中文摘要：

目的 探讨在瓦里安TrueBeam^TM直线加速器中使用无均整器出束容积弧形调强（RA-FFF）及常规固定野调强（IMRT）两种计划剂量学差异.方法 选择10例分期为cT2-3 N0.1 M0-1a胸上段食管癌患者定位CT资料,使用ECLIPSE^TM 10.0.4治疗计划系统分别设计RA-FFF、IMRT根治性放疗计划,处方剂量为60 Gy/30次,比较2种计划的剂量学参数和执行效率.结果 2种计划靶区适形度相似,差异无统计学意义;IMRT计划的均匀性指数高于RA-FFF计划（t=7.298,P=0.008）;RA-FFF计划中肺组织的V20、V5低于IMRT计划（t=2.451、2.604,P＜0.05）.RA-FFF及IMRT两种计划制定时间分别为（5.3±1.4）、（3.5±1.7）h（t =2.585,P＜0.05）,机器总跳数分别为632±213及734±132（t＝-1.287,P=0.084）,治疗执行时间分别为（2.2±0.9）、（4.5±1.3） min（t=4.60,P＜0.01）.结论 与IMRT计划相比,RA-FFF在胸上段食管癌治疗中具有相似的靶区剂量分布,可更好地保护肺组织,计划制定时间较长但执行效率较高.

英文摘要：

Objective To compare the dosimetric difference between RapidArc with flattening filter-free Beams （RA-FFF） and static gantry intensity-modulated radiotherapy （IMRT） for upper thoracic esophageal cancer by means of Vanan TrueBeam^TM accelerator.Methods A total of 10 patients with upper thoracic esophageal cancer staged cT2-3 N0-1 M0 were enrolled.RA-FFF and IMRT treatment plans with radical intent were generated by Varian Eclipse^TM TPS 10.0.4 for each patient.All plans were prescribed 60 Gy in 30 fractions.The RA-FFF plans were compared with IMRT in terms of dosimetric quality and delivery efficiency.Results Both of the two plans provided similar conformity index,while IMRT had a improved homogeneity index than that of RA-FFF（t =7.298,P =0.008）.For the lung,the values of V20,V5 in RA-FFF plan was lower than that of IMRT plan （t =2.451,2.604 P 〈 0.05）.The treatment planning time of RA-FFF plans were longer than that of IMRT plans[（5.3 ± 1.4）,（3.5 ± 1.7） h,t =2.585,P 〈 0.05].The monitor units for RA-FFF and IMRT were 632 ± 213 and 734 ± 132（t =-1.287,P =0.084）,respectively.The treatment time of RA-FFF and IMRT were 2.2 ± 0.9 and 4.5 ± 1.3,respectively（t =4.60,P 〈 0.01）.Conclusions For patients with upper thoracic esophageal cancer,RA-FFF plan,compared with IMRT plan,has a similar target coverage and better dose sparing to the lungs.In addition,RA-FFF plan has fewer MUs,less treatment time and better treatment efficiency.