ARDC Research Link Australia

ORCID Profile
Orcid icon. 0000-0003-4803-6507

Current Organisation
University of Sydney

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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.

ANZSRC Field of Research (FoR)

ANZSRC Socio-Economic Objective (SEO)

Publication

An analysis of thoracic and abdominal tumour motion for stereotactic body radiotherapy patients

Publisher: IOP Publishing

Date: 17-06-2008

DOI: 10.1088/0031-9155/53/13/016

Abstract: An analysis of thoracic and abdominal tumour motion for stereotactic body radiotherapy patients was performed using more than 70 h of tumour motion estimated from the correlation between the external and internal motion for 143 treatment fractions in 42 patients. The tumour sites included lungs (30 patients) and retroperitoneum (12 patients). The overall mean respiratory-induced peak-to-trough distance was 0.48 cm, with in idual treatment fraction means ranging from 0.02 to 1.44 cm. The overall mean respiratory period was 3.8 s, with in idual treatment fraction means ranging from 2.2 to 6.4 s. In 57 treatment fractions (40%), the mean respiratory-induced peak-to-trough distance was greater than 0.5 cm. In general, tumour motion was predominantly superior-inferior (60% of all the treatment fractions), while anterior-posterior and left-right motion were 22% and 18%, respectively. The motion was predominantly linear, and the overall mean of the first principal component was 94%. However, for motion magnitude, direction and linearity, large variations were observed from patient to patient, fraction to fraction and cycle to cycle.

Publication

Geometric uncertainty analysis of MLC tracking for lung SABR

Publisher: IOP Publishing

Date: 30-11-2020

DOI: 10.1088/1361-6560/ABB0C6

Abstract: Purpose. The purpose of this work was to report on the geometric uncertainty for patients treated with multi-leaf collimator (MLC) tracking for lung SABR to verify the accuracy of the system. Methods. Seventeen patients were treated as part of the MLC tracking for lung SABR clinical trial using electromagnetic beacons implanted around the tumor acting as a surrogate for target motion. Sources of uncertainties evaluated in the study included the surrogate-target positional uncertainty, the beam-surrogate tracking uncertainty, the surrogate localization uncertainty, and the target delineation uncertainty. Probability density functions (PDFs) for each source of uncertainty were constructed for the cohort and each patient. The total PDFs was computed using a convolution approach. The 95% confidence interval (CI) was used to quantify these uncertainties. Results. For the cohort, the surrogate-target positional uncertainty 95% CIs were ±2.5 mm (−2.0/3.0 mm) in left-right (LR), ±3.0 mm (−1.6/4.5 mm) in superior–inferior (SI) and ±2.0 mm (−1.8/2.1 mm) in anterior–posterior (AP). The beam-surrogate tracking uncertainty 95% CIs were ±2.1 mm (−2.1/2.1 mm) in LR, ±2.8 mm (−2.8/2.7 mm) in SI and ±2.1 mm (−2.1/2.0 mm) in AP directions. The surrogate localization uncertainty minimally impacted the total PDF with a width of ±0.6 mm. The target delineation uncertainty distribution 95% CIs were ±5.4 mm. For the total PDF, the 95% CIs were ±5.9 mm (−5.8/6.0 mm) in LR, ±6.7 mm (−5.8/7.5 mm) in SI and ±6.0 mm (−5.5/6.5 mm) in AP. Conclusion. This work reports the geometric uncertainty of MLC tracking for lung SABR by accounting for the main sources of uncertainties that occurred during treatment. The overall geometric uncertainty is within ±6.0 mm in LR and AP directions and ±6.7 mm in SI. The dominant uncertainty was the target delineation uncertainty. This geometric analysis helps put into context the range of uncertainties that may be expected during MLC tracking for lung SABR (ClinicalTrials.gov registration number: NCT02514512).

Publication

Quantifying the image quality and dose reduction of respiratory triggered 4D cone-beam computed tomography with patient-measured breathing

Publisher: IOP Publishing

Date: 24-11-2015

DOI: 10.1088/0031-9155/60/24/9493

Abstract: Respiratory triggered four dimensional cone-beam computed tomography (RT 4D CBCT) is a novel technique that uses a patient's respiratory signal to drive the image acquisition with the goal of imaging dose reduction without degrading image quality. This work investigates image quality and dose using patient-measured respiratory signals for RT 4D CBCT simulations. Studies were performed that simulate a 4D CBCT image acquisition using both the novel RT 4D CBCT technique and a conventional 4D CBCT technique. A set containing 111 free breathing lung cancer patient respiratory signal files was used to create 111 pairs of RT 4D CBCT and conventional 4D CBCT image sets from realistic simulations of a 4D CBCT system using a Rando phantom and the digital phantom, XCAT. Each of these image sets were compared to a ground truth dataset from which a mean absolute pixel difference (MAPD) metric was calculated to quantify the degradation of image quality. The number of projections used in each simulation was counted and was assumed as a surrogate for imaging dose. Based on 111 breathing traces, when comparing RT 4D CBCT with conventional 4D CBCT, the average image quality was reduced by 7.6% (Rando study) and 11.1% (XCAT study). However, the average imaging dose reduction was 53% based on needing fewer projections (617 on average) than conventional 4D CBCT (1320 projections). The simulation studies have demonstrated that the RT 4D CBCT method can potentially offer a 53% saving in imaging dose on average compared to conventional 4D CBCT in simulation studies using a wide range of patient-measured breathing traces with a minimal impact on image quality.

Publication

SU‐GG‐J‐19: Electromagnetic Detection and Real‐Time DMLC Correction of Rotation during Radiotherapy

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3468243

Publication

A retrospective 4D-MRI based on 2D diaphragm profiles for lung cancer patients.

Publisher: Wiley

Date: 04-2019

DOI: 10.1111/1754-9485.12877

Abstract: 4D-MRI, compared to 4D-CT, provides better soft-tissue contrast for target delineation. However, motion artefacts are often observed due to residual breathing variations. This study is to present a retrospective 4D-MRI reconstruction method based on 2D diaphragm profiles to improve the quality of 4D-MR images in the presence of significant breathing variations. The proposed 4D-MRI reconstruction method utilized diaphragm profiles (2D cine images on a single sagittal plan at the peak diaphragm) in conjunction with 4D-MR scans (2D-cine images on multiple pre-determined coronal planes along the anterior-posterior direction over a volume of interest). The diaphragm profile images were exploited to sort the 4D-MR scans by matching respiratory litude of diaphragm on the 4D-MR scans to the diaphragm profiles. To evaluate reconstructed 4D-MR images (ten 3D-MR images), sagittal images on ten 3D-MR images under free breathing (FB) and respiratory guidance (GB) were compared with diaphragm profile images (reference) from 13 healthy volunteers. Forty-four 4D-MR scan datasets were successfully reconstructed without distinct respiratory-related motion artefacts even with the presence of breathing variation. The differences in diaphragm profiles between the reference and corresponding reconstructed images in the mean of root mean square were similar between FB (3.5 mm) and GB (3.0 mm), confirming that the 4D-MRI reconstruction method was effective even with significant breathing variation. The diaphragm profiles were utilized to reconstruct 4D-MR images with spatial reliability and a fixed scan time under FB and GB. Our method can provide reliable 4D information of thoracic and abdominal regions for MRI-guided radiotherapy.

Publication

Experimental investigation of a general real-time 3D target localization method using sequential kV imaging combined with respiratory monitoring

Publisher: IOP Publishing

Date: 24-10-2012

DOI: 10.1088/0031-9155/57/22/7395

Publication

Tracking latency in image-based dynamic MLC tracking with direct image access

Publisher: Informa UK Limited

Date: 18-07-2011

DOI: 10.3109/0284186X.2011.581693

Publication

Real‐time radial reconstruction with domain transform manifold learning for MRI‐guided radiotherapy

Publisher: Wiley

Date: 27-01-2023

DOI: 10.1002/MP.16224

Abstract: MRI‐guidance techniques that dynamically adapt radiation beams to follow tumor motion in real time will lead to more accurate cancer treatments and reduced collateral healthy tissue damage. The gold‐standard for reconstruction of unders led MR data is compressed sensing (CS) which is computationally slow and limits the rate that images can be available for real‐time adaptation. Once trained, neural networks can be used to accurately reconstruct raw MRI data with minimal latency. Here, we test the suitability of deep‐learning‐based image reconstruction for real‐time tracking applications on MRI‐Linacs. We use automated transform by manifold approximation (AUTOMAP), a generalized framework that maps raw MR signal to the target image domain, to rapidly reconstruct images from unders led radial k‐space data. The AUTOMAP neural network was trained to reconstruct images from a golden‐angle radial acquisition, a benchmark for motion‐sensitive imaging, on lung cancer patient data and generic images from ImageNet. Model training was subsequently augmented with motion‐encoded k‐space data derived from videos in the YouTube‐8M dataset to encourage motion robust reconstruction. AUTOMAP models fine‐tuned on retrospectively acquired lung cancer patient data reconstructed radial k‐space with equivalent accuracy to CS but with much shorter processing times. Validation of motion‐trained models with a virtual dynamic lung tumor phantom showed that the generalized motion properties learned from YouTube lead to improved target tracking accuracy. AUTOMAP can achieve real‐time, accurate reconstruction of radial data. These findings imply that neural‐network‐based reconstruction is potentially superior to alternative approaches for real‐time image guidance applications.

Publication

Publisher: Elsevier

Date: 2010

DOI: 10.1016/B978-1-4160-5897-7.00012-3

Publication

Stereotactic prostate adaptive radiotherapy utilising kilovoltage intrafraction monitoring: the TROG 15.01 SPARK trial

Publisher: Springer Science and Business Media LLC

Date: 08-03-2017

DOI: 10.1186/S12885-017-3164-1

Publication

Evaluating the accuracy of 4D‐CT ventilation imaging: First comparison with Technegas SPECT ventilation

Publisher: Wiley

Date: 16-06-2017

DOI: 10.1002/MP.12317

Abstract: Computed tomography ventilation imaging (CTVI) is a highly accessible functional lung imaging modality that can unlock the potential for functional avoidance in lung cancer radiation therapy. Previous attempts to validate CTVI against clinical ventilation single-photon emission computed tomography (V-SPECT) have been hindered by radioaerosol clumping artifacts. This work builds on those studies by performing the first comparison of CTVI with Eleven lung cancer radiotherapy patients with early stage (T1/T2N0) disease received treatment planning four-dimensional CT (4DCT) scans paired with Technegas V/Q-SPECT/CT. For each patient, we applied three different CTVI methods. Two of these used deformable image registration (DIR) to quantify breathing-induced lung density changes (CTVI Interestingly, the overall best performing method (CTVI We performed a validation of CTVI using clinically available 4DCT and Technegas V/Q-SPECT for 11 lung cancer patients. The results reinforce earlier findings that the spatial accuracy of CTVI exhibits significant interpatient and intermethod variability. We propose that the most likely factor affecting CTVI accuracy was poor image quality of clinical 4DCT.

Publication

Publisher: Wiley

Date: 18-02-2019

DOI: 10.1002/MP.13408

Publication

MLC tracking for lung SABR is feasible, efficient and delivers high-precision target dose and lower normal tissue dose

Publisher: Elsevier BV

Date: 02-2021

DOI: 10.1016/J.RADONC.2020.10.036

Publication

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

Publisher: Wiley

Date: 11-10-2013

DOI: 10.1118/1.4824434

Publication

Publisher: IOP Publishing

Date: 28-05-2013

DOI: 10.1088/0031-9155/58/12/4195

Publication

Real-time profiling of respiratory motion: baseline drift, frequency variation and fundamental pattern change

Publisher: IOP Publishing

Date: 22-07-2009

DOI: 10.1088/0031-9155/54/15/009

Abstract: To precisely ablate tumor in radiation therapy, it is important to locate the tumor position in real time during treatment. However, respiration-induced tumor motions are difficult to track. They are semi-periodic and exhibit variations in baseline, frequency and fundamental pattern (oscillatory litude and shape). In this study, we try to decompose the above-mentioned components from discrete observations in real time. Baseline drift, frequency (equivalently phase) variation and fundamental pattern change characterize different aspects of respiratory motion and have distinctive clinical indications. Furthermore, smoothness is a valid assumption for each one of these components in their own spaces, and facilitates effective extrapolation for the purpose of estimation and prediction. We call this process 'profiling' to reflect the integration of information extraction, decomposition, processing and recovery. The proposed method has three major ingredients: (1) real-time baseline and phase estimation based on elliptical shape tracking in augmented state space and Poincaré sectioning principle (2) estimation of the fundamental pattern by unwarping the observation with phase estimate from the previous step (3) filtering of in idual components and assembly in the original temporal-displacement signal space. We tested the proposed method with both simulated and clinical data. For the purpose of prediction, the results are comparable to what one would expect from a human operator. The proposed approach is fully unsupervised and data driven, making it ideal for applications requiring economy, efficiency and flexibility.

Publication

SU‐EE‐A3‐03: Audiovisual Biofeedback Significantly Reduces Motion Blurring Artifacts in Four‐Dimensional (4D) PET Images

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3468020

Abstract: Purpose : To investigate the hypothesis that audiovisual biofeedback reduces motion blurring artifacts in 4D PET images. Method and Materials : 4D PET scans were acquired on a GE PET/CT scanner using audiovisual biofeedback guided and free breathing traces. A static image was used as the reference. The physical phantom consisted of six hollow spheres (NEMA ICE body phantom) with 10, 13, 17, 22, 28 and 37 mm in diameter as targets and a cylinder (Hoffman 3D brain phantom) as background. The sphere targets were filled with 18 F‐FDG at a fixed target‐to‐background ratio (8:1) based on 10 mCi/70 kg. The phantom was placed on a 3D programmable motion platform which produced the breathing patterns of four subjects with and without audiovisual biofeedback. 4D PET images with five respiratory bins were reconstructed for each breathing pattern. The segmented volumes, dice coefficients, 1D profiles, and 2D profiles were determined for evaluation and compared for each respiratory bin. The breathing patterns were analyzed for correlation between irregularity of breathing and motion blurring. Results : Audiovisual biofeedback significantly reduced motion blurring by 16.5% (1D profile, p=0.004), 22.6% (2D profile, p=0.003), 34.5% (volume, p=0.009) and 6.5% (dice coefficient, p=0.004) on average for the small spheres (≤17 mm), and by 4.3% (p=0.008), 2.7% (p=0.104), 0.7% (p=0.446) and 5.0% (p=0.014), respectively, for the large spheres (≥20 mm). In general, 4D PET motion blurring was dependent on the magnitude and irregularity of motion. Conclusion : The first investigation of the effect of breathing training on 4D PET images has been performed. The results indicate that audiovisual biofeedback can significantly reduce motion blurring in 4D PET images and may facilitate improved identification and localization of small lung tumors. Conflict of Interest : Supported by NIH/NCI R01 93626

Publication

Quantification of Artifact Reduction With Real-Time Cine Four-Dimensional Computed Tomography Acquisition Methods

Publisher: Elsevier BV

Date: 03-2010

DOI: 10.1016/J.IJROBP.2009.07.013

Abstract: To quantify the magnitude and frequency of artifacts in simulated four-dimensional computed tomography (4D CT) images using three real-time acquisition methods- direction-dependent displacement acquisition, simultaneous displacement and phase acquisition, and simultaneous displacement and velocity acquisition- and to compare these methods with commonly used retrospective phase sorting. Image acquisition for the four 4D CT methods was simulated with different displacement and velocity tolerances for spheres with radii of 0.5 cm, 1.5 cm, and 2.5 cm, using 58 patient-measured tumors and respiratory motion traces. The magnitude and frequency of artifacts, CT doses, and acquisition times were computed for each method. The mean artifact magnitude was 50% smaller for the three real-time methods than for retrospective phase sorting. The dose was approximately 50% lower, but the acquisition time was 20% to 100% longer for the real-time methods than for retrospective phase sorting. Real-time acquisition methods can reduce the frequency and magnitude of artifacts in 4D CT images, as well as the imaging dose, but they increase the image acquisition time. The results suggest that direction-dependent displacement acquisition is the preferred real-time 4D CT acquisition method, because on average, the lowest dose is delivered to the patient and the acquisition time is the shortest for the resulting number and magnitude of artifacts.

Publication

Experimental evaluation of the dosimetric impact of intrafraction prostate rotation using film measurement with a 6DoF robotic arm

Publisher: Wiley

Date: 30-10-2020

DOI: 10.1002/MP.14502

Abstract: Tumor motion during radiotherapy can cause a reduction in target dose coverage and an increase in healthy tissue exposure. Tumor motion is not strictly translational and often exhibits complex six degree‐of‐freedom (6DoF) translational and rotational motion. Although the dosimetric impact of prostate tumor translational motion is well investigated, the dosimetric impact of 6DoF motion has only been studied with simulations or dose reconstruction. This study aims to experimentally quantify the dose error caused by 6DoF motion. The experiment was designed to test the hypothesis that 6DoF motion would cause larger dose errors than translational motion alone through gamma analyses of two‐dimensional film measurements. Four patient‐measured intrafraction prostate motion traces and four VMAT 7.25 Gy/Fx SBRT treatment plans were selected for the experiment. The traces represented typical motion patterns, including small‐angle rotations ( °), transient movement, persistent excursion, and erratic rotations ( °). Gafchromic film was placed inside a custom‐designed phantom, held by a high‐precision 6DoF robotic arm for dose measurements in the coronal plane during treatment delivery. For each combination of the motion trace and treatment plan, two film measurements were made, one with 6DoF motion and the other with the three‐dimensional (3D) translation components of the same trace. A gamma pass rate criteria of 2% relative dose/2 mm distance‐to‐agreement was used in this study and evaluated for each measurement with respect to the static reference film. Two test thresholds, 90% and 50% of the reference dose, were applied to investigate the difference in dose coverage for the PTV region and surrounding areas, respectively. The hypothesis was tested using a Wilcoxon signed‐rank test. For each of the 16 plan and motion trace pairs, a reduction in the gamma pass rate was observed for 6DoF motion compared with 3D translational motion. With 90% gamma‐test threshold, the reduction was 5.8% ± 7.1% ( P 0.01). With 50% gamma‐test threshold, the reduction was 4.1% ± 4.8% ( P 0.01). For the first time, the dosimetric impact of intrafraction prostate rotation during SBRT treatment was measured experimentally. The experimental results support the hypothesis that 6DoF tumor motion causes higher dose error than translation motion alone.

Publication

AAPM Task Group 264: The safe clinical implementation of MLC tracking in radiotherapy

Publisher: Wiley

Date: 23-03-2021

DOI: 10.1002/MP.14625

Publication

SU-FF-T-648: Time Analysis of Image-Based Dynamic MLC Tracking

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182146

Publication

Publisher: Elsevier BV

Date: 04-2008

DOI: 10.1016/J.RADONC.2007.12.016

Publication

The impact of Monte Carlo dose calculations on treatment outcomes

Publisher: Springer Berlin Heidelberg

Date: 2000

DOI: 10.1007/978-3-642-59758-9_161

Publication

TH-D-213A-03: Physiological Validation of 4D-CT-Based Ventilation Imaging in Patients with Chronic Obstructive Pulmonary Disease (COPD)

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182715

Publication

Audiovisual biofeedback improves motion prediction accuracy

Publisher: Wiley

Date: 13-03-2013

DOI: 10.1118/1.4794497

Publication

Technical Note: The design and function of a horizontal patient rotation system for the purposes of fixed-beam cancer radiotherapy

Publisher: Wiley

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182394

Publication

Four‐dimensional computed tomography pulmonary ventilation images vary with deformable image registration algorithms and metrics

Publisher: Wiley

Date: 16-02-2011

DOI: 10.1118/1.3547719

Abstract: A novel pulmonary ventilation imaging technique based on four-dimensional (4D) CT has advantages over existing techniques and could be used for functional avoidance in radiotherapy. There are various deformable image registration (DIR) algorithms and two classes of ventilation metric that can be used for 4D-CT ventilation imaging, each yielding different images. The purpose of this study was to quantify the variability of the 4D-CT ventilation to DIR algorithms and metrics. 4D-CT ventilation images were created for 12 patients using different combinations of two DIR algorithms, volumetric (DIR(vol)) and surface-based (DIR(sur)), yielding two displacement vector fields (DVFs) per patient (DVF(voI) and DVF(sur)), and two metrics, Hounsfield unit (HU) change (V(HU)) and Jacobian determinant of deformation (V(Jac)), yielding four ventilation image sets (V(HU)(vol), V(HU)(sur), V(Jac)(voI), and V(Jac)(sur). First DVF(vol) and DVF(sur) were compared visually and quantitatively to the length of 3D displacement vector difference. Second, four ventilation images were compared based on voxel-based Spearman's rank correlation coefficients and coefficients of variation as a measure of spatial heterogeneity. V(HU)(vol) was chosen as the reference for the comparison. The mean length of 3D vector difference between DVF(vol) and DVF(sur) was 2.0 +/- 1.1 mm on average, which was smaller than the voxel dimension of the image set and the variations. Visually, the reference V(HU)(vol) demonstrated similar regional distributions with V(HU)(sur) the reference, however, was markedly different from V(Jac)(vol) and V((Jac)(sur). The correlation coefficients of V(HU)(vol) with V(HU)(sur), V(Jac)(vol) and V(Jac)(sur) were 0.77 +/- 0.06, 0.25 +/- 0.06 and 0.15 +/- 0.07, respectively, indicating that the metric introduced larger variations in the ventilation images than the DIR algorithm. The spatial heterogeneities for V(HU)(vol), 'V(HU)(sur), V(Jac)(vol), and V(Jac)(sur) were 1.8 +/- 1.6, 1.8 +/- 1.5 (p = 0. 85), 0.6 +/- 0.2 (p = 0.02), and 0.7 +/- 0.2 (p = 0.03), respectively, also demonstrating that the metric introduced larger variations. 4D-CT pulmonary ventilation images vary widely with DIR algorithms and metrics. Careful physiologic validation to determine the appropriate DIR algorithm and metric is needed prior to its applications.

Publication

An augmented correlation framework for the estimation of tumour translational and rotational motion during external beam radiotherapy treatments using intermittent monoscopic x-ray imaging and an external respiratory signal

Publisher: IOP Publishing

Date: 09-10-2018

DOI: 10.1088/1361-6560/AADF2C

Abstract: Increasing evidence shows that intrafraction tumour motion monitoring must include both six degrees of freedom (6DoF): 3D translations and 3D rotations. Existing real-time algorithms for 6DoF target motion estimation require continuous intrafraction fluoroscopic imaging at high frequency, thereby exposing patients to additional high imaging dose. This paper presents the first method capable of 6DoF motion monitoring using intermittent 2D kV imaging and a continuous external respiratory signal. Our approach is to optimise a state-augmented linear correlation model between an external signal and internal 6DoF motion. In standard treatments, the model can be built using information obtained during pre-treatment cone beam CT (CBCT). Real-time 6DoF tumor motion can then be estimated using just the external signal. Intermittent intrafraction kV images are used to update the model parameters, accounting for changes in correlation and baseline shifts. The method was evaluated in silico using data from 6 lung SABR patients, with the internal tumour motion recorded with electromagnetic beacons and the external signal from a bellows belt. Projection images from CBCT (10 Hz) and intermittent kV images were simulated by projecting the 3D Calypso beacon positions onto an imager. IMRT and VMAT treatments were simulated with increasing imaging update intervals: 0.1 s, 1 s, 3 s, 10 s and 30 s. For all the tested clinical scenarios, translational motion estimates with our method had sub-mm accuracy (mean) and precision (standard deviation) while rotational motion estimates were accurate to <[Formula: see text] and precise to [Formula: see text]. Motion estimation errors increased as the imaging update interval increased. With the largest imaging update interval (30 s), the errors were [Formula: see text] mm, [Formula: see text] mm and [Formula: see text] mm for translation in the left-right, superior-inferior and anterior-posterior directions, respectively, and [Formula: see text], [Formula: see text] and [Formula: see text] for rotation around the aforementioned axes for both VMAT and IMRT treatments. In conclusion, we developed and evaluated a novel method for highly accurate real-time 6DoF motion monitoring on a standard linear accelerator without requiring continuous kV imaging. The proposed method achieved sub-mm and sub-degree accuracy on a lung cancer patient dataset.

Publication

The Australian Magnetic Resonance Imaging-Linac Program

Publisher: Elsevier BV

Date: 07-2014

DOI: 10.1016/J.SEMRADONC.2014.02.015

Abstract: The Australian magnetic resonance imaging (MRI)-Linac program is a $16-million government-funded project to advance the science and clinical practice of exquisite real-time anatomical and physiological adaptive cancer therapy. The centerpiece of the program is a specifically designed 1-T open-bore MRI/6-MV linac system that is planned for delivery and completion of installation in 2014. Current scientific endeavors include engineering discovery in MRI component design, quantifying MRI and linac interactions, and developing image guidance and adaptation strategies.

Publication

SU‐E‐J‐156: A Feasibility Study for Real‐Time Tumor Tracking Using Positron Emission Tomography (PET)

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3611924

Publication

An in silico performance characterization of respiratory motion guided 4DCT for high-quality low-dose lung cancer imaging

Publisher: IOP Publishing

Date: 27-07-2018

DOI: 10.1088/1361-6560/AACECA

Abstract: This work aims to characterize the performance of an improved 4DCT technique aiming to overcome irregular breathing-related image artifacts. To address this, we have developed respiratory motion guided (RMG) 4DCT, which uses real-time breathing motion analysis to prospectively gate scans based on detection of irregular breathing. This is the first investigation of RMG-4DCT using a real-time software prototype, testing the hypothesis that it can reduce breathing irregularities during imaging, reduce image overs ling and improve image quality compared to a 'conventional' 4DCT protocol without breathing guidance. RMG-4DCT scans were simulated based on 100+ hours of breathing motion acquired for 20 lung cancer patients. Scan performance was quantified in terms of the beam on time (a surrogate for imaging dose), total scan time and the breathing irregularity during imaging (via RMSE of the breathing motion during acquisition). A conventional 4DCT protocol was also implemented using the same software prototype for a direct comparator to the RMG-4DCT results. We investigated the impact of key RMG-4DCT parameters such as gating tolerance, gantry rotation time and the use of baseline drift correction. Using a representative set of algorithm parameters, RMG-4DCT achieved significant mean reductions in estimated imaging dose (-17.8%, p < 0.001) and breathing RMSE during imaging (-12.6%, p < 0.001) compared to conventional 4DCT. These improvements came with increased scan times, roughly doubled on average (104%, p < 0.001). Image quality simulations were performed using the deformable digital XCAT phantom, with image quality quantified based on the normalized cross correlation (NCC) between axial slices. RMG-4DCT demonstrated qualitative image quality improvements for three out of 10 phase bins, however the improvement was not significant across all 10 phases (p = 0.08) at a population level. In choosing RMG-4DCT scan parameters, the trade-off between gating sensitivity and scan time may be optimized, demonstrating potential for RMG-4DCT as a viable pathway to improve clinical 4DCT imaging.

