P. Tingtian; Peking Union Medical Colloege Hospital, Beijign, China
Purpose/Objective(s): To verify the plan delivery accuracy and commissioning of the intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) on TaiChi linac. Materials/
Methods: The test cases recommended by the AAPM task group 119 (TG119) were adopted for plan delivery verification. IMRT and VMAT treatment plans were generated for multi-target, mock prostate, mock head and neck, and C shape (easy & hard) targets. These plans were delivered on TaiChi linac. An ionization chamber was used to measure the point dose in the phantom and a 3D dose verification phantom was used to verify 3D dose distribution, respectively. The consistency between measured dose and calculated dose was evaluated by confidence. Results: The treatment plan quality are comparable with the TGl19 report. The point dose deviations for the high dose point in the PTV were 0.39%±1.02% (range, -0.66%~2.19%) for the IMRT plans and 1.27%±0.64% (range, 0.55%~2.22%) for the VMAT plans. The confidence interval of 0.95 were 2.39% and 2.52%, respectively. For low-point dose in the avoidance structures, the deviations were 0.53%±1.73% (range, -2.3%~2.4%) for the IMRT plans and 0.88%±1.11% (range, -0.46%~2.3%) for the VMAT plans. The confidence interval of 0.95 were 3.92% and 3.06%, respectively. The percentage of ? passing points(±3%/3mm) for the IMRT plans was 99.52%±0.366% and 99.86%±0.136% for the VMAT plans. The confidence interval of 0.95 were 1.196% and 0.406%, respectively. Conclusion: The performance test results of TaiChi accelerator and the 6MV-FFF calculation model of the treatment planning system both meet the verification standard of the TG 119 report, and a more appropriate action level is set according to the test results, which provides a reference standard for the quality control of the clinical treatment plan in the future.
