Objective To compare the therapeutic dose and efficacy between the single arc and double arc stereotac-tic body radiotherapy plans for early lung cancer patients with flattening filter free patterns.Methods Eighteen patients with lung cancer of the early stage were selected in this study,and each patient was arranged single arc stereotactic body ra-diotherapy (S-RA)and double arc stereotactic body radiotherapy (D-RA)plans using the Eclipse 10.0 treatment planning system with 6 MV flattening filter-free (FFF)photon beams.The prescription dose was 48 Gy,12 Gy/time and for 4 times.Comparisons between D-RA and S-RA plans in the target volume received 95%prescription dose (V95%),the tar-get volume received 90%prescription dose (V90%),the target volume received 105%prescription dose (V105%),con-formity index (CI),homogeneity index (HI),organs at risk (OARs)doses,planning time (PT),monitor units (MU) and treatment time (TT)were conducted.Results No significant difference was found in V90%,V95%,and V105%;in PT and MU between D-RA and S-RA,all P>0.05.Significant difference was found in CI and TT between D-RA and S-RA,all P<0.05.For the OAR,there was no significant difference between the D-RA and S-RA,P>0.05.Conclusions D-RA and S-RA provids a superior PTV coverage,and all OAR dose meets the constraint level of RTOG 0915 protocol. S-RA shows no significantly difference in PTV coverage and OAR as compared with D-RA.The CI and HI of D-RA are bet-ter than those of S-RA.S-RA shows shorter treatment time and less MU number as compared with D-SA.%目的：比较无均整滤过器模式单、双弧体部立体定向放射治疗计划对早期肺癌的剂量和效率的预测结果。方法选取18例早期肺癌患者，先行胸部CT检查，将CT影像导入Eclipse10．0计划系统，分别设计无均整滤过器模式6 MV X射线双弧体部立体定向放射治疗计划（D-RA ）和单弧体部立体定向放射治疗计划（S-RA ），处方剂量48 Gy，12 Gy／次，照射4次。比较D-RA、S-RA计划95％的处方剂量覆盖靶区体积的百分数（V95％）、90％的处方剂量覆盖靶区体积的百分数（V90％）、105％的处方剂量覆盖靶区体积的百分数（V105％）、适形指数（CI）、均匀指数（HI）、危机器官（OAR）受照剂量、计划设计时间（PT）、机器跳数（MU）、治疗时间（TT）。结果 D-RA、S-RA的V90％、V95％、V105％间比较，P均＞0．05。D-RA、S-RA的CI、TT间比较，P＜0．05。D-RA、S-RA各OAR受照剂量比较差异无统计学意义，P均＞0．05。D-RA、S-RA的PT、MU间比较P均＞0．05。结论无均整滤过器模式D-RA、S-RA计划的照射剂量均能覆盖早期肺癌患者的肿瘤靶区，各OAR受照剂量均满足限量要求。D-RA和S-RA计划的靶区覆盖情况及各OAR受照剂量差异较小。D-RA的适形性和均匀性均优于S-RA，S-RA治疗时间短、机器跳数少。
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