Comprehensive end-to-end test for intensity-modulated radiation therapy for nasopharyngeal carcinoma using an anthropomorphic phantom and EBT3 film

Background: In head and neck radiotherapy, immobilization devices can affect dose delivery. In this study, a comprehensive end-to-end test was developed to evaluate the accuracy of radiotherapy treatment. Materials andMethods: An Alderson Radiation Therapy (ART) anthropomorphic phantom with EBT3 film was used to mimic the actual patient treatment process. Ten patients treated for nasopharyngeal carcinomas with IMRT were retrospectively selected. For each patient, the treatment plan, as well as the targets and OARs was transplanted onto the phantom, and the IMRT plan was subsequently recalculated to the phantom with EBT3 film. Two quality assurance (QA) plans were generated, namely “Plan-with” wherein the immobilization device was contoured and “Plan-without” wherein it was omitted. EBT3 measurements were compared with the results of the TPS calculation. Results: With different gamma calculation criteria applied, the results obtained for Plan-with were closer to the dose measured with the EBT3 film. Moreover, 1.8% deviation was observed in the posterior neck skin dose for Plan-with when compared to the film measurements while the value was 33.1% lower for Plan-without. When compared to Plan-without, each target volume in Plan-with exhibited a 1–4% reduction in the maximum dose (D2%), minimum dose (D98%) and mean dose (Dmean). Conclusion: Immobilization devices decrease the radiation dose to target volumes while increasing the skin dose and should be included within the body contour to ensure an accurate planning dose. The end-to-end IMRT test using an ART anthropomorphic phantom is a valuable tool to identify discrepancies between calculated and delivered radiation doses.

背景：在头颈部放射治疗中，固定装置会对辐射剂量递送产生影响。本研究开发了一套完整的端到端（end-to-end）测试方案，用于评估放射治疗的准确性。
材料与方法：采用搭载EBT3胶片的阿尔德森放射治疗（Alderson Radiation Therapy, ART）拟人模体，模拟真实患者的治疗流程。回顾性选取10例接受调强放射治疗（Intensity-Modulated Radiation Therapy, IMRT）的鼻咽癌患者。将每例患者的治疗计划、靶区及危及器官（Organ at Risk, OAR）移植至该模体中，随后针对搭载EBT3胶片的模体重算调强放射治疗计划。生成两套质量保证（QA）计划：其一为「带固定装置计划」（Plan-with），即勾画固定装置轮廓；其二为「无固定装置计划」（Plan-without），即不纳入固定装置。将EBT3胶片的测量结果与治疗计划系统（Treatment Planning System, TPS）的计算结果进行比对。
结果：采用不同伽马计算评判标准时，「带固定装置计划」的结果与EBT3胶片测得的剂量更为接近。相较于胶片测量结果，「带固定装置计划」的颈后皮肤剂量偏差为1.8%，而「无固定装置计划」的该数值较测量结果低33.1%。与「无固定装置计划」相比，「带固定装置计划」中各靶区的最大剂量（D2%）、最小剂量（D98%）及平均剂量（Dmean）均降低1%~4%。
结论：固定装置会降低靶区接收的辐射剂量，同时提升皮肤受照剂量，因此应将其纳入人体轮廓勾画范围，以确保计划剂量的准确性。采用阿尔德森放射治疗拟人模体开展的端到端调强放射治疗测试，是识别辐射剂量计算值与实际递送值之间差异的有效工具。