dependence on the scintillator thickness used during a comparison of the PDD to the ionizing chamber was identified. A 1‐mm‐thick scintillator coupled with the OPD demonstrated the best agreement of ± 3%. The response of OPDs to ionizing radiation has been characterized, showing promising use as a dosimeter when coupled with a plastic scintillator. The mechanisms of charge transport and trapping within organic materials varies for visible and ionizing radiation, due to differing properties for direct and indirect detection mechanisms and observing a substantial decrease in sensitivity to the visible spectrum after 40 kGy. This study proved that OPDs produce a stable response to 6‐MV photons, and with a deeper understanding of the charge transport mechanisms due to exposure to ionizing radiation, they are promising candidates as the first flexible, water equivalent, real‐time dosimeter.
Effect of transverse magnetic fields on dose distribution and RBE of photon beams: Comparing PENELOPE and EGS4 Monte Carlo codes
Publisher: IOP Publishing
Date: 22-08-2008
DOI: 10.1088/0031-9155/53/18/018
Abstract: The application of a strong transverse magnetic field to a volume undergoing irradiation by a photon beam can produce localized regions of dose enhancement and dose reduction. This study uses the PENELOPE Monte Carlo code to investigate the effect of a slice of uniform transverse magnetic field on a photon beam using different magnetic field strengths and photon beam energies. The maximum and minimum dose yields obtained in the regions of dose enhancement and dose reduction are compared to those obtained with the EGS4 Monte Carlo code in a study by Li et al (2001), who investigated the effect of a slice of uniform transverse magnetic field (1 to 20 Tesla) applied to high-energy photon beams. PENELOPE simulations yielded maximum dose enhancements and dose reductions as much as 111% and 77%, respectively, where most results were within 6% of the EGS4 result. Further PENELOPE simulations were performed with the Sheikh-Bagheri and Rogers (2002) input spectra for 6, 10 and 15 MV photon beams, yielding results within 4% of those obtained with the Mohan et al (1985) spectra. Small discrepancies between a few of the EGS4 and PENELOPE results prompted an investigation into the influence of the PENELOPE elastic scattering parameters C(1) and C(2) and low-energy electron and photon transport cut-offs. Repeating the simulations with smaller scoring bins improved the resolution of the regions of dose enhancement and dose reduction, especially near the magnetic field boundaries where the dose deposition can abruptly increase or decrease. This study also investigates the effect of a magnetic field on the low-energy electron spectrum that may correspond to a change in the radiobiological effectiveness (RBE). Simulations show that the increase in dose is achieved predominantly through the lower energy electron population.
Skin dosimetry of thyroid radioiodine with MOSkin detector: A phantom study
Publisher: IEEE
Date: 10-2011
Report on G4-Med, a Geant4 benchmarking system for medical physics applications developed by the Geant4 Medical Simulation Benchmarking Group
Publisher: Wiley
Date: 12-12-2021
DOI: 10.1002/MP.14226
Fast and accurate dose predictions for novel radiotherapy treatments in heterogeneous phantoms using conditional 3D-UNet generative adversarial networks
Publisher: Wiley
Date: 03-03-2022
DOI: 10.1002/MP.15555
Abstract: Novel radiotherapy techniques like synchrotron X‐ray microbeam radiation therapy (MRT) require fast dose distribution predictions that are accurate at the sub‐mm level, especially close to tissue/bone/air interfaces. Monte Carlo (MC) physics simulations are recognized to be one of the most accurate tools to predict the dose delivered in a target tissue but can be very time consuming and therefore prohibitive for treatment planning. Faster dose prediction algorithms are usually developed for clinically deployed treatments only. In this work, we explore a new approach for fast and accurate dose estimations suitable for novel treatments using digital phantoms used in preclinical development and modern machine learning techniques. We develop a generative adversarial network (GAN) model, which is able to emulate the equivalent Geant4 MC simulation with adequate accuracy and use it to predict the radiation dose delivered by a broad synchrotron beam to various phantoms. The energy depositions used for the training of the GAN are obtained using full Geant4 MC simulations of a synchrotron radiation broad beam passing through the phantoms. The energy deposition is scored and predicted in voxel matrices of size 140 × 18 × 18 with a voxel edge length of 1 mm. The GAN model consists of two competing 3D convolutional neural networks, which are conditioned on the photon beam and phantom properties. The generator network has a U‐Net structure and is designed to predict the energy depositions of the photon beam inside three phantoms of variable geometry with increasing complexity. The critic network is a relatively simple convolutional network, which is trained to distinguish energy depositions predicted by the generator from the ones obtained with the full MC simulation. The energy deposition predictions inside all phantom geometries under investigation show deviations of less than 3% of the maximum deposited energy from the simulation for roughly 99% of the voxels in the field of the beam. Inside the most realistic phantom, a simple pediatric head, the model predictions deviate by less than 1% of the maximal energy deposition from the simulations in more than 96% of the in‐field voxels. For all three phantoms, the model generalizes the energy deposition predictions well to phantom geometries, which have not been used for training the model but are interpolations of the training data in multiple dimensions. The computing time for a single prediction is reduced from several hundred hours using Geant4 simulation to less than a second using the GAN model. The proposed GAN model predicts dose distributions inside unknown phantoms with only small deviations from the full MC simulation with computations times of less than a second. It demonstrates good interpolation ability to unseen but similar phantom geometries and is flexible enough to be trained on data with different radiation scenarios without the need for optimization of the model parameter. This proof‐of‐concept encourages to apply and further develop the model for the use in MRT treatment planning, which requires fast and accurate predictions with sub‐mm resolutions.
BrachyView: A novel in-body imaging system for prostate brachytherapy
Publisher: IEEE
Date: 10-2011
Optimisation of the design of SOI microdosimeters for hadron therapy quality assurance
Publisher: IOP Publishing
Date: 24-10-2018
Abstract: Silicon-on-insulator (SOI) microdosimeters offer a promising method for routine quality assurance (QA) for hadron therapy due to their ease of operation and high spatial resolution. However, one complication which has been shown previously is that the traditional use of the mean chord length, [Formula: see text], calculated using Cauchy's formula, for SOI devices in clinical carbon ion fields is not appropriate due to the strong directionality of the radiation field. In a previous study, we demonstrated that the mean path length, [Formula: see text], which is the mean path of charged particles in the sensitive volume (SV), is a more appropriate method to obtain microdosimetric quantities and biological relevant values, namely the relative biological effectiveness (RBE) by means of the microdosimetric kinetic model. The previous work, which was limited to mono-energetic [Formula: see text] ion beams typical of heavy ion therapy (HIT), is extended here to investigate the [Formula: see text] in a pristine proton beam as well as for spread out Bragg peaks (SOBP) for both proton and carbon ion clinical beams. In addition, the angular dependence of the SOI device for a number of different SV designs is also investigated to quantify the effects which the alignment has on the [Formula: see text]. It is demonstrated that the [Formula: see text] can be accurately estimated along the depth of a pristine or SOBP using the energy deposition spectra for both proton and [Formula: see text] ion beams. This observation allows a quick and accurate estimation of the [Formula: see text] for experimental use.
