胸中段食管癌有无均整器模式下的固定野调强与容积旋转调强放疗剂量学比较

Dosimetric comparison of VMAT and ssIMRT for mid-thoracic esophageal carcinoma using flattening filter and flattening filter-free modes

目的比较瓦里安的Trilogy直线加速器6MVX射线应用均整器模式(FF)及无均整器模式(FFF)下的固定野调强(ssIMRT)与容积旋转调强(VMAT)在胸中段食管癌放疗靶区中的剂量学差异。方法选取2018年10月至2019年9月在揭阳市人民医院就诊并行根治性放疗的胸中段食管癌患者20例(男15例,女5例,平均年龄63.5岁),在瓦里安Eclipse 15.5版本的计划系统上分别设计ssIMRT-FF、ssIMRT-FFF、VMAT-FF、VMAT-FFF 4种计划。处方剂量为CTV1的计划靶区(PCTV1)总剂量6000 cGy/28 F,CTV2的计划靶区(PCTV2)总剂量5400 cGy/28 F。在95%的靶区体积达处方剂量条件下,比较4种计划靶区(PTV)最大剂量(Dmax)、平均剂量(Dmean)、适形指数(CI)、均匀性指数(HI)、机器跳数(MU)、加速器的出束时间(DT)以及危及器官(OAR)剂量。结果4种计划的PTV Dmax、Dmean、CI、HI及OAR剂量均未见明显区别。但VMAT-FF的MU最低[572.00(82.00)]、VMAT-FFF的DT最短[(37.08±17.32)s],差异均有统计学意义(均P<0.05);计划之间的两两比较发现VMAT相比于IMRT有更短的DT以及更低的MU,而FFF相比于FF具有更短的DT但更高的MU,差异均有统计学意义(均P<0.05)。结论胸中段食管癌的4种靶区计划均能满足临床治疗需求,其中VMAT-FF的MU最低、VMAT-FFF的DT最短,提高了治疗效率。

Objective To compare the dosimetric differences between volumetric modulated arc therapy(VMAT)and step&shoot intensity modulated radiation therapy(ssIMRT)in radiotherapy target area of mid-thoracic esophageal carcinoma using 6MV X-ray flattening filter(FF)and flattening filter-free(FFF)modes on a Varian Trilogy accelerator.Methods A total of 20 patients with mid-thoracic esophageal carcinoma who received radical radiotherapy in Jieyang People's Hospital from October 2018 to September 2019 were selected,including 15 males and 5 females,with an average age of 63.5 years old.Treatment plans of ssIMRT-FF,ssIMRT-FFF,VMAT-FF,and VMAT-FFF were generated for 20 patients with mid-thoracic esophageal carcinoma with Eclipse time(DT)of accelerator,and organ at risk(OAR)doses of the four plans were compared under the condition that 95%of the target volume reached the prescribed dose.Results Dmax,Dmean,CI,and HI of PTV and OAR dose were not significantly different among the four plans.However,the MU of VMAT-FF was the lowest[572.00(82.00)],the DT of VMAT-FFF was the shortest[(37.08±17.32)s],with statistically significant differences(all P<0.05).Pair-to-plan comparisons found that VMAT had shorter DT and lower MU than IMRT,and FFF had shorter DT but higher MU than FF,with statistically significant differences(all P<0.05).Conclusions The four plans for mid-thoracic esophageal carcinoma can all meet the clinical treatment needs,among which the MU of VMAT-FF is the lowest and the DT of VMAT-FFF is the lowest,which improves the treatment efficiency.