Publication

SU‐E‐J‐159: Correlation of Respiration‐Induced Motion of an External Surrogate and Implanted Internal Markers

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3611927

Publication

Influence of respiratory motion management technique on radiation pneumonitis risk with robotic stereotactic body radiation therapy

Publisher: Wiley

Date: 26-04-2018

DOI: 10.1002/ACM2.12338

Publication

Three-dimensional prostate position estimation with a single x-ray imager utilizing the spatial probability density

Publisher: IOP Publishing

Date: 25-07-2008

DOI: 10.1088/0031-9155/53/16/008

Abstract: In radiotherapy, target motion during treatment delivery can be managed either by motion inclusive margins or by gating or tracking based on intrafraction target position monitoring. If radio-opaque fiducial markers are used the required three-dimensional (3D) target position signal for gating or tracking can be obtained by simultaneous acquisition of two x-ray images from different angles. However, most treatment machines do not have such stereoscopic imaging capability. Alternatively, the 3D target position may be estimated with a single imager (monoscopic imaging) although it only provides the projected target position in the two dimensions of the imager plane. In this study, we developed a probability-based method to estimate the unresolved motion component parallel to the imager axis from the projected motion. A 3D Gaussian probability density was assumed for the target position. Projection of the target into a certain point on the imager means that it is located on the ray line that connects this point with the focus point of the x-ray source. The 1D probability density along this line was calculated from the 3D probability density and its expectation value was used as the estimate for the unresolved position. The mathematical framework of the method was developed including analytical expressions for the estimated unresolved component as a function of resolved components and for the estimation uncertainty. Use of the method was demonstrated for prostate in a simulation study of monoscopic imaging. First, the required 3D probability density was constructed as a population average from a data set consisting of 536 continuous prostate position tracks from 17 patients recorded at 10 Hz. Next, monoscopic imaging at a fixed imaging angle and imaging frequency was simulated for each prostate track. Estimated 3D prostate tracks were constructed from the simulated projection images by the proposed method and compared with the actual tracks in order to determine the root-mean-square (rms) error. The simulations were performed with imaging angles in the range from 0 degrees to 180 degrees (relative to vertical) and imaging frequencies in the range from 0.1 s (corresponding to continuous imaging) to 600 s (corresponding to no intrafraction imaging). For comparison, simulations were also performed with stereoscopic imaging, where perfect position determination in all three directions was assumed, and with monoscopic imaging without estimation of the unresolved motion, where the motion component along the imager axis was assumed to be zero. For continuous imaging, the accuracy of monoscopic imaging was limited by the uncertainty in the unresolved position estimation. The resulting vector rms error for the population corresponded closely to the theoretically derived estimation uncertainty. The estimation did not improve the accuracy of lateral monoscopic imaging, but it reduced the population rms error from 1.59 mm to 1.11 mm for vertical imaging. This improvement was most prominent for outlying tracks with large unresolved motion. Stereoscopic imaging was clearly superior to monoscopic imaging for high frequency imaging. For less frequent imaging, the accuracy of both monoscopic and stereoscopic imaging decreased due to target motion between images. Since this was most prominent for stereoscopic imaging, the difference in accuracy between monoscopic and stereoscopic imaging decreased with increasing imaging period. In conclusion, a method for estimation of the 3D target position from 2D projections has been developed and its use has been demonstrated in a simulation study of monoscopic prostate tracking.

Publication

Decoupling Respiratory and Angular Variation in Rotational X-ray Scans Using a Prior Bilinear Model

Publisher: Springer International Publishing

Date: 2019

DOI: 10.1007/978-3-030-12939-2_40

Publication

Hypofractionation Results in Reduced Tumor Cell Kill Compared to Conventional Fractionation for Tumors With Regions of Hypoxia

Publisher: Elsevier BV

Date: 03-2011

DOI: 10.1016/J.IJROBP.2010.10.007

Publication

Investigation of four-dimensional computed tomography-based pulmonary ventilation imaging in patients with emphysematous lung regions

Publisher: IOP Publishing

Date: 16-03-2011

DOI: 10.1088/0031-9155/56/7/023

Abstract: A pulmonary ventilation imaging technique based on four-dimensional (4D) computed tomography (CT) has advantages over existing techniques. However, physiologically accurate 4D-CT ventilation imaging has not been achieved in patients. The purpose of this study was to evaluate 4D-CT ventilation imaging by correlating ventilation with emphysema. Emphysematous lung regions are less ventilated and can be used as surrogates for low ventilation. We tested the hypothesis: 4D-CT ventilation in emphysematous lung regions is significantly lower than in non-emphysematous regions. Four-dimensional CT ventilation images were created for 12 patients with emphysematous lung regions as observed on CT, using a total of four combinations of two deformable image registration (DIR) algorithms: surface-based (DIR(sur)) and volumetric (DIR(vol)), and two metrics: Hounsfield unit (HU) change (V(HU)) and Jacobian determinant of deformation (V(Jac)), yielding four ventilation image sets per patient. Emphysematous lung regions were detected by density masking. We tested our hypothesis using the one-tailed t-test. Visually, different DIR algorithms and metrics yielded spatially variant 4D-CT ventilation images. The mean ventilation values in emphysematous lung regions were consistently lower than in non-emphysematous regions for all the combinations of DIR algorithms and metrics. V(HU) resulted in statistically significant differences for both DIR(sur) (0.14 ± 0.14 versus 0.29 ± 0.16, p = 0.01) and DIR(vol) (0.13 ± 0.13 versus 0.27 ± 0.15, p < 0.01). However, V(Jac) resulted in non-significant differences for both DIR(sur) (0.15 ± 0.07 versus 0.17 ± 0.08, p = 0.20) and DIR(vol) (0.17 ± 0.08 versus 0.19 ± 0.09, p = 0.30). This study demonstrated the strong correlation between the HU-based 4D-CT ventilation and emphysema, which indicates the potential for HU-based 4D-CT ventilation imaging to achieve high physiologic accuracy. A further study is needed to confirm these results.

Publication

Development of a Micro-Computed Tomography–Based Image-Guided Conformal Radiotherapy System for Small Animals

Publisher: Elsevier BV

Date: 09-2010

DOI: 10.1016/J.IJROBP.2009.11.008

Publication

SU-FF-T-155: Four-Dimensional Inverse Treatment Planning with Inclusion of Implanted Fiducials in IMRT Segmented Fields

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181629

Publication

Atrial fibrillation cardiac radioablation target visibility on magnetic resonance imaging

Publisher: Springer Science and Business Media LLC

Date: 10-06-2022

DOI: 10.1007/S13246-022-01141-3

Abstract: Magnetic resonance imaging (MRI) guided cardiac radioablation (CR) for atrial fibrillation (AF) is a promising treatment concept. However, the visibility of AF CR targets on MRI acquisitions requires further exploration and MRI sequence and parameter optimization has not yet been performed for this application. This pilot study explores the feasibility of MRI-guided tracking of AF CR targets by evaluating AF CR target visualization on human participants using a selection of 3D and 2D MRI sequences.MRI datasets were acquired in healthy and AF participants using a range of MRI sequences and parameters. MRI acquisition categories included 3D free-breathing acquisitions ( 3D acq ), 2D breath-hold ECG-gated acquisitions ( 2D ECG-gated ), stacks of 2D breath-hold ECG-gated acquisitions which were retrospectively interpolated to 3D datasets ( 3D interp ), and 2D breath-hold ungated acquisitions ( 2D real-time ). The ease of target delineation and the presence of artifacts were qualitatively analyzed. Image quality was quantitatively analyzed using signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and non-uniformity. Confident 3D target delineation was achievable on all 3D interp datasets but was not possible on any of the 3D acq datasets. Fewer artifacts and significantly better SNR, CNR and non-uniformity metrics were observed with 3D interp compared to 3D acq . 2D real-time datasets had slightly lower SNR and CNR than 2D ECG-gated and 3D interp n datasets. AF CR target visualization on MRI was qualitatively and quantitatively evaluated. The study findings indicate that AF CR target visualization is achievable despite the imaging challenges associated with these targets, warranting further investigation into MRI-guided AF CR treatments.

Publication

Publisher: Elsevier BV

Date: 07-2020

DOI: 10.1016/J.IJROBP.2020.03.014

Publication

4-dimensional computed tomography imaging and treatment planning

Publisher: Elsevier BV

Date: 2004

DOI: 10.1053/J.SEMRADONC.2003.10.006

Abstract: In the era of conformal therapy and intensity-modulated therapy, there is an increased desire to raise tumor dose to facilitate improved survival and decrease normal tissue dose to reduce treatment-related complications. Setup accuracy and internal motion limit our ability to reduce margins. Internal motion has both interfraction and intrafraction components, although only the intrafraction component will be addressed here. Intrafraction motion is significant for lung, liver, and pancreatic radiotherapy and to a lesser extent breast and prostate radiotherapy. A method to explicitly account for intrafraction motion is to temporally adjust the treatment beam based on the tumor position with time such that the motion of the radiation beam is synchronized with the tumor motion. This addition of time into the 3-dimensional treatment process is termed 4-dimensional (4D) radiotherapy. Four-dimensional radiotherapy may allow safe clinical target volume-planning target volume margin reduction to achieve the goals of raised tumor dose and decreased normal tissue dose. This article discusses methodology for 4D CT imaging and 4D treatment planning, with some comments on 4D radiation delivery.

Publication

Technical Note: A novel leaf sequencing optimization algorithm which considers previous underdose and overdose events for MLC tracking radiotherapy

Publisher: Wiley

Date: 22-12-2015

DOI: 10.1118/1.4937781

Abstract: Multileaf collimator (MLC) tracking radiotherapy is complex as the beam pattern needs to be modified due to the planned intensity modulation as well as the real-time target motion. The target motion cannot be planned therefore, the modified beam pattern differs from the original plan and the MLC sequence needs to be recomputed online. Current MLC tracking algorithms use a greedy heuristic in that they optimize for a given time, but ignore past errors. To overcome this problem, the authors have developed and improved an algorithm that minimizes large underdose and overdose regions. Additionally, previous underdose and overdose events are taken into account to avoid regions with high quantity of dose events. The authors improved the existing MLC motion control algorithm by introducing a cumulative underdose/overdose map. This map represents the actual projection of the planned tumor shape and logs occurring dose events at each specific regions. These events have an impact on the dose cost calculation and reduce recurrence of dose events at each region. The authors studied the improvement of the new temporal optimization algorithm in terms of the L1-norm minimization of the sum of overdose and underdose compared to not accounting for previous dose events. For evaluation, the authors simulated the delivery of 5 conformal and 14 intensity-modulated radiotherapy (IMRT)-plans with 7 3D patient measured tumor motion traces. Simulations with conformal shapes showed an improvement of L1-norm up to 8.5% after 100 MLC modification steps. Experiments showed comparable improvements with the same type of treatment plans. A novel leaf sequencing optimization algorithm which considers previous dose events for MLC tracking radiotherapy has been developed and investigated. Reductions in underdose/overdose are observed for conformal and IMRT delivery.

Publication

See, Think, and Act: Real-Time Adaptive Radiotherapy

Publisher: Elsevier BV

Date: 07-2019

DOI: 10.1016/J.SEMRADONC.2019.02.005

Abstract: The world is embracing the information age, with real-time data at hand to assist with many decisions. Similarly, in cancer radiotherapy we are inexorably moving toward using information in a smarter and faster fashion, to usher in the age of real-time adaptive radiotherapy. The three critical steps of real-time adaptive radiotherapy, aligned with driverless vehicle technology are a continuous see, think, and act loop. See: use imaging systems to probe the patient anatomy or physiology as it evolves with time. Think: use current and prior information to optimize the treatment using the available adaptive degrees of freedom. Act: deliver the real-time adapted treatment. This paper expands upon these three critical steps for real-time adaptive radiotherapy, provides a historical context, reviews the clinical rationale, and gives a future outlook for real-time adaptive radiotherapy.

Publication

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182680

Publication

SU‐F‐500‐05: MRI‐Linac Systems: Can a Standard MLC Be Incorporated Into Such a Device?

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815195

Publication

Realistic CT data augmentation for accurate deep‐learning based segmentation of head and neck tumors in kV images acquired during radiation therapy

Publisher: Wiley

Publisher: Elsevier BV

Date: 10-2016

DOI: 10.1016/J.ADRO.2016.10.004

Publication

WE‐A‐134‐06: Performance Characterization of Kilovoltage Intrafraction Monitoring; a Novel Real‐Time Tumor Localization Modality

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815512

Publication

A Feasibility Study of Single-inhalation, Single-energy Xenon-enhanced CT for High-resolution Imaging of Regional Lung Ventilation in Humans

Publisher: Elsevier BV

Date: 2019

DOI: 10.1016/J.ACRA.2018.03.006

Abstract: The objective of this study was to assess the feasibility of single-inhalation xenon-enhanced computed tomography (XeCT) to provide clinically practical, high-resolution pulmonary ventilation imaging to clinics with access to only a single-energy computed tomography scanner, and to reduce the subject's overall exposure to xenon by utilizing a higher (70%) concentration for a much shorter time than has been employed in prior studies. We conducted an institutional review board-approved prospective feasibility study of XeCT for 15 patients undergoing thoracic radiotherapy. For XeCT, we acquired two breath-hold single-energy computed tomography images of the entire lung with a single inhalation each of 100% oxygen and a mixture of 70% xenon and 30% oxygen, respectively. A video biofeedback system for coached patient breathing was used to achieve reproducible breath holds. We assessed the technical success of XeCT acquisition and side effects. We then used deformable image registration to align the breath-hold images with each other to accurately subtract them, producing a map of lung xenon distribution. Additionally, we acquired ventilation single-photon emission computed tomography-computed tomography (V-SPECT-CT) images for 11 of the 15 patients. For a comparative analysis, we partitioned each lung into 12 sectors, calculated the xenon concentration from the Hounsfield unit enhancement in each sector, and then correlated this with the corresponding V-SPECT-CT counts. XeCT scans were tolerated well overall, with a mild (grade 1) dizziness as the only side effect in 5 of the 15 patients. Technical failures in five patients occurred because of inaccurate breathing synchronization with xenon gas delivery, leaving seven patients analyzable for XeCT and single-photon emission computed tomography correlation. Sector-wise correlations were strong (Spearman coefficient >0.75, Pearson coefficient >0.65, P value <.002) for two patients for whom ventilation deficits were visibly pronounced in both scans. Correlations were nonsignificant for the remaining five who had more homogeneous XeCT ventilation maps, as well as strong V-SPECT-CT imaging artifacts attributable to airway deposition of the aerosolized imaging agent. Qualitatively, XeCT demonstrated higher resolution and no central airway deposition artifacts compared to V-SPECT-CT. In this pilot study, single-breath XeCT ventilation imaging was generally feasible for patients undergoing thoracic radiotherapy, using an imaging protocol that is clinically practical and potentially widely available. In the future, the xenon delivery failures can be addressed by straightforward technical improvements to the patient biofeedback coaching system.

Publication

WE‐A‐134‐11: Registration of Clinical Volumes to Beams‐Eye‐View Images for Real‐Time Tracking

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815517

Publication

Linking computer-aided design (CAD) to Geant4-based Monte Carlo simulations for precise implementation of complex treatment head geometries

Publisher: IOP Publishing

Date: 26-03-2010

DOI: 10.1088/0031-9155/55/8/N03

Publication

First experimental investigation of simultaneously tracking two independently moving targets on an MRI-linac using real-time MRI and MLC tracking

Publisher: Wiley

Publisher: Wiley

Date: 02-08-2017

DOI: 10.1002/ACM2.12151

Publication

Publisher: Springer Science and Business Media LLC

Date: 15-06-2009

DOI: 10.1186/1748-717X-4-18

Publication

Real-time dynamic MLC tracking for inversely optimized arc radiotherapy

Publisher: Elsevier BV

Date: 02-2010

DOI: 10.1016/J.RADONC.2009.12.022

Publication

TU‐A‐BRB‐11: 4D Optimization for Respiratory Phase‐Dependent IMRT Treatment Planning

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3613076

Publication

Passive magnetic shielding in MRI-Linac systems

Publisher: IOP Publishing

Date: 26-03-2018

DOI: 10.1088/1361-6560/AAB138

Abstract: Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Publication

Publisher: Wiley

Date: 02-2019

DOI: 10.1002/MP.13346

Publication

SU‐GG‐J‐14: Failure Mode and Effect Analysis (FMEA)‐Based Quality Assurance for Dynamic MLC Tracking Systems

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3468237

Publication

Future of medical physics: Real‐time MRI‐guided proton therapy

Publisher: Wiley

Date: 04-07-2017

DOI: 10.1002/MP.12371

Abstract: With the recent clinical implementation of real-time MRI-guided x-ray beam therapy (MRXT), attention is turning to the concept of combining real-time MRI guidance with proton beam therapy MRI-guided proton beam therapy (MRPT). MRI guidance for proton beam therapy is expected to offer a compelling improvement to the current treatment workflow which is warranted arguably more than for x-ray beam therapy. This argument is born out of the fact that proton therapy toxicity outcomes are similar to that of the most advanced IMRT treatments, despite being a fundamentally superior particle for cancer treatment. In this Future of Medical Physics article, we describe the various software and hardware aspects of potential MRPT systems and the corresponding treatment workflow. Significant software developments, particularly focused around adaptive MRI-based planning will be required. The magnetic interaction between the MRI and the proton beamline components will be a key area of focus. For ex le, the modeling and potential redesign of a magnetically compatible gantry to allow for beam delivery from multiple angles towards a patient located within the bore of an MRI scanner. Further to this, the accuracy of pencil beam scanning and beam monitoring in the presence of an MRI fringe field will require modeling, testing, and potential further development to ensure that the highly targeted radiotherapy is maintained. Looking forward we envisage a clear and accelerated path for hardware development, leveraging from lessons learnt from MRXT development. Within few years, simple prototype systems will likely exist, and in a decade, we could envisage coupled systems with integrated gantries. Such milestones will be key in the development of a more efficient, more accurate, and more successful form of proton beam therapy for many common cancer sites.

Publication

WE‐C‐WAB‐04: Comparison of 4D‐CT Ventilation Imaging with SPECT Ventilation Imaging for Thoracic Cancer Patients

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815540

Publication

SU‐E‐J‐118: Quantifying Intrafractional Prostate Rotation From Cone‐Beam Computed Tomography with Radiopaque Markers

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4814330

Publication

SU-C-224-01: 3D Dosimetry with Gels and Optical Tomography of Dynamic MLC Tracking Based on an Electromagnetic Transponder System

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3611449

Publication

Publisher: IOP Publishing

Date: 16-10-2014

DOI: 10.1088/0031-9155/59/21/6583

Publication

The first patient treatment of electromagnetic-guided real time adaptive radiotherapy using MLC tracking for lung SABR

Publisher: Elsevier BV

Date: 10-2016

DOI: 10.1016/J.RADONC.2016.08.025

Abstract: Real time adaptive radiotherapy that enables smaller irradiated volumes may reduce pulmonary toxicity. We report on the first patient treatment of electromagnetic-guided real time adaptive radiotherapy delivered with MLC tracking for lung stereotactic ablative body radiotherapy. A clinical trial was developed to investigate the safety and feasibility of MLC tracking in lung. The first patient was an 80-year old man with a single left lower lobe lung metastasis to be treated with SABR to 48Gy in 4 fractions. In-house software was integrated with a standard linear accelerator to adapt the treatment beam shape and position based on electromagnetic transponders implanted in the lung. MLC tracking plans were compared against standard ITV-based treatment planning. MLC tracking plan delivery was reconstructed in the patient to confirm safe delivery. Real time adaptive radiotherapy delivered with MLC tracking compared to standard ITV-based planning reduced the PTV by 41% (18.7-11cm An emerging technology, MLC tracking, has been translated into the clinic and used to treat lung SABR patients for the first time. This milestone represents an important first step for clinical real-time adaptive radiotherapy that could reduce pulmonary toxicity in lung radiotherapy.

Publication

Monte Carlo-based inverse treatment planning

Publisher: IOP Publishing

Date: 22-07-1999

DOI: 10.1088/0031-9155/44/8/303

Abstract: A Monte Carlo based inverse treatment planning system (MCI) has been developed which combines arguably the most accurate dose calculation method (Monte Carlo particle transport) with a 'guaranteed' optimization method (simulated annealing). A distribution of photons is specified in the tumour volume they are transported using an adjoint calculation method to outside the patient surface to build up an intensity distribution. This intensity distribution is used as the initial input into an optimization algorithm. The dose distribution from each beam element from a number of fields is pre-calculated using Monte Carlo transport. Simulated annealing optimization is then used to find the weighting of each beam element, to yield the optimal dose distribution for the given criteria and constraints. MCI plans have been generated in various theoretical phantoms and patient geometries. These plans show conformation of the dose to the target volume and avoidance of critical structures. To verify the code, an experiment was performed on an anthropomorphic phantom.

Publication

SU‐C‐213CD‐05: Respiratory Signal Triggered 4D Cone‐Beam Computed Tomography on a Linear Accelerator

Publisher: Wiley

Date: 06-2012

DOI: 10.1118/1.4734634

Publication

TH‐E‐BRA‐11: Real‐Time Tumor Localization with Kilovoltage Intrafraction Monitoring: First Clinical Implementation for Prostate Intensity Modulated Arc Therapy

Publisher: Wiley

Date: 06-2012

DOI: 10.1118/1.4736372

Publication

SU‐E‐J‐03: Impact of Gated and Conventional 4DCT Acquisition On Imaging Artifacts in a Digital Phantom

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4814215

Publication

Publisher: Elsevier BV

Date: 04-2016

DOI: 10.1016/J.RADONC.2016.03.006

Publication

A Method to Estimate Mean Position, Motion Magnitude, Motion Correlation, and Trajectory of a Tumor From Cone-Beam CT Projections for Image-Guided Radiotherapy

Publisher: Elsevier BV

Date: 12-2008

DOI: 10.1016/J.IJROBP.2008.07.037

Abstract: To develop a probability-based method for estimating the mean position, motion magnitude, and trajectory of a tumor using cone-beam CT (CBCT) projections. CBCT acquisition was simulated for more than 80 hours of patient-measured trajectories for thoracic/abdominal tumors and prostate. The trajectories were ided into 60-second segments for which CBCT was simulated by projecting the tumor position onto a rotating imager. Tumor (surrogate) visibility on all projections was assumed. The mean and standard deviation of the tumor position and motion correlation along the three axes were determined with maximum likelihood estimation based on the projection data, assuming a Gaussian spatial distribution. The unknown position component along the imager axis was approximated by its expectation value, determined by the Gaussian distribution. Transformation of the resulting three-dimensional position to patient coordinates provided the estimated trajectory. Two trajectories were experimentally investigated by CBCT acquisition of a phantom. The root-mean-square error of the estimated mean position was 0.05 mm. The root-mean-square error of the trajectories was <1 mm in 99.1% of the thorax/abdomen cases and in 99.7% of the prostate cases. The experimental trajectory estimation agreed with the actual phantom trajectory within 0.44 mm in any direction. Clinical applicability was demonstrated by estimating the tumor trajectory for a pancreas cancer case. A method for estimation of mean position, motion magnitude, and trajectory of a tumor from CBCT projections has been developed. The accuracy was typically much better than 1 mm. The method is applicable to motion-inclusive, respiratory-gated, and tumor-tracking radiotherapy.

Publication

Towards patient connected imaging with ACROBEAT: Adaptive CaRdiac cOne BEAm computed Tomography

Publisher: IOP Publishing

TU‐E‐204B‐04: DMLC Implementation of a Prostate Intrafraction Motion Correction Strategy Based on Failure Detection Concept

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469295

Publication

Publisher: British Institute of Radiology

Date: 31-01-2018

DOI: 10.1259/BJR.20170807

Publication

Locating and Targeting Moving Tumors with Radiation Beams

Publisher: S. Karger AG

Date: 2011

DOI: 10.1159/000322413

Abstract: 3D knowledge of the tumor position during abdominal and thoracic radiotherapy is an important component of motion management in radiation therapy. A wide variety of real-time position monitoring systems are available or under development. These are based on a ersity of modalities including radiofrequency, radioisotopes, ultrasound and MRI in addition to the optical, kilovoltage and megavoltage imaging systems available on conventional accelerators. These systems are also providing new insights into the magnitude and complexity of target and normal tissue motion during a course of therapy, and are driving the development of real-time targeting systems. Real-time targeting devices to align the tumor and the radiation beam have built upon technologies of robots, multileaf collimators, and couch-based and gimbaled positioning systems. The integration and widespread dissemination of systems that locate and target moving tumors are ongoing developments in the early 21st century, and future systems are likely to include the functionality of targeting temporally changing tumors and normal tissue physiology as well as anatomy.

Publication

Implementation of a New Method for Dynamic Multileaf Collimator Tracking of Prostate Motion in Arc Radiotherapy Using a Single kV Imager

Publisher: Elsevier BV

Date: 03-2010

DOI: 10.1016/J.IJROBP.2009.06.073

Abstract: To implement a method for real-time prostate motion estimation with a single kV imager during arc radiotherapy and to integrate it with dynamic multileaf collimator (DMLC) target tracking. An arc field with a circular aperture and 358 degrees gantry rotation was delivered to a motion phantom with a fiducial marker under continuous kV X-ray imaging at 5 Hz, perpendicular to the treatment beam. A pretreatment gantry rotation of 120 degrees in 20 sec with continuous imaging preceded the treatment. During treatment, each kV image was first used together with all previous images to estimate the three-dimensional (3D) target probability density function and then used together with this probability density function to estimate the 3D target position. The MLC aperture was then adapted to the estimated 3D target position. Tracking was performed with five patient-measured prostate trajectories that represented characteristic prostate motion patterns. Two data sets were recorded during tracking: (1) the estimated 3D target positions, for off-line comparison with the actual phantom motion and (2) continuous portal images, for independent off-line calculation of the 2D tracking error as the positional difference between the marker and the MLC aperture center in each portal image. All experiments were also made with 1- Hz kV imaging. The mean 3D root-mean-square error of the trajectory estimation was 0.6 mm. The mean root-mean-square tracking error was 0.7 mm, both parallel and perpendicular to the MLC. The accuracy degraded slightly for 1- Hz imaging. Single-imager DMLC prostate tracking that allows arbitrary beam modulation during arc radiotherapy was implemented. It has submillimeter accuracy for most prostate motion types.

Publication

Using anecdotal reports to clarify the distribution and status of a near mythical species: Australia’s Night Parrot (Pezoporus occidentalis)

Publisher: Informa UK Limited

Date: 22-06-2021

DOI: 10.1080/01584197.2021.1927760

Publication

First experimental evaluation of multi-target multileaf collimator tracking during volumetric modulated arc therapy for locally advanced prostate cancer

Publisher: Elsevier BV

Date: 07-2021

DOI: 10.1016/J.RADONC.2021.05.001

Publication

A review of specimens of Buff-breasted Button-quail Turnix olivii suggests serious concern for its conservation outlook

Publisher: Informa UK Limited

Date: 03-04-2022

DOI: 10.1080/01584197.2022.2090962

Publication

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182418

Publication

Megavoltage Image-Based Dynamic Multileaf Collimator Tracking of a NiTi Stent in Porcine Lungs on a Linear Accelerator

Publisher: Elsevier BV

Date: 02-2012

DOI: 10.1016/J.IJROBP.2011.03.023

Publication

First clinical implementation of audiovisual biofeedback in liver cancer stereotactic body radiation therapy

Publisher: Wiley

Date: 06-08-2015

DOI: 10.1111/1754-9485.12343

Publication

Considerations and limitations of fast Monte Carlo electron transport in radiation therapy based on precalculated data

Publisher: Wiley

Date: 26-01-2009

DOI: 10.1118/1.3058480

Abstract: The purpose of this work is to revisit the impediments and characteristics of fast Monte Carlo techniques for applications in radiation therapy treatment planning using new methods of utilizing pregenerated electron tracks. The limitations of various techniques for the improvement of speed and accuracy of electron transport have been evaluated. A method is proposed that takes advantage of large available memory in current computer hardware for extensive generation of precalculated data. Primary tracks of electrons are generated in the middle of homogeneous materials (water, air, bone, lung) and with energies between 0.2 and 18 MeV using the EGSnrc code. Secondary electrons are not transported, but their position, energy, charge, and direction are saved and used as a primary particle. Based on medium type and incident electron energy, a track is selected from the precalculated set. The performance of the method is tested in various homogeneous and heterogeneous configurations and the results were generally within 2% compared to EGSnrc but with a 40-60 times speed improvement. In a second stage the authors studied the obstacles for further increased speed-ups in voxel geometries by including ray-tracing and particle fluence information in the pregenerated track information. The latter method leads to speed increases of about a factor of 500 over EGSnrc for voxel-based geometries. In both approaches, no physical calculation is carried out during the runtime phase after the pregenerated data has been stored even in the presence of heterogeneities. The precalculated data are generated for each particular material and this improves the performance of the precalculated Monte Carlo code both in terms of accuracy and speed. Precalculated Monte Carlo codes are accurate, fast, and physics independent and therefore applicable to different radiation types including heavy-charged particles.