Comparative study of alternative Geant4 hadronic ion inelastic physics models for prediction of positron-emitting radionuclide production in carbon and oxygen ion therapy
Publisher: IOP Publishing
Date: 07-08-2019
Abstract: The distribution of fragmentation products predicted by Monte Carlo simulations of heavy ion therapy depend on the hadronic physics model chosen in the simulation. This work aims to evaluate three alternative hadronic inelastic fragmentation physics options available in the Geant4 Monte Carlo radiation physics simulation framework to determine which model most accurately predicts the production of positron-emitting fragmentation products observable using in-beam PET imaging. Fragment distributions obtained with the BIC, QMD, and INCL + + physics models in Geant4 version 10.2.p03 are compared to experimental data obtained at the HIMAC heavy-ion treatment facility at NIRS in Chiba, Japan. For both simulations and experiments, monoenergetic beams are applied to three different block phantoms composed of gelatin, poly(methyl methacrylate) and polyethylene. The yields of the positron-emitting nuclei
Feasibility of online adaptive HDR prostate brachytherapy: A novel treatment concept
Publisher: Elsevier BV
Date: 11-2022
DOI: 10.1016/J.BRACHY.2022.07.011
Abstract: The purpose of this study was to determine the feasibility of online adaptive transrectal ultrasound (TRUS)-based high-dose-rate prostate brachytherapy (HDRPBT) through retrospective simulation of source positioning and catheter swap errors on patient treatment plans. Source positioning errors (catheter shifts in 1 mm increments in the cranial/caudal, anterior osterior, and medial/lateral directions up to ±6 mm) and catheter swap errors (between the most and least heavily weighted) were introduced retrospectively into DICOM treatment plans of 20 patients that previously received TRUS HDRPBT. Dose volume histogram (DVH) indices were monitored as errors were introduced sequentially into in idual catheters, simulating potential errors throughout treatment. Whenever DVH indices were outside institution thresholds: prostate V100% 118% and rectum Dmax >80%, the plan was adapted using remaining catheters (i.e., simulating previous catheters as previously delivered). The final DVH indices were recorded. Prostate coverage (V100% >95%) could be maintained for source position errors up to 6 mm through online plan adaptation. The source position error at which the urethra D0.1cc and rectum Dmax was able to return to clinically acceptable levels using online adaptation varied between 6 mm to 1 mm, depending on the direction of the source position error and patient anatomy. After introduction of catheter swap errors to patient plans, prostate V100% was recoverable using online adaptation to near original plan characteristics. Urethra D0.1cc and rectum Dmax showed less recoverability. Online adaptive HDRPBT maintains the prostate V100% to clinically acceptable values for majority of directional shifts. However, the current online adaptive method may not correct for source position errors near organs at risk.
Direct and pulsed current annealing of p-MOSFET based dosimeter: The MOSkin
Publisher: Springer Science and Business Media LLC
Date: 20-03-2014
DOI: 10.1007/S13246-014-0261-1
Abstract: Contemporary radiation therapy (RT) is complicated and requires sophisticated real-time quality assurance (QA). While 3D real-time dosimetry is most preferable in RT, it is currently not fully realised. A small, easy to use and inexpensive point dosimeter with real-time and in vivo capabilities is an option for routine QA. Such a dosimeter is essential for skin, in vivo or interface dosimetry in phantoms for treatment plan verification. The metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector is one of the best choices for these purposes, however, the MOSFETs sensitivity and its signal stability degrade after essential irradiation which limits its lifespan. The accumulation of positive charge on the gate oxide and the creation of interface traps near the silicon-silicon dioxide layer is the primary physical phenomena responsible for this degradation. The aim of this study is to investigate MOSFET dosimeter recovery using two proposed annealing techniques: direct current (DC) and pulsed current (PC), both based on hot charged carrier injection into the gate oxide of the p-MOSFET dosimeter. The investigated MOSFETs were reused multiple times using an irradiation-annealing cycle. The effect of the current-annealing parameters was investigated for the dosimetric characteristics of the recovered MOSFET dosimeters such as linearity, sensitivity and initial threshold voltage. Both annealing techniques demonstrated excellent results in terms of maintaining a stable response, linearity and sensitivity of the MOSFET dosimeter. However, PC annealing is more preferable than DC annealing as it offers better dose response linearity of the reused MOSFET and has a very short annealing time.
Introduction and implementation of the CMRP radiodosimeter - A novel wireless microdosimetry system
Publisher: IOP Publishing
Date: 03-2022
DOI: 10.1088/1748-0221/17/03/P03006
Abstract: Microdosimetry is a useful method to evaluate the relative biological effectiveness (RBE) as well as dose equivalent of any mixed radiation field without prior knowledge of type of charged particles and their spectra. The need of portable, user friendly devices for microdosimetric Quality Assurance measurements in particle therapy are greatly preferable to avoid sophisticated setup and time-consuming data analysis. Currently, the ability to perform microdosimetric measurements is restricted to those with extensive prior knowledge of the electronics involved and their experimental setup. The Centre for Medical Radiation Physics (CMRP) has developed a compact microdosimetric system named Radiodosimeter - a novel acquisition system that combines both wireless communication and plug-and-play design to provide a device that can be used with minimal setup. The system is compatible with current CMRP MicroPlus probe technology. The Radiodosimeter communicates with the client computer via Wi-Fi, allowing remote management and monitoring of acquisitions. The system was bench-marked against the standard microdosimetric setup at Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan and was found to have the same response. Several redundancy methods were demonstrated such as continuing an acquisition following disconnection from the client software and the ability to connect through different Wi-Fi modes (WPA2 Personal/Enterprise). These features prove that the Radiodosimeter can operate independently of a client computer, indicating its potential to be used as a portable device for personal monitoring in mixed radiation fields, including for microdosimetric quantity verification predicted by Treatment Planning Software in particle therapy.
A method for measuring tissue-equivalent dose using a pin diode and activation foil in epithermal neutron beams with EN < 100 keV
Publisher: Oxford University Press (OUP)
Date: 27-04-2006
DOI: 10.1093/RPD/NCI598
Abstract: Silicon (Si) pin diodes can be used for neutron dosimetry by observing the change in forward bias voltage caused by neutron induced displacement damage in the diode junction. Pin diode energy response depends on Si displacement damage KERMA (K(Si)). It is hypothesised that tissue-equivalent (TE) neutron dose could be expressed as a linear combination of K(Si) and foil activation terms. Monte Carlo simulations (MCNP) of parallel monoenergetic neutron beams incident on a cylindrical TE phantom were used to calculate TE dose, K(Si) and Au, Cu and Mn foil activations along the central axis of the phantom. For spectra with neutron energies <100 keV, it is possible to estimate the TE kerma based on silicon damage kerma and Cu or Mn foil measurements. More accurate estimates are possible for spectra where the maximum neutron energy does not exceed 30 keV.
