Vivas Maiques Begoña, Ruiz Igor Olaciregui, Janssen Tomas, Mans Anton
Department of Radiation Oncology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Phys Imaging Radiat Oncol. 2022 Jun 11;23:16-23. doi: 10.1016/j.phro.2022.06.005. eCollection 2022 Jul.
In magnetic resonance guided online adaptive radiotherapy, the patient model used for plan adaptation and dose calculation is created online under stringent time constraints. This study investigated the ability of portal dosimetry to detect deviations between the online patient model used for plan adaptation and the actual anatomy of the patient during delivery.
Portal images acquired during treatment were used to reconstruct the delivered dose corresponding to online adapted plans of 42 prostate and 20 rectal cancer patients. The reconstructed dose distributions were compared with the dose distributions calculated online by the treatment planning system by γ-analysis and by the difference in median dose to the high-dose volume.
Out of 245 prostate and 145 rectal cancer adapted plans, deviations were detected in 5 prostate and in 17 rectal adapted plans corresponding to 3 prostate and 6 rectal patients, respectively. For all but one of the alerts, deviations were explained due to discrepancies observed between the patient model used for plan adaptation and online magnetic resonance images. A single workflow incident in which the supporting arm of the anterior receive coil was accidentally moved in the treatment field was also detected.
There is need for independent end-to-end checks in magnetic resonance guided online adaptive workflows including the verification of the online patient model. portal dosimetry can be used for such purpose as it can detect both patient related deviations and workflow incidents.
在磁共振引导的在线自适应放疗中，用于计划调整和剂量计算的患者模型是在严格的时间限制下在线创建的。本研究调查了射野剂量测定法在放疗过程中检测用于计划调整的在线患者模型与患者实际解剖结构之间偏差的能力。
利用治疗期间采集的射野图像来重建与42例前列腺癌患者和20例直肠癌患者的在线调整计划相对应的实际 delivered 剂量。通过γ分析以及高剂量体积的中位剂量差异，将重建的剂量分布与治疗计划系统在线计算的剂量分布进行比较。
在245个前列腺癌和145个直肠癌调整计划中，分别在与3例前列腺癌患者和6例直肠癌患者相对应的5个前列腺癌和17个直肠癌调整计划中检测到偏差。除一次警报外，所有偏差均因用于计划调整的患者模型与在线磁共振图像之间存在差异而得到解释。还检测到一次工作流程事件，即前接收线圈的支撑臂在治疗野中意外移动。
在包括在线患者模型验证在内的磁共振引导在线自适应工作流程中，需要进行独立的端到端检查。射野剂量测定法可用于此目的，因为它既能检测与患者相关的偏差，也能检测工作流程事件。