Publication

A phantom study to create synthetic CT from orthogonal twodimensional cine MRI and evaluate the effect of irregular breathing

Publisher: IEEE

Date: 07-2018

DOI: 10.1109/EMBC.2018.8513236

Publication

SU‐FF‐J‐155: The Influence of Material Assignment On Monte Carlo Dose Calculations for Kilovoltage Small Animal Radiotherapy

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181448

Publication

Quantifying the accuracy and precision of a novel real-time 6 degree-of-freedom kilovoltage intrafraction monitoring (KIM) target tracking system

Publisher: IOP Publishing

Date: 23-06-2017

DOI: 10.1088/1361-6560/AA6ED7

Abstract: Target rotation can considerably impact the delivered radiotherapy dose depending on the tumour shape. More accurate tumour pose during radiotherapy treatment can be acquired through tracking in 6 degrees-of-freedom (6 DoF) rather than in translation only. A novel real-time 6 DoF kilovoltage intrafraction monitoring (KIM) target tracking system has recently been developed. In this study, we experimentally evaluated the accuracy and precision of the 6 DoF KIM implementation. Real-time 6 DoF KIM motion measurements were compared against the ground truth motion retrospectively derived from kV/MV triangulation for a range of lung and prostate tumour motion trajectories as well as for various static poses using a phantom. The accuracy and precision of 6 DoF KIM were calculated as the mean and standard deviation of the differences between KIM and kV/MV triangulation for each DoF, respectively. We found that KIM is able to provide 6 DoF motion with sub-degree and sub-millimetre accuracy and precision for a range of realistic tumour motion.

Publication

The integration of MRI in radiation therapy: collaboration of radiographers and radiation therapists

Publisher: Wiley

Date: 16-02-2017

DOI: 10.1002/JMRS.225

Publication

SU‐FF‐J‐30: Experimental Investigation of Moving Average Algorithm for Tracking Organ Motion

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181322

Publication

TU-C-214-04: Prototype of a Real-Time Adaptive Therapy System Integrating Automatic Soft Tissue Localization with Dynamic Multileaf Collimator (DMLC) Adaptation

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3613136

Publication

Reconstruction of implanted marker trajectories from cone-beam CT projection images using interdimensional correlation modeling

Publisher: Wiley

Date: 18-07-2016

DOI: 10.1118/1.4958678

Abstract: Cone-beam CT (CBCT) is a widely used imaging modality for image-guided radiotherapy. Most vendors provide CBCT systems that are mounted on a linac gantry. Thus, CBCT can be used to estimate the actual 3-dimensional (3D) position of moving respiratory targets in the thoracic/abdominal region using 2D projection images. The authors have developed a method for estimating the 3D trajectory of respiratory-induced target motion from CBCT projection images using interdimensional correlation modeling. Because the superior-inferior (SI) motion of a target can be easily analyzed on projection images of a gantry-mounted CBCT system, the authors investigated the interdimensional correlation of the SI motion with left-right and anterior-posterior (AP) movements while the gantry is rotating. A simple linear model and a state-augmented model were implemented and applied to the interdimensional correlation analysis, and their performance was compared. The parameters of the interdimensional correlation models were determined by least-square estimation of the 2D error between the actual and estimated projected target position. The method was validated using 160 3D tumor trajectories from 46 thoracic/abdominal cancer patients obtained during CyberKnife treatment. The authors' simulations assumed two application scenarios: (1) retrospective estimation for the purpose of moving tumor setup used just after volumetric matching with CBCT and (2) on-the-fly estimation for the purpose of real-time target position estimation during gating or tracking delivery, either for full-rotation volumetric-modulated arc therapy (VMAT) in 60 s or a stationary six-field intensity-modulated radiation therapy (IMRT) with a beam delivery time of 20 s. For the retrospective CBCT simulations, the mean 3D root-mean-square error (RMSE) for all 4893 trajectory segments was 0.41 mm (simple linear model) and 0.35 mm (state-augmented model). In the on-the-fly simulations, prior projections over more than 60° appear to be necessary for reliable estimations. The mean 3D RMSE during beam delivery after the simple linear model had established with a prior 90° projection data was 0.42 mm for VMAT and 0.45 mm for IMRT. The proposed method does not require any internal/external correlation or statistical modeling to estimate the target trajectory and can be used for both retrospective image-guided radiotherapy with CBCT projection images and real-time target position monitoring for respiratory gating or tracking.

Publication

4D Treatment Planning

Publisher: Springer Berlin Heidelberg

Date: 2006

DOI: 10.1007/3-540-30356-1_21

Publication

Adapting to the motion of multiple independent targets using multileaf collimator tracking for locally advanced prostate cancer: Proof of principle simulation study

Publisher: Wiley

Date: 23-11-2020

DOI: 10.1002/MP.14572

Publication

Toward the development of intrafraction tumor deformation tracking using a dynamic multi-leaf collimator

Publisher: Wiley

Date: 05-05-2014

DOI: 10.1118/1.4873682

Publication

Using intrinsic and contextual information associated with automated signal detections to improve call recognizer performance: A case study using the cryptic and critically endangered Night Parrot

Publisher: Wiley

Date: 25-09-2020

DOI: 10.1111/2041-210X.13475

Publication

SU‐E‐J‐139: Real‐Time Motion Management Will Increase the Patient Population Eligible for Lung SBRT

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4814351

Publication

Audiovisual biofeedback guided breath-hold improves lung tumor position reproducibility and volume consistency

Publisher: Elsevier BV

Date: 07-1970

DOI: 10.1016/J.ADRO.2017.03.002

Publication

Breathing guidance in radiation oncology and radiology: A systematic review of patient and healthy volunteer studies

Publisher: Wiley

Date: 24-08-2015

DOI: 10.1118/1.4928488

Abstract: The advent of image-guided radiation therapy has led to dramatic improvements in the accuracy of treatment delivery in radiotherapy. Such advancements have highlighted the deleterious impact tumor motion can have on both image quality and radiation treatment delivery. One approach to reducing tumor motion irregularities is the use of breathing guidance systems during imaging and treatment. These systems aim to facilitate regular respiratory motion which in turn improves image quality and radiation treatment accuracy. A review of such research has yet to be performed it was therefore their aim to perform a systematic review of breathing guidance interventions within the fields of radiation oncology and radiology. From August 1-14, 2014, the following online databases were searched: Medline, Embase, PubMed, and Web of Science. Results of these searches were filtered in accordance to a set of eligibility criteria. The search, filtration, and analysis of articles were conducted in accordance with preferred reporting items for systematic reviews and meta-analyses. Reference lists of included articles, and repeat authors of included articles, were hand-searched. The systematic search yielded a total of 480 articles, which were filtered down to 27 relevant articles in accordance to the eligibility criteria. These 27 articles detailed the intervention of breathing guidance strategies in controlled studies assessing its impact on such outcomes as breathing regularity, image quality, target coverage, and treatment margins, recruiting either healthy adult volunteers or patients with thoracic or abdominal lesions. In 21/27 studies, significant (p < 0.05) improvements from the use of breathing guidance were observed. There is a trend toward the number of breathing guidance studies increasing with time, indicating a growing clinical interest. The results found here indicate that further clinical studies are warranted that quantify the clinical impact of breathing guidance, along with the health technology assessment to determine the advantages and disadvantages of breathing guidance.

Publication

Magnetization curves of sintered heavy tungsten alloys for applications in MRI‐guided radiotherapy

Publisher: Wiley

Date: 09-05-2014

DOI: 10.1118/1.4873679

Abstract: Due to the current interest in MRI-guided radiotherapy, the magnetic properties of the materials commonly used in radiotherapy are becoming increasingly important. In this paper, measurement results for the magnetization (BH) curves of a range of sintered heavy tungsten alloys used in radiation shielding and collimation are presented. Sintered heavy tungsten alloys typically contain >90% tungsten and <10% of a combination of iron, nickel, and copper binders. S les of eight different grades of sintered heavy tungsten alloys with varying binder content were investigated. Using a superconducting quantum interference detector magnetometer, the induced magnetic moment m was measured for each s le as a function of applied external field H0 and the BH curve derived. The iron content of the alloys was found to play a dominant role, directly influencing the magnetization M and thus the nonlinearity of the BH curve. Generally, the saturation magnetization increased with increasing iron content of the alloy. Furthermore, no measurable magnetization was found for all alloys without iron content, despite containing up to 6% of nickel. For two s les from different manufacturers but with identical quoted nominal elemental composition (95% W, 3.5% Ni, 1.5% Fe), a relative difference in the magnetization of 11%-16% was measured. The measured curves show that the magnetic properties of sintered heavy tungsten alloys strongly depend on the iron content, whereas the addition of nickel in the absence of iron led to no measurable effect. Since a difference in the BH curves for two s les with identical quoted nominal composition from different manufacturers was observed, measuring of the BH curve for each in idual batch of heavy tungsten alloys is advisable whenever accurate knowledge of the magnetic properties is crucial. The obtained BH curves can be used in FEM simulations to predict the magnetic impact of sintered heavy tungsten alloys.

Publication

SU‐E‐J‐142: Respiratory Guidance for Lung Cancer Patients: An Investigation of Audiovisual Biofeedback Training and Effectiveness

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4814354

Publication

WE‐C‐116‐05: Residual Respiratory Motion Management Within a Gating Window Using Quasi‐Breath‐Hold (QBH) Biofeedback

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815567

Publication

Real‐time intrafraction prostate motion during linac based stereotactic radiotherapy with rectal displacement

Publisher: Wiley

Date: 27-09-2017

DOI: 10.1002/ACM2.12195

Publication

Quantification of lung tumor rotation with automated landmark extraction using orthogonal cine MRI images

Publisher: IOP Publishing

Date: 03-09-2015

DOI: 10.1088/0031-9155/60/18/7165

Abstract: The quantification of tumor motion in sites affected by respiratory motion is of primary importance to improve treatment accuracy. To account for motion, different studies analyzed the translational component only, without focusing on the rotational component, which was quantified in a few studies on the prostate with implanted markers. The aim of our study was to propose a tool able to quantify lung tumor rotation without the use of internal markers, thus providing accurate motion detection close to critical structures such as the heart or liver. Specifically, we propose the use of an automatic feature extraction method in combination with the acquisition of fast orthogonal cine MRI images of nine lung patients. As a preliminary test, we evaluated the performance of the feature extraction method by applying it on regions of interest around (i) the diaphragm and (ii) the tumor and comparing the estimated motion with that obtained by (i) the extraction of the diaphragm profile and (ii) the segmentation of the tumor, respectively. The results confirmed the capability of the proposed method in quantifying tumor motion. Then, a point-based rigid registration was applied to the extracted tumor features between all frames to account for rotation. The median lung rotation values were -0.6 ± 2.3° and -1.5 ± 2.7° in the sagittal and coronal planes respectively, confirming the need to account for tumor rotation along with translation to improve radiotherapy treatment.

Publication

Motion prediction in MRI-guided radiotherapy based on interleaved orthogonal cine-MRI

Publisher: IOP Publishing

Date: 07-01-2016

DOI: 10.1088/0031-9155/61/2/872

Abstract: In-room cine-MRI guidance can provide non-invasive target localization during radiotherapy treatment. However, in order to cope with finite imaging frequency and system latencies between target localization and dose delivery, tumour motion prediction is required. This work proposes a framework for motion prediction dedicated to cine-MRI guidance, aiming at quantifying the geometric uncertainties introduced by this process for both tumour tracking and beam gating. The tumour position, identified through scale invariant features detected in cine-MRI slices, is estimated at high-frequency (25 Hz) using three independent predictors, one for each anatomical coordinate. Linear extrapolation, auto-regressive and support vector machine algorithms are compared against systems that use no prediction or surrogate-based motion estimation. Geometric uncertainties are reported as a function of image acquisition period and system latency. Average results show that the tracking error RMS can be decreased down to a [0.2 1.2] mm range, for acquisition periods between 250 and 750 ms and system latencies between 50 and 300 ms. Except for the linear extrapolator, tracking and gating prediction errors were, on average, lower than those measured for surrogate-based motion estimation. This finding suggests that cine-MRI guidance, combined with appropriate prediction algorithms, could relevantly decrease geometric uncertainties in motion compensated treatments.

Publication

Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI‐linac therapy

Publisher: Wiley

Date: 07-10-2016

DOI: 10.1118/1.4963216

Publication

Technical Note: Experimental results from a prototype high‐field inline MRI‐linac

Publisher: Wiley

Date: 24-08-2016

DOI: 10.1118/1.4961395

Abstract: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enabling shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom (2) the noise as a function of beam state measured using a 6-channel surface coil array and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.

Publication

A novel electron accelerator for MRI‐Linac radiotherapy

Publisher: Wiley

Date: 17-02-2016

DOI: 10.1118/1.4941309

Abstract: MRI guided radiotherapy is a rapidly growing field however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI‐Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in‐line MRI‐Linac systems. Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m the impact on the electron beam was quantified. For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full‐width‐tenth‐maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in‐line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in‐line magnetic fields. This would enable the development of MRI‐Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of magnetic fringe field, simplify design of the high‐field magnet, and increase system flexibility.

Publication

SU‐FF‐J‐164: A Calibration Method for Positioning Small Animal Radiotherapy Subjects Using MicroCT

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181457

Publication

Minimizing 4DCBCT imaging dose and scan time with Respiratory Motion Guided 4DCBCT: a pre-clinical investigation

Publisher: IOP Publishing

Date: 28-01-2021

DOI: 10.1088/2057-1976/ABDC82

Abstract: Current conventional 4D Cone Beam Computed Tomography (4DCBCT) imaging is h ered by inconsistent patient breathing that leads to long scan times, reduced image quality and high imaging dose. To address these limitations, Respiratory Motion Guided 4D cone beam computed tomography (RMG-4DCBCT) uses mathematical optimization to adapt the gantry rotation speed and projection acquisition rate in real-time in response to changes in the patient’s breathing rate. Here, RMG-4DCBCT is implemented on an Elekta Synergy linear accelerator to determine the minimum achievable imaging dose. 8 patient-measured breathing traces were programmed into a 1D motion stage supporting a 3D-printed anthropomorphic thorax phantom. The respiratory phase and current gantry position were calculated in real-time with the RMG-4DCBCT software, which in turn modulated the gantry rotation speed and suppressed projection acquisition. Specifically, the effect of acquiring 20, 25, 30, 35 and 40 projections/respiratory phase bin RMG scans on scan time and image quality was assessed. Reconstructed image quality was assessed via the contrast-to-noise ratio (CNR) and the Edge Response Width (ERW) metrics. The performance of the system in terms of gantry control accuracy was also assessed via an analysis of the angular separation between adjacent projections. The median CNR increased linearly from 5.90 (20 projections/bin) to 8.39 (40 projections/bin). The ERW did not significantly change from 1.08 mm (20 projections/bin) to 1.07 mm (40 projections/bin), indicating the sharpness is not dependent on the total number of projections acquired. Scan times increased with increasing total projections and slower breathing rates. Across all 40 RMG-4DCBCT scans performed, the average difference in the acquired and desired angular separation between projections was 0.64°. RMG-4DCBCT provides the opportunity to enable fast low-dose 4DCBCT (∼70 s, 200 projections), without compromising on current clinical image quality.

Publication

Image‐based retrospective 4D MRI in external beam radiotherapy: A comparative study with a digital phantom

Publisher: Wiley

Date: 28-05-2018

DOI: 10.1002/MP.12965

Abstract: Several image-based retrospective sorting methods of 4D magnetic resonance imaging (4D MRI) have been proposed for respiratory motion reconstruction in external beam radiotherapy. However, the optimal strategy for providing accurate and artifact-free 4D MRI, ideally corresponding to an average breathing cycle, is not yet defined. This study presents a proactive comparison of three published image-based sorting methods, to define a groundwork for benchmarking in 4D MRI. Three published 4D MRI methods were selected for image retrospective sorting: body area, mutual information, and navigator slice. The three image-based methods were compared against a conventional retrospective sorting method based on an external surrogate. Comparisons were performed by means of an MRI digital phantom, derived from the XCAT CT phantom generated with different patient-derived signals, for a total of 12 cases. Specific multislice MRI acquisitions were simulated for slice sorting and sagittal, coronal, and axial orientations were tested. An average 4D cycle was generated as ground truth. In idual and grouped patient analyses showed better performance of the navigator slice and mutual information in litude binning with respect to the body area strategy. Binning artifacts were reduced on the diaphragm with the slice navigator method due to the acquired internal information. Tumor motion description accurately matched the ground truth in the mutual information strategy with litude binning. The body area method followed the performance of the external surrogate and presented larger errors, since was not correlated with the internal anatomy. Sagittal and coronal orientations reported lower errors than axial slicing. In idual analysis showed the need of a patient-specific evaluation for the selection of the best method. A comparison between three different image-based retrospective sorting methods for 4D MRI is proposed, providing guidelines for benchmark definition in MRI-guided radiotherapy.

Publication

SU‐D‐110‐04: Visual Biofeedback Combined with MRI for Respiratory‐Gated MR Imaging

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3611540

Publication

DMLC motion tracking of moving targets for intensity modulated arc therapy treatment – a feasibility study

Publisher: Informa UK Limited

Date: 2009

DOI: 10.1080/02841860802266722

Abstract: Intensity modulated arc therapy offers great advantages with the capability of delivering a fast and highly conformal treatment. However, moving targets represent a major challenge. By monitoring a moving target it is possible to make the beam follow the motion, shaped by a Dynamic MLC (DMLC). The aim of this work was to evaluate the dose delivered to moving targets using the RapidArc (Varian Medical Systems, Inc.) technology with and without a DMLC tracking algorithm. A Varian Clinac iX was equipped with a preclinical RapidArc and a 3D DMLC tracking application. A motion platform was placed on the couch, with the detectors on top: a PTW seven29 and a Scandidos Delta4. One lung plan and one prostate plan were delivered. Motion was monitored using a Real-time Position Management (RPM) system. Reference measurements were performed for both plans with both detectors at state (0) "static, no tracking". Comparing measurements were made at state (1) "motion, no tracking" and state (2) "motion, tracking". Gamma analysis showed a significant improvement from measurements of state (1) to measurements of state (2) compared to the state (0) measurements: Lung plan from 87 to 97% pass. Prostate plan from 81 to 88% pass. Sub-beam information gave a much reduced pattern of periodically spatial deviating dose points for state (2) than for state (1). Iso-dose curve comparisons showed a slightly better agreement between state (0) and state (2) than between state (0) and state (1). DMLC tracking together with RapidArc make a feasible combination and is capable of improving the dose distribution delivered to a moving target. It seems to be of importance to minimize noise influencing the tracking, to gain the full benefit from the application.

Publication

SU‐FF‐J‐162: In Vivo Biological Evaluation of Micro‐CT Based 3D Conformal Radiotherapy System

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181455

Publication

Toward improved 3D carotid artery imaging with Adaptive CaRdiac cOne BEAm computed Tomography (ACROBEAT)

Publisher: Wiley

Date: 10-2020

DOI: 10.1002/MP.14462

Publication

Imaging performance of a dedicated radiation transparent RF coil on a 1.0 Tesla inline MRI-linac

Publisher: IOP Publishing

Date: 25-06-2018

DOI: 10.1088/1361-6560/AAC813

Abstract: This work describes the first imaging studies on a 1.0 Tesla inline MRI-Linac using a dedicated transmit/receive RF body coil that has been designed to be completely radio transparent and provide optimum imaging performance over a large patient opening. A series of experiments was performed on the MRI-Linac to investigate the performance and imaging characteristics of a new dedicated volumetric RF coil: (1) numerical electromagnetic simulations were used to measure transmit efficiency in two patient positions (2) image quality metrics of signal-to-noise ratio (SNR), ghosting and uniformity were assessed in a large diameter phantom with no radiation beam (3) radiation induced effects were investigated in both the raw data (k-space) and image sequences acquired with simultaneous irradiation (4) radiation dose was measured with and without image acquisition (5) RF heating was studied using an MR-compatible fluoroptic thermometer and (6) the in vivo image quality and versatility of the coil was demonstrated in normal healthy subjects for both supine and standing positions. Daily phantom measurements demonstrated excellent imaging performance with stable SNR over a period of 3 months (42.6 ± 0.9). Simultaneous irradiation produced no statistical change in image quality (p > 0.74) and no interference in raw data for a 20 × 20 cm radiation field. The coil was found to be efficient over large volumes and negligible RF heating was observed. Volunteer scans acquired in both supine and standing positions provided artefact free images with good anatomical visualisation. The first completely radio transparent RF coil for use on a 1.0 Tesla MRI-Linac has been described. There is no impact on either the imaging or dosimetry performance with a simultaneous radiation beam. The open design enables imaging and radiotherapy guidance in a variety of positons.

Publication

SU-GG-J-21: Accuracy in the Localization of Thoracic Tumors Using Respiratory Displacement, Velocity, and Phase

Publisher: Wiley

Date: 06-2008

DOI: 10.1118/1.2961578

Publication

Innovative detectors for quality assurance dosimetry in SBRT of stationary and movable targets

Publisher: IOP Publishing

Date: 2017

DOI: 10.1088/1742-6596/777/1/012014

Publication

SU‐FF‐J‐158: An Open Source Software Tool for Treatment Planning for Small Animal Conformal Radiotherapy

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181451

Publication

Modeling the TrueBeam linac using a CAD to Geant4 geometry implementation: Dose and IAEA‐compliant phase space calculations

Publisher: Wiley

Date: 20-06-2011

DOI: 10.1118/1.3598439

Abstract: To create an accurate 6 MV Monte Carlo simulation phase space for the Varian TrueBeam treatment head geometry imported from CAD (computer aided design) without adjusting the input electron phase space parameters. GEANT4 v4.9.2.p01 was employed to simulate the 6 MV beam treatment head geometry of the Varian TrueBeam linac. The electron tracks in the linear accelerator were simulated with Parmela, and the obtained electron phase space was used as an input to the Monte Carlo beam transport and dose calculations. The geometry components are tessellated solids included in GEANT4 as GDML (generalized dynamic markup language) files obtained via STEP (standard for the exchange of product) export from Pro/Engineering, followed by STEP import in Fastrad, a STEP-GDML converter. The linac has a compact treatment head and the small space between the shielding collimator and the ergent are of the upper jaws forbids the implementation of a plane for storing the phase space. Instead, an IAEA (International Atomic Energy Agency) compliant phase space writer was implemented on a cylindrical surface. The simulation was run in parallel on a 1200 node Linux cluster. The 6 MV dose calculations were performed for field sizes varying from 4 x 4 to 40 x 40 cm2. The voxel size for the 60 x 60 x 40 cm3 water phantom was 4 x 4 x 4 mm3. For the 10 x 10 cm2 field, surface buildup calculations were performed using 4 x 4 x 2 mm3 voxels within 20 mm of the surface. For the depth dose curves, 98% of the calculated data points agree within 2% with the experimental measurements for depths between 2 and 40 cm. For depths between 5 and 30 cm, agreement within 1% is obtained for 99% (4 x 4), 95% (10 x 10), 94% (20 x 20 and 30 x 30), and 89% (40 x 40) of the data points, respectively. In the buildup region, the agreement is within 2%, except at 1 mm depth where the deviation is 5% for the 10 x 10 cm2 open field. For the lateral dose profiles, within the field size for fields up to 30 x 30 cm2, the agreement is within 2% for depths up to 10 cm. At 20 cm depth, the in-field maximum dose difference for the 30 x 30 cm2 open field is within 4%, while the smaller field sizes agree within 2%. Outside the field size, agreement within 1% of the maximum dose difference is obtained for all fields. The calculated output factors varied from 0.938 +/- 0.015 for the 4 x 4 cm2 field to 1.088 +/- 0.024 for the 40 x 40 cm2 field. Their agreement with the experimental output factors is within 1%. The authors have validated a GEANT4 simulated IAEA-compliant phase space of the TrueBeam linac for the 6 MV beam obtained using a high accuracy geometry implementation from CAD. These files are publicly available and can be used for further research.

Publication

The dosimetric error due to uncorrected tumor rotation during real‐time adaptive prostate stereotactic body radiation therapy

Publisher: Wiley

Date: 28-11-2022

DOI: 10.1002/MP.16094

Abstract: During prostate stereotactic body radiation therapy (SBRT), prostate tumor translational motion may deteriorate the planned dose distribution. Most of the major advances in motion management to date have focused on correcting this one aspect of the tumor motion, translation. However, large prostate rotation up to 30° has been measured. As the technological innovation evolves toward delivering increasingly precise radiotherapy, it is important to quantify the clinical benefit of translational and rotational motion correction over translational motion correction alone. The purpose of this work was to quantify the dosimetric impact of intrafractional dynamic rotation of the prostate measured with a six degrees‐of‐freedom tumor motion monitoring technology. The delivered dose was reconstructed including (a) translational and rotational motion and (b) only translational motion of the tumor for 32 prostate cancer patients recruited on a 5‐fraction prostate SBRT clinical trial. Patients on the trial received 7.25 Gy in a treatment fraction. A 5 mm clinical target volume (CTV) to planning target volume (PTV) margin was applied in all directions except the posterior direction where a 3 mm expansion was used. Prostate intrafractional translational motion was managed using a gating strategy, and any translation above the gating threshold was corrected by applying an equivalent couch shift. The residual translational motion is denoted as . Prostate intrafractional rotational motion was recorded but not corrected. The dose differences from the planned dose due to + , ΔD( + ) and due to alone, ΔD(), were then determined for CTV D98, PTV D95, bladder V6Gy, and rectum V6Gy. The residual dose error due to uncorrected rotation, was then quantified: = ΔD( + ) ‐ ΔD(). Fractional data analysis shows that the dose differences from the plan (both ΔD( + ) and ΔD()) for CTV D98 was less than 5% in all treatment fractions. ΔD( + ) was larger than 5% in one fraction for PTV D95, in one fraction for bladder V6Gy, and in five fractions for rectum V6Gy. Uncorrected rotation, induced residual dose error, , resulted in less dose to CTV and PTV in 43% and 59% treatment fractions, respectively, and more dose to bladder and rectum in 51% and 53% treatment fractions, respectively. The cumulative dose over five fractions, ∑D( + ) and ∑D(), was always within 5% of the planned dose for all four structures for every patient. The dosimetric impact of tumor rotation on a large prostate cancer patient cohort was quantified in this study. These results suggest that the standard 3–5 mm CTV‐PTV margin was sufficient to account for the intrafraction prostate rotation observed for this cohort of patients, provided an appropriate gating threshold was applied to correct for translational motion. Residual dose errors due to uncorrected prostate rotation were small in magnitude, which may be corrected using different treatment adaptation strategies to further improve the dosimetric accuracy.

