脑胶质瘤共面、非共面容积旋转调强及螺旋断层放射治疗技术的剂量学比较研究

A comparative study on the dosimetry of coplanar VMAT, non-coplanar VMAT and tomotherapy for brain glioma

目的:对比不同类型脑胶质瘤患者术后在共面容积旋转调强放射治疗(VMAT)、非共面VMAT(non VMAT)调强放射治疗计划及螺旋断层(TOMO)放射治疗计划之间的剂量学差异,评价不同放射治疗计划的差别。方法:收集7例脑胶质瘤患者CT图像,由主治医生在磁共振成像(MRI)横断面上勾画靶区、危及器官及正常脑组织。对每个病例分别制定共面VMAT、non VMAT和TOMO治疗的三组放射治疗计划,并将其定义为VMAT计划组、non VMAT计划组和TOMO计划组。放射治疗处方为60 Gy/30 F,水肿区为54 Gy/30 F。评价:(1)计划肿瘤体积(PGTV)和计划临床靶体积(PCTV)的最大剂量(D_(max))、平均剂量(D_(mean))及最小剂量(D_(min));(2)均匀性指数(HI)及适形度指数(CI);(3)危及器官的D_(max)、D_(mean)。比较3个评价指标在三组治疗计划之间的剂量差异。结果:靶区在PCTV、PGTV各参考指标的不同计划模式下,三组计划均能很好地满足靶区要求。TOMO计划组的均匀度HI稍优于其他两组计划;三组计划的适行性CI无明显差异。对于脑胶质瘤,TOMO计划组中PCTV D_(mean)、PGTV D_(mean)的平均值均低于共面VMAT组和non VMAT组,其差异有统计学意义(F=6.500,F=12.755;P<0.05),且更接近处方要求。结论:对不同部位胶质瘤,Varian Eclipse放射治疗计划系统下的共面VMAT、non VMAT及TOMO治疗计划均能较好地满足靶区剂量覆盖、均匀性和适形性的要求,对于危及器官的保护,TOMO治疗计划比共面VMAT和non VMAT治疗计划对危及器官的保护更好。

Objective To compare the differences of dosimetry among coplanar volumetric modulated arc therapy （VMAT）, non-coplanar VMAT and tomotherapy for patients with brain glioma at post operation, and evaluate the differences of different radiotherapy plan. Methods： The CT images of 7 patients with brain glioma were collected, and the target area, the endangered organs and normal tissue were sketched on the cross section of magnetic resonance imaging （MRI） by attending doctor. Three radiotherapy plans included of coplanar VMAT, non-coplanar VMAT and tomography （TOMO） were formulated for each case, and all of cases were divided into coplanar VMAT group, non-coplanar VMAT group and TOMO group. The prescription of radiotherapy was 60Gy/30F and the edema area was 54Gy/30F. The evaluation index included：①maximum dose （Dmax）of PGTV and Dmax of PCTV, average dose （Dmean） and minimum dose （Dmin）. ②homogeneity index （HI） and conformity index （CI）. 3）The Dmax and Dmean that endangered organ. The differences of three evaluation indexes among the three groups were compared. Results： When the target area was under the different planning model, the three groups planning could well meet the requirements of target area. The HI of TOMO planning group was slightly better than that of other two groups. And the CI of the three groups was no significant difference. For brain glioma, the mean values of PCTV Dmