ABSTRACT

This study aims to evaluate the dose accuracy of synthetic CT based bulk relative electron density (rED) assignment for application in 1.5 T MR-Linac for cervical carcinoma patients. Five cervix patients previously treated on 1.5 T MR-Linac were retrospectively investigated. Two sCTs were generated assigning bulk values to the different bone regions: the sCT_FH was generated with delineation of femoral head, and the sCT_AB was generated with the delineation of all the bone regions. The rest tissue of the patient data was set to mean rED values of the region of interests in CT. The same treatment plan based on original CT was recalculated or reoptimized on the sCT_FH and sCT_AB. The result of gamma analysis showed that gamma passing rate of treatment plans based on sCT_AB was higher than plans based on sCT_FH. And the differences of dose volume parameters between plans on sCTs and original CT showed that the differences for plan based on sCT_AB were much smaller than sCT_FH. The sCT generated with bulk rED assignment approach guarantees an acceptable level of dose accuracy for cervix carcinoma patients with 1.5 T MR-Linac. The accuracy can be improved by using complete delineation of the pelvic bone regions.

摘要

这项研究旨在评估基于合成CT的体积相对电子密度（rED）分配在1.5 T MR-Linac宫颈癌患者中应用的剂量准确性。回顾性研究了5例先前接受过1.5 T MR-Linac治疗的子宫颈患者。生成了两个sCT，将体积值分配给了不同的骨骼区域：sCT _FH生成了股骨头轮廓，sCT _AB生成了所有骨骼区域的轮廓。将患者数据的其余组织设置为CT中感兴趣区域的平均rED值。在sCT _FH和sCT _AB上重新计算或重新优化了基于原始CT的相同治疗方案。γ分析结果表明，基于sCT _AB的治疗方案的γ合格率高于基于sCT _FH的治疗方案。sCTs计划与原始CT的剂量体积参数的差异表明，基于sCT _AB的计划的差异远小于sCT _FH。采用批量rED分配方法生成的sCT可确保1.5 T MR-Linac宫颈癌患者的剂量准确性达到可接受的水平。可以通过完整描绘骨盆骨区域来提高准确性。