Publication

TH-A-WAB-03: Radiation Dose Changes Pulmonary Function Measured by 4D-CT Ventilation Imaging

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815697

Publication

Results from the AAPM Task Group 324 respiratory motion management in radiation oncology survey

Publisher: Wiley

Date: 31-10-2022

DOI: 10.1002/ACM2.13810

Abstract: To quantify the clinical practice of respiratory motion management in radiation oncology. A respiratory motion management survey was designed and conducted based on clinician survey guidelines. The survey was administered to American Association of Physicists in Medicine (AAPM) members on 17 August 2020 and closed on 13 September 2020. A total of 527 respondents completed the entire survey and 651 respondents completed part of the survey, with the partially completed surveys included in the analysis. Overall, 84% of survey respondents used deep inspiration breath hold for left‐sided breast cancer. Overall, 83% of respondents perceived respiratory motion management for thoracic and abdominal cancer radiotherapy patients to be either very important or required. Overall, 95% of respondents used respiratory motion management for thoracic and abdominal sites, with 36% of respondents using respiratory motion management for at least 90% of thoracic and abdominal patients. The majority (60%) of respondents used the internal target volume method to treat thoracic and abdominal cancer patients, with 25% using breath hold or abdominal compression and 13% using gating or tracking. A respiratory motion management survey has been completed by AAPM members. Respiratory motion management is generally considered very important or required and is widely used for breast, thoracic, and abdominal cancer treatments.

Publication

A novel semiautomated method for background activity and biological tumour volume definition to improve standardisation of 18F-FET PET imaging in glioblastoma

Publisher: Springer Science and Business Media LLC

Date: 05-02-2022

DOI: 10.1186/S40658-022-00438-2

Abstract: Multicentre clinical trials evaluating the role of 18 F-Fluoroethyl- l -tyrosine ( 18 F-FET) PET as a diagnostic biomarker in glioma management have highlighted a need for standardised methods of data analysis. 18 F-FET uptake normalised against background in the contralateral brain is a standard imaging technique to delineate the biological tumour volume (BTV). Quantitative analysis of 18 F-FET PET images requires a consistent and robust background activity. Currently, defining background activity involves the manual selection of an arbitrary region of interest, a process that is subject to large variability. This study aims to eliminate methodological errors in background activity definition through the introduction of a semiautomated method for region of interest selection. A new method for background activity definition, involving the semiautomated generation of mirror-image (MI) reference regions, was compared with the current state-of-the-art method, involving manually drawing crescent-shape (gCS) reference regions. The MI and gCS methods were tested by measuring values of background activity and resulting BTV of 18 F-FET PET scans of ten patients with recurrent glioblastoma multiforme generated from inputs provided by seven readers. To assess intra-reader variability, each scan was evaluated six times by each reader. Intra- and inter-reader variability in background activity and BTV definition was assessed by means of coefficient of variation. Compared to the gCS method, the MI method showed significantly lower intra- and inter-reader variability both in background activity and in BTV definition. The proposed semiautomated MI method minimises intra- and inter-reader variability, providing a valuable approach for standardisation of 18 F-FET PET quantitative parameters. Trial registration ANZCTR, ACTRN12618001346268. Registered 9 August 2018, www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374253

Publication

Deep learning enables MV-based real-time image guided radiation therapy for prostate cancer patients

Publisher: IOP Publishing

Date: 26-04-2023

DOI: 10.1088/1361-6560/ACC77C

Abstract: Objective . Using MV images for real-time image guided radiation therapy (IGRT) is ideal as it does not require additional imaging equipment, adds no additional imaging dose and provides motion data in the treatment beam frame of reference. However, accurate tracking using MV images is challenging due to low contrast and modulated fields. Here, a novel real-time marker tracking system based on a convolutional neural network (CNN) classifier was developed and evaluated on retrospectively acquired patient data for MV-based IGRT for prostate cancer patients. Approach . MV images, acquired from 29 volumetric modulated arc therapy (VMAT) prostate cancer patients treated in a multi-institutional clinical trial, were used to train and evaluate a CNN-based marker tracking system. The CNN was trained using labelled MV images from 9 prostate cancer patients (35 fractions) with implanted markers. CNN performance was evaluated on an independent cohort of unseen MV images from 20 patients (78 fractions), using a Precision–Recall curve (PRC), area under the PRC plot (AUC) and sensitivity and specificity. The accuracy of the tracking system was evaluated on the same unseen dataset and quantified by calculating mean absolute (±1 SD) and [1st, 99th] percentiles of the geometric tracking error in treatment beam co-ordinates using manual identification as the ground truth. Main results . The CNN had an AUC of 0.99, sensitivity of 98.31% and specificity of 99.87%. The mean absolute geometric tracking error was 0.30 ± 0.27 and 0.35 ± 0.31 mm in the lateral and superior–inferior directions of the MV images, respectively. The [1st, 99th] percentiles of the error were [−1.03, 0.90] and [−1.12, 1.12] mm in the lateral and SI directions, respectively. Significance . The high classification performance on unseen MV images demonstrates the CNN can successfully identify implanted prostate markers. Furthermore, the sub-millimetre accuracy and precision of the marker tracking system demonstrates potential for adaptation to real-time applications.

Publication

The internal–external respiratory motion correlation is unaffected by audiovisual biofeedback

Publisher: Springer Science and Business Media LLC

Date: 08-02-2014

DOI: 10.1007/S13246-014-0247-Z

Abstract: This study evaluated if an audiovisual (AV) biofeedback causes variation in the level of external and internal correlation due to its interactive intervention in natural breathing. The internal (diaphragm) and external (abdominal wall) respiratory motion signals of 15 healthy human subjects under AV biofeedback and free breathing (FB) were analyzed and measures of correlation and regularity taken. Regularity metrics (root mean square error and spectral power dispersion metric) were obtained and the correlation between these metrics and the internal and external correlation was investigated. For FB and AV biofeedback assisted breathing the mean correlations found between internal and external respiratory motion were 0.96±0.02 and 0.96±0.03, respectively. This means there is no evidence to suggest (p-value=0.88) any difference in the correlation between internal and external respiratory motion with the use of AV biofeedback. Our results confirmed the hypothesis that the internal-external correlation with AV biofeedback is the same as for free breathing. Should this correlation be maintained for patients, AV biofeedback can be implemented in the clinic with confidence as regularity improvements using AV biofeedback with an external signal will be reflected in increased internal motion regularity.

Publication

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.

Publication

TU‐B‐204B‐02: A Study of the Effect of Inline and Perpendicular Magnetic Fields on Beam Characteristics of Medical Linear Accelerator Electron Guns

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469191

Publication

Six Degrees-of-Freedom Prostate and Lung Tumor Motion Measurements Using Kilovoltage Intrafraction Monitoring

Publisher: Elsevier BV

Date: 02-2015

DOI: 10.1016/J.IJROBP.2014.09.040

Abstract: Tumor positional uncertainty has been identified as a major issue that deteriorates the efficacy of radiation therapy. Tumor rotational movement, which is not well understood, can result in significant geometric and dosimetric inaccuracies. The objective of this study was to measure 6 degrees-of-freedom (6 DoF) prostate and lung tumor motion, focusing on the more novel rotation, using kilovoltage intrafraction monitoring (KIM). Continuous kilovoltage (kV) projections of tumors with gold fiducial markers were acquired during radiation therapy for 267 fractions from 10 prostate cancer patients and immediately before or after radiation therapy for 50 fractions from 3 lung cancer patients. The 6 DoF motion measurements were determined from the in idual 3-dimensional (3D) marker positions, after using methods to reject spurious and smooth noisy data, using an iterative closest point algorithm. There were large variations in the magnitude of the tumor rotation among different fractions and patients. Various rotational patterns were observed. The average prostate rotation angles around the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) axes were 1.0 ± 5.0°, 0.6 ± 3.3°, and 0.3 ± 2.0°, respectively. For 35% of the time, the prostate rotated more than 5° about the LR axis, indicating the need for intrafractional adaptation during radiation delivery. For lung patients, the average LR, SI, and AP rotation angles were 0.8 ± 4.2°, -0.8 ± 4.5°, and 1.7 ± 3.1°, respectively. For about 30% of the time, the lung tumors rotated more than 5° around the SI axis. Respiration-induced rotation was detected in 2 of the 3 lung patients. The prostate and lung tumors were found to undergo rotations of more than 5° for about a third of the time. The lung tumor data represent the first 6 DoF tumor motion measured by kV images. The 6 DoF KIM method can enable rotational and translational adaptive radiation therapy and potentially reduce treatment margins.

Publication

Introduction and a Word of Thanks

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3183407

Publication

CT ventilation functional image-based IMRT treatment plans are comparable to SPECT ventilation functional image-based plans

Publisher: Elsevier BV

Date: 03-2016

DOI: 10.1016/J.RADONC.2016.02.019

Abstract: To investigate the hypothesis that CT ventilation functional image-based IMRT plans designed to avoid irradiating highly-functional lung regions are comparable to single-photon emission CT (SPECT) ventilation functional image-based plans. Three IMRT plans were created for eight thoracic cancer patients using: (1) CT ventilation functional images, (2) SPECT ventilation functional images, and (3) anatomic images (no functional images). CT ventilation images were created by deformable image registration of 4D-CT image data sets and quantitative analysis. The resulting plans were analyzed for the relationship between the deviations of CT-functional plan metrics from anatomic plan metrics (ΔCT-anatomic) and those of SPECT-functional plans (ΔSPECT-anatomic), and moreover for agreements of various metrics between the CT-functional and SPECT-functional plans. The relationship between ΔCT-anatomic and ΔSPECT-anatomic was strong (e.g., R=0.94 linear regression slope 0.71). The average differences and 95% limits of agreement between the CT-functional and SPECT-functional plan metrics (except for monitor units) for various structures were mostly less than 1% and 2%, respectively. This study demonstrated a reasonable agreement between the CT ventilation functional image-based IMRT plans and SPECT-functional plans, suggesting the potential for CT ventilation imaging to serve as a surrogate for SPECT ventilation in functional image-guided radiotherapy.

Publication

Patient reported outcomes of slow, single arc rotation: Do we need rotating gantries?

Publisher: Wiley

Date: 15-11-2017

DOI: 10.1111/1754-9485.12688

Abstract: Patient rotation could greatly simplify radiation therapy delivery, with particularly important ramifications for fixed beam treatment with protons, heavy ions, MRI-Linacs, and low cost Linacs. Patient tolerance is often cited as a barrier to widespread implementation to patient rotation however, no quantitative data addressing this issue exists. In this study, patient reported experiences of slow, single arc rotation in upright (sitting) and lying orientations are reported. Fifteen patients currently or previously treated for cancer were slowly (~2 rpm) rotated in upright and lying orientations using an existing medical device. Patients were rotated 360° in 45° increments. Rotation was paused for 30 seconds at each angle to simulate beam delivery. Claustrophobia, anxiety and motion sickness were monitored via validated questionnaires. The Wilcoxon signed rank test was used to test for significant differences in anxiety and motion sickness before, during and after the study. No significant differences in anxiety or motion sickness were found between before and after the study, or upright and lying rotation (P > 0.05). The median percentage scores for anxiety and motion sickness immediately following the study were both 0. In general, anxiety and motion sickness scores were low throughout the study. All patients except one completed the study. Slow, single arc rotation in upright and lying orientations was well tolerated in this study. These results support the need for further studies into the clinical implementation of patient rotation, which could have a major impact on the practice and cost of radiotherapy.

Publication

Investigating the use of machine learning to generate ventilation images from CT scans

Publisher: Wiley

Date: 15-05-2022

DOI: 10.1002/MP.15688

Abstract: Radiotherapy treatment planning incorporating ventilation imaging can reduce the incidence of radiation‐induced lung injury. The gold‐standard of ventilation imaging, using nuclear medicine, has limitations with respect to availability and cost. An alternative type of ventilation imaging to nuclear medicine uses 4DCT (or breath‐hold CT [BHCT] pair) with deformable image registration (DIR) and a ventilation metric to produce a CT ventilation image (CTVI). The purpose of this study is to investigate the application of machine learning as an alternative to DIR‐based methods when producing CTVIs. A patient dataset of 15 inhale and exhale BHCTs and Galligas PET ventilation images were used to train and test a 2D U‐Net style convolutional neural network. The neural network established relationships between axial input BHCT image pairs and axial labeled Galligas PET images and was evaluated using eightfold cross‐validation. Once trained, the neural network could produce a CTVI from an input BHCT image pair. The CTVIs produced by the neural network were qualitatively assessed visually and quantitatively compared to a Galligas PET ventilation image using a Spearman correlation and Dice similarity coefficient (DSC). The DSC measured the spatial overlap between three segmented equal lung volumes by ventilation (high, medium, and low functioning lung [LFL]). The mean Spearman correlation between the CTVIs and the Galligas PET ventilation images was 0.58 ± 0.14. The mean DSC over high, medium, and LFL between the CTVIs and Galligas PET ventilation images was 0.55 ± 0.06. Visually, a systematic overprediction of ventilation within the lung was observed in the CTVIs with respect to the Galligas PET ventilation images, with jagged regions of ventilation in the sagittal and coronal planes. A convolutional neural network was developed that could produce a CTVI from a BHCT image pair, which was then compared with a Galligas PET ventilation image. The performance of this machine learning method was comparable to previous benchmark studies investigating a DIR‐based CTVI, warranting future development, and investigation of applying machine learning to a CTVI.

Publication

A longitudinal four‐dimensional computed tomography and cone beam computed tomography dataset for image‐guided radiation therapy research in lung cancer

Publisher: Wiley

Date: 02-2017

DOI: 10.1002/MP.12059

Publication

Evaluating reconstruction algorithms for respiratory motion guided acquisition

Publisher: IOP Publishing

Date: 31-08-2020

DOI: 10.1088/1361-6560/AB98D3

Publication

The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

Publisher: Wiley

Date: 29-02-2012

DOI: 10.1118/1.3685583

Publication

Dosimetric Optimization and Commissioning of a High Field Inline MRI-Linac

Publisher: Frontiers Media SA

Date: 14-02-2020

DOI: 10.3389/FONC.2020.00136

Publication

Experimental investigation of a moving averaging algorithm for motion perpendicular to the leaf travel direction in dynamic MLC target tracking

Publisher: Wiley

Date: 16-06-2011

DOI: 10.1118/1.3590384

Publication

Dynamic Multileaf Collimator Tracking of Respiratory Target Motion Based on a Single Kilovoltage Imager During Arc Radiotherapy

Publisher: Elsevier BV

Date: 06-2010

DOI: 10.1016/J.IJROBP.2009.08.030

Abstract: To demonstrate and characterize dynamic multileaf collimator (DMLC) tracking of respiratory moving targets that are spatially localized with a single kV X-ray imager during arc radiotherapy. During delivery of an arc field (358 degrees gantry rotation, 72-sec duration, circular field shape), the three-dimensional (3D) position of a fiducial marker in a phantom was estimated in real time from fluoroscopic kV X-ray images acquired orthogonally to the treatment beam axis. A prediction algorithm was applied to account for system latency (570 ms) before the estimated marker position was used for DMLC aperture adaptation. Experiments were performed with 12 patient-measured tumor trajectories that were selected from 160 trajectories (46 patients) and reproduced by a programmable phantom. Offline, the 3D deviation of the estimated phantom position from the actual position was quantified. The two-dimensional (2D) beam-target deviation was quantified as the positional difference between the MLC aperture center and the marker in portal images acquired continuously during experiments. Simulations of imaging and treatment delivery extended the study to all 160 tumor trajectories and to arc treatments of 3-min and 5-min duration. In the experiments, the mean root-mean-square deviation was 1.8 mm for the 3D target position and 1.5 mm for the 2D aperture position. Simulations agreed with this to within 0.1 mm and resulted in mean 2D root-mean-square beam-target deviations of 1.1 mm for all 160 trajectories for all treatment durations. The deviations were mainly caused by system latency (570 ms). Single-imager DMLC tracking of respiratory target motion during arc radiotherapy was implemented, providing less than 2-mm geometric uncertainty for most trajectories.

Publication

The Nano-X Linear Accelerator

Publisher: SAGE Publications

Date: 2014

DOI: 10.7785/TCRT.2012.500436

Abstract: Rapid technological improvements in radiotherapy delivery results in improved outcomes to patients, yet current commercial systems with these technologies on board are costly. The aim of this study was to develop a state-of-the-art cancer radiotherapy system that is economical and space efficient fitting with current world demands. The Nano-X system is a compact design that is light weight combining a patient rotation system with a vertical 6 MV fixed beam. In this paper, we present the Nano-X system design configuration, an estimate of the system dimensions and its potential impact on shielding cost reductions. We provide an assessment of implementing such a radiotherapy system clinically, its advantages and disadvantages compared to a compact conventional gantry rotating linac. The Nano-X system has several differentiating features from current radiotherapy systems, it is [1] compact and therefore can fit into small vaults, [2] light weight, and [3] engineering efficient, i.e., it rotates a relatively light component and the main treatment delivery components are not under rotation ( e.g., DMLCs). All these features can have an impact on reducing the costs of the system. In terms of shielding requirements, leakage radiation was found to be the dominant contributor to the Nano-X vault and as such no primary shielding was necessary. For a low leakage design, the Nano-X vault footprint and concrete volume required is 17 m2 and 35 m3 respectively, compared to 54 m2 and 102 m3 for a conventional compact linac vault, resulting in decreased costs in shielding. Key issues to be investigated in future work are the possible patient comfort concerns associated with the patient rotation system, as well as the magnitude of deformation and subsequent adaptation requirements.

Publication

Technical Note: Real-time image-guided adaptive radiotherapy of a rigid target for a prototype fixed beam radiotherapy system

Publisher: Wiley

Date: 18-09-2018

DOI: 10.1002/MP.13143

Abstract: Fixed beam radiotherapy systems utilize couch movement and rotation instead of gantry rotation in order to simplify linear accelerator design. We investigate the ability to deliver fixed beam treatments with the same level of clinical accuracy as conventional (rotating beam) treatments using real-time image guidance to maintain this accuracy in the presence of rigid target motion. A prototype fixed beam radiotherapy system was built using a standard linac with the beam fixed in the vertical position and a computer controlled rotation stage that rotated a rigid phantom about the superior-inferior axis. Kilovoltage Intrafraction Monitoring (KIM) and real-time beam adaptation with MLC tracking was applied to a five-field IMRT treatment plan with motion introduced to the phantom. The same IMRT treatment was also delivered with real-time adaptation using the conventional rotating beam geometry. Film dosimetry was used to measure the dose delivered with a fixed beam compared to a rotating beam, as well as to compare treatments delivered with and without real-time adaptation. The dose distributions were found to be equivalent between the fixed beam and rotating beam geometry for real-time adaptive radiotherapy using KIM and MLC tracking beam adaptation. Gamma analysis on the films showed agreement >98% using a 2%/2 mm criteria with adaptation for static shifts and periodic motion. Fixed beam treatments with real-time beam adaptation are dosimetrically equivalent to conventional treatments with a rotating beam, even in the presence of rigid target motion. This suggests that, for a rigid target, the high clinical accuracy of real-time adaptive radiotherapy can be achieved with simpler beam geometry.

Publication

TU‐A‐WAB‐08: Strong Evidence for Physiologic Correlation of 4D‐CT Ventilation Imaging with Respiratory‐Correlated Gallium 68 PET/CT in Humans

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815342

Publication

Repeatability of radiotherapy dose-painting prescriptions derived from a multiparametric magnetic resonance imaging model of glioblastoma infiltration

Publisher: Elsevier BV

Date: 07-2022

DOI: 10.1016/J.PHRO.2022.06.004

Publication

SU‐D‐BRB‐01: 4D‐CT Lung Ventilation Images Vary with 4D‐CT Sorting Techniques

Publisher: Wiley

Date: 06-2012

DOI: 10.1118/1.4734673

Abstract: 4D-CT ventilation imaging is a novel promising technique for lung functional imaging and has potential as a biomarker for radiation pneumonitis, but has not been validated in human subjects. The current 4D- CT technique with phase-based sorting results in artifacts at an alarmingly high frequency (90%), which may introduce variations into ventilation calculations. The purpose of this study was to quantify the variability of 4D- CT ventilation imaging to 4D-CT sorting techniques. Two 4D-CT images were generated from the same data set by: (1) phase-based (2) anatomic similarity- and abdominal displacement-based sorting for five patients. Two ventilation image sets (V_phase and V_anat) were then calculated by deformable image registration of peak-exhale and peak-inhale4D-CT images and quantification of regional volume change based on Hounsfield unit change. The variability of 4D-CT ventilation imaging wasquantified using the voxel-based Spearman rank correlation coefficients and Dice similarity coefficients (DSC) for the spatial overlap of segmented low- functional lung regions. The relationship between the abdominal motionrange variation and ventilation variation was also assessed using linearregression. Furthermore, the correlations between V_phase or V_anat and SPECT ventilation images (assumed ground-truth) were compared. In general, displacement- and anatomic similarity-based sorting reduced 4D- CT artifacts compared to phase-based sorting. The voxel-based correlationsbetween V_phase and V_anat were only moderate (range, 0.57-0.77). The DSCs for the low-functional lung regions were moderate to substantial (0.58-0.70). The relationship between the motion range variation and ventilation variation was strong on average (R2=0.79±0.25), suggesting that ventilation variations are related to 4D-CT artifacts. Vanat was found to improve correlations with SPECT ventilation images compared to V_phase. 4D-CT ventilation images vary markedly with 4D-CT sorting techniques. 4D-CT artifacts should be considered as a significant source of variation in 4D-CT ventilation imaging during its validation. This study wassupported in part by NIH/NCI R01 93626. SK and CL are employees ofPhilips Research.

Publication

Image quality in thoracic 4D cone-beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing

Publisher: Wiley

Date: 20-03-2014

DOI: 10.1118/1.4868510

Abstract: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone‐beam CT (4D‐CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors in idually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D‐CBCT for IGRT. Fourteen 4D‐CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real‐time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal‐projection‐density displacement binning), and (iii) reconstruction algorithm [Feldk –Davis–Kress (FDK), McKinnon–Bates (MKB), or adaptive‐steepest‐descent projection‐onto‐convex‐sets (ASD‐POCS)]. The image quality was quantified using signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio, and edge‐response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root‐mean‐squared‐error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality. The choice of respiratory signals was found to have no significant impact on image quality. Displacement‐based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD‐POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR values were found to increase with decreasing RMSE values of projection angular gaps with strong correlations ( r ≈ −0.7) regardless of the reconstruction algorithm used. Based on the authors’ results, displacement‐based binning methods, better reconstruction algorithms, and the acquisition of even projection angular views are the most important factors to consider for improving thoracic 4D‐CBCT image quality. In view of the practical issues with displacement‐based binning and the fact that projection angular spacing is not currently directly controllable, development of better reconstruction algorithms represents the most effective strategy for improving image quality in thoracic 4D‐CBCT for IGRT applications at the current stage.

Publication

Real-time prostate trajectory estimation with a single imager in arc radiotherapy: a simulation study

Publisher: IOP Publishing

Date: 05-06-2009

DOI: 10.1088/0031-9155/54/13/005

Abstract: Real-time prostate tracking during intensity-modulated arc radiotherapy requires a reliable prostate position signal during treatment. Many modern linear accelerators have a single gantry-mounted x-ray imager that could be used for intrafraction imaging of implanted prostate markers. The aim of this study was to develop a method to use such a single x-ray imager to estimate the three-dimensional (3D) prostate position in real time during arc treatment delivery and quantify the accuracy of this method in simulations based on 548 prostate trajectories for 17 patients measured with electromagnetic transponders. Imaging at 0.5, 1, 2 and 5 Hz during 360 degrees arc treatments of 1, 2 and 3 min duration was simulated by projecting the prostate position onto the rotating imager. When an image was acquired, a Gaussian probability density function (PDF) for the prostate position was first estimated by maximum likelihood optimization from the set of images acquired so far and then used to estimate the 3D prostate position from the projected position in the image. Since this method needed a PDF right from the onset of the treatment, an initial PDF was obtained with a series of pre-treatment images acquired in 10 s, 20 s or 30 s during a gantry rotation of 60 degrees , 120 degrees or 180 degrees . The accuracy of the estimations was quantified by calculating the root-mean-square (RMS) estimation error for each simulated treatment. The 3D RMS estimation error had a mean value of 0.22 mm and exceeded 1 mm in 0.8% of the cases for 1 min treatments with 5 Hz imaging and 20 s pre-treatment imaging. The position estimation accuracy degraded slightly with reduced imaging frequency or reduced pre-treatment imaging duration. Prolonged treatment duration of 2 and 3 min increased the mean 3D RMS errors to 0.27 mm and 0.30 mm, respectively. The single-imager trajectory estimation method would allow image-guided real-time prostate tracking based on standard equipment for modern linear accelerators.

Publication

The first patient treatment of computed tomography ventilation functional image-guided radiotherapy for lung cancer

Publisher: Elsevier BV

Date: 02-2016

DOI: 10.1016/J.RADONC.2015.11.006

Abstract: Radiotherapy that selectively avoids irradiating highly-functional lung regions may reduce pulmonary toxicity. We report on the first clinical implementation and patient treatment of lung functional image-guided radiotherapy using an emerging technology, computed tomography (CT) ventilation imaging. A protocol was developed to investigate the safety and feasibility of CT ventilation functional image-guided radiotherapy. CT ventilation imaging is based on (1) deformable image registration of four-dimensional (4D) CT images, and (2) quantitative image analysis for regional volume change, a surrogate for ventilation. CT ventilation functional image-guided radiotherapy plans were designed to minimize specific lung dose-function metrics, including functional V20 (fV20), while maintaining target coverage and meeting standard constraints to other critical organs. CT ventilation functional image-guided treatment planning reduced the lung fV20 by 5% compared to an anatomic image-guided plan for an enrolled patient with stage IIIB non-small cell lung cancer. Although the doses to several other critical organs increased, the necessary constraints were all met. An emerging technology, CT ventilation imaging has been translated into the clinic and used in functional image-guided radiotherapy for the first time. This milestone represents an important first step toward hypothetically reduced pulmonary toxicity in lung cancer radiotherapy.

Publication

Simulated multileaf collimator tracking for stereotactic liver radiotherapy guided by kilovoltage intrafraction monitoring: Dosimetric gain and target overdose trends

Publisher: Elsevier BV

Date: 03-2020

DOI: 10.1016/J.RADONC.2019.11.008

Abstract: To investigate the potential benefit of multileaf collimator (MLC) tracking guided by kilovoltage intrafraction monitoring (KIM) during stereotactic body radiotherapy (SBRT) in the liver, and to understand trends of target overdose with MLC tracking. Six liver SBRT patients with 2-3 implanted gold markers received SBRT delivered with volumetric modulated arc therapy (VMAT) in three fractions using daily cone-beam CT setup. The CTV-to-PTV margins were 5 mm in the axial plane and 10 mm in the cranio-caudal directions, and the plans were designed to give minimum target doses of 95% (CTV) and 67% (PTV). The three-dimensional marker trajectory estimated by post-treatment analysis of kV fluoroscopy images acquired throughout treatment delivery was assumed to represent the tumor motion. MLC tracking guided by real-time KIM was simulated. The reduction in CTV D95 (minimum dose to 95% of the clinical target volume) relative to the planned D95 (ΔD95) was compared between actual non-tracking and simulated MLC tracking treatments. MLC tracking maintained a high CTV dose coverage for all 18 fractions with ΔD95 (mean: 0.2 percentage points (pp), range: -1.7 to 1.9 pp) being significantly lower than for the actual non-tracking treatments (mean: 6.3 pp range: 0.6-16.0 pp) (p = 0.002). MLC tracking of large target motion perpendicular to the MLC leaves created dose artifacts with regions of overdose in the CTV. As a result, the mean dose in spherical volumes centered in the middle of the CTV was on average 2.4 pp (5 mm radius sphere) and 1.3 pp (15 mm radius sphere) higher than planned (p = 0.002). Intrafraction tumor motion can deteriorate the CTV dose of liver SBRT. The planned CTV dose coverage may be restored with KIM-guided MLC tracking. However, MLC tracking may have a tendency to create hotspots in the CTV.