Electron contamination modeling and skin dose in 6 MV longitudinal field MRIgRT: Impact of the MRI and MRI fringe field
Publisher: Wiley
Date: 25-01-2012
DOI: 10.1118/1.3676181
Abstract: In recent times, longitudinal field MRI-linac systems have been proposed for 6 MV MRI-guided radiotherapy (MRIgRT). The magnetic field is parallel with the beam axis and so will alter the transport properties of any electron contamination particles. The purpose of this work is to provide a first investigation into the potential effects of the MR and fringe magnetic fields on the electron contamination as it is transported toward a phantom, in turn, providing an estimate of the expected patient skin dose changes in such a modality. Geant4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam were performed. Longitudinal magnetic fields of strengths between 0 and 3 T were applied to a 30 × 30 × 20 cm(3) phantom. Surrounding the phantom there is a region where the magnetic field is at full MRI strength, consistent with clinical MRI systems. Beyond this the fringe magnetic field entering the collimation system is also modeled. The MRI-coil thickness, fringe field properties, and isocentric distance are varied and investigated. Beam field sizes of 5 × 5, 10 × 10, 15 × 15 and 20 × 20 cm(2) were simulated. Central axis dose, 2D virtual entry skin dose films, and 70 μm skin depth doses were calculated using high resolution scoring voxels. In the presence of a longitudinal magnetic field, electron contamination from the linear accelerator is encouraged to travel almost directly toward the patient surface with minimal lateral spread. This results in a concentration of electron contamination within the x-ray beam outline. This concentration is particularly encouraged if the fringe field encompasses the collimation system. Skin dose increases of up to 1000% were observed for certain configurations and increases above Dmax were common. In nonmagnetically shielded cases, electron contamination generated from the jaw faces and air column is trapped and propagated almost directly to the phantom entry region, giving rise to intense dose hot spots inside the x-ray treatment field. These range up to 1000% or more of Dmax at the CAX, depending on field size, isocenter, and coil thickness. In the case of a fully magnetically shielded collimation system and the lowest MRI field of 0.25 T, the entry skin dose is expected to increase to at least 40%, 50%, 65%, and 80% of Dmax for 5 × 5, 10 × 10, 15 × 15, and 20 × 20 cm(2), respectively. Electron contamination from the linac head and air column may cause considerable skin dose increases or hot spots at the beam central axis on the entry side of a phantom or patient in longitudinal field 6 MV MRIgRT. This depends heavily on the properties of the magnetic fringe field entering the linac beam collimation system. The skin dose increase is also related to the MRI-coil thickness, the fringe field, and the isocenter distance of the linac. The results of this work indicate that the properties of the MRI fringe field, electron contamination production, and transport must be considered carefully during the design stage of a longitudinal MRI-linac system.
X-ray microbeam measurements with a high resolution scintillator fibre-optic dosimeter
Publisher: Springer Science and Business Media LLC
Date: 29-09-2017
DOI: 10.1038/S41598-017-12697-6
Abstract: Synchrotron microbeam radiation therapy is a novel external beam therapy under investigation, that uses highly brilliant synchrotron x-rays in microbeams 50 μ m width, with separation of 400 μ m, as implemented here. Due to the fine spatial fractionation dosimetry of these beams is a challenging and complicated problem. In this proof-of-concept work, we present a fibre optic dosimeter that uses plastic scintillator as the radiation conversion material. We claim an ideal one-dimensional resolution of 50 μ m. Using plastic scintillator and fibre optic makes this dosimeter water-equivalent, a very desirable dosimetric property. The dosimeter was tested at the Australian Synchrotron, on the Imaging and Medical Beam-Line. The in idual microbeams were able to be resolved and the peak-to-valley dose ratio and the full width at half maximum of the microbeams was measured. These results are compared to a semiconductor strip detector of the same spatial resolution. A percent depth dose was measured and compared to data acquired by an ionisation chamber. The results presented demonstrate significant steps towards the development of an optical dosimeter with the potential to be applied in quality assurance of microbeam radiation therapy, which is vital if clinical trials are to be performed on human patients.
3D-mesa 'bridge' silicon microdosimeter: Charge collection study and application to rbe studies in 12rm c radiation therapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2015
A novel quality assurance system for eye plaque brachytherapy
Publisher: Springer Science and Business Media LLC
Date: 14-11-2019
DOI: 10.1007/S13246-019-00808-8
Abstract: Eye Plaque brachytherapy pre-treatment quality assurance (QA) conducted clinically involves an activity verification of in idual seeds via well chamber and does not include a physical measurement of dose-rate of the final assembly. A novel spectroscopic, dose-rate detection system, was evaluated for pre-treatment QA of eye plaque brachytherapy. The system includes a water phantom with sterility management. The system was calibrated using a known-activity I-125 seed, measured at 1 cm in water along the radial axis, compared to TG-43 U1 calculations and verified over a number of distances. A depth dose curve was acquired for a clinical, mixed activity eye plaque and two 'error' plaques. The probe was stepped from a water equivalent source to a detector distance (SDD) of 2.5 to 12 mm along the plaque central axis. The latter measurements aimed to characterise the sensitivity of the system. The calculated and measured single-seed dose-rates agreed to within 0.5 cGy/h from a SDD of 3 mm and above. The clinical plaque showed agreement between measured and treatment planning system (TPS) calculated dose-rates within 2%. Sensitivity testing resulted in a maximum deviation from TPS data of 18%, therefore was able to detect the presence of packing errors. The dose-rate detection system was successfully evaluated for verification of I-125 based eye plaques without compromising sterility, allowing for quick pre-treatment, dose-rate verification of patient-ready plaques. Its agreement with TPS data for the unmodified plaque and its deviation when introducing errors confirms the approach suggested is a viable QA tool.
Ion beam induced charge collection time imaging of a silicon microdosimeter
Publisher: Elsevier BV
Date: 09-2003
Quantitative analysis of dose-averaged linear energy transfer (LETd) robustness in pencil beam scanning proton lung plans
Publisher: Wiley
Date: 07-03-2022
DOI: 10.1002/MP.15569
Abstract: The primary objective of our study was to perform a quantitative robustness analysis of the dose‐averaged linear energy transfer (LET d ) and related RBE‐weighted dose in robustly optimized (in terms of the range and set up uncertainties) pencil beam scanning (PBS) proton lung cancer plans. In this study, we utilized the 4DCT dataset of six anonymized lung patients. PBS lung plans were generated using a robust optimization technique (range uncertainty: ±3.5% and setup errors: ±5 mm) on the CTV for a total dose of 5000 cGy (RBE) in five fractions using the RBE of 1.1. For each patient, the LET d distributions were calculated for the nominal plan and three groups. Group 1 : two plan robustness scenarios for range uncertainties of ±3.5% Group 2 : twelve plan robustness scenarios (range uncertainty (±3.5%) in conjunction with setup errors (±5 mm)) and Group 3 : ten different breathing phases of the 4DCT dataset. The RBE‐weighted dose to the OARs was evaluated for all robustness scenarios and breathing phases. The variation (∆) in the mean LET d and mean RBE‐weighted dose from each group was recorded. The mean LET d in the CTV of nominal PBS lung plans among six patients ranged from 2.2 to 2.6 keV/µm. On average, for the combined range and setup uncertainties, the ∆ in the mean LET d among 12 scenarios of all six patients was 0.6 keV/µm, which is slightly higher than when only the range uncertainties were considered (0.4 keV/µm). The ∆ in the mean LET d in a patient was ≤1.7 keV/µm in the heart and ≤1.2 keV/µm in the esophagus and total lung. The ∆ in the mean RBE‐weighted dose in a patient was up to 79 cGy for the total lung, 165 cGy for the heart, and 258 cGy for the esophagus. For ten breathing phases, the ∆ in the mean LET d in a patient was ≤0.3 keV/µm in the CTV, ≤0.5 keV/µm in the heart, ≤0.4 keV/µm in the esophagus, and ≤0.7 keV/µm in the total lung. The addition of setup errors to the range uncertainties resulted in slightly less homogeneous LET d distributions. The variations in the mean LET d among the ten breathing phases were slightly larger in the total lung than in the heart and esophagus. The combination of setup and range uncertainties had a greater impact than the effect of breathing phases on the variations in the mean RBE‐weighted dose to the OARs. Overall, the LET d distributions in the CTV were less sensitive than those in the OARs to setup errors, range uncertainties, and breathing phases for robustly optimized (in terms of range and setup uncertainities) PBS proton lung cancer plans.
