The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
Foresea Life Insurance Guangzhou General Hospital, Guangzhou, China.
PLoS One. 2022 Nov 8;17(11):e0277332. doi: 10.1371/journal.pone.0277332. eCollection 2022.
This study aimed to explore the effect of carbon fiber couch on radiotherapy dose attenuation and gamma pass rate in intensity-modulated radiotherapy (IMRT) plans. A phantom inserted with an ionization chamber was placed at different positions of the couch, and the dose was measured by the chamber. Under the same positioning, the phantom dose was calculated using the real and virtual couch images, and the difference in the planned dose of radiotherapy was compared. Ten clinical IMRT plans were selected as dose verification data, and the gamma pass rates were compared between couch addition and non-addition conditions. When the radiation field was near 110° and 250°, the measured value attenuation coefficient of the ionization chamber at the joint of the couch was up to 34%; the attenuation coefficient of the treatment couch from the actual couch image calculated using the treatment planning system (TPS) was up to 33%; the attenuation coefficient of the virtual couch calculated using the TPS was up to 4.0%. The gamma pass rate of the dose verification near gantry angles 110° and 250° was low, and that of the joint could be lower than 85% under the condition of 3%/3 mm. The gamma pass rates of the radiation field passing through the couch were all affected. The dose was affected by the radiation field passing through the couch, with the largest effect when passing through the joint part of the treatment couch, followed by that of the main couch plate and extension plate. When the irradiation field passed through the joint and near 110° and 250° of the main couch, the dose difference was large, making it unsuitable for treatment.
本研究旨在探讨碳纤维治疗床对调强放射治疗（IMRT）计划中放射剂量衰减和伽马通过率的影响。将一个插入电离室的体模放置在治疗床的不同位置，并通过腔室测量剂量。在相同的定位下，使用真实和虚拟治疗床图像计算体模剂量，并比较放疗计划剂量的差异。选择十个临床 IMRT 计划作为剂量验证数据，比较在添加和不添加治疗床的情况下的伽马通过率。当辐射场接近 110°和 250°时，治疗床连接处电离室的测量值衰减系数高达 34%；治疗计划系统（TPS）中使用实际治疗床图像计算的治疗床衰减系数高达 33%；TPS 中计算的虚拟治疗床衰减系数高达 4.0%。在接近龙门角 110°和 250°的剂量验证中，伽马通过率较低，在 3%/3mm 的条件下，接头处的伽马通过率可能低于 85%。辐射场穿过治疗床的伽马通过率都受到影响。剂量受到穿过治疗床的辐射场的影响，穿过治疗床接头部分的影响最大，其次是主床板和延伸板。当照射场穿过接头且靠近主床的 110°和 250°时，剂量差异较大，不适合治疗。