Publication

Audiovisual biofeedback improves diaphragm motion reproducibility in MRI

Publisher: Wiley

Date: 25-10-2012

DOI: 10.1118/1.4761866

Publication

Integration of Real-Time Internal Electromagnetic Position Monitoring Coupled With Dynamic Multileaf Collimator Tracking: An Intensity-Modulated Radiation Therapy Feasibility Study

Publisher: Elsevier BV

Date: 07-2009

DOI: 10.1016/J.IJROBP.2009.01.031

Abstract: Continuous tumor position measurement coupled with a tumor tracking system would result in a highly accurate radiation therapy system. Previous internal position monitoring systems have been limited by fluoroscopic radiation dose and low delivery efficiency. We aimed to incorporate a continuous, electromagnetic, three-dimensional position tracking system (Calypso 4D Localization System) with a dynamic multileaf collimator (DMLC)-based dose delivery system. A research version of the Calypso System provided real-time position of three Beacon transponders. These real-time three-dimensional positions were sent to research MLC controller with a motion-tracking algorithm that changed the planned leaf sequence. Electromagnetic transponders were embedded in a solid water film phantom that moved with patient lung trajectories while being irradiated with two different plans: a step-and-shoot intensity-modulated radiation therapy (S-IMRT) field and a dynamic IMRT (D-IMRT) field. Dosimetric results were recorded under three conditions: no intervention, DMLC tracking, and a spatial gating system. Dosimetric accuracy was comparable for gating and DMLC tracking. Failure rates for gating/DMLC tracking are as follows: +/-3 cGy 10.9/ 7.5% for S-IMRT, 3.3/7.2% for D-IMRT gamma (3mm/3%) 0.2/1.2% for S-IMRT, 0.2/0.2% for D-IMRT. DMLC tracking proved to be as efficient as standard delivery, with a two- to fivefold efficiency increase over gating. Real-time target position information was successfully integrated into a DMLC effector system to modify dose delivery. Experimental results show both comparable dosimetric accuracy as well as improved efficiency compared with spatial gating.

Publication

Comparison of Intensity-Modulated Radiotherapy Planning Based on Manual and Automatically Generated Contours Using Deformable Image Registration in Four-Dimensional Computed Tomography of Lung Cancer

Publisher: Elsevier BV

Date: 02-2008

DOI: 10.1016/J.IJROBP.2007.09.035

Publication

TU‐G‐141‐09: Real Time Estimation of Prostate Tumor Rotation and Translation with a KV Imaging System Based On An Iterative Closest Point Algorithm

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815469

Publication

TU‐G‐141‐08: Impact of Audiovisual Biofeedback Respiratory Training On 4D‐PET Image Quality

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815468

Publication

Rapid and recent range collapse of Australia’s Red Goshawk Erythrotriorchis radiatus

Publisher: Informa UK Limited

Date: 19-02-2023

DOI: 10.1080/01584197.2023.2172735

Publication

Review of Real-Time 3-Dimensional Image Guided Radiation Therapy on Standard-Equipped Cancer Radiation Therapy Systems: Are We at the Tipping Point for the Era of Real-Time Radiation Therapy?

Publisher: Elsevier BV

Date: 11-2018

DOI: 10.1016/J.IJROBP.2018.04.016

Publication

Potential improvements of lung and prostate MLC tracking investigated by treatment simulations

Publisher: Wiley

Date: 06-04-2018

DOI: 10.1002/MP.12868

Abstract: Intrafraction tumor motion during external radiotherapy is a challenge for the treatment accuracy. A novel technique to mitigate the impact of tumor motion is real-time adaptation of the multileaf collimator (MLC) aperture to the motion, also known as MLC tracking. Although MLC tracking improves the dosimetric accuracy, there are still residual errors. Here, we investigate and rank the performance of five prediction algorithms and seven improvements of an MLC tracking system by extensive tracking treatment simulations. An in-house-developed MLC tracking simulator that has been experimentally validated against an electromagnetic-guided MLC tracking system was used to test the prediction algorithms and tracking system improvements. The simulator requires a Dicom treatment plan and a motion trajectory as input and outputs all motion of the accelerator during MLC tracking treatment delivery. For lung tumors, MLC tracking treatments were simulated with a low and a high modulation VMAT plan using 99 patient-measured lung tumor trajectories. For prostate, tracking was also simulated with a low and a high modulation VMAT plan, but with 695 prostate trajectories. For each simulated treatment, the tracking error was quantified as the mean MLC exposure error, which is the sum of the overexposed area (irradiated area that should have been shielded according to the treatment plan) and the underexposed area (shielded area that should have been irradiated). First, MLC tracking was simulated with the current MLC tracking system without prediction, with perfect prediction (Perfect), and with the following five prediction algorithms: linear Kalman filter (Kalman), kernel density estimation (KDE), linear adaptive filtering (LAF), wavelet-based multiscale autoregression (wLMS), and time variant seasonal autoregression (TVSAR). Next, MLC tracking was simulated using the best prediction algorithm and seven different tracking system improvements: no localization signal latency (a), doubled maximum MLC leaf speed (b), halved MLC leaf width (c), use of Y backup jaws to track motion perpendicular to the MLC leaves (d), dynamic collimator rotation for alignment of the MLC leaves with the dominant target motion direction (e), improvements 4 and 5 combined (f), and all improvements combined (g). All results are presented as the mean residual MLC exposure error compared to no tracking. In the prediction study, the residual MLC exposure error was 47.0% (no prediction), 45.1% (Kalman), 43.8% (KDE), 43.7% (LAF), 42.1% (wLMS), 40.1% (TVSAR), and 36.5% (Perfect) for lung MLC tracking. For prostate MLC tracking, it was 66.0% (no prediction), 66.9% (Kalman), and 63.4% (Perfect). For lung with TVSAR prediction, the residual MLC exposure error for the seven tracking system improvements was 37.2%(1), 38.3%(2), 37.4%(3), 34.2%(4), 30.6%(5), 27.7%(6), and 20.7%(7). For prostate with no prediction, the residual MLC exposure error was 61.7%(1), 61.4%(2), 55.4%(3), 57.2%(4), 47.5%(5), 43.7%(6), and 38.7%(7). For prostate, MLC tracking was slightly better without prediction than with linear Kalman filter prediction. For lung, the TVSAR prediction algorithm performed best. Dynamic alignment of the collimator with the dominant motion axis was the most efficient MLC tracking improvement except for lung tracking with the low modulation VMAT plan, where jaw tracking was slightly better.

Publication

WE‐C‐204B‐03: 4D Treatment Delivery to Account for Motion, Rotation, and Deformation of Tumors and Normal Tissues

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469375

Abstract: Purpose : To experimentally investigate 4D treatment delivery to account for motion, rotation, and deformation of tumors and normal tissues. Method and Materials : A 4D treatment plan was generated as a function of respiratory phase for an elliptical tumor that translates, rotates, deforms, and exhibits motion hysteresis throughout the respiratory cycle. A programmable motion platform with a marker block simulates the tumor motion. An independent patient position monitoring system monitors motion of marker block and provides 3D position and respiratory phase information in real time for the dynamic MLC motion‐tracking software. Using the position and phase information and the 4D treatment plan, the dynamic MLC motion‐tracking software repositions and/or reshapes the radiation beams to deliver treatment. An MV imager operating in a cine mode was used to acquire images to quantify tumor motion, rotation, and deformation. 4D treatment delivery was performed when the target motion during treatment delivery was the same as, smaller than, and larger than during imaging. For comparison, static delivery of treatment plans for each of the respiratory phases was performed. Results : The elliptical tumor segmented from MV images between 4D and static delivery showed the difference of centroid positions less than 5 mm, rotation less than 10 degrees, and major and minor axis lengths less than 2 mm each. 4D treatment delivery was comparable to static delivery of each phase treatment plan, demonstrating the ability of dynamic MLC to account for changes in anatomic motion, rotation, and deformation by varying MLC leaves as a function of phase. Conclusion : 4D treatment plans generated to account for motion, rotation, and deformation of tumors and normal tissues within a respiratory cycle at the planning stage can be delivered while still accounting for different target motion during delivery at the delivery stage. Research supported by NIH/NCIR01‐93626 and Varian Medical Systems

Publication

Four-dimensional IMRT treatment planning using a DMLC motion-tracking algorithm

Publisher: IOP Publishing

Date: 28-05-2009

DOI: 10.1088/0031-9155/54/12/014

Abstract: The purpose of this study is to develop a four-dimensional (4D) intensity-modulated radiation therapy (IMRT) treatment-planning method by modifying and applying a dynamic multileaf collimator (DMLC) motion-tracking algorithm. The 4D radiotherapy treatment scenario investigated is to obtain a 4D treatment plan based on a 4D computed tomography (CT) planning scan and to have the delivery flexible enough to account for changes in tumor position during treatment delivery. For each of 4D CT planning scans from 12 lung cancer patients, a reference phase plan was created with its MLC leaf positions and three-dimensional (3D) tumor motion, the DMLC motion-tracking algorithm generated MLC leaf sequences for the plans of other respiratory phases. Then, a deformable dose-summed 4D plan was created by merging the leaf sequences of in idual phase plans. In idual phase plans, as well as the deformable dose-summed 4D plan, are similar for each patient, indicating that this method is dosimetrically robust to the variations of fractional time spent in respiratory phases on a given 4D CT planning scan. The 4D IMRT treatment-planning method utilizing the DMLC motion-tracking algorithm explicitly accounts for 3D tumor motion and thus hysteresis and nonlinear motion, and is deliverable on a linear accelerator.

Publication

First Demonstration of Combined kV/MV Image-Guided Real-Time Dynamic Multileaf-Collimator Target Tracking

Publisher: Elsevier BV

Date: 07-2009

DOI: 10.1016/J.IJROBP.2009.02.012

Publication

Study protocol of the LARK (TROG 17.03) clinical trial: a phase II trial investigating the dosimetric impact of Liver Ablative Radiotherapy using Kilovoltage intrafraction monitoring

Publisher: Springer Science and Business Media LLC

Date: 03-05-2021

DOI: 10.1186/S12885-021-08184-X

Abstract: Stereotactic Ablative Body Radiotherapy (SABR) is a non-invasive treatment which allows delivery of an ablative radiation dose with high accuracy and precision. SABR is an established treatment for both primary and secondary liver malignancies, and technological advances have improved its efficacy and safety. Respiratory motion management to reduce tumour motion and image guidance to achieve targeting accuracy are crucial elements of liver SABR. This phase II multi-institutional TROG 17.03 study, L iver A blative R adiotherapy using K ilovoltage intrafraction monitoring (LARK), aims to investigate and assess the dosimetric impact of the KIM real-time image guidance technology. KIM utilises standard linear accelerator equipment and therefore has the potential to be a widely available real-time image guidance technology for liver SABR. Forty-six patients with either hepatocellular carcinoma or oligometastatic disease to the liver suitable for and treated with SABR using Kilovoltage Intrafraction Monitoring (KIM) guidance will be included in the study. The dosimetric impact will be assessed by quantifying accumulated patient dose distribution with or without the KIM intervention. The patient treatment outcomes of local control, toxicity and quality of life will be measured. Liver SABR is a highly effective treatment, but precise dose delivery is challenging due to organ motion. Currently, there is a lack of widely available options for performing real-time tumour localisation to assist with accurate delivery of liver SABR. This study will provide an assessment of the impact of KIM as a potential solution for real-time image guidance in liver SABR. This trial was registered on December 7th 2016 on ClinicalTrials.gov under the trial-ID NCT02984566 .

Publication

WE‐C‐204B‐07: Real‐Time MRI for Soft‐Tissue‐Based IGRT of Moving and Deforming Lung Tumors

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469379

Abstract: Purpose : Integrated MRI+Linacs can potentially provide real‐time soft‐tissue‐based image‐guidance for lung cancer IGRT. Towards this, we investigate guidance strategies using prospective rapid lung MRI coupled with deformable image registration. Method and Materials : All experiments were performed on a 1.5 T MRI scanner, using a 4‐channel cardiac coil, under free‐breathing conditions, without extrinisic contrast. A balanced steady‐state free precession (b‐SSFP) imaging sequence was optimized for prospective imaging and reconstruction. Two lung cancer patients (Pt#l: 4 cm tumor, right lower lobe, Pt#2: 6 cm tumor, left upper lobe) were imaged. A viscous fluid‐flow‐based deformable registration was applied to each MRI time series in order to determine motion trajectories of voxels within the field of view. These trajectories were used to characterize: (i) motion of the tumor centroid. (ii) relative trajectories of the tumor centroid and the diaphragmrelative trajectories of different points on the tumor — characterizing tumor rotation/deformation. Results : The modified b‐SSFP sequence yielded acquisition times of ∼0.16s and ∼1.5s for 2D and 3D acquisition, respectively. Tumor trajectory analysis: (i) significant cycle‐to‐cycle variation in tumor motion was observed in both patients (ii) For Pt#l, the tumor centroid showed good correlation with diaphragmatic motion. For Pt#2, this correlation was relatively poor (iii) Pt#l did not exhibit significant tumor rotation/deformation. In Pt.#2, the trajectories of two points on the tumor showed maximum deviations of ∼8 mm (superior‐inferior) and 3.4 mm (anterior‐posterior), indicating non‐negligible rotation/deformation likely due to the influence of the adjacent cardiac wall. Conclusion : To our knowledge, this is the first demonstration of MRI for real‐time imaging of lung cancer. The incorporation of these strategies into MRI+Linacs offers image‐guidance capabilities that are not possible using current techniques: (i) soft‐tissue‐based rather than surrogate‐based monitoring (ii) no fiducial implantation or imaging dose (iii) arbitrary slice selection and (iv) ability to monitor complex motion.

Publication

SU‐E‐T‐304: Proposed Design and Shielding Requirements of a Mini Linear Accelerator Treatment System

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3612255

Publication

SU-FF-T-671: Investigation of Effects of Treatment Planning Variables On Small Animal Therapy Dose Distributions

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182169

Publication

Feasibility study on 3D image reconstruction from 2D orthogonal cine‐MRI for MRI‐guided radiotherapy

Publisher: Wiley

Date: 11-02-2018

DOI: 10.1111/1754-9485.12713

Abstract: In-room MRI is a promising image guidance strategy in external beam radiotherapy to acquire volumetric information for moving targets. However, limitations in spatio-temporal resolution led several authors to use 2D orthogonal images for guidance. The aim of this work is to present a method to concurrently compensate for non-rigid tumour motion and provide an approach for 3D reconstruction from 2D orthogonal cine-MRI slices for MRI-guided treatments. Free-breathing sagittal/coronal interleaved 2D cine-MRI were acquired in addition to a pre-treatment 3D volume in two patients. We performed deformable image registration (DIR) between cine-MRI slices and corresponding slices in the pre-treatment 3D volume. Based on an extrapolation of the interleaved 2D motion fields, the 3D motion field was estimated and used to warp the pre-treatment volume. Due to the lack of a ground truth for patients, the method was validated on a digital 4D lung phantom. On the phantom, the 3D reconstruction method was able to compensate for tumour motion and compared favourably to the results of previously adopted strategies. The difference in the 3D motion fields between the phantom and the extrapolated motion was 0.4 ± 0.3 mm for tumour and 0.8 ± 1.5 mm for whole anatomy, demonstrating feasibility of performing a 3D volumetric reconstruction directly from 2D orthogonal cine-MRI slices. Application of the method to patient data confirmed the feasibility of utilizing this method in real world scenarios. Preliminary results on phantom and patient cases confirm the feasibility of the proposed approach in an MRI-guided scenario, especially for non-rigid tumour motion compensation.

Publication

In Reply to Dahele and Verbakel

Publisher: Elsevier BV

Date: 2019

DOI: 10.1016/J.IJROBP.2018.08.063

Publication

Real-time estimation of prostate tumor rotation and translation with a kV imaging system based on an iterative closest point algorithm

Publisher: IOP Publishing

Date: 15-11-2013

DOI: 10.1088/0031-9155/58/23/8517

Abstract: Previous studies have shown that during cancer radiotherapy a small translation or rotation of the tumor can lead to errors in dose delivery. Current best practice in radiotherapy accounts for tumor translations, but is unable to address rotation due to a lack of a reliable real-time estimate. We have developed a method based on the iterative closest point (ICP) algorithm that can compute rotation from kilovoltage x-ray images acquired during radiation treatment delivery. A total of 11 748 kilovoltage (kV) images acquired from ten patients (one fraction for each patient) were used to evaluate our tumor rotation algorithm. For each kV image, the three dimensional coordinates of three fiducial markers inside the prostate were calculated. The three dimensional coordinates were used as input to the ICP algorithm to calculate the real-time tumor rotation and translation around three axes. The results show that the root mean square error was improved for real-time calculation of tumor displacement from a mean of 0.97 mm with the stand alone translation to a mean of 0.16 mm by adding real-time rotation and translation displacement with the ICP algorithm. The standard deviation (SD) of rotation for the ten patients was 2.3°, 0.89° and 0.72° for rotation around the right-left (RL), anterior-posterior (AP) and superior-inferior (SI) directions respectively. The correlation between all six degrees of freedom showed that the highest correlation belonged to the AP and SI translation with a correlation of 0.67. The second highest correlation in our study was between the rotation around RL and rotation around AP, with a correlation of -0.33. Our real-time algorithm for calculation of rotation also confirms previous studies that have shown the maximum SD belongs to AP translation and rotation around RL. ICP is a reliable and fast algorithm for estimating real-time tumor rotation which could create a pathway to investigational clinical treatment studies requiring real-time measurement and adaptation to tumor rotation.

Publication

An MRI-compatible patient rotation system - design, construction, and first organ deformation results

Publisher: Wiley

Date: 02-2017

DOI: 10.1002/MP.12065

Abstract: Conventionally in radiotherapy, a very heavy beam forming apparatus (gantry) is rotated around a patient. From a mechanical perspective, a more elegant approach is to rotate the patient within a stationary beam. Key obstacles to this approach are patient tolerance and anatomical deformation. Very little information on either aspect is available in the literature. The purpose of this work was therefore to design and test an MRI-compatible patient rotation system such that the feasibility of a patient rotation workflow could be tested. A patient rotation system (PRS) was designed to fit inside the bore of a 3T MRI scanner (Skyra, Siemens) such that 3D images could be acquired at different rotation angles. Once constructed, a pelvic imaging study was carried out on a healthy volunteer. T2-weighted MRI images were taken every 45° between 0° and 360°, (with 0° equivalent to supine). The prostate, bladder, and rectum were segmented using atlas-based auto contouring. The images from each angle were registered back to the 0° image in three steps: (a) Rigid registration was based on MRI visible markers on the couch. (b) Rigid registration based on the prostate contour (equivalent to a rigid shift to the prostate). (c) Nonrigid registration. The Dice similarity coefficient (DSC) and mean average surface distance (MASD) were calculated for each organ at each step. The PRS met all design constraints and was successfully integrated with the MRI scanner. Phantom images showed minimal difference in signal or noise with or without the PRS in the MRI scanner. For the MRI images, the DSC (mean ± standard deviation) over all angles in the prostate, rectum, and bladder was 0.60 ± 0.11, 0.56 ± 0.15, and 0.76 ± 0.06 after rigid couch registration, 0.88 ± 0.03, 0.81 ± 0.08, and 0.86 ± 0.03 after rigid prostate guided registration, and 0.85 ± 0.03, 0.88 ± 0.02, 0.87 ± 0.02 after nonrigid registration. An MRI-compatible patient rotation system has been designed, constructed, and tested. A pelvic study was carried out on a healthy volunteer. Rigid registration based on the prostate contour yielded DSC overlap statistics in the prostate superior to interobserver contouring variability reported in the literature.

Publication

Is multileaf collimator tracking or gating a better intrafraction motion adaptation strategy? An analysis of the TROG 15.01 stereotactic prostate ablative radiotherapy with KIM (SPARK) trial

Publisher: Elsevier BV

Date: 10-2020

DOI: 10.1016/J.RADONC.2020.08.010

Publication

SU‐DD‐A3‐04: Monte Carlo Simulation of a MicroCT‐Based Small Animal Radiotherapy System

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181084

Publication

WE‐G‐213CD‐07: Enhancing Respiratory Motion Prediction Accuracy Using Audiovisual (AV) Biofeedback

Publisher: Wiley

Date: 06-2012

DOI: 10.1118/1.4736208

Abstract: Prediction of respiratory-related tumor motion is h ered by irregularities present in the patient breathing patterns. Audiovisual (AV) biofeedback reduces irregularities, thereby producing a less complex breathing pattern. The aim of this project is to improve respiratory motion prediction accuracy using an AV biofeedback system. An AV biofeedback system combined with real-time MRI was implemented in this project (4 human subjects across 5 studies (one subject had both an initial and follow-up study)). The AV biofeedback system consists of external marker positioned on the abdomen of human subjects, being tracked using an RPM system (Real-time Position Management, Varian) to guide the subject's breathing. Acquired respiratory data has been used as input for motion prediction through a dynamic multi-leaf collimator (DMLC) simulator developed by Prof. Keall. The prediction algorithm utilized was a kernel density estimation-based real-time prediction algorithm. A variety of prediction parameters were tested to determine optimum prediction performance. Prediction parameters adjusted were the delay time (DT) and training ex les (TE) the parameters tested here were: DT/TE = 2500/1500, 2500/100, 1000/250, 500/250 Given that the data s ling rate was kept at 30 Hz, the resultant prediction training window lengths were 49.5, 8.25, 3.3 and 3.3seconds respectively. The mean difference between measured and predicted data for free breathing was 1.98±2.32mm and 0.65±0.65mm for when AV biofeedback was implemented (reduction of error of 67%). The most accurate prediction results were attained using the parameters: DT/TE = 500 ms/250. This study demonstrates the improvement of respiratory motion prediction accuracy when AV biofeedback is implemented to produce a more regular breathing pattern.

Publication

Real-time intrafraction motion monitoring in external beam radiotherapy

Publisher: IOP Publishing

Date: 08-2019

DOI: 10.1088/1361-6560/AB2BA8

Abstract: Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to ‘see what we treat, as we treat’ and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-time treatment adaptation. Additional equipment, such as stereoscopic kilovoltage (kV) imaging, ultrasound transducers and electromagnetic transponders, has been developed for intrafraction motion monitoring on conventional linacs. Magnetic resonance imaging (MRI) has been integrated with cobalt treatment units and more recently with linacs. In addition to hardware innovation, software development has played a substantial role in the development of motion monitoring methods based on respiratory motion surrogates and planar kV or Megavoltage (MV) imaging that is available on standard equipped linacs. In this paper, we review and compare the different intrafraction motion monitoring methods proposed in the literature and demonstrated in real-time on clinical data as well as their possible future developments. We then discuss general considerations on validation and quality assurance for clinical implementation. Besides photon RT, particle therapy is increasingly used to treat moving targets. However, transferring motion monitoring technologies from linacs to particle beam lines presents substantial challenges. Lessons learned from the implementation of real-time intrafraction monitoring for photon RT will be used as a basis to discuss the implementation of these methods for particle RT.

Publication

Quantifying the impact of respiratory‐gated 4D CT acquisition on thoracic image quality: A digital phantom study

Publisher: Wiley

Date: 2015

DOI: 10.1118/1.4903936

Abstract: Prospective respiratory-gated 4D CT has been shown to reduce tumor image artifacts by up to 50% compared to conventional 4D CT. However, to date no studies have quantified the impact of gated 4D CT on normal lung tissue imaging, which is important in performing dose calculations based on accurate estimates of lung volume and structure. To determine the impact of gated 4D CT on thoracic image quality, the authors developed a novel simulation framework incorporating a realistic deformable digital phantom driven by patient tumor motion patterns. Based on this framework, the authors test the hypothesis that respiratory-gated 4D CT can significantly reduce lung imaging artifacts. Our simulation framework synchronizes the 4D extended cardiac torso (XCAT) phantom with tumor motion data in a quasi real-time fashion, allowing simulation of three 4D CT acquisition modes featuring different levels of respiratory feedback: (i) "conventional" 4D CT that uses a constant imaging and couch-shift frequency, (ii) "beam paused" 4D CT that interrupts imaging to avoid overs ling at a given couch position and respiratory phase, and (iii) "respiratory-gated" 4D CT that triggers acquisition only when the respiratory motion fulfills phase-specific displacement gating windows based on prescan breathing data. Our framework generates a set of ground truth comparators, representing the average XCAT anatomy during beam-on for each of ten respiratory phase bins. Based on this framework, the authors simulated conventional, beam-paused, and respiratory-gated 4D CT images using tumor motion patterns from seven lung cancer patients across 13 treatment fractions, with a simulated 5.5 cm(3) spherical lesion. Normal lung tissue image quality was quantified by comparing simulated and ground truth images in terms of overall mean square error (MSE) intensity difference, threshold-based lung volume error, and fractional false positive/false negative rates. Averaged across all simulations and phase bins, respiratory-gating reduced overall thoracic MSE by 46% compared to conventional 4D CT (p ∼ 10(-19)). Gating leads to small but significant (p < 0.02) reductions in lung volume errors (1.8%-1.4%), false positives (4.0%-2.6%), and false negatives (2.7%-1.3%). These percentage reductions correspond to gating reducing image artifacts by 24-90 cm(3) of lung tissue. Similar to earlier studies, gating reduced patient image dose by up to 22%, but with scan time increased by up to 135%. Beam paused 4D CT did not significantly impact normal lung tissue image quality, but did yield similar dose reductions as for respiratory-gating, without the added cost in scanning time. For a typical 6 L lung, respiratory-gated 4D CT can reduce image artifacts affecting up to 90 cm(3) of normal lung tissue compared to conventional acquisition. This image improvement could have important implications for dose calculations based on 4D CT. Where image quality is less critical, beam paused 4D CT is a simple strategy to reduce imaging dose without sacrificing acquisition time.

Publication

Cultural Adaptation and Psychometric Properties of the Diabetes Quality of Life Scale in Afaan Oromoo among People Living with Type 2 Diabetes in Ethiopia

Publisher: MDPI AG

Date: 12-07-2021

DOI: 10.3390/IJERPH18147435

Abstract: Background: The original 46-item diabetes quality of life (DQOL) scale has been translated into different languages, and the translated DQOL has shown good reliability and validity after deleting some items. The aim of this study was to translate the diabetes quality of life (DQOL) scale into Afaan Oromoo and to culturally adapt and evaluate the psychometric properties of the DQOL-Afaan Oromoo (DQOL-AO) among people living with T2D in Ethiopia. Methods: A cross-sectional study with a convenience s ling technique was conducted in 2020. The DQOL was translated and adapted to Afaan Oromoo. Item–total correlations and exploratory factor analysis (EFA) assessed factor structure the Cronbach’s alpha assessed internal consistency and relationships with gender, educational status, marital status, age, and employment status and status of diabetes-related disease assessed the construct validity of the DQOL-AO. Results: 417 participants responded to all items of the DQOL. Item–total correlation analysis and EFA produced a 34-item DQOL-AO with four subscales, which demonstrated that the internal consistency of the overall DQOL-AO was 0.867, and scores were 0.827, 0.846, 0.654, and 0.727 for the impact, satisfaction, social/vocational worry, and diabetes-related worry subscales, respectively. Statistically significant differences between QOL were obtained in educational status (F = 7.164, p 0.001) and employment status (F = 4.21, p = 0.002). In iduals who attended college and above and government employees had better QOL. Conclusion: The 34-item DQOL-AO provided preliminary evidence as a reliable and valid tool to measure diabetic-related QOL before it can be widely used among adults living with T2D who speak Afaan Oromoo.