Feasibility of a dual detector system to perform transit dosimetry and MV imaging in-vivo
Publisher: IOP Publishing
Date: 21-01-2019
Brachyview: An in-body imaging system for real-time QA in HDR prostate brachytherapy
Publisher: IEEE
Date: 10-2013
A portable magnet for radiation biology and dosimetry studies in magnetic fields
Publisher: Wiley
Date: 28-01-2022
DOI: 10.1002/MP.15447
Abstract: In the current and rapidly evolving era of real‐time MRI‐guided radiotherapy, our radiation biology and dosimetry knowledge is being tested in a novel way. This paper presents the successful design and implementation of a portable device used to generate strong localized magnetic fields. These are ideally suited for small‐scale experiments that mimic the magnetic field environment inside an MRI‐linac system, or more broadly MRI‐guided particle therapy as well. A portable permanent magnet‐based device employing an adjustable steel yoke and magnetic field focusing cones has been designed, constructed, and tested. The apparatus utilizes two banks of NdFeB permanent magnets totaling around 50 kg in mass to generate a strong magnetic field throughout a small volume between two pole tips. The yoke design allows adjustment of the pole tip gap and exchanging of the focusing cones. Further to this, beam portal holes are present in the yoke and focusing cones, allowing for radiation beams of up to 5 5 cm to pass through the region of high magnetic field between the focusing cone tips. Finite element magnetic modeling was performed to design and characterize the performance of the device. Automated physical measurements of the magnetic field components at various locations were measured to confirm the performance. The adjustable pole gap and interchangeable cones allows rapid changing of the experimental set‐up to allow different styles of measurements to be performed. A mostly uniform magnetic field of 1.2 T can be achieved over a volume of at least 3 3 3 cm. This can be reduced in strength to 0.3 T but increased in volume to 10 10 10 cm via removal of the cone tips and/or adjustment of the steel yoke. Although small, these volumes are sufficient to house radiation detectors, cell culture dishes, and various phantom arrangements targeted at examining small radiation field dosimetry inside magnetic field strengths that can be changed with ease. Most important is the ability to align the magnetic field both perpendicular to, or inline with, the radiation beam. To date, the system has been successfully used to conduct published research in the areas of radiation detector performance, lung phantom dosimetry, and how small clinical electron beams behave in these strong magnetic fields. A portable, relatively inexpensive, and simple to operate device has successfully been constructed and used for performing radiation oncology studies around the theme of MRI‐guided radiotherapy. This can be in either inline and perpendicular magnetic fields of up to 1.2 T with x‐ray and particle beams.
Silicon planar structures as detectors for microbeam radiation therapy
Publisher: IEEE
Date: 10-2013
Investigation of optimized prompt gamma detection strategy for real-time Bragg Peak tracking in proton radiation therapy
Publisher: IEEE
Date: 10-2016
An algorithmic approach to single-probe Cherenkov removal in pulsed x-ray beams
Publisher: Wiley
Date: 14-02-2019
DOI: 10.1002/MP.13383
Abstract: The removal of Cherenkov light in an optical dosimetry system is an important process to ensure accurate dosimetry without compromising spatial resolution. Many solutions have been presented in the literature, each with advantages and disadvantages. We present a methodology to remove Cherenkov light from a scintillator fiber optic dosimeter in a pulsed megavoltage x-ray beam using the temporal waveform across the pulse. A s le waveform of Cherenkov light can be measured by exposing only the fiber to the beam. By assuming that the Cherenkov waveform closely matches the intensity of incident radiation, this waveform can be convoluted with the instantaneous scintillation response function to generate an expected scintillation signal. By finding the least-squares fit between these two functions and the experimental data, the estimated Cherenkov contribution can be subtracted off the net signal. This can be applied for arbitrarily complex Cherenkov waveforms (within the 2 ns timing resolution of the data acquisition), and in fact, the results suggest more fluctuations in the waveforms provide a better fit to data. Four beam profiles for different field sizes and energies were found with this method. They closely matched references data measured with ionization chamber with average differences across the beam no more than 4%. Noisy waveforms are assumed to be the primary cause of differences between the analyzed scintillator and IC results. We propose methods for improving the results and optimizing the data acquisition and analysis processes. These results demonstrate that it is possible and effective with a single probe to use function fitting of expected data to experimental to remove a complicated Cherenkov signal from the net light signal in pulsed-beam optical dosimetry.
The effect of rectal heterogeneity on wall dose in high dose rate brachytherapy
Publisher: Wiley
Date: 22-12-2009
DOI: 10.1118/1.3031111
Abstract: When treating prostate cancer using high dose rate (HDR) brachytherapy, overdosing the rectal wall may lead to post-treatment rectal complications. An area of concern is related to how the rectal wall dose is calculated by treatment planning systems (TPSs). TPSs are used to calculate the dose delivered to the rectal wall, but they assume that the rectum is a water-equivalent homogeneous medium of infinite size and do not consider the effect that an air-filled "empty" rectal cavity would have on the dose absorbed along the rectal wall. The aim of this research is to quantify the effect that an air cavity has on the rectal wall dose, as its presence changes the backscatter conditions in the region. The MO Skin and RADFET dosimeters proved capable of measuring absolute dose with increasing distance from the HDR Ir-192 brachytherapy source. However, the anterior rectal wall doses measured by the MOSkin and RADFET in an empty rectal cavity were 14.7 +/- 0.2% and 13.7 +/- 0.6% lower than the dose measured in a homogeneous rectal phantom. Monte Carlo simulations corroborated the experimentally obtained results, reporting a -13.2 +/- 0.6% difference. The dose measured at the posterior wall of an empty rectal cavity was between 22% and 26% greater than the dose measured in a full rectal cavity. The heterogeneity of the rectal volume appears to have a significant effect on the rectal dose when compared to calculated rectal dose.
A 2D silicon detector array for quality assurance in small field dosimetry: DUO:
Publisher: Wiley
Date: 02-2017
DOI: 10.1002/MP.12060
Abstract: Nowadays, there are many different applications that use small fields in radiotherapy treatments. The dosimetry of small radiation fields is not trivial due to the problems associated with lateral disequilibrium and source occlusion and requires reliable quality assurance (QA). Ideally such a QA tool should provide high spatial resolution, minimal beam perturbation and real time fast measurements. Many different types of silicon diode arrays are used for QA in radiotherapy however, their application in small filed dosimetry is limited, in part, due to a lack of spatial resolution. The Center of Medical Radiation Physics (CMRP) has developed a new generation of a monolithic silicon diode array detector that will be useful for small field dosimetry in SRS/SRT. The objective of this study is to characterize a monolithic silicon diode array designed for dosimetry QA in SRS/SRT named DUO that is arranged as two orthogonal 1D arrays with 0.2 mm pitch. DUO is two orthogonal 1D silicon detector arrays in a monolithic crystal. Each orthogonal array contains 253 small pixels with size 0.04 × 0.8 mm The DUO detector shows a dose per pulse dependence of 5% for a range of dose rates from 2.7 × 10 The CMRP's monolithic silicon detector array, DUO, is suitable for SRS/SRT dosimetry and QA because of its very high spatial resolution (0.2 mm) and real time operation.
