Patient-specific quality assurance and plan dose errors on breast intensity-modulated proton therapy |
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| Institution: | 1. Department of Radiation Oncology, University of Florida College of Medicine, Jacksonville, FL, USA;2. Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA;3. School of Physical Sciences, University of Science and Technology of China, Hefei, China;1. Department of Radiation Oncology, Medical University Vienna, Austria;2. Division of Radiation Therapy, Department of Diagnostic and Therapeutic Radiology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand;3. University of Applied Science Wiener, Neustadt, Austria;4. MedAustron Ion Therapy Center, Wiener Neustadt, Austria;1. Radiation Physics Section, Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Kingdom of Saudi Arabia;2. Cyclotron and Radiopharmaceuticals Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Kingdom of Saudi Arabia;3. Radiation Biology Section, Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Kingdom of Saudi Arabia;4. Oncology Centre, King Faisal Specialist Hospital & Research Centre, Riyadh, Kingdom of Saudi Arabia;5. Medical Physics Unit, McGill University, Montréal, Québec, Canada;6. Department of Oncology, Faculty of Medicine, McGill University, Montréal, Québec, Canada;7. Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec, Canada;1. Department of Nephrology, West China Second University Hospital, Chengdu, China;2. Department of Pediatrics, West China Second University Hospital, Chengdu, China;3. Outpatient Department, West China Hospital, Sichuan University, Chengdu, China |
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| Abstract: | PurposeTo investigate, in proton therapy, whether the Gamma passing rate (GPR) is related to the patient dose error and whether MU scaling can improve dose accuracy.MethodsAmong 20 consecutively treated breast patients selected for analysis, two IMPT plans were retrospectively generated: (1) the pencil-beam (PB) plan and (2) the Monte Carlo (MC) plan. Patient-specific QA was performed. A 3%/3-mm Gamma analysis was conducted to compare the TPS-calculated PB algorithm dose distribution with the measured 2D dose. Dose errors were compared between the plans that passed the Gamma testing and those that failed. The MU was then scaled to obtain a better GPR. MU-scaled PB plan dose errors were compared to the original PB plan.ResultsOf the 20 PB plans, 8 were passed Gamma testing (G_pass_group) and 12 failed (G_fail_group). Surprisingly, the G_pass_group had a greater dose error than the G_fail_group. The median (range) of the PTV DVH RMSE and PTV ΔDmean were 1.36 (1.00–1.91) Gy vs 1.18 (1.02–1.80) Gy and 1.23 (0.92–1.71) Gy vs 1.10 (0.87–1.49) Gy for the G_pass_group and the G_fail_group, respectively. MU scaling reduced overall dose error. However, for PTV D99 and D95, MU scaling worsened some cases.ConclusionFor breast IMPT, the PB plans that passed the Gamma testing did not show smaller dose errors compared to the plans that failed. For individual plans, the MU scaling technique leads to overall smaller dose errors. However, we do not suggest use of the MU scaling technique to replace the MC plans when the MC algorithm is available. |
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| Keywords: | Patient-specific QA Intensity-modulated proton therapy Breast cancer |
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