Publication

Geometric accuracy of dynamic MLC tracking with an implantable wired electromagnetic transponder

Publisher: Informa UK Limited

Date: 18-07-2011

DOI: 10.3109/0284186X.2011.590524

Publication

A real-time IGRT method using a Kalman filter framework to extract 3D positions from 2D projections

Publisher: IOP Publishing

Date: 19-10-2021

DOI: 10.1088/1361-6560/AC06E3

Publication

BRAVEHeart: a randomised trial comparing the accuracy of Breathe Well and RPM for deep inspiration breath hold breast cancer radiotherapy

Publisher: Springer Science and Business Media LLC

Date: 22-02-2023

DOI: 10.1186/S13063-023-07072-Y

Abstract: Deep inspiration breath hold (DIBH) reduces radiotherapy cardiac dose for left-sided breast cancer patients. The primary aim of the BRAVEHeart (Breast Radiotherapy Audio Visual Enhancement for sparing the Heart) trial is to assess the accuracy and usability of a novel device, Breathe Well, for DIBH guidance for left-sided breast cancer patients. Breathe Well will be compared to an adapted widely available monitoring system, the Real-time Position Management system (RPM). BRAVEHeart is a single institution prospective randomised trial of two DIBH devices. BRAVEHeart will assess the DIBH accuracy for Breathe Well and RPM during left-sided breast cancer radiotherapy. After informed consent has been obtained, 40 patients will be randomised into two equal groups, the experimental arm (Breathe Well) and the control arm (RPM with in-house modification of an added patient screen). The primary hypothesis of BRAVEHeart is that the accuracy of Breathe Well in maintaining the position of the chest during DIBH is superior to the RPM system. Accuracy will be measured by comparing chest wall motion extracted from images acquired of the treatment field during breast radiotherapy for patients treated using the Breathe Well system and those using the RPM system. The Breathe Well device uses a depth camera to monitor the chest surface while the RPM system monitors a block on the patient’s abdomen. The hypothesis of this trial is that the chest surface is a better surrogate for the internal chest wall motion used as a measure of treatment accuracy. The Breathe Well device aims to deliver an easy-to-use implementation of surface monitoring. The findings from the study will help inform the technology choice for other centres performing DIBH. ClinicalTrials.gov NCT02881203 . Registered on 26 August 2016.

Publication

System requirements to improve adaptive 4-dimensional computed tomography (4D CT) imaging

Publisher: IOP Publishing

Date: 18-10-2022

DOI: 10.1088/2057-1976/AC9849

Abstract: Four-Dimensional Computed Tomography (4D CT) is of increasing importance in stereotactic body radiotherapy (SBRT) treatments affected by respiratory motion. However, 4D CT images are commonly impacted by irregular breathing, causing image artifacts that can propagate through to treatment, negatively effecting local control. REspiratory Adaptive CT (REACT) is a real-time gating method demonstrated to reduce motion artifacts by avoiding imaging during irregular respiration. Despite artifact reduction seen through in silico and clinical phantom-based studies, REACT has not been able to remove all artifacts. Here, we explore several hardware and software latencies (gantry rotation time, couch shifts, acquisition delays and phase calculation method) inherently linked to REACT and 4D CT in general and investigate their contribution to artifacts beyond those caused by irregular breathing. Imaging was simulated using the digital extended cardiac-torso (XCAT) phantom for fifty patient-measured respiratory traces. Imaging protocols included conventional cine 4D CT and five REACT scans with systematically varied parameters to test the effect of different latencies on artifacts. Artifacts were quantified by comparing the image normalized cross correlation across couch transition points and determining the volume error compared to a static phantom ground truth both as a total error and in idually across pixel rows in the main plane of motion. Artifacts were determined for each lung, the whole heart and lung tumour and were compared back to conventional 4D CT and REACT with standard clinical scanning parameters. The gantry rotation time and acquisition delay were found to have the largest impact on reducing image artifacts and should be the focus of future development. The phase calculation method was also found to influence motion artifacts and should potentially be assessed on a patient-to-patient basis. Finally, the correlation between an increase in artifacts and baseline drift suggests that longer scan times allowing drift to occur may impact image quality.

Publication

Reproducibility of Four-dimensional Computed Tomography-based Lung Ventilation Imaging

Publisher: Elsevier BV

Date: 12-2012

DOI: 10.1016/J.ACRA.2012.07.006

Publication

Time-resolved dose reconstruction by motion encoding of volumetric modulated arc therapy fields delivered with and without dynamic multi-leaf collimator tracking

Publisher: Informa UK Limited

Date: 29-08-2013

DOI: 10.3109/0284186X.2013.818248

Publication

Measurements of human tolerance to horizontal rotation within an MRI scanner: Towards gantry‐free radiation therapy

Publisher: Wiley

Date: 29-12-2021

DOI: 10.1111/1754-9485.13130

Abstract: Recent advances in image guidance and adaptive radiotherapy could enable gantry‐free radiotherapy using patient rotation. Gantry‐free radiotherapy could substantially reduce the cost of radiotherapy systems and facilities. MRI guidance complements a gantry‐free approach because of its ability to visualise soft tissue deformation during rotation. A potential barrier to gantry‐free radiotherapy is patient acceptability, especially when combined with MRI. This study investigates human experiences of horizontal rotation within an MRI scanner. Ten healthy human participants and nine participants previously treated with radiotherapy were rotated within an MRI scanner. Participants' anxiety and motion sickness was assessed before being rotated in 45‐degree increments and paused, representing a multi‐field intensity‐modulated radiotherapy treatment. An MR image was acquired at each 45‐degree angle. Following imaging, anxiety and motion sickness were re‐assessed, followed by a comfort questionnaire and exit interview. The significance of the differences in anxiety and motion sickness pre‐ versus post‐imaging was assessed using Wilcoxon signed‐rank tests. Content analysis was performed on exit interview transcripts. Eight of ten healthy and eight of nine patient participants completed the imaging session. Mean anxiety scores before and after imaging were 7.9/100 and 11.8/100, respectively ( P = 0.26), and mean motion sickness scores were 5.3/100 and 13.7/100, respectively ( P = 0.02). Most participants indicated likely acceptance of rotation if MRI were to be used in a hypothetical treatment. Physical discomfort was reported to be the biggest concern. Horizontal rotation within an MRI scanner was acceptable for most (17/19) participants.

Publication

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.

Publication

The potential of positron emission tomography for intratreatment dynamic lung tumor tracking: A phantom study

Publisher: Wiley

Date: 23-01-2014

DOI: 10.1118/1.4861816

Publication

Audiovisual biofeedback improves the correlation between internal/external surrogate motion and lung tumor motion

Publisher: Wiley

Date: 19-02-2018

DOI: 10.1002/MP.12758

Abstract: Breathing management can reduce breath-to-breath (intrafraction) and day-by-day (interfraction) variability in breathing motion while utilizing the respiratory motion of internal and external surrogates for respiratory guidance. Audiovisual (AV) biofeedback, an interactive personalized breathing motion management system, has been developed to improve reproducibility of intra- and interfraction breathing motion. However, the assumption of the correlation of respiratory motion between surrogates and tumors is not always verified during medical imaging and radiation treatment. Therefore, the aim of the study was to test the hypothesis that the correlation of respiratory motion between surrogates and tumors is the same under free breathing without guidance (FB) and with AV biofeedback guidance for voluntary motion management. For 13 lung cancer patients receiving radiotherapy, 2D coronal and sagittal cine-MR images were acquired across two MRI sessions (pre- and mid-treatment) with two breathing conditions: (a) FB and (b) AV biofeedback, totaling 88 patient measurements. Simultaneously, the external respiratory motion of the abdomen was measured. The internal respiratory motion of the diaphragm and lung tumor was retrospectively measured from 2D coronal and sagittal cine-MR images. The correlation of respiratory motion between surrogates and tumors was calculated using Pearson's correlation coefficient for: (a) abdomen to tumor (abdomen-tumor) and (b) diaphragm to tumor (diaphragm-tumor). The correlations were compared between FB and AV biofeedback using several metrics: abdomen-tumor and diaphragm-tumor correlations with/without ≥5 mm tumor motion range and with/without adjusting for phase shifts between the signals. Compared to FB, AV biofeedback improved abdomen-tumor correlation by 11% (p = 0.12) from 0.53 to 0.59 and diaphragm-tumor correlation by 13% (p = 0.02) from 0.55 to 0.62. Compared to FB, AV biofeedback improved abdomen-tumor correlation by 17% (p = 0.01) and diaphragm-tumor correlation by 15% (p < 0.01) while correcting 0.3 s (p = 0.54) and 0.2 s (p = 0.19) phase shifts, respectively. In addition, AV biofeedback with ≥5 mm tumor motion range, compared to FB improved abdomen-tumor correlation by 14% (p = 0.18) and diaphragm-tumor correlation by 17% (p = 0.01). The highest abdomen-tumor and diaphragm-tumor correlations were found using ≥5 mm tumor motion range and phase shifts, resulting in a 12% improvement in AV biofeedback. Our results demonstrated that AV biofeedback improves the correlation of respiratory motion between surrogates and the tumor. This suggests a need for AV biofeedback for respiratory guidance utilizing respiratory surrogates during image-guided and MRI-guided radiotherapy in thoracic regions.

Publication

WE‐C‐204B‐08: Sensitivity of 4D‐CT Pulmonary Ventilation Imaging to Deformable Image Registration Algorithms and Metrics

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469380

Abstract: Purpose : A novel pulmonary ventilation imaging technique based on 4D‐CT has advantages over existing techniques ( e.g. , SPECT). 4D‐CT ventilation imaging consists of deformable image registration (DIR) and displacement vector analysis for computing the ventilation metric. However, there are various DIR algorithms and metrics that yield different ventilation images. The purpose of this study was to quantify the sensitivity of 4D‐CT ventilation imaging to DIR algorithms and metrics. Method and Materials : 4D‐CT ventilation images were created for 9 patients in an IRB‐approved study using different combinations of two DIR algorithms: surface‐based registration ( DIR sur ) and volume‐based registration ( DIR vol ), and two metrics: Hounsfield unit (HU)‐change ( V HU ) and Jacobian determinant of deformation ( V Jac ), i.e. , four different ventilation images for each patient. The analysis compared voxel‐based correlations between different ventilation images, and coefficients of variation (CV) as a measure of heterogeneity. The relative and absolute lung volume changes were also compared, i.e. , calculated vs. measured (ground truth). Results : Different DIR algorithms and metrics yielded spatially variant 4D‐CT ventilation images. The voxel‐based correlations between different ventilation images were inconsistent and ranged from weak (Patient 3, V Jac sur vs. V HU vol , r = 0.084) to strong (Patient 7, V HU sur vs. V HU vol , r = 0.819) correlations, V HU resulted in significantly higher CVs ( e.g. , 3.17 ± 1.64 for V HU sur ) than V Jac (0.71 ± 0.27 for V Jac sur ) ( p = 0.001). There were high correlations between the calculated and measured lung volume changes for all of four ventilation images ( r range, 0.965–0.993, p .001). Conclusion : This study has demonstrated that the regional distribution and heterogeneity of 4D‐CT ventilation are sensitive to DIR algorithms and/or metrics, while the global accuracy is not sensitive. Careful validation studies are needed prior to its clinical application. Conflict of Interest : SK, CL and JB are employees of Philips Research Europe.

Publication

Impact of the MLC on the MRI field distortion of a prototype MRI‐linac

Publisher: Wiley

Date: 08-11-2013

DOI: 10.1118/1.4828792

Abstract: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality. The finite element method was employed to model a MRI-linac assembly comprised of a 1.0 T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps of the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30 cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300 μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200 cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20 cm(2), to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B0 of 0.5, 1.0, and 1.5 T, to estimate how the MLC impact changes with B0. (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field distortion was generally smaller in the perpendicular beam orientation. The peak-to-peak DSV distortion was below 300 μT at SID≥130 cm (perpendicular) and SID≥140 cm (inline) for the 1.0 T design. (4) The simulation of different treatment fields was identified to cause dynamic changes in the field distribution. However, the estimated residual distortion was below 1.2 mm geometric distortion at SID≥120 cm (perpendicular) and SID≥130 cm (inline) for a 10 mT/m frequency-encoding gradient. (5) Due to magnetic saturation of the MLC materials, the field distortion remained constant at B0>1.0 T. This work shows that the MRI field distortions caused by the MLC cannot be ignored and must be thoroughly investigated for any MRI-linac system. The numeric distortion values obtained for our 1.0 T magnet may vary for other magnet designs with substantially different fringe fields, however the concept of modest increases in the SID to reduce the distortion to a shimmable level is generally applicable.

Publication

Adaptive CaRdiac cOne BEAm computed Tomography (ACROBEAT): Developing the next generation of cardiac cone beam CT imaging.

Publisher: Wiley

Date: 23-03-2021

DOI: 10.1002/MP.14811

Publication

4D Dosimetry

Publisher: CRC Press

Date: 31-10-2017

DOI: 10.1201/9781315118826-11

Publication

Quantifying the reproducibility of lung ventilation images between 4‐Dimensional Cone Beam CT and 4‐Dimensional CT

Publisher: Wiley

Date: 17-04-2017

DOI: 10.1002/MP.12199

Abstract: Computed tomography ventilation imaging derived from four-dimensional cone beam CT (CTVI We analysed 51 pairs of 4DCBCT and 4DCT scans acquired within 1 day of each other for nine lung cancer patients. To assess the impact of image quality, CTVIs were derived from 4DCBCT scans reconstructed using both standard Feldk -Davis-Kress backprojection (CTVIFDK4DCBCT) and an iterative McKinnon-Bates Simultaneous Algebraic Reconstruction Technique (CTVIMKBSART4DCBCT). Also, the influence of FOV was assessed by deriving CTVIs from 4DCT scans that were cropped to a similar FOV as the 4DCBCT scans (CTVIcrop4DCT), or uncropped (CTVIuncrop4DCT). All CTVIs were derived by performing deformable image registration (DIR) between the exhale and inhale phases and evaluating the Jacobian determinant of deformation. Reproducibility between corresponding CTVI The (mean ± SD) Spearman correlation between CTVIFDK4DCBCT and CTVIuncrop4DCT was 0.60 ± 0.23 (range -0.03-0.88) and the DSC was 0.64 ± 0.12 (0.34-0.83). By comparison, correlations between CTVIMKBSART4DCBCT and CTVIuncrop4DCT showed a small but statistically significant improvement with = 0.64 ± 0.20 (range 0.06-0.90, P = 0.03) and DSC = 0.66 ± 0.13 (0.31-0.87, P = 0.02). Intermodal correlations were noted to decrease with an increasing fraction of lung truncation in 4DCBCT relative to 4DCT, albeit not significantly (Pearson correlation R = 0.58, P = 0.002). This study demonstrates that DIR based CTVIs derived from 4DCBCT can exhibit reasonable to good voxel-level agreement with CTVIs derived from 4DCT. These correlations outperform previous cross-modality comparisons between 4DCT-based ventilation and nuclear medicine. The use of 4DCBCT scans with iterative reconstruction and minimal lung truncation is recommended to ensure better reproducibility between 4DCBCT- and 4DCT-based CTVIs.

Publication

SU‐FF‐T‐400: Monte Carlo Simulations of Compact Plasma Accelerators for Proton Radiotherapy

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3181882

Publication

Impact of audiovisual biofeedback on interfraction respiratory motion reproducibility in liver cancer stereotactic body radiotherapy.

Publisher: Wiley

Date: 02-2018

DOI: 10.1111/1754-9485.12702

Abstract: Irregular breathing motion exacerbates uncertainties throughout a course of radiation therapy. Breathing guidance has demonstrated to improve breathing motion consistency. This was the first clinical implementation of audiovisual biofeedback (AVB) breathing guidance over a course of liver stereotactic body radiotherapy (SBRT) investigating interfraction reproducibility. Five liver cancer patients underwent a screening procedure prior to CT sim during which patients underwent breathing conditions (i) AVB, or (ii) free breathing (FB). Whichever breathing condition was more regular was utilised for the patient's subsequent course of SBRT. Respiratory motion was obtained from the Varian respiratory position monitoring (RPM) system (Varian Medical Systems). Breathing motion reproducibility was assessed by the variance of displacement across 10 phase-based respiratory bins over each patient's course of SBRT. The screening procedure yielded the decision to utilise AVB for three patients and FB for two patients. Over the course of SBRT, AVB significantly improved the relative interfraction motion by 32%, from 22% displacement difference for FB patients to 15% difference for AVB patients. Further to this, AVB facilitated sub-millimetre interfraction reproducibility for two AVB patients. There was significantly less interfraction motion with AVB than FB. These findings demonstrate that AVB is potentially a valuable tool in ensuring reproducible interfraction motion.

Publication

Estimation of effective imaging dose for kilovoltage intratreatment monitoring of the prostate position during cancer radiotherapy

Publisher: IOP Publishing

Date: 12-08-2013

DOI: 10.1088/0031-9155/58/17/5983

Publication

TU‐D‐204B‐09: Rapid MR Imaging for Real‐Time Target Tracking Using Temporal Sparsity

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469267

Publication

Investigating the Feasibility of Rapid MRI for Image-Guided Motion Management in Lung Cancer Radiotherapy

Publisher: Hindawi Limited

Date: 2014

DOI: 10.1155/2014/485067

Abstract: Cycle-to-cycle variations in respiratory motion can cause significant geometric and dosimetric errors in the administration of lung cancer radiation therapy. A common limitation of the current strategies for motion management is that they assume a constant, reproducible respiratory cycle. In this work, we investigate the feasibility of using rapid MRI for providing long-term imaging of the thorax in order to better capture cycle-to-cycle variations. Two nonsmall-cell lung cancer patients were imaged (free-breathing, no extrinsic contrast, and 1.5 T scanner). A balanced steady-state-free-precession (b-SSFP) sequence was used to acquire cine-2D and cine-3D (4D) images. In the case of Patient 1 (right midlobe lesion, ~40 mm diameter), tumor motion was well correlated with diaphragmatic motion. In the case of Patient 2, (left upper-lobe lesion, ~60 mm diameter), tumor motion was poorly correlated with diaphragmatic motion. Furthermore, the motion of the tumor centroid was poorly correlated with the motion of in idual points on the tumor boundary, indicating significant rotation and/or deformation. These studies indicate that image quality and acquisition speed of cine-2D MRI were adequate for motion monitoring. However, significant improvements are required to achieve comparable speeds for truly 4D MRI. Despite several challenges, rapid MRI offers a feasible and attractive tool for noninvasive, long-term motion monitoring.

Publication

Inverse planning for four‐dimensional (4D) volumetric modulated arc therapya)

Publisher: Wiley

Date: 07-10-2010

DOI: 10.1118/1.3497271

Publication

Evaluation of 4-dimensional Computed Tomography to 4-dimensional Cone-Beam Computed Tomography Deformable Image Registration for Lung Cancer Adaptive Radiation Therapy

Publisher: Elsevier BV

Date: 06-2013

DOI: 10.1016/J.IJROBP.2012.12.023

Publication

Superposition dose calculation incorporating Monte Carlo generated electron track kernels

Publisher: Wiley

Date: 04-1996

DOI: 10.1118/1.597679

Abstract: The superposition/convolution method and the transport of pregenerated Monte Carlo electron track data have been combined into the Super-Monte Carlo (SMC) method, an accurate 3-D x-ray dose calculation algorithm. The primary dose (dose due to electrons ejected by primary photons) is calculated by transporting pregenerated (in water) Monte Carlo electron tracks from each primary photon interaction site, weighted by the terma for that site. The length of each electron step is scaled by the inverse of the density of the medium at the beginning of the step. Because the density scaling of the electron tracks is performed for each in idual transport step, the limitations of the macroscopic scaling of kernels (in the superposition algorithm) are overcome. This time-consuming step-by-step transport is only performed for the primary dose calculation, where current superposition methods are most lacking. The scattered dose (dose due to electrons set in motion by scattered photons) is calculated by superposition. In both a water-lung-water phantom and a two lung-block phantom, SMC dose distributions are more consistent with Monte Carlo generated dose distributions than are superposition dose distributions, especially for small fields and high energies-for an 18-MV, 5 X 5-cm(2) beam, the central axis dose discrepancy from Monte Carlo is reduced from 4.5% using superposition to 1.5% using SMC. The computation time for this technique is approximately 2 h (depending on the simulation history), 20 times slower than superposition, but 15 times faster than a full Monte Carlo simulation (on our platform).

Publication

Towards real-time MRI-guided 3D localization of deforming targets for non-invasive cardiac radiosurgery

Publisher: IOP Publishing

Date: 25-10-2016

DOI: 10.1088/0031-9155/61/22/7848

Abstract: Radiosurgery to the pulmonary vein antrum in the left atrium (LA) has recently been proposed for non-invasive treatment of atrial fibrillation (AF). Precise real-time target localization during treatment is necessary due to complex respiratory and cardiac motion and high radiation doses. To determine the 3D position of the LA for motion compensation during radiosurgery, a tracking method based on orthogonal real-time MRI planes was developed for AF treatments with an MRI-guided radiotherapy system. Four healthy volunteers underwent cardiac MRI of the LA. Contractile motion was quantified on 3D LA models derived from 4D scans with 10 phases acquired in end-exhalation. Three localization strategies were developed and tested retrospectively on 2D real-time scans (sagittal, temporal resolution 100 ms, free breathing). The best-performing method was then used to measure 3D target positions in 2D-2D orthogonal planes (sagittal-coronal, temporal resolution 200-252 ms, free breathing) in 20 configurations of a digital phantom and in the volunteer data. The 3D target localization accuracy was quantified in the phantom and qualitatively assessed in the real data. Mean cardiac contraction was ⩽ 3.9 mm between maximum dilation and contraction but anisotropic. A template matching approach with two distinct template phases and ECG-based selection yielded the highest 2D accuracy of 1.2 mm. 3D target localization showed a mean error of 3.2 mm in the customized digital phantoms. Our algorithms were successfully applied to the 2D-2D volunteer data in which we measured a mean 3D LA motion extent of 16.5 mm (SI), 5.8 mm (AP) and 3.1 mm (LR). Real-time target localization on orthogonal MRI planes was successfully implemented for highly deformable targets treated in cardiac radiosurgery. The developed method measures target shifts caused by respiration and cardiac contraction. If the detected motion can be compensated accordingly, an MRI-guided radiotherapy system could potentially enable completely non-invasive treatment of AF.

Publication

Evaluation of deep learning based implanted fiducial markers tracking in pancreatic cancer patients

Publisher: IOP Publishing

Date: 07-03-2023

DOI: 10.1088/2057-1976/ACB550

Abstract: Real-time target position verification during pancreas stereotactic body radiation therapy (SBRT) is important for the detection of unplanned tumour motions. Fast and accurate fiducial marker segmentation is a Requirement of real-time marker-based verification. Deep learning (DL) segmentation techniques are ideal because they don’t require additional learning imaging or prior marker information (e.g., shape, orientation). In this study, we evaluated three DL frameworks for marker tracking applied to pancreatic cancer patient data. The DL frameworks evaluated were (1) a convolutional neural network (CNN) classifier with sliding window, (2) a pretrained you-only-look-once (YOLO) version-4 architecture, and (3) a hybrid CNN-YOLO. Intrafraction kV images collected during pancreas SBRT treatments were used as training data (44 fractions, 2017 frames). All patients had 1-4 implanted fiducial markers. Each model was evaluated on unseen kV images (42 fractions, 2517 frames). The ground truth was calculated from manual segmentation and triangulation of markers in orthogonal paired kV/MV images. The sensitivity, specificity, and area under the precision-recall curve (AUC) were calculated. In addition, the mean-absolute-error (MAE), root-mean-square-error (RMSE) and standard-error-of-mean (SEM) were calculated for the centroid of the markers predicted by the models, relative to the ground truth. The sensitivity and specificity of the CNN model were 99.41% and 99.69%, respectively. The AUC was 0.9998. The average precision of the YOLO model for different values of recall was 96.49%. The MAE of the three models in the left-right, superior-inferior, and anterior-posterior directions were under 0.88 ± 0.11 mm, and the RMSE were under 1.09 ± 0.12 mm. The detection times per frame on a GPU were 48.3, 22.9, and 17.1 milliseconds for the CNN, YOLO, and CNN-YOLO, respectively. The results demonstrate submillimeter accuracy of marker position predicted by DL models compared to the ground truth. The marker detection time was fast enough to meet the requirements for real-time application.

Publication

Development and preliminary evaluation of a prototype audiovisual biofeedback device incorporating a patient-specific guiding waveform

Publisher: IOP Publishing

Date: 12-05-2008

DOI: 10.1088/0031-9155/53/11/N01

Publication

Experimental characterisation of the magnetic field correction factor, kB⃗, for Roos chambers in a parallel MRI-linac

Publisher: IOP Publishing

Date: 28-04-2022

DOI: 10.1088/1361-6560/AC66B8

Abstract: Objective. Reference dosimetry on an MRI-linac requires a chamber specific magnetic field correction factor, k B ⃗ . This work aims to measure the correction factor for a parallel plate chamber on a parallel MRI-linac. Approach. k B ⃗ is defined as the ratio of the absorbed dose to water calibration coefficient in the presence of the magnetic field, N D , w B ⃗ relative to that under 0 T conditions, N D , w 0 T . k B ⃗ was measured via a N D , w transfer to a field chamber at each magnetic field strength from a chamber with known N D , w and k B ⃗ . This was achieved on the parallel MRI-linac by moving the measurement set-up between a high magnetic field strength region at the MRI-isocentre and a low magnetic field strength region at the end of the bore whilst maintaining consistent set-up and scatter conditions. Three PTW 34001 Roos chambers were investigated as well as a PTW 30013 Farmer used to validate methodology. Main Results. The beam quality used for the measurements of k B ⃗ was TPR 20 / 10 = 0.632. The k B ⃗ for the PTW Farmer chamber at 1 T on a parallel MRI-linac was 0.993 ± 0.013 ( k = 1). The average k B ⃗ factor measured for the three Roos chambers on a 1 T parallel MRI-linac was 0.999 ± 0.014 ( k = 1). Significance. The results presented are the first measurements of k B ⃗ for a Roos chamber on a parallel MRI-linac. The Roos chamber results demonstrate the potential for the chamber as a reference dosimeter in parallel MRI-linacs.

Publication

Integrated MRI-guided radiotherapy — opportunities and challenges

Publisher: Springer Science and Business Media LLC

Date: 19-04-2022

DOI: 10.1038/S41571-022-00631-3

Abstract: MRI can help to categorize tissues as malignant or non-malignant both anatomically and functionally, with a high level of spatial and temporal resolution. This non-invasive imaging modality has been integrated with radiotherapy in devices that can differentially target the most aggressive and resistant regions of tumours. The past decade has seen the clinical deployment of treatment devices that combine imaging with targeted irradiation, making the aspiration of integrated MRI-guided radiotherapy (MRIgRT) a reality. The two main clinical drivers for the adoption of MRIgRT are the ability to image anatomical changes that occur before and during treatment in order to adapt the treatment approach, and to image and target the biological features of each tumour. Using motion management and biological targeting, the radiation dose delivered to the tumour can be adjusted during treatment to improve the probability of tumour control, while simultaneously reducing the radiation delivered to non-malignant tissues, thereby reducing the risk of treatment-related toxicities. The benefits of this approach are expected to increase survival and quality of life. In this Review, we describe the current state of MRIgRT, and the opportunities and challenges of this new radiotherapy approach.

Publication

The adaptation and investigation of cone-beam CT reconstruction algorithms for horizontal rotation fixed-gantry scans of rabbits

Publisher: IOP Publishing

Date: 14-05-2021

DOI: 10.1088/1361-6560/ABF9DD

Abstract: Fixed-gantry radiation therapy has been proposed as a low-cost alternative to the conventional rotating-gantry radiation therapy, that may help meet the rising global treatment demand. Fixed-gantry systems require gravitational motion compensated reconstruction algorithms to produce cone-beam CT (CBCT) images of sufficient quality for image guidance. The aim of this work was to adapt and investigate five CBCT reconstruction algorithms for fixed-gantry CBCT images. The five algorithms investigated were Feldk –Davis–Kress (FDK), prior image constrained compressed sensing (PICCS), gravitational motion compensated FDK (GMCFDK), motion compensated PICCS (MCPICCS) (a novel CBCT reconstruction algorithm) and simultaneous motion estimation and iterative reconstruction (SMEIR). Fixed-gantry and rotating-gantry CBCT scans were acquired of 3 rabbits, with the rotating-gantry scans used as a reference. Projections were sorted into rotation bins, based on the angle of rotation of the rabbit during image acquisition. The algorithms were compared using the structural similarity index measure root mean square error, and reconstruction time. Evaluation of the reconstructed volumes showed that, when compared with the reference rotating-gantry volume, the conventional FDK algorithm did not accurately reconstruct fixed-gantry CBCT scans. Whilst the PICCS reconstruction algorithm reduced some motion artefacts, the motion estimation reconstruction methods (GMCFDK, MCPICCS and SMEIR) were able to greatly reduce the effect of motion artefacts on the reconstructed volumes. This finding was verified quantitatively, with GMCFDK, MCPICCS and SMEIR reconstructions having RMSE 17%–19% lower and SSIM 1% higher than a conventional FDK. However, all motion compensated fixed-gantry CBCT reconstructions had a 56%–61% higher RMSE and 1.5% lower SSIM than FDK reconstructions of conventional rotating-gantry CBCT scans. The results show that motion compensation is required to reduce motion artefacts for fixed-gantry CBCT reconstructions. This paper further demonstrates the feasibility of fixed-gantry CBCT scans, and the ability of CBCT reconstruction algorithms to compensate for motion due to horizontal rotation.

Publication

Genitourinary Quality-of-Life Comparison Between Urethral Sparing Prostate Stereotactic Body Radiation Therapy Monotherapy and Virtual High-Dose-Rate Brachytherapy Boost

Publisher: Elsevier BV

Date: 08-2023

DOI: 10.1016/J.IJROBP.2023.02.049

Publication

Optimizing 4DCBCT projection allocation to respiratory bins

Publisher: IOP Publishing

Date: 05-09-2014

DOI: 10.1088/0031-9155/59/19/5631

Abstract: 4D cone beam computed tomography (4DCBCT) is an emerging image guidance strategy used in radiotherapy where projections acquired during a scan are sorted into respiratory bins based on the respiratory phase or displacement. 4DCBCT reduces the motion blur caused by respiratory motion but increases streaking artefacts due to projection under-s ling as a result of the irregular nature of patient breathing and the binning algorithms used. For displacement binning the streak artefacts are so severe that displacement binning is rarely used clinically. The purpose of this study is to investigate if sharing projections between respiratory bins and adjusting the location of respiratory bins in an optimal manner can reduce or eliminate streak artefacts in 4DCBCT images. We introduce a mathematical optimization framework and a heuristic solution method, which we will call the optimized projection allocation algorithm, to determine where to position the respiratory bins and which projections to source from neighbouring respiratory bins. Five 4DCBCT datasets from three patients were used to reconstruct 4DCBCT images. Projections were sorted into respiratory bins using equispaced, equal density and optimized projection allocation. The standard deviation of the angular separation between projections was used to assess streaking and the consistency of the segmented volume of a fiducial gold marker was used to assess motion blur. The standard deviation of the angular separation between projections using displacement binning and optimized projection allocation was 30%-50% smaller than conventional phase based binning and 59%-76% smaller than conventional displacement binning indicating more uniformly spaced projections and fewer streaking artefacts. The standard deviation in the marker volume was 20%-90% smaller when using optimized projection allocation than using conventional phase based binning suggesting more uniform marker segmentation and less motion blur. Images reconstructed using displacement binning and the optimized projection allocation algorithm were clearer, contained visibly fewer streak artefacts and produced more consistent marker segmentation than those reconstructed with either equispaced or equal-density binning. The optimized projection allocation algorithm significantly improves image quality in 4DCBCT images and provides, for the first time, a method to consistently generate high quality displacement binned 4DCBCT images in clinical applications.

Publication

A Deliverable Four-Dimensional Intensity-Modulated Radiation Therapy-Planning Method for Dynamic Multileaf Collimator Tumor Tracking Delivery

Publisher: Elsevier BV

Date: 08-2008

DOI: 10.1016/J.IJROBP.2008.04.018

Publication

Quantifying the accuracy of the tumor motion and area as a function of acceleration factor for the simulation of the dynamic keyhole magnetic resonance imaging method

Publisher: Wiley

Date: 02-05-2016

DOI: 10.1118/1.4947508

Abstract: The dynamic keyhole is a new MR image reconstruction method for thoracic and abdominal MR imaging. To date, this method has not been investigated with cancer patient magnetic resonance imaging (MRI) data. The goal of this study was to assess the dynamic keyhole method for the task of lung tumor localization using cine-MR images reconstructed in the presence of respiratory motion. The dynamic keyhole method utilizes a previously acquired a library of peripheral k-space datasets at similar displacement and phase (where phase is simply used to determine whether the breathing is inhale to exhale or exhale to inhale) respiratory bins in conjunction with central k-space datasets (keyhole) acquired. External respiratory signals drive the process of sorting, matching, and combining the two k-space streams for each respiratory bin, thereby achieving faster image acquisition without substantial motion artifacts. This study was the first that investigates the impact of k-space unders ling on lung tumor motion and area assessment across clinically available techniques (zero-filling and conventional keyhole). In this study, the dynamic keyhole, conventional keyhole and zero-filling methods were compared to full k-space dataset acquisition by quantifying (1) the keyhole size required for central k-space datasets for constant image quality across sixty four cine-MRI datasets from nine lung cancer patients, (2) the intensity difference between the original and reconstructed images in a constant keyhole size, and (3) the accuracy of tumor motion and area directly measured by tumor autocontouring. For constant image quality, the dynamic keyhole method, conventional keyhole, and zero-filling methods required 22%, 34%, and 49% of the keyhole size (P < 0.0001), respectively, compared to the full k-space image acquisition method. Compared to the conventional keyhole and zero-filling reconstructed images with the keyhole size utilized in the dynamic keyhole method, an average intensity difference of the dynamic keyhole reconstructed images (P < 0.0001) was minimal, and resulted in the accuracy of tumor motion within 99.6% (P < 0.0001) and the accuracy of tumor area within 98.0% (P < 0.0001) for lung tumor monitoring applications. This study demonstrates that the dynamic keyhole method is a promising technique for clinical applications such as image-guided radiation therapy requiring the MR monitoring of thoracic tumors. Based on the results from this study, the dynamic keyhole method could increase the imaging frequency by up to a factor of five compared with full k-space methods for real-time lung tumor MRI.

Publication

The impact of audiovisual biofeedback on 4D functional and anatomic imaging: Results of a lung cancer pilot study

Publisher: Elsevier BV

Date: 08-2016

DOI: 10.1016/J.RADONC.2016.05.016

Abstract: The impact of audiovisual (AV) biofeedback on four dimensional (4D) positron emission tomography (PET) and 4D computed tomography (CT) image quality was investigated in a prospective clinical trial (NCT01172041). 4D-PET and 4D-CT images of ten lung cancer patients were acquired with AV biofeedback (AV) and free breathing (FB). The 4D-PET images were analyzed for motion artifacts by comparing 4D to 3D PET for gross tumor volumes (GTVPET) and maximum standardized uptake values (SUVmax). The 4D-CT images were analyzed for artifacts by comparing normalized cross correlation-based scores (NCCS) and quantifying a visual assessment score (VAS). A Wilcoxon signed-ranks test was used for statistical testing. The impact of AV biofeedback varied widely. Overall, the 3D to 4D decrease of GTVPET was 1.2±1.3cm(3) with AV and 0.6±1.8cm(3) for FB. The 4D-PET increase of SUVmax was 1.3±0.9 with AV and 1.3±0.8 for FB. The 4D-CT NCCS were 0.65±0.27 with AV and 0.60±0.32 for FB (p=0.08). The 4D-CT VAS was 0.0±2.7. This study demonstrated a high patient dependence on the use of AV biofeedback to reduce motion artifacts in 4D imaging. None of the hypotheses tested were statistically significant. Future development of AV biofeedback will focus on optimizing the human-computer interface and including patient training sessions for improved comprehension and compliance.

Publication

The accuracy and precision of Kilovoltage Intrafraction Monitoring (KIM) six degree-of-freedom prostate motion measurements during patient treatments

Publisher: Elsevier BV

Date: 02-2018

DOI: 10.1016/J.RADONC.2017.10.030

Abstract: To perform a quantitative analysis of the accuracy and precision of Kilovoltage Intrafraction Monitoring (KIM) six degree-of-freedom (6DoF) prostate motion measurements during treatments. Real-time 6DoF prostate motion was acquired using KIM for 14 prostate cancer patients (377 fractions). KIM outputs the 6DoF prostate motion, combining 3D translation and 3D rotational motion information relative to its planning position. The corresponding groundtruth target motion was obtained post-treatment based on kV/MV triangulation. The accuracy and precision of the 6DoF KIM motion estimates were calculated as the mean and standard deviation differences compared with the ground-truth. The accuracy ± precision of real-time 6DoF KIM-measured prostate motion were 0.2 ± 1.3° for rotations and 0.1 ± 0.5 mm for translations, respectively. The magnitude of KIM-measured motion was well-correlated with the magnitude of ground-truth motion resulting in Pearson correlation coefficients of ≥0.88 in all DoF. The results demonstrate that KIM is capable of providing the real-time 6DoF prostate target motion during patient treatments with an accuracy ± precision of within 0.2 ± 1.3° and 0.1 ± 0.5 mm for rotation and translation, respectively. As KIM only requires a single X-ray imager, which is available on most modern cancer radiotherapy devices, there is potential for widespread adoption of this technology.

Publication

Electron contamination modeling and reduction in a 1 T open bore inline MRI-linac system

Publisher: Wiley

Date: 21-04-2014

DOI: 10.1118/1.4871618

Abstract: A potential side effect of inline MRI-linac systems is electron contamination focusing causing a high skin dose. In this work, the authors reexamine this prediction for an open bore 1 T MRI system being constructed for the Australian MRI-Linac Program. The efficiency of an electron contamination deflector (ECD) in purging electron contamination from the linac head is modeled, as well as the impact of a helium gas region between the deflector and phantom surface for lowering the amount of air-generated contamination. Magnetic modeling of the 1 T MRI was used to generate 3D magnetic field maps both with and without the presence of an ECD located immediately below the MLC's. Forty-seven different ECD designs were modeled and for each the magnetic field map was imported into Geant4 Monte Carlo simulations including the linac head, ECD, and a 30 × 30 × 30 cm(3) water phantom located at isocenter. For the first generation system, the x-ray source to isocenter distance (SID) will be 160 cm, resulting in an 81.2 cm long air gap from the base of the ECD to the phantom surface. The first 71.2 cm was modeled as air or helium gas, with the latter encased between two windows of 50 μm thick high density polyethlyene. 2D skin doses (at 70 μm depth) were calculated across the phantom surface at 1 × 1 mm(2) resolution for 6 MV beams of field size of 5 × 5, 10 × 10, and 20 × 20 cm(2). The skin dose was predicted to be of similar magnitude as the generic systems modeled in previous work, 230% to 1400% of D(max) for 5 × 5 to 20 × 20 cm(2), respectively. Inclusion of the ECD introduced a nonuniformity to the MRI imaging field that ranged from ∼20 to ∼140 ppm while the net force acting on the ECD ranged from ∼151 N to ∼1773 N. Various ECD designs were 100% efficient at purging the electron contamination into the ECD magnet banks however, a small percentage were scattered back into the beam and continued to the phantom surface. Replacing a large portion of the extended air-column between the ECD and phantom surface with helium gas is a key element as it significantly minimized the air-generated contamination. When using an optimal ECD and helium gas region, the 70 μm skin dose is predicted to increase moderately inside a small hot spot over that of the case with no magnetic field present for the jaw defined square beams examined here. These increases include from 12% to 40% of [Formula: see text] for 5 × 5 cm(2), 18% to 55% of D(max) for 10 × 10 cm(2), and from 23% to 65% of D(max) for 20 × 20 cm(2). Coupling an efficient ECD and helium gas region below the MLCs in the 160 cm isocenter MRI-linac system is predicted to ameliorate the impact electron contamination focusing has on skin dose increases. An ECD is practical as its impact on the MRI imaging distortion is correctable, and the mechanical forces acting on it manageable from an engineering point of view.

Publication

Detailed analysis of latencies in image‐based dynamic MLC trackinga)

Publisher: Wiley

Date: 27-08-2010

DOI: 10.1118/1.3480504

Publication

The development and investigation of a prototype three-dimensional compensator for whole brain radiation therapy

Publisher: IOP Publishing

Date: 09-04-2008

DOI: 10.1088/0031-9155/53/9/004

Abstract: Whole brain radiation therapy (WBRT) is the standard treatment for patients with brain metastases, and is often used in conjunction with stereotactic radiotherapy for patients with a limited number of brain metastases, as well as prophylactic cranial irradiation. The use of open fields (conventionally used for WBRT) leads to higher doses to the brain periphery if dose is prescribed to the brain center at the largest lateral radius. These dose variations potentially compromise treatment efficacy and translate to increased side effects. The goal of this research was to design and construct a 3D 'brain wedge' to compensate dose heterogeneities in WBRT. Radiation transport theory was invoked to calculate the desired shape of a wedge to achieve a uniform dose distribution at the sagittal plane for an ellipsoid irradiated medium. The calculations yielded a smooth 3D wedge design to account for the missing tissue at the peripheral areas of the brain. A wedge was machined based on the calculation results. Three ellipsoid phantoms, spanning the mean and +/- two standard deviations from the mean cranial dimensions were constructed, representing 95% of the adult population. Film was placed at the sagittal plane for each of the three phantoms and irradiated with 6 MV photons, with the wedge in place. Sagittal plane isodose plots for the three phantoms demonstrated the feasibility of this wedge to create a homogeneous distribution with similar results observed for the three phantom sizes, indicating that a single wedge may be sufficient to cover 95% of the adult population. The sagittal dose is a reasonable estimate of the off-axis dose for whole brain radiation therapy. Comparing the dose with and without the wedge the average minimum dose was higher (90% versus 86%), the maximum dose was lower (107% versus 113%) and the dose variation was lower (one standard deviation 2.7% versus 4.6%). In summary, a simple and effective 3D wedge for whole brain radiotherapy has been developed. The wedge gives a more uniform dose distribution than commonly used techniques. Further development and shape optimization may be necessary prior to clinical implementation.

Publication

Electromagnetic-Guided Dynamic Multileaf Collimator Tracking Enables Motion Management for Intensity-Modulated Arc Therapy

Publisher: Elsevier BV

Date: 2011

DOI: 10.1016/J.IJROBP.2010.03.011

Publication

MArkerless image Guidance using Intrafraction Kilovoltage x-ray imaging (MAGIK): study protocol for a phase I interventional study for lung cancer radiotherapy

Publisher: BMJ

Date: 2022

DOI: 10.1136/BMJOPEN-2021-057135

Abstract: In radiotherapy, tumour tracking leads the radiation beam to accurately target the tumour while it moves in a complex and unpredictable way due to respiration. Several tumour tracking techniques require the implantation of fiducial markers around the tumour, a procedure that involves unnecessary risks and costs. Markerless tumour tracking (MTT) negates the need for implanted markers, potentially enabling accurate and optimal radiotherapy in a non-invasive way. We will perform a phase I interventional trial called MA rkerless image G uidance using I ntrafraction K ilovoltage x-ray imaging (MAGIK) to investigate the technical feasibility of the MTT technology developed at the University of Sydney (sponsor). 30 participants will undergo the current standard of care lung stereotactic ablative radiation therapy, with the exception that kilovoltage X-ray images will be acquired continuously during treatment delivery to enable MTT. If MTT indicates that the mean lung tumour position has shifted mm, a warning message will be displayed to indicate the need for a treatment intervention. The radiation therapist will then pause the treatment, shift the treatment couch to account for the shift in tumour position and resume the treatment. Participants will be implanted with fiducial markers, which act as the ground truth for evaluating the accuracy of MTT. MTT is considered feasible if the tracking accuracy is mm in each dimension for % of the treatment time. The MAGIK trial has received ethical approval from The Alfred Human Research Ethics Committee and has been registered with ClinicalTrials.gov with the Identifier: NCT04086082 . Estimated time of first recruitment is early 2022. The study recruitment and data analysis phases will be performed concurrently. Treatment for all 30 participants is expected to be completed within 2 years and participant follow-up within a total duration of 7 years. Findings will be disseminated through peer-reviewed publications and conference presentations. NCT04086082 Pre-result.

Publication

Public Theology and the Challenge of Feminism

Publisher: Routledge

Date: 05-2015

DOI: 10.4324/9781315744223

Publication

Measuring interfraction and intrafraction lung function changes during radiation therapy using four‐dimensional cone beam CT ventilation imaging

Publisher: Wiley

Date: 20-02-2015

DOI: 10.1118/1.4907991

Publication

Reducing 4DCBCT imaging time and dose: the first implementation of variable gantry speed 4DCBCT on a linear accelerator

Publisher: IOP Publishing

Date: 05-05-2017

DOI: 10.1088/1361-6560/62/11/4300

Abstract: Four dimensional cone beam computed tomography (4DCBCT) uses a constant gantry speed and imaging frequency that are independent of the patient's breathing rate. Using a technique called respiratory motion guided 4DCBCT (RMG-4DCBCT), we have previously demonstrated that by varying the gantry speed and imaging frequency, in response to changes in the patient's real-time respiratory signal, the imaging dose can be reduced by 50-70%. RMG-4DCBCT optimally computes a patient specific gantry trajectory to eliminate streaking artefacts and projection clustering that is inherent in 4DCBCT imaging. The gantry trajectory is continuously updated as projection data is acquired and the patient's breathing changes. The aim of this study was to realise RMG-4DCBCT for the first time on a linear accelerator. To change the gantry speed in real-time a potentiometer under microcontroller control was used to adjust the current supplied to an Elekta Synergy's gantry motor. A real-time feedback loop was developed on the microcontroller to modulate the gantry speed and projection acquisition in response to the real-time respiratory signal so that either 40, RMG-4DCBCT

Publication

TH‐C‐BRC‐09: Commissioning of a 3D MicroCT‐Based Small Animal Radiotherapy System

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182623

Publication

A comparison of gantry-mounted x-ray-based real-Time target tracking methods:

Publisher: Wiley

Date: 13-02-2018

DOI: 10.1002/MP.12765

Abstract: Most modern radiotherapy machines are built with a 2D kV imaging system. Combining this imaging system with a 2D-3D inference method would allow for a ready-made option for real-time 3D tumor tracking. This work investigates and compares the accuracy of four existing 2D-3D inference methods using both motion traces inferred from external surrogates and measured internally from implanted beacons. Tumor motion data from 160 fractions (46 thoracic/abdominal patients) of Synchrony traces (inferred traces), and 28 fractions (7 lung patients) of Calypso traces (internal traces) from the LIGHT SABR trial (NCT02514512) were used in this study. The motion traces were used as the ground truth. The ground truth trajectories were used in silico to generate 2D positions projected on the kV detector. These 2D traces were then passed to the 2D-3D inference methods: interdimensional correlation, Gaussian probability density function (PDF), arbitrary-shape PDF, and the Kalman filter. The inferred 3D positions were compared with the ground truth to determine tracking errors. The relationships between tracking error and motion magnitude, interdimensional correlation, and breathing periodicity index (BPI) were also investigated. Larger tracking errors were observed from the Calypso traces, with RMS and 95th percentile 3D errors of 0.84-1.25 mm and 1.72-2.64 mm, compared to 0.45-0.68 mm and 0.74-1.13 mm from the Synchrony traces. The Gaussian PDF method was found to be the most accurate, followed by the Kalman filter, the interdimensional correlation method, and the arbitrary-shape PDF method. Tracking error was found to strongly and positively correlate with motion magnitude for both the Synchrony and Calypso traces and for all four methods. Interdimensional correlation and BPI were found to negatively correlate with tracking error only for the Synchrony traces. The Synchrony traces exhibited higher interdimensional correlation than the Calypso traces especially in the anterior-posterior direction. Inferred traces often exhibit higher interdimensional correlation, which are not true representation of thoracic/abdominal motion and may underestimate kV-based tracking errors. The use of internal traces acquired from systems such as Calypso is advised for future kV-based tracking studies. The Gaussian PDF method is the most accurate 2D-3D inference method for tracking thoracic/abdominal targets. Motion magnitude has significant impact on 2D-3D inference error, and should be considered when estimating kV-based tracking error.

Publication

TH‐C‐BRC‐10: Evaluation of a Micro‐CT Based 3D Conformal Animal Radiotherapy System

Publisher: Wiley

Date: 06-2009

DOI: 10.1118/1.3182624

Publication

Changes in Regional Ventilation During Treatment and Dosimetric Advantages of CT Ventilation Image Guided Radiation Therapy for Locally Advanced Lung Cancer

Publisher: Elsevier BV

Date: 11-2018

DOI: 10.1016/J.IJROBP.2018.04.063

Publication

Nests and eggs of the Chestnut-backed Button-quail Turnix castanotus: Two new nests and a review of previous descriptions

Publisher: BirdLife Australia, Ltd.

Date: 2022

DOI: 10.20938/AFO39012018

Abstract: The Chestnut-backed Button-quail Turnix castanotus is a small, cryptic, ground-dwelling species endemic to savanna ecosystems of northern Australia. Due to aspects of its ecology, cryptic plumage and behaviour, and the remoteness of most of its distribution, there are few published observations from the field documenting its breeding biology. The eggs were first described in 1856 and have subsequently been described by other authors. Two nests were detected in the Northern Territory in March 2021. We compare nesting events there with previous descriptions and museum collections. Our findings are mostly consistent with other literature on this species, but are inconsistent with two contemporary accounts, which we suggest are based on misidentification of Painted Button-quail T. varius.

Publication

WE‐D‐204B‐02: Correlated 3D Respiratory Motion Prediction with Low‐Dimensional Feature‐Based Learning

Publisher: Wiley

Date: 06-2010

DOI: 10.1118/1.3469399

Publication

Linac-Based Image Guided Intensity Modulated Radiation Therapy

Publisher: Springer Berlin Heidelberg

Date: 2011

DOI: 10.1007/174_2011_325

Publication

MO‐F‐BRC‐01: 3D Target Trajectory Reconstruction Using CBCT Projection Images

Publisher: Wiley

Date: 06-2011

DOI: 10.1118/1.3613008

Publication

Image-Based Dynamic Multileaf Collimator Tracking of Moving Targets During Intensity-Modulated Arc Therapy

Publisher: Elsevier BV

Date: 06-2012

DOI: 10.1016/J.IJROBP.2011.12.053

Publication

Radiotherapy beyond cancer: Target localization in real‐time MRI and treatment planning for cardiac radiosurgery

Publisher: Wiley

Date: 17-11-2014

DOI: 10.1118/1.4901414

Abstract: Atrial fibrillation (AFib) is the most common cardiac arrhythmia that affects millions of patients world-wide. AFib is usually treated with minimally invasive, time consuming catheter ablation techniques. While recently noninvasive radiosurgery to the pulmonary vein antrum (PVA) in the left atrium has been proposed for AFib treatment, precise target location during treatment is challenging due to complex respiratory and cardiac motion. A MRI linear accelerator (MRI-Linac) could solve the problems of motion tracking and compensation using real-time image guidance. In this study, the authors quantified target motion ranges on cardiac magnetic resonance imaging (MRI) and analyzed the dosimetric benefits of margin reduction assuming real-time motion compensation was applied. For the imaging study, six human subjects underwent real-time cardiac MRI under free breathing. The target motion was analyzed retrospectively using a template matching algorithm. The planning study was conducted on a CT of an AFib patient with a centrally located esophagus undergoing catheter ablation, representing an ideal case for cardiac radiosurgery. The target definition was similar to the ablation lesions at the PVA created during catheter treatment. Safety margins of 0 mm (perfect tracking) to 8 mm (untracked respiratory motion) were added to the target, defining the planning target volume (PTV). For each margin, a 30 Gy single fraction IMRT plan was generated. Additionally, the influence of 1 and 3 T magnetic fields on the treatment beam delivery was simulated using Monte Carlo calculations to determine the dosimetric impact of MRI guidance for two different Linac positions. Real-time cardiac MRI showed mean respiratory target motion of 10.2 mm (superior-inferior), 2.4 mm (anterior-posterior), and 2 mm (left-right). The planning study showed that increasing safety margins to encompass untracked respiratory motion leads to overlapping structures even in the ideal scenario, compromising either normal tissue dose constraints or PTV coverage. The magnetic field caused a slight increase in the PTV dose with the in-line MRI-Linac configuration. The authors' results indicate that real-time tracking and motion compensation are mandatory for cardiac radiosurgery and MRI-guidance is feasible, opening the possibility of treating cardiac arrhythmia patients completely noninvasively.

Publication

Proof-of-concept for x-ray based real-time image guidance during cardiac radioablation

Publisher: IOP Publishing

Date: 24-08-2021

DOI: 10.1088/1361-6560/AC1834

Publication

Accounting for both automated recording unit detection space and signal recognition performance in acoustic surveys: A protocol applied to the cryptic and critically endangered Night Parrot (Pezopo

Publisher: Wiley

Date: 03-12-2021

DOI: 10.1111/AEC.13128

Abstract: Research into the suitability of autonomous recording units (ARUs) when surveying for vocal species is increasing. Simultaneously, there has been extensive research into methods for efficiently extracting signals of interest from the acoustic data sets that accrue from the deployment of ARUs. For some species, bioacoustic monitoring supported by computerised signal detection offers the only effective and efficient method for widespread survey. In these circumstances, the detection space of both the ARU and the performance of the signal detection process must be considered concurrently, but typically, these two elements have been considered separately. Here, using the Night Parrot ( Pezoporus occidentalis ) as a case study, we consider both ARU detection space and the signal detection process to develop a robust and repeatable survey protocol for the species. After developing a call recogniser for the Night Parrot, we test its performance on a data set of Night Parrot calls given at a known distance from an array of ARUs. Having established a relationship between ARU type, recogniser performance and distance, we determine the s ling radius of an ARU for a given recogniser score cut‐off, and the associated probability of detecting a Night Parrot that calls within that s ling radius. Using these data, we outline how to develop a robust and repeatable survey protocol for the Night Parrot, with a defined probability of detection. This protocol could be adapted for other scenarios where deployment of ARUs is necessary to determine a species’ status and distribution.