Solid state microdosimetry
Publisher: Elsevier BV
Date: 09-2001
DOI: 10.1016/S0168-583X(01)00715-7
Abstract: A review of solid state microdosimetry is presented with an emphasis on silicon-based devices. The historical foundations and basics of microdosimetry are briefly provided. Various methods of experimental regional microdosimetry are discussed to facilitate a comparison with the more recent development of silicon microdosimetry. In particular, the performance characteristics of a proportional gas counter and a silicon microdosimeter are compared. Recent improvements in silicon microdosimetry address the issues of requirement specification, non-spherical shape, tissue equivalence, sensitive volume definition (charge collection complexity) and low noise requirements which have previously impeded the implementation of silicon-based microdosimetry. A prototype based on silicon-on-insulator technology is described along with some ex le results from clinical high LET radiotherapy facilities. A brief summary of the applications of microdosimetry is included.
Characterization of prompt gamma ray emission for in vivo range verification in particle therapy: A simulation study
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.EJMP.2019.04.023
Abstract: In this paper we investigate the emission and detection characteristics of prompt gamma (PG) rays for in vivo range verification during hadron therapy, using Geant4 simulations. Proton,
Analytical Modelling and Simulation of Single and Double Cone Pinholes for Real-Time In-Body Tracking of an HDR Brachytherapy Source
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2016
MOSFET dosimetry with high spatial resolution in intense synchrotron-generated x-ray microbeams
Publisher: Wiley
Date: 11-03-2009
DOI: 10.1118/1.3081934
Abstract: Various dosimeters have been tested for assessing absorbed doses with microscopic spatial resolution in targets irradiated by high-flux, synchrotron-generated, low-energy (approximately 30-300 keV) x-ray microbeams. A MOSFET detector has been used for this study since its radio sensitive element, which is extraordinarily narrow (approximately 1 microm), suits the main applications of interest, microbeam radiation biology and microbeam radiation therapy (MRT). In MRT, micrometer-wide, centimeter-high, and vertically oriented swaths of tissue are irradiated by arrays of rectangular x-ray microbeams produced by a multislit collimator (MSC). We used MOSFETs to measure the dose distribution, produced by arrays of x-ray microbeams shaped by two different MSCs, in a tissue-equivalent phantom. Doses were measured near the center of the arrays and maximum/minimum (peak/valley) dose ratios (PVDRs) were calculated to determine how variations in heights and in widths of the microbeams influenced this for the therapy, potentially important parameter. Monte Carlo (MC) simulations of the absorbed dose distribution in the phantom were also performed. The results show that when the heights of the irradiated swaths were below those applicable to clinical therapy (< 1 mm) the MC simulations produce estimates of PVDRs that are up to a factor of 3 higher than the measured values. For arrays of higher microbeams (i.e., 25 microm x 1 cm instead of 25 x 500 microm2), this difference between measured and simulated PVDRs becomes less than 50%. Closer agreement was observed between the measured and simulated PVDRs for the Tecomet MSC (current collimator design) than for the Archer MSC. Sources of discrepancies between measured and simulated doses are discussed, of which the energy dependent response of the MOSFET was shown to be among the most important.
Modelling of the Silicon-On-Insulator microdosimeter response within the International Space Station for astronauts’ radiation protection
Publisher: Elsevier BV
Date: 09-2019
Characterization of an innovative p-type epitaxial diode for dosimetry in modern external beam radiotherapy
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2013
Measurement and production of electron deflection using a sweeping magnetic device in radiotherapy
Publisher: Springer Science and Business Media LLC
Date: 09-2006
DOI: 10.1007/BF03178575
Assessment of cross-dose contributions from tumors within computational phantoms using a Geant4 radiation dosimetry tool exploiting hybrid analytical/voxelised geometries
Publisher: Wiley
Date: 08-06-2023
DOI: 10.1002/MP.16544
Abstract: Dosimetry software tools developed for Radiopharmaceutical Therapy, such as OLINDA/EXM or IDAC‐Dose, account only for radiation dose to organs from radiopharmaceutical taken up in other organs. The aim of this study is to present a methodology, that can be applied to any voxelised computational model, able to account for cross‐dose to organs from tumors of any shape and number enclosed within an organ. A Geant4 application using hybrid analytical/voxelised geometries has been developed as an extension to the ICRP110_HumanPhantom Geant4 advanced ex le and validated against ICRP publication 133. In this new Geant4 application, tumors are defined using the Geant4 Parallel Geometry functionality, which allows the co‐existence of two independent geometries in the same Monte Carlo simulation. The methodology was validated by estimating total dose to healthy tissue from 90 Y and from 177 Lu distributed within tumors of various sizes localized within the liver of the ICRP110 adult male phantom. Agreement of the Geant4 application with ICRP133 was within 5% when masses were adjusted for blood content. Total dose to healthy liver and to tumors was found to agree within 1% when compared to the ground truth. The methodology presented in this work can be extended to investigate total dose to healthy tissue from systemic uptake of radiopharmaceuticals in tumors of different sizes using any voxelised computational dosimetric model.
Temporally separating Cherenkov radiation in a scintillator probe exposed to a pulsed X-ray beam
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.EJMP.2017.09.134
Abstract: Cherenkov radiation is generated in optical systems exposed to ionising radiation. In water or plastic devices, if the incident radiation has components with high enough energy (for ex le, electrons or positrons with energy greater than 175keV), Cherenkov radiation will be generated. A scintillator dosimeter that collects optical light, guided by optical fibre, will have Cherenkov radiation generated throughout the length of fibre exposed to the radiation field and compromise the signal. We present a novel algorithm to separate Cherenkov radiation signal that requires only a single probe, provided the radiation source is pulsed, such as a linear accelerator in external beam radiation therapy. We use a slow scintillator (BC-444) that, in a constant beam of radiation, reaches peak light output after 1 microsecond, while the Cherenkov signal is detected nearly instantly. This allows our algorithm to separate the scintillator signal from the Cherenkov signal. The relative beam profile and depth dose of a linear accelerator 6MV X-ray field were reconstructed using the algorithm. The optimisation method improved the fit to the ionisation chamber data and improved the reliability of the measurements. The algorithm was able to remove 74% of the Cherenkov light, at the expense of only 1.5% scintillation light. Further characterisation of the Cherenkov radiation signal has the potential to improve the results and allow this method to be used as a simpler optical fibre dosimeter for quality assurance in external beam therapy.
Investigation of track structure and condensed history physics models for applications in radiation dosimetry on a micro and nano scale in Geant4
Publisher: IOP Publishing
Date: 15-02-2018
Ultra-thin 3-D detector: Charge collection characterization and application for microdosimetry
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2014
Parametrization of in-air spot size as a function of energy and air gap for the ProteusPLUS pencil beam scanning proton therapy system
Publisher: Springer Science and Business Media LLC
Date: 10-10-2020
Contributions of secondary fragmentation by carbon ion beams in water phantom: Monte Carlo simulation
Publisher: IOP Publishing
Date: 05-2017
Opportunistic dose amplification for proton and carbon ion therapy via capture of internally generated thermal neutrons
Publisher: Springer Science and Business Media LLC
Date: 02-11-2018
DOI: 10.1038/S41598-018-34643-W
Abstract: This paper presents Neutron Capture Enhanced Particle Therapy (NCEPT), a method for enhancing the radiation dose delivered to a tumour relative to surrounding healthy tissues during proton and carbon ion therapy by capturing thermal neutrons produced inside the treatment volume during irradiation. NCEPT utilises extant and in-development boron-10 and gadolinium-157-based drugs from the related field of neutron capture therapy. Using Monte Carlo simulations, we demonstrate that a typical proton or carbon ion therapy treatment plan generates an approximately uniform thermal neutron field within the target volume, centred around the beam path. The tissue concentrations of neutron capture agents required to obtain an arbitrary 10% increase in biological effective dose are estimated for realistic treatment plans, and compared to concentrations previously reported in the literature. We conclude that the proposed method is theoretically feasible, and can provide a worthwhile improvement in the dose delivered to the tumour relative to healthy tissue with readily achievable concentrations of neutron capture enhancement drugs.
Semiconductor real-time quality assurance dosimetry in brachytherapy
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.BRACHY.2017.08.013
Abstract: With the increase in complexity of brachytherapy treatments, there has been a demand for the development of sophisticated devices for delivery verification. The Centre for Medical Radiation Physics (CMRP), University of Wollongong, has demonstrated the applicability of semiconductor devices to provide cost-effective real-time quality assurance for a wide range of brachytherapy treatment modalities. Semiconductor devices have shown great promise to the future of pretreatment and in vivo quality assurance in a wide range of brachytherapy treatments, from high-dose-rate (HDR) prostate procedures to eye plaque treatments. The aim of this article is to give an insight into several semiconductor-based dosimetry instruments developed by the CMRP. Applications of these instruments are provided for breast and rectal wall in vivo dosimetry in HDR brachytherapy, urethral in vivo dosimetry in prostate low-dose-rate (LDR) brachytherapy, quality assurance of HDR brachytherapy afterloaders, HDR pretreatment plan verification, and real-time verification of LDR and HDR source dwell positions.
In vivo dosimetry using MOSkin detector during Cobalt-60 high-dose-rate (HDR) brachytherapy of skin cancer
Publisher: Springer Science and Business Media LLC
Date: 24-10-2019
DOI: 10.1007/S13246-019-00809-7
Abstract: The MOSkin, a metal-oxide semiconductor field-effect transistor based detector, is suitable for evaluating skin dose due to its water equivalent depth (WED) of 0.07 mm. This study evaluates doses received by target area and unavoidable normal skin during a the case of skin brachytherapy. The MOSkin was evaluated for its feasibility as detector of choice for in vivo dosimetry during skin brachytherapy. A high-dose rate Cobalt-60 brachytherapy source was administered to the tumour located at the medial aspect of the right arm, complicated with huge lymphedema thus limiting the arm motion. The source was positioned in the middle of patients' right arm with supine, hands down position. A 5 mm lead and 5 mm bolus were sandwiched between the medial aspect of the arm and lateral chest to reduce skin dose to the chest. Two calibrated MOSkin detectors were placed on the target and normal skin area for five treatment sessions for in vivo dose monitoring. The mean dose to the target area ranged between 19.9 and 21.1 Gy and was higher in comparison with the calculated dose due to contribution of backscattered dose from lead. The mean measured dose at normal skin chest area was 1.6 Gy (1.3-1.9 Gy), less than 2 Gy per fraction. Total dose in EQD
Effect of a static magnetic field on nanodosimetric quantities in a DNA volume
Publisher: Informa UK Limited
Date: 12-0010
DOI: 10.3109/09553002.2011.641436
Abstract: With the advent of magnetic resonance imaging (MRI)-guided radiation therapy it is becoming increasingly important to consider the potential influence of a magnetic field on ionising radiation. This paper aims to study the effect of a magnetic field on the track structure of radiation to determine if the biological effectiveness may be altered. Using the Geant4-DNA (GEometry ANd Tracking 4) Monte Carlo simulation toolkit, nanodosimetric track structure parameters were calculated for electrons, protons and alpha particles moving in transverse magnetic fields up to 10 Tesla. Applying the model proposed by Garty et al., the track structure parameters were used to derive the probability of producing a double-strand break (DSB). For simulated primary particles of electrons (200 eV-10 keV), protons (300 keV-30 MeV) and alpha particles (1-9 MeV) the application of a magnetic field was shown to have no significant effect (within statistical uncertainty limits) on the parameters characterizing radiation track structure or the probability of producing a DSB. The null result found here implies that if the presence of a magnetic field were to induce a change in the biological effectiveness of radiation, the effect would likely not be due to a change in the track structure of the radiation.
Dose verification of eye plaque brachytherapy using spectroscopic dosimetry
Publisher: Springer Science and Business Media LLC
Date: 19-07-2016
DOI: 10.1007/S13246-016-0453-Y
Abstract: Eye plaque brachytherapy has been developed and refined for the last 80 years, demonstrating effective results in the treatment of ocular malignancies. Current dosimetry techniques for eye plaque brachytherapy (such as TLD- and film-based techniques) are time consuming and cannot be used prior to treatment in a sterile environment. The measurement of the expected dose distribution within the eye, prior to insertion within the clinical setting, would be advantageous, as any errors in source loading will lead to an erroneous dose distribution and inferior treatment outcomes. This study investigated the use of spectroscopic dosimetry techniques for real-time quality assurance of I-125 based eye plaques, immediately prior to insertion. A silicon detector based probe, operating in spectroscopy mode was constructed, containing a small (1 mm(3)) silicon detector, mounted within a ceramic holder, all encapsulated within a rubber sheath to prevent water infiltration of the electronics. Preliminary tests of the prototype demonstrated that the depth dose distribution through the central axis of an I-125 based eye plaque may be determined from AAPM Task Group 43 recommendations to a deviation of 6 % at 3 mm depth, 7 % at 5 mm depth, 1 % at 10 mm depth and 13 % at 20 mm depth, with the deviations attributed to the construction of the probe. A new probe design aims to reduce these discrepancies, however the concept of spectroscopic dosimetry shows great promise for use in eye plaque quality assurance in the clinical setting.
Verification of CT number to density conversion for a simulator-CT attachment
Publisher: Springer Science and Business Media LLC
Date: 06-2002
DOI: 10.1007/BF03178469
Decoupling of bowtie and object effects for beam hardening and scatter artefact reduction in iterative cone-beam CT
Publisher: Springer Science and Business Media LLC
Date: 19-08-2020
Dosimetric effects of brass mesh bolus on skin dose and dose at depth for postmastectomy chest wall irradiation
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.EJMP.2018.09.009
Abstract: To investigate the feasibility of using the brass mesh bolus as an alternative to tissue- equivalent bolus for post mastectomy chest wall cancer by characterizing the dosimetric effects of the 2-mm fine brass bolus on both the skin dose, the dose at depth and spatial distribution. Surface dose and percent depth dose data were acquired for a 6 MV photon beam in a solid water phantom using MOSkin™, Gafchromic EBT3 film and an Advanced Markus ionization chamber. Data were acquired for the case of: no bolus, Face-up bass bolus, Face-down brass bolus, double brass bolus, 0.5 cm and 1.0 cm of Superflab TE bolus. The exit doses were also measured via MOSkin™ dosimeter and Markus ionization chamber. Gafchromic EBT3 film strips were used to plot dose profile at surface and 10 cm depth for Face-up brass, Face-down brass, double brass, 0.5 cm and 1.0 cm of Superflab TE bolus. The surface dose measured via MOSkin™ dosimeter increased from 19.2 ± 1.0% to 63.1 ± 2.1% under Face-up brass discs, 51.2 ± 1.2% under Face-up brass spaces, 61.5 ± 0.5% under Face-down brass discs, and 41.3 ± 2.1% under Face-down brass spaces. The percentage difference in the dose measured under brass discs between Face-up versus Face-down was less than 2% for entrance dose and 10% for exit dose, whereas the percentage difference under brass spaces was approximately 3% for entrance dose and about 5% for the exit dose. Gafchromic EBT3 film strip measurements show that the mesh bolus produced ripple beam profiles due to the mesh brass construction. Brass bolus does not significantly change dose at depth (less than 0.5%), and the surface dose is increased similar to TE bolus. Considering this, brass mesh may be used as a substitute for TE bolus to increase superficial dose for chest wall tangent plans.
