DMLC tracking and gating can improve dose coverage for prostate VMAT

Colvill, Emma; Poulsen, Per Rugaard; Booth, Jeremy; O’Brien, Ricky; Ng, Jin Aun; Keall, Paul J.

doi:10.1118/1.4892605

Cited by 43 publications

(52 citation statements)

References 17 publications

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“…These prospective results are consistent with a retrospective preclinical MLC tracking dose reconstruction study (11). A simulation study performed using dose reconstruction for conventional and subvolume boost treatments for prostate showed that MLC tracking is effective at mitigating the dosimetric effects of prostate motion and allows for successful GTV and PTV dose delivery (14), as demonstrated in the present study.…”

Section: Discussionsupporting

confidence: 89%

“…Application of real-time adaptation necessitates innovative solutions for treatment delivery validation, and dose reconstruction methods have been developed to be used as a posttreatment quality assurance step for clinical implementation of MLC tracking (11,12). Dose reconstruction techniques allow the calculation of dose after each treatment fraction to provide an estimate of the treated dose delivered to the patient.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Multileaf Collimator Tracking Improves Dose Delivery for Prostate Cancer Radiation Therapy: Results of the First Clinical Trial

Colvill

Booth

O’Brien

et al. 2015

International Journal of Radiation Oncology*Biology*Physics

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Funding: This study was supported by Varian Medical Systems through partial trial funding and an equipment loan.Conflict of interest: P.J.K. is one of the inventors on an issued patent and a submitted patent application on multileaf collimator tracking. Acknowledgments:The authors thank Esben Worm and Prabhjot Juneja for their valuable help with dose reconstruction development, and Julie Baz for improving the clarity and readability of the manuscript. SummaryMultileaf collimator tracking has been implemented for the first time in a prospective prostate cancer clinical trial. Dose reconstruction was performed for 475 treatment fractions for 15 patients. Comparison of patients' original planned dose with the calculated treated dose with and without MLC tracking demonstrates that implementation of MLC tracking results in a higher agreement between delivered and planned doses. The implications are potentially improved patient outcomes and more reliable radiobiological parameter determination. AbstractPurpose: To test the hypothesis that multileaf collimator (MLC) tracking improves the consistency between the planned and delivered dose compared with the dose without MLC tracking, in the setting of a prostate cancer volumetric modulated arc therapy trial. Methods and Materials:Multileaf collimator tracking was implemented for 15 patients in a prostate cancer radiation therapy trial; in total, 513 treatment fractions were delivered. During each treatment fraction, the prostate trajectory and treatment MLC positions were collected. These data were used as input for dose reconstruction (multiple isocenter shift method) to calculate the treated dose (with MLC tracking) and the dose that would have been delivered had MLC tracking not been applied (without MLC tracking). The percentage difference from planned for target and normal tissue dose-volume points were calculated. The hypothesis was tested for each dose-volume value via analysis of variance using the F test. Results:Of the 513 fractions delivered, 475 (93%) were suitable for analysis. The mean difference and standard deviation between the planned and treated MLC tracking doses and the planned and without-MLC tracking doses for all 475 fractions were, respectively, PTV D99% -0.8% ± 1.1% versus -2.1% ± 2.7%; CTV D99% -0.6% ± 0.8% versus -0.6% ± 1.1%; rectum V65% 1.6% ± 7.9% versus -1.2% ± 18%; and bladder V65% 0.5% ± 4.4% versus -0.0% ± 9.2% (P<.001 for all dose-volume results). Conclusion:This study shows that MLC tracking improves the consistency between the planned and delivered doses compared with the modeled doses without MLC tracking. The implications of this finding are potentially improved patient outcomes, as well as more reliable dose-volume data for radiobiological parameter determination.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Multileaf Collimator Tracking Improves Dose Delivery for Prostate Cancer Radiation Therapy: Results of the First Clinical Trial

Colvill

Booth

O’Brien

et al. 2015

International Journal of Radiation Oncology*Biology*Physics

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“…There may also be some effects with latency of MLC leaf motion not providing the ideal beam shape with time; however, preliminary clinical data from non-MRI-linac systems are showing great promise. 29 With regard to patient-specific quality assurance (QA), we note the process followed for the real-time adaptive plan QA performed on ViewRay system while the patient is on the treatment couch. 30 In this process, all the updated plan details are exported through an independent format, i.e., DICOM, to an in-house dose plan check system based on Monte Carlo methods.…”

Section: A Mrxt Workflowmentioning

confidence: 99%

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

et al. 2017

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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; MRIguided 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 example, 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.