Publication

The first-in-human implementation of adaptive 4D cone beam CT for lung cancer radiotherapy: 4DCBCT in less time with less dose

Publisher: Elsevier BV

Date: 08-2021

DOI: 10.1016/J.RADONC.2021.05.021

Publication

The impact of audio-visual biofeedback on 4D PET images: Results of a phantom study

Publisher: Wiley

Date: 03-02-2012

DOI: 10.1118/1.3679012

Publication

MRI-guided cardiac-induced target motion tracking for atrial fibrillation cardiac radioablation

Publisher: Elsevier BV

Date: 11-2021

DOI: 10.1016/J.RADONC.2021.09.025

Publication

A method of dose reconstruction for moving targets compatible with dynamic treatments

Publisher: Wiley

Date: 25-09-2012

DOI: 10.1118/1.4754297

Publication

Four-Dimensional Computed Tomography Ventilation Image-Guided Lung Functional Avoidance Radiation Therapy: A Single-Arm Prospective Pilot Clinical Trial

Publisher: Elsevier BV

Date: 04-2023

DOI: 10.1016/J.IJROBP.2022.11.026

Abstract: The primary objective of this prospective pilot trial was to assess the safety and feasibility of lung functional avoidance radiotherapy (RT) with 4-dimensional (4D) computed tomography (CT) ventilation imaging. Patients with primary lung cancer or metastatic disease to the lungs to receive conventionally fractionated RT (CFRT) or stereotactic body RT (SBRT) were eligible. Standard-of-care 4D-CT scans were used to generate ventilation images through image processing/analysis. Each patient required a standard intensity-modulated RT plan and ventilation image-guided functional avoidance plan. The primary endpoint was the safety of functional avoidance RT, defined as the rate of grade ≥3 adverse events (AEs) that occurred ≤12 months after treatment. Protocol treatment was considered safe if the rates of grade ≥3 pneumonitis and esophagitis were <13% and <21%, respectively for CFRT, and if the rate of any grade ≥3 AEs was <28% for SBRT. Feasibility of functional avoidance RT was assessed by comparison of dose metrics between the two plans using the Wilcoxon signed-rank test. Between May 2015 and November 2019, 34 patients with non-small cell lung cancer were enrolled, and 33 patients were evaluable (n=24 for CFRT n=9 for SBRT). Median follow-up was 14.7 months. For CFRT, the rates of grade ≥3 pneumonitis and esophagitis were 4.2% (95% confidence interval, 0.1%-21.1%) and 12.5% (2.7%-32.4%). For SBRT, no patients developed grade ≥3 AEs. Compared with the standard plans, the functional avoidance plans significantly (p<0.01) reduced the lung dose-function metrics without compromising target coverage or adherence to standard organs at risk constraints. This study, representing one of the first prospective investigations on lung functional avoidance RT, demonstrated that the 4D-CT ventilation image-guided functional avoidance RT that significantly reduced dose to ventilated lung regions could be safely administered, adding to the growing body of evidence for its clinical utility.

Publication

Reducing 4DCBCT scan time and dose through motion compensated acquisition and reconstruction

Publisher: IOP Publishing

Date: 23-03-2021

DOI: 10.1088/1361-6560/ABEBFB

Abstract: Conventional 4DCBCT captures 1320 projections across 4 min. Adaptive 4DCBCT has been developed to reduce imaging dose and scan time. This study investigated reconstruction algorithms that best complement adaptive 4DCBCT acquisition for reducing imaging dose and scan time whilst maintaining or improving image quality compared to conventional 4DCBCT acquisition using real patient data from the first 10 adaptive 4DCBCT patients. Adaptive 4DCBCT was implemented in the ADaptive CT Acquisition for Personalized Thoracic imaging clinical trial. Adaptive 4DCBCT modulates gantry rotation speed and kV acquisition rate in response to the patient’s real-time respiratory signal, ensuring even angular spacing between projections at each respiratory phase. We examined the first 10 lung cancer radiotherapy patients that received adaptive 4DCBCT. Fast, 200-projection scans over 60–80 s, and slower, 600-projection scans over ∼240 s, were obtained after routine patient treatment and compared against conventional 4DCBCT acquisition. Adaptive 4DCBCT acquisitions were reconstructed using Feldk −Davis−Kress (FDK), McKinnon–Bates (MKB), Motion Compensated FDK (MCFDK) and Motion Compensated MKB (MCMKB) algorithms. Reconstructions were assessed via, Structural SIMilarity (SSIM), Signal-to-Noise-Ratio (SNR), Contrast-to-Noise-Ratio (CNR), Tissue Interface Sharpness of Diaphragm (TIS-D) and Tumor (TIS-T). The 200- and 600-projection adaptive 4DCBCT acquisition corresponded to 85% and 55% reduction in imaging dose, shorter and similar scan times of approximately 90 s and 236 s respectively, compared to conventional 4DCBCT acquisition. 200- and 600-projection adaptive 4DCBCT reconstructions achieved more than 0.900 SSIM relative to conventional 4DCBCT acquisition. Compared to conventional 4DCBCT acquisition, 200-projection adaptive 4DCBCT reconstructions achieved higher SNR, CNR, TIS-T, TIS-D with motion compensated algorithms, MCFDK (208%, 159%, 174%, 247%) and MCMKB (214%, 173%, 266%, 245%) respectively. The 200-projection adaptive 4DCBCT MCFDK- and MCMKB-reconstruction results show image quality improvements are possible even with 85% fewer projections acquired. We established acquisition-reconstruction protocols that provide substantial reductions in imaging time and dose whilst improving image quality.

Publication

Real-time dose-guidance in radiotherapy: Proof of principle

Publisher: Elsevier BV

Date: 11-2021

DOI: 10.1016/J.RADONC.2021.09.024

Publication

4-Dimensional Cone Beam Computed Tomography–Measured Target Motion Underrepresents Actual Motion

Publisher: Elsevier BV

Date: 11-2018

DOI: 10.1016/J.IJROBP.2018.04.056

Abstract: Four-dimensional cone beam computed tomography (4DCBCT) facilitates verification of lung tumor motion before each treatment fraction and enables accurate patient setup in lung stereotactic ablative body radiation therapy. This work aims to quantify the real-time motion represented in 4DCBCT, depending on the reconstruction algorithm and the respiratory signal utilized for reconstruction. Eight lung cancer patients were implanted with electromagnetic Calypso beacons in airways close to the tumor, enabling real-time motion measurements. 4DCBCT scans were reconstructed from projections for treatment setup CBCT for 1 to 2 fractions of 8 patients with the Feldk -Davis-Kress (FDK) algorithm or the prior image constrained compressed sensing (PICCS) method and internal real-time Calypso beacon trajectories or an external respiratory signal (bellows belt). The real-time beacon centroid ("target") motion was compared with beacon centroid positions segmented in the 4DCBCT reconstructions. We tested the hypotheses that (1) the actual target motion was accurately represented in the reconstructions and (2) the reconstruction/respiratory signal combinations performed similarly in the representation of the real-time motion. On average the target motion was significantly underrepresented and exceeded the 4DCBCT motion for 48%, 25%, and 40% of the time in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions, respectively. The average underrepresentation for the LR, SI, and AP direction was 1.7 mm, 4.2 mm, and 2.5 mm, respectively. No difference could be shown between the reconstruction algorithms or respiratory signals in LR direction (FDK vs PICCS: P = .47, Calypso vs bellows: P = .19), SI direction (FDK vs PICCS: P = .49, Calypso vs bellows: P = .22), and AP direction (FDK vs PICCS: P = .62, Calypso vs bellows: P = .34). The 4DCBCT scans all underrepresented the real-time target motion. The selection of the reconstruction algorithm and respiratory signal for the 4DCBCT reconstruction does not have an impact on the reconstructed motion range.

Publication

Cone-beam CT reconstruction with gravity-induced motion

Publisher: IOP Publishing

Date: 16-10-2018

DOI: 10.1088/1361-6560/AAE1BB

Abstract: Fixed-gantry cone-beam computed tomography (CBCT), where the imaging hardware is fixed while the subject is continuously rotated 360° in the horizontal position, has implications for building compact and affordable fixed-gantry linear accelerators (linacs). Fixed-gantry imaging with a rotating subject presents a challenging image reconstruction problem where the gravity-induced motion is coupled to the subject's rotation angle. This study is the first to investigate the feasibility of fixed-gantry CBCT using imaging data of three live rabbits in an ethics-approved study. A novel data-driven motion correction method that combines partial-view reconstruction and motion compensation was developed to overcome this challenge. Fixed-gantry CBCT scans of three live rabbits were acquired on a standard radiotherapy system with the imaging beam fixed and the rabbits continuously rotated using an in-house programmable rotation cradle. The reconstructed images of the thoracic region were validated against conventional CBCT scans acquired at different cradle rotation angles. Results showed that gravity-induced motion caused severe motion blur in all of the cases if unaccounted for. The proposed motion correction method yielded clinically usable image quality with <1 mm gravity-induced motion blur for rabbits that were securely immobilized on the rotation cradle. Shapes of the anatomic structures were correctly reconstructed with <0.5 mm accuracy. Translational motion accounted for the majority of gravity-induced motion. The motion-corrected reconstruction represented the time-averaged location of the thoracic region over a 360° rotation. The feasibility of fixed-gantry CBCT has been demonstrated. Future work involves the validation of imaging accuracy for human subjects, which will be useful for emerging compact fixed-gantry radiotherapy systems.

Publication

Rapid distortion correction enables accurate magnetic resonance imaging-guided real-time adaptive radiotherapy

Publisher: Elsevier BV

Date: 2023

DOI: 10.1016/J.PHRO.2023.100414

Publication

Magnetic resonance imaging (MRI) guided proton therapy: A review of the clinical challenges, potential benefits and pathway to implementation.

Publisher: Elsevier BV

Date: 05-2022

DOI: 10.1016/J.RADONC.2022.02.031

Publication

Toward Submillimeter Accuracy in the Management of Intrafraction Motion: The Integration of Real-Time Internal Position Monitoring and Multileaf Collimator Target Tracking

Publisher: Elsevier BV

Date: 06-2009

DOI: 10.1016/J.IJROBP.2008.12.057

Abstract: We report on an integrated system for real-time adaptive radiation delivery to moving tumors. The system combines two promising technologies-three-dimensional internal position monitoring using implanted electromagnetically excitable transponders and corresponding real-time beam adaptation using a dynamic multileaf collimator (DMLC). In a multi-institutional academic and industrial collaboration, a research version of the Calypso position monitoring system was integrated with a DMLC-based four-dimensional intensity-modulated radiotherapy delivery system using a Varian 120-leaf multileaf collimator (MLC). Two important determinants of system performance-latency (i.e., elapsed time between target motion and MLC response) and geometric accuracy-were investigated. Latency was quantified by acquiring continuous megavoltage X-ray images of a moving phantom (with embedded transponders) that was tracked in real time by a circular MLC field. The latency value was input into a motion prediction algorithm within the DMLC tracking system. Geometric accuracy was calculated as the root-mean-square positional error between the target and the centroid of the MLC aperture for patient-derived three-dimensional motion trajectories comprising two lung tumor traces and one prostate trace. System latency was determined to be approximately 220 milliseconds. Tracking accuracy was observed to be sub-2 mm for the respiratory motion traces and sub-1 mm for prostate motion. We have developed and characterized a research version of a novel four-dimensional delivery system that integrates nonionizing radiation-based internal position monitoring and accurate real-time DMLC-based beam adaptation. This system represents a significant step toward achieving the eventual goal of geometrically ideal dose delivery to moving tumors.

Publication

SU‐DD‐A3‐05: Experimental Investigation of a Monoscopic Real‐Time Tumor Tracking Method Combining Occasional X‐Ray Imaging and Continuous External Respiratory Monitoring

Publisher: Wiley

Date: 06-2008

DOI: 10.1118/1.2961366

Publication

Commissioning and quality assurance for a respiratory training system based on audiovisual biofeedback

Publisher: Wiley

Date: 12-07-2010

DOI: 10.1120/JACMP.V11I4.3262

Publication

Retrospective Analysis of Artifacts in Four-Dimensional CT Images of 50 Abdominal and Thoracic Radiotherapy Patients

Publisher: Elsevier BV

Date: 11-2008

DOI: 10.1016/J.IJROBP.2008.06.1937

Publication

Development and testing of a database of NIH research funding of AAPM members: A report from the AAPM Working Group for the Development of a Research Database (WGDRD)

Publisher: Wiley

Date: 04-2017

DOI: 10.1002/MP.12098

Publication

MRI Linac Systems

Publisher: Springer International Publishing

Date: 2019

DOI: 10.1007/978-3-030-14442-5_10

Publication

Real‐time soft tissue motion estimation for lung tumors during radiotherapy delivery

Publisher: Wiley

Date: 26-08-2013

DOI: 10.1118/1.4818655

Publication

MRI-guidance for motion management in external beam radiotherapy: current status and future challenges

Publisher: IOP Publishing

Date: 20-11-2018

DOI: 10.1088/1361-6560/AAEBCF

Abstract: High precision conformal radiotherapy requires sophisticated imaging techniques to aid in target localisation for planning and treatment, particularly when organ motion due to respiration is involved. X-ray based imaging is a well-established standard for radiotherapy treatments. Over the last few years, the ability of magnetic resonance imaging (MRI) to provide radiation-free images with high-resolution and superb soft tissue contrast has highlighted the potential of this imaging modality for radiotherapy treatment planning and motion management. In addition, these advantageous properties motivated several recent developments towards combined MRI radiation therapy treatment units, enabling in-room MRI-guidance and treatment adaptation. The aim of this review is to provide an overview of the state-of-the-art in MRI-based image guidance for organ motion management in external beam radiotherapy. Methodological aspects of MRI for organ motion management are reviewed and their application in treatment planning, in-room guidance and adaptive radiotherapy described. Finally, a roadmap for an optimal use of MRI-guidance is highlighted and future challenges are discussed.

Publication

Commissioning of a novel microCT/RT system for small animal conformal radiotherapy

Publisher: IOP Publishing

Date: 28-05-2009

DOI: 10.1088/0031-9155/54/12/008

Publication

Dose enhancement in radiotherapy of small lung tumors using inline magnetic fields: A Monte Carlo based planning study

Publisher: Wiley

Date: 29-12-2016

DOI: 10.1118/1.4938580

Abstract: To report on significant dose enhancement effects caused by magnetic fields aligned parallel to 6 MV photon beam radiotherapy of small lung tumors. Findings are applicable to future inline MRI-guided radiotherapy systems. A total of eight clinical lung tumor cases were recalculated using Monte Carlo methods, and external magnetic fields of 0.5, 1.0, and 3 T were included to observe the impact on dose to the planning target volume (PTV) and gross tumor volume (GTV). Three plans were 6 MV 3D-CRT plans while 6 were 6 MV IMRT. The GTV's ranged from 0.8 to 16 cm(3), while the PTV's ranged from 1 to 59 cm(3). In addition, the dose changes in a 30 cm diameter cylindrical water phantom were investigated for small beams. The central 20 cm of this phantom contained either water or lung density insert. For single beams, an inline magnetic field of 1 T has a small impact in lung dose distributions by reducing the lateral scatter of secondary electrons, resulting in a small dose increase along the beam. Superposition of multiple small beams leads to significant dose enhancements. Clinically, this process occurs in the lung tissue typically surrounding the GTV, resulting in increases to the D98% (PTV). Two isolated tumors with very small PTVs (3 and 6 cm(3)) showed increases in D98% of 23% and 22%. Larger PTVs of 13, 26, and 59 cm(3) had increases of 9%, 6%, and 4%, describing a natural fall-off in enhancement with increasing PTV size. However, three PTVs bounded to the lung wall showed no significant increase, due to lack of dose enhancement in the denser PTV volume. In general, at 0.5 T, the GTV mean dose enhancement is around 60% lower than that at 1 T, while at 3 T, it is 5%-60% higher than 1 T. Monte Carlo methods have described significant and predictable dose enhancement effects in small lung tumor plans for 6 MV radiotherapy when an external inline magnetic field is included. Results of this study indicate that future clinical inline MRI-guided radiotherapy systems will be able to deliver a dosimetrically superior treatment to small (PTV < 15 cm(3)), isolated lung tumors over non-MRI-Linac systems. This increased efficacy coincides with the reimbursement in the United States of lung CT screening and the likely rapid growth in the number of patients with small lung tumors to be treated with radiotherapy.

Publication

Dose-based optimisation for multi-leaf collimator tracking during radiation therapy

Publisher: IOP Publishing

Date: 15-03-2021

DOI: 10.1088/1361-6560/ABE836

Abstract: Motion in the patient anatomy causes a reduction in dose delivered to the target, while increasing dose to healthy tissue. Multi-leaf collimator (MLC) tracking has been clinically implemented to adapt dose delivery to account for intrafraction motion. Current methods shift the planned MLC aperture in the direction of motion, then optimise the new aperture based on the difference in fluence. The drawback of these methods is that 3D dose, a function of patient anatomy and MLC aperture sequence, is not properly accounted for. To overcome the drawback of current fluence-based methods, we have developed and investigated real-time adaptive MLC tracking based on dose optimisation. A novel MLC tracking algorithm, dose optimisation, has been developed which accounts for the moving patient anatomy by optimising the MLC based on the dose delivered during treatment, simulated using a simplified dose calculation algorithm. The MLC tracking with dose optimisation method was applied in silico to a prostate cancer VMAT treatment dataset with observed intrafraction motion. Its performance was compared to MLC tracking with fluence optimisation and, as a baseline, without MLC tracking. To quantitatively assess performance, we computed the dose error and 3D γ failure rate (2 mm/2%) for each fraction and method. Dose optimisation achieved a γ failure rate of (4.7 ± 1.2)% (mean and standard deviation) over all fractions, which was significantly lower than fluence optimisation (7.5 ± 2.9)% (Wilcoxon sign-rank test p 0.01). Without MLC tracking, a γ failure rate of (15.3 ± 12.9)% was achieved. By considering the accumulation of dose in the moving anatomy during treatment, dose optimisation is able to optimise the aperture to actively target regions of underdose while avoiding overdose.

Publication

Investigation of the effects of treatment planning variables in small animal radiotherapy dose distributions

Publisher: Wiley

Date: 13-01-2010

DOI: 10.1118/1.3276738

Abstract: Methods used for small animal radiation treatment have yet to achieve the same dose targeting as in clinical radiation therapy. Toward understanding how to better plan small animal radiation using a system recently developed for this purpose, the authors characterized dose distributions produced from conformal radiotherapy of small animals in a microCT scanner equipped with a variable-aperture collimator. Dose distributions delivered to a cylindrical solid water phantom were simulated using a Monte Carlo algorithm. Phase-space files for 120 kVp x-ray beams and collimator widths of 1-10 mm at isocenter were generated using BEAMnrc software, and dose distributions for evenly spaced beams numbered from 5 to 80 were generated in DOSXYZnrc for a variety of targets, including centered spherical targets in a range of sizes, spherical targets offset from centered by various distances, and various ellipsoidal targets. Dose distributions were analyzed using dose volume histograms. The dose delivered to a mouse bearing a spontaneous lung tumor was also simulated, and dose volume histograms were generated for the tumor, heart, left lung, right lung, and spinal cord. Results indicated that for centered, symmetric targets, the number of beams required to achieve a smooth dose volume histogram decreased with increased target size. Dose distributions for noncentered, symmetric targets did not exhibit any significant loss of conformality with increasing offset from the phantom center, indicating sufficient beam penetration through the phantom for targeting superficial targets from all angles. Even with variable collimator widths, targeting of asymmetric targets was found to have less conformality than that of spherical targets. Irradiation of a mouse lung tumor with multiple beam widths was found to effectively deliver dose to the tumor volume while minimizing dose to other critical structures. Overall, this method of generating and analyzing dose distributions provides a quantitative method for developing practical guidelines for small animal radiotherapy treatment planning. Future work should address methods to improve conformality in asymmetric targets.

Publication

TH-A-WAB-09: The Potential of Positron Emission Tomography (PET) for Intra-Treatment Dynamic Tumor Tracking During Radiotherapy: A Phantom Study

Publisher: Wiley

Date: 06-2013

DOI: 10.1118/1.4815703

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University Of Sydney

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Paul Keall

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Publications

Optimising multi-target multileaf collimator tracking using real-time dose for locally advanced prostate cancer patients

Time-resolved volumetric MRI in MRI-guided radiotherapy: an in silico comparative analysis

IGRT and motion management during lung SBRT delivery

An EPID-based system for gantry-resolved MLC quality assurance for VMAT

An analysis of thoracic and abdominal tumour motion for stereotactic body radiotherapy patients

Geometric uncertainty analysis of MLC tracking for lung SABR

Quantifying the image quality and dose reduction of respiratory triggered 4D cone-beam computed tomography with patient-measured breathing

SU‐GG‐J‐19: Electromagnetic Detection and Real‐Time DMLC Correction of Rotation during Radiotherapy

A retrospective 4D-MRI based on 2D diaphragm profiles for lung cancer patients.

Experimental investigation of a general real-time 3D target localization method using sequential kV imaging combined with respiratory monitoring

Tracking latency in image-based dynamic MLC tracking with direct image access

Real‐time radial reconstruction with domain transform manifold learning for MRI‐guided radiotherapy

WE‐G‐214‐05: Robotic Linac Adaptation (RLA) with a Novel Electron Gun Design for the In‐Line MRI‐Linac Configuration

Improving thoracic four-dimensional cone-beam CT reconstruction with anatomical-adaptive image regularization (AAIR)

Accounting for primary electron scatter in x‐ray beam convolution calculations

Audiovisual biofeedback improves image quality and reduces scan time for respiratory-gated 3D MRI

Dynamic keyhole: A novel method to improve MR images in the presence of respiratory motion for real-time MRI

Time‐resolved dose distributions to moving targets during volumetric modulated arc therapy with and without dynamic MLC tracking

Image-Guided Adaptive Radiotherapy

Stereotactic prostate adaptive radiotherapy utilising kilovoltage intrafraction monitoring: the TROG 15.01 SPARK trial

Evaluating the accuracy of 4D‐CT ventilation imaging: First comparison with Technegas SPECT ventilation

Measurement of patient imaging dose for real-time kilovoltage x-ray intrafraction tumour position monitoring in prostate patients

The impact of breathing guidance and prospective gating during thoracic 4DCT imaging: an XCAT study utilizing lung cancer patient motion

Estimating lung ventilation directly from 4D CT Hounsfield unit values

In the future, emission‐guided radiation therapy will play a critical role in clinical radiation oncology

MLC tracking for lung SABR is feasible, efficient and delivers high-precision target dose and lower normal tissue dose

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

Dynamic MLC tracking of moving targets with a single kV imager for 3D conformal and IMRT treatments

Pre-treatment and real-time image guidance for a fixed-beam radiotherapy system

Both four-dimensional computed tomography and four-dimensional cone beam computed tomography under-predict lung target motion during radiotherapy

The first clinical implementation of a real-time six degree of freedom target tracking system during radiation therapy based on Kilovoltage Intrafraction Monitoring (KIM)

TU‐C‐204B‐03: Reducing Imaging Dose without Sacrificing Target Localization Accuracy: A Feasibility Study

Motion management during IMAT treatment of mobile lung tumors—A comparison of MLC tracking and gated delivery

IMRT Treatment Planning on 4D Geometries for the Era of Dynamic MLC Tracking

A Bayesian approach for three-dimensional markerless tumor tracking using kV imaging during lung radiotherapy

An investigation of the conformity, feasibility, and expected clinical benefits of multiparametric MRI-guided dose painting radiotherapy in glioblastoma

SU‐GG‐T‐407: Modeling a New Varian Linac Using a CAD to Geant4 Geometry Implementation: Dose and IAEA‐Compliant Phase Space Calculations

MO-F-BRA-02: Evaluation of 4D CT to 4D Cone-Beam CT Deformable Image Registration for Lung Cancer Adaptive Radiation Therapy

Kilovoltage intrafraction monitoring for prostate intensity modulated arc therapy: First clinical results

Impact of Four-Dimensional Computed Tomography Pulmonary Ventilation Imaging-Based Functional Avoidance for Lung Cancer Radiotherapy

Failure mode and effect analysis‐based quality assurance for dynamic MLC tracking systems

Markerless EPID image guided dynamic multi-leaf collimator tracking for lung tumors

Real-time profiling of respiratory motion: baseline drift, frequency variation and fundamental pattern change

SU‐EE‐A3‐03: Audiovisual Biofeedback Significantly Reduces Motion Blurring Artifacts in Four‐Dimensional (4D) PET Images

Quantification of Artifact Reduction With Real-Time Cine Four-Dimensional Computed Tomography Acquisition Methods

Experimental evaluation of the dosimetric impact of intrafraction prostate rotation using film measurement with a 6DoF robotic arm

AAPM Task Group 264: The safe clinical implementation of MLC tracking in radiotherapy

SU-FF-T-648: Time Analysis of Image-Based Dynamic MLC Tracking

Reducing 4D CT imaging artifacts at the source: first experimental results from the respiratory adaptive computed tomography (REACT) system

Proton beam deflection in MRI fields: Implications for MRI‐guided proton therapy

TopasOpt: An open‐source library for optimization with Topas Monte Carlo

Evolving technological changes and the impact on our profession

Tumor-tracking radiotherapy of moving targets; verification using 3D polymer gel, 2D ion-chamber array and biplanar diode array

SU‐E‐J‐167: Estimation of Effective Dose from a Single KV Imager for Real‐Time Intrafraction Tumor Position Monitoring

Four‐dimensional inverse treatment planning with inclusion of implanted fiducials in IMRT segmented fields

SU-E-T-329: An Oracle Solution for Performance Benchmarking of Dynamic Multi-Leaf Collimator Algorithms

A ROI-based global motion model established on 4DCT and 2D cine-MRI data for MRI-guidance in radiation therapy

Respiratory triggered 4D cone‐beam computed tomography: A novel method to reduce imaging dose

An interdimensional correlation framework for real-time estimation of six degree of freedom target motion using a single x-ray imager during radiotherapy

WE‐G‐217A‐03: Respiratory‐Related External/Internal Motion Based MR Image Reconstruction Using Dynamic Keyhole for Real‐Time Tumor Monitoring

Esophagus and spinal cord motion relative to GTV motion in four-dimensional CTs of lung cancer patients

The impact of Monte Carlo dose calculations on treatment outcomes

TH-D-213A-03: Physiological Validation of 4D-CT-Based Ventilation Imaging in Patients with Chronic Obstructive Pulmonary Disease (COPD)

Audiovisual biofeedback improves motion prediction accuracy

Technical Note: The design and function of a horizontal patient rotation system for the purposes of fixed-beam cancer radiotherapy

Towards MR-guided electron therapy: Measurement and simulation of clinical electron beams in magnetic fields

Kilovoltage beam Monte Carlo dose calculations in submillimeter voxels for small animal radiotherapy

WE‐G‐214‐09: Validation of 4D‐CT Pulmonary Ventilation Imaging: Characterization of the Reproducibility

Technical Note: In silico and experimental evaluation of two leaf‐fitting algorithms for MLC tracking based on exposure error and plan complexity

Technical Requirements for Lung Cancer Radiotherapy

The first implementation of respiratory triggered 4DCBCT on a linear accelerator

Measurement of preoperative lobar lung function with computed tomography ventilation imaging: progress towards rapid stratification of lung cancer lobectomy patients with abnormal lung function

Validating and improving CT ventilation imaging by correlating with ventilation 4D-PET/CT using ⁶⁸Ga-labeled nanoparticles