Assessment of out-of-field absorbed dose and equivalent dose in proton fields
Publisher: Wiley
Date: 15-12-2010
DOI: 10.1118/1.3271390
High resolution silicon array detector implementation in an inline MRI-linac
Publisher: Wiley
Date: 28-01-2020
DOI: 10.1002/MP.14016
Abstract: Dynamic dosimaging is a concept whereby a detector in motion is tracked with magnetic resonance imaging (MRI) to validate the amount and position of dose in a radiation therapy treatment on an MRI-linac. This work takes steps toward the realization of dynamic dosimaging with the novel high resolution silicon array detector: MagicPlate-512 (M512). The performance of the M512 was assessed in a 1.0 T inline MRI-linac, without simultaneous imaging and then during an imaging sequence, both during dosimetry. MR images were acquired to determine the effect of the detector and its components on image quality. Beam profiles were measured using the M512 on the Australian MRI-Linac and a comparison made with Gafchromic EBT3 film to investigate any intrinsic magnetic field effects in the silicon. The M512 has 512 sensitive volumes, each 0.5 × 0.5 × 0.037 mm Good agreement was observed between the M512 and film, with average differences in penumbral width and FWHM of <1 mm in the absence of the imaging sequence. Concurrent imaging widened the penumbra by up to 1.2 mm due to RF noise affecting the detector film profiles were unchanged. Magnetic resonance images were affected by noise, in particular, due to the large amount of aluminum present, as well as from the USB cable, which acted as an antenna. Unfortunately, due to these issues, suitable dynamic dose imaging was not achieved with the current M512 hantom configuration and the MRI-linac. However, progress was made toward achieving this goal for future work. The M512 silicon array detector successfully measured high-resolution beam profiles in agreement with Gafchromic film to within an average of <1 mm on the first MRI-linac in Australia. More effective noise reduction will be required for the achievement of dynamic dosimaging in the future.
Dosimetry of intensive synchrotron microbeams
Publisher: Elsevier BV
Date: 12-2011
Welcome address from ISSDO
Publisher: Elsevier BV
Date: 03-2021
A computational technique for simulating ionization energy deposition by energetic ions in complex targets
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2000
DOI: 10.1109/23.903787
Supercapacitor Electrodes with Remarkable Specific Capacitance Converted from Hybrid Graphene Oxide/NaCl/Urea Films
Publisher: American Chemical Society (ACS)
Date: 26-06-2017
Abstract: A novel approach to improve the specific capacitance of reduced graphene oxide (rGO) films is reported. We combine the aqueous dispersion of liquid-crystalline GO incorporating salt and urea with a blade-coating technique to make hybrid films. After drying, stacked GO sheets mediated by solidified NaCl and urea are hydrothermally reduced, resulting in a nanoporous film consisting of rumpled N-doped rGO sheets. As a supercapacitor electrode, the film exhibits a high gravimetric specific capacitance of 425 F g
A Monte Carlo study on the feasibility of real-time in vivo source tracking during ultrasound based HDR prostate brachytherapy treatments
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.EJMP.2019.02.012
Abstract: This study aims to assess the accuracy of in-vivo source tracking during real-time trans-rectal ultrasound (TRUS) based high dose rate (HDR) prostate brachytherapy (pBT) through Monte Carlo simulations of multiple HDR pBT treatments with a two-dimensional (2D) diode array, the Magic Plate 900 (MP900), embedded below the patient in a carbon-fibre couch. Monte Carlo simulations of source positions representing three separate real-time TRUS based HDR pBT treatments were performed using the Geant4 toolkit. For each source position, an Ir-192 source was simulated inside a voxelized patient geometry. Dose deposited from each source position to the MP900 diodes was used to perform source tracking, and the MP900 calculated position compared to known source positions from the treatment plan. Thresholding techniques were implemented to improve source tracking accuracy with the TRUS probe present. The average three-dimensional source position reconstruction discrepancy was 11.9 ± 2.4 mm and 1.5 ± 0.3 mm with and without the TRUS probe, respectively. Thresholding techniques improved the source position reconstruction discrepancy in the presence of the TRUS probe to 1.8 ± 0.4 mm. Inclusion of the TRUS probe inside the patient negatively affects source tracking accuracy when using the MP900 diode array for HDR pBT verification. Modification of the source tracking algorithm using thresholding techniques improves source tracking in the presence of the TRUS probe, achieving similar accuracy as when the TRUS probe is not present. This study demonstrates that accurate in-vivo source tracking during real-time TRUS based HDR pBT is feasible using the Magic Plate system.
High toxicity of Bi(OH)3 and α-Bi2 O3 nanoparticles towards malignant 9L and MCF-7 cells
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.MSEC.2018.09.001
Abstract: Here we report the extreme toxicity in vitro of Bi(OH)
Investigation of a pulsed current annealing method in reusing MOSFET dosimeters for in vivo IMRT dosimetry
Publisher: Wiley
Date: 24-04-2014
DOI: 10.1118/1.4871619
Abstract: To explore the feasibility of pulsed current annealing in reusing metal oxide semiconductor field-effect transistor (MOSFET) dosimeters for in vivo intensity modulated radiation therapy (IMRT) dosimetry. Several MOSFETs were irradiated at d(max) using a 6 MV x-ray beam with 5 V on the gate and annealed with zero bias at room temperature. The percentage recovery of threshold voltage shift during multiple irradiation-annealing cycles was evaluated. Key dosimetry characteristics of the annealed MOSFET such as the dosimeter's sensitivity, reproducibility, dose linearity, and linearity of response within the dynamic range were investigated. The initial results of using the annealed MOSFETs for IMRT dosimetry practice were also presented. More than 95% of threshold voltage shift can be recovered after 24-pulse current continuous annealing in 16 min. The mean sensitivity degradation was found to be 1.28%, ranging from 1.17% to 1.52%, during multiple annealing procedures. Other important characteristics of the annealed MOSFET remained nearly consistent before and after annealing. Our results showed there was no statistically significant difference between the annealed MOSFETs and their control s les in absolute dose measurements for IMRT QA (p = 0.99). The MOSFET measurements agreed with the ion chamber results on an average of 0.16% ± 0.64%. Pulsed current annealing provides a practical option for reusing MOSFETs to extend their operational lifetime. The current annealing circuit can be integrated into the reader, making the annealing procedure fully automatic.