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“…Previously, motion inclusive dose reconstruction for the trial data used in this study has been reported [7,8,9,16]. Dose delivered in the presence of prostate motion, with and without motion compensation, during each fraction was estimated using a motion-synchronized isocenter shift dose reconstruction method developed and validated by Poulsen et al [20].…”

Section: Measure Of Prostate Motionmentioning

confidence: 99%

“…However, the applicability of their result is also limited to helical Tomotherapy systems; whereas other delivery techniques such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) are more widely available and utilised, and may show correlation. Colvill et al [7] in their study assessed the dosimetric impact of multi-leaf collimator (MLC) tracking and gating as intrafraction motion correction strategies and compared these with no motion correction using 20 fractions from five patients. They showed strong correlation between the motion and its dosimetric impact on the target.…”

Section: Introductionmentioning

confidence: 99%

Quantification of intrafraction prostate motion and its dosimetric effect on VMAT

Juneja

Colvill

Kneebone

et al. 2017

Australas Phys Eng Sci Med

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Compliance with ethical standards Conflict of interestRoyal North Shore Hospital has a collaborative research agreement with Varian Medical Systems to support Calypso® and Kilovoltage intrafraction monitoring (KIM) clinical trials. PK holds part ownership of the patent, between Stanford University and Varian Medical Systems, on KIM technology. Ethical approvalAll procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.Intrafraction prostate motion degrades the accuracy of radiation therapy (RT) delivery. Whilst a number of metrics in the literature have been used to quantify intrafraction prostate motion, it has not been established whether these metrics reflect the effect of motion on the RT dose delivered to the patients. In this study, prostate motion during volumetric modulated arc therapy (VMAT) treatment of 18 patients and a total of 294 fractions was quantified through novel metrics as well as those available in the literature. The impact of the motion on VMAT dosimetry was evaluated using these metrics and dose reconstructions based on a previously validated and published method. The dosimetric impact of the motion on planning target volume (PTV) and clinical target volume (CTV) coverage and organs at risk (OARs) was correlated with the motion metrics, using the coefficient of determination (R 2 ), to evaluate their utility. Action level threshold for the prostate motion metric that best described the dosimetric impact on the PTV D95% was investigated through iterative regression analysis. The average (range) of the mean motion for the patient cohort was 1.5 mm (0.3-9.9 mm). A number of motion metrics were found to be strongly correlated with PTV D95%, the range of R 2 was 0.43-0.81. For all the motion measures, correlations with CTV D99% (range of R 2 was 0.12-0.62), rectum V65% (range of R 2 was 0.33-0.58) and bladder V65% (range of R 2 was 0.51-0.69) were not as strong as for PTV D95%. The mean of the highest 50% of motion metric was one of the best indicator of dosimetric impact on PTV D95%. Action level threshold value for this metric was found to be 3.0 mm. For an individual fraction, when the metric value was greater than 3.0 mm then the PTV D95% was reduced on average by 6.2%. This study demonstrated that several motion metrics are well correlated with the dosimetric impact (PTV D95%) of individual fraction prostate motion on VMAT delivery and could be used for treatment course adaptation.

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DMLC tracking and gating can improve dose coverage for prostate VMAT

Cited by 43 publications

References 17 publications

Multileaf Collimator Tracking Improves Dose Delivery for Prostate Cancer Radiation Therapy: Results of the First Clinical Trial

Multileaf Collimator Tracking Improves Dose Delivery for Prostate Cancer Radiation Therapy: Results of the First Clinical Trial

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

Quantification of intrafraction prostate motion and its dosimetric effect on VMAT

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