Monaco设计直肠癌固定机架角调强和容积旋转调强治疗的剂量学比较

摘要

目的:对比Monaco治疗计划系统设计7野静态调强(Step& Shoot IMRT)、7野动态调强(DMLC IMRT)及容积旋转调强(VMAT)在直肠癌中的剂量学差异.方法:回顾分析13例Monaco设计的直肠癌患者,行CT模拟定位并勾画靶区和危及器官.相同优化条件下分别使用7野Step&Shoot、7野DMLC及VMAT进行剂量优化和评估.比较两种优化模式的靶区剂量、适形指数(CI)、均匀指数(HI)和危及器官受量.结果:与7野Step&Shoot计划相比较,7野DMLC及VMAT计划很大程度上提高了靶区内剂量分布的均匀性,HI均有所降低,PGTV的CI也有所提高.7野DMLC计划可以获得更加良好的靶区剂量分布,对于PCTV的Dmin、V45及CI,Step&Shoot也有所提高,差异有统计学意义(P＜0.05).7野DMLC和VMAT计划使膀胱、小肠的平均剂量Dmean、小肠的V30有所降低;DMLC计划更好地降低了膀胱Dmax和小肠V40;VMAT计划更好降低了右侧股骨头Dmean的剂量和左侧股骨头Dmax及V40,差异均有统计学意义(P＜0.05).DMLC和VMAT计划总机器跳数、计划子野数均有所增加,DMLC计划治疗时间有所增加,VMAT计划则有所减少,差异均具有统计学意义(P＜0.05).结论:在使用Monaco设计直肠癌的治疗计划时,推荐使用VMAT治疗方式以获得好的剂量分布和治疗效率.%Objective To compare the dosimetric differences of 7-field (7F) Step & Shoot intensity-modulated radiotherapy (IMRT),7F dynamic multi-leaf collimator (DMLC) IMRT,and volumetric modulated arc therapy (VMAT) designed in Monaco treatment planning system for rectal cancer.Methods CT simulation location was performed and target areas and organs-atrisk (OARs) were delineated for 13 patients with rectal cancer.With the same optimization conditions,7F Step & Shoot IMRT,7F DMLC IMRT and VMAT designed in Monaco system were used for dose optimization and evaluation.The dose to target areas and OARs,conformal index (CI),heterogeneous index (HI) were compared.Results Compared with 7F Step & Shoot IMRT plan,7F DMLC IMRT and VMAT plans showed greatly improved the homogeneity of dose distribution inside target areas,reduced HI,and better CI of planning gross target volume.7F DMLC IMRT plan achieved a better dose distribution in target areas,and 7F Step & Shoot IMRT also showed higher Dmin,V45 and CI of planning clinical target volume,with statistical significance (P＜0.05).7F DMLC IMRT and VMAT plans achieved lower Dmean of the bladder and intestine,and V30 of the intestine.7F DMLC IMRT plans decreased the Dmax of the bladder and V40 of the intestine,while VMAT plans decreased the Dmean of the right femoral head,and Dmax and V40 of the left femoral head (P＜0.05).7F DMLC IMRT and VMAT plans showed increased monitor units and segments.The treatment time was longer in 7F DMLC IMRT plan,but shorter in VMAT plan (P＜ 0.05).Conclusion VMAT plans which can archive a better target dose distribution and efficiency is recommended when the Monaco treatment planning system was used to design radiotherapy plan for rectal cancer.