Cylindrical silicon-on-insulator microdosimeter: Charge collection characteristics
Publisher: IEEE
Date: 2007
Use of Ukrainian Semiconductor Dosimeters in a CERN Particle Accelerator Field
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-1994
DOI: 10.1109/23.322849
Spatial resolution of a small cubic LYSO scintillator crystal detector with depth-of-interaction capabilities in a small animal PET scanner
Publisher: IEEE
Date: 2007
Validation and practical implementation of seated position radiotherapy in a commercial TPS for proton therapy
Publisher: Elsevier BV
Date: 12-2020
Dual detector system for measuring out-of-field neutron dose in proton therapy
Publisher: IEEE
Date: 10-2009
Nanodosimetric cluster size distributions of therapeutic proton beams
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2006
TU‐D‐AUD C‐06: Direct RBE Determination of Therapeutic Protons Using a DE‐E Telescope
Publisher: Wiley
Date: 06-2008
DOI: 10.1118/1.2962587
A comparative analysis of multichannel Data Acquisition Systems for quality assurance in external beam radiation therapy
Publisher: IOP Publishing
Date: 05-06-2014
Characterization of MOSkin detector for in vivo skin dose measurement during megavoltage radiotherapy
Publisher: Wiley
Date: 09-2014
Design and simulation of continuous scintillator with pixellated photodetector
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2001
DOI: 10.1109/23.958369
Cerium oxide nanoparticles: Influence of the high-Z component revealed on radioresistant 9L cell survival under X-ray irradiation
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.NANO.2013.02.008
Abstract: This article pioneers a study into the influence of the high-Z component of nanoparticles on the efficacy of radioprotection some nanoparticles offer to exposed cells irradiated with X-rays. We reveal a significant decrease in the radioprotection efficacy for cells exposed to CeO2 nanoparticles and irradiated with 10 MV and 150 kVp X-rays. In addition, analysis of the 150 kVp survival curve data indicates a change in radiation quality, becoming more lethal for irradiated cells exposed to CeO2 nanoparticles. We attribute the change in efficacy to an increase in high linear energy transfer Auger electron production at 150 kVp which counterbalances the CeO2 nanoparticle radioprotection capability and locally changes the radiation quality. This study highlights an interesting phenomenon that must be considered if radiation protection drugs for use in radiotherapy are developed based on CeO2 nanoparticles. CeO2 nanoparticles are thought to offer radioprotection however, this study reveals significant decrease in the radioprotection efficacy for cells exposed to CeO2 nanoparticles and irradiated with 10 MV and 150 kVp X-rays. This phenomenon must be considered when developing radiation protection drugs based on CeO2 nanoparticles.
A convenient verification method of the entrance photo-neutron dose for an 18 MV medical linac using silicon p-i-n diodes
Publisher: Elsevier BV
Date: 11-2017
Skin Dose Modeling and Measurement in a High Field In-Line MRI-Linac System
Publisher: Frontiers Media SA
Date: 27-06-2022
Abstract: The Australian MRI-Linac prototype radiotherapy system has been shown to generate significant entry skin or surface dose increases. This arises from electron contamination focusing toward the isocenter caused by the 1 T MRI field being in-line with the x-ray beam. The aim of this study is to present accurate Monte Carlo modeling of these skin dose changes and to compare them with previous experimental measurements. Accurate skin dose modeling will improve confidence in the pathway forward to treatment planning for clinical trials. A COMSOL Multiphysics model of the Australian MRI-Linac system was used to generate a 3D magnetic field map to be used in corresponding Geant4 Monte Carlo simulations. The Geant4 simulations included the x-ray source (6 MV Linac), multileaf collimators (MLCs), and a 30 cm × 30 cm × 30 cm water phantom located with its front surface at the beam isocenter. Simulations were performed with a source to surface distance (SSD) of 1,819 mm for nominal field sizes 2 cm × 2 cm, 6 cm × 6 cm, and 10 cm × 10 cm. Central axis percentage depth dose (PDD) and surface (or skin) doses at 70 μm depth were calculated by using high-resolution scoring voxels of 10 μm thickness. The results were compared with corresponding experimental data collected using MO Skin ™ on the Australian MRI-Linac prototype system. The accurate modeling provides great detail into how the electron contamination is heavily confined and focused toward the beam central axis due to the presence of in-line magnetic field. This concentration significantly increases the skin dose up to 320% for the field size of 10 cm × 10 cm. For 2 cm × 2 cm and 6 cm × 6 cm, the surface skin dose is 128% and 217%, respectively, as compared to the skin dose in the absence of the magnetic field. The simulation results are in generally good agreement, ±10%, with previously collected experimental data for the same nominal field sizes. For the first time, detailed Geant4 Monte Carlo simulations of the electron contamination in the Australian MRI-Linac system have been performed and confirmed to be sufficiently accurate. These simulations will provide a solid framework for estimating the skin dose changes in more clinically relevant treatment plan scenarios that are envisaged in the near future.
Application of silicon planar structures for the spectrum determination of the proton beams produced by laser-driven particle accelerators. Theoretical approach.
Publisher: IEEE
Date: 10-2018
Characterisation of a cobalt-60 small-beam animal irradiator using a realtime silicon pixelated detector
Publisher: IOP Publishing
Date: 11-04-2016
Characterisation of a MOSFET-based detector for dose measurement under megavoltage electron beam radiotherapy
Publisher: Elsevier BV
Date: 03-2018
Evaluation of transmission methodology and attenuation correction for the microPET Focus 220 animal scanner
Publisher: IOP Publishing
Date: 02-08-2006
DOI: 10.1088/0031-9155/51/16/008
Abstract: An accurate, low noise estimate of photon attenuation in the subject is required for quantitative microPET studies of molecular tracer distributions in vivo. In this work, several transmission-based measurement techniques were compared, including coincidence mode with and without rod windowing, singles mode with two different energy sources ((68)Ge and (57)Co), and postinjection transmission scanning. In addition, the effectiveness of transmission segmentation and the propagation of transmission bias and noise into the emission images were examined. The (57)Co singles measurements provided the most accurate attenuation coefficients and superior signal-to-noise ratio, while (68)Ge singles measurements were degraded due to scattering from the object. Scatter correction of (68)Ge transmission data improved the accuracy for a 10 cm phantom but over-corrected for a mouse phantom. (57)Co scanning also resulted in low bias and noise in postinjection transmission scans for emission activities up to 20 MBq. Segmentation worked most reliably for transmission data acquired with (57)Co but the minor improvement in accuracy of attenuation coefficients and signal-to-noise may not justify its use, particularly for small subjects. We conclude that (57)Co singles transmission scanning is the most suitable method for measured attenuation correction on the microPET Focus 220 animal scanner.
Bridging Global and Local Models of Service-Oriented Systems
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2008
Endo-rectal balloon cavity dosimetry in a phantom: Performance under IMRT and helical tomotherapy beams
Publisher: Elsevier BV
Date: 07-2009
Tissue equivalence correction for silicon microdosimetry detectors in boron neutron capture therapy
Publisher: Wiley
Date: 28-10-1998
DOI: 10.1118/1.598421
Abstract: Reverse-biased silicon p-n junction arrays have been proposed as microdosimetry detectors. The tissue equivalence of such detectors in boron neutron capture therapy (BNCT) is discussed. A comparison of the range-energy relationships of H, He, C, and Li ions in tissue (ICRU-muscle) and silicon is given. A simple geometrical scaling (approximately 0.63) of linear dimensions is required to convert microdosimetric energy deposition measurements performed in silicon to equivalent deposition in tissue. The Monte Carlo technique is used to examine energy deposition for two simple geometrical cases applicable to BNCT.
Thulium Oxide Nanoparticles: A new candidate for image-guided radiotherapy
Publisher: IOP Publishing
Date: 14-06-2018
Organ point dose measurements in clinical multi slice computed tomography (MSCT) examinations with the MOSkin™ radiation dosimeter
Publisher: Elsevier BV
Date: 08-2013
Comparison of SOI microdosimeter and tissue equivalent proportional counter measurements at the CERF facility
Publisher: IEEE
Date: 10-2009
X-Tream dosimetry of highly brilliant X-ray microbeams in the MRT hutch of the Australian Synchrotron
Publisher: Elsevier BV
Date: 2016
Three-dimensional dosimetry imaging of I-125 plaque for eye cancer treatment
Publisher: Elsevier BV
Date: 05-2011
Multichannel Data Acquisition System comparison for Quality Assurance in external beam radiation therapy
Publisher: Elsevier BV
Date: 12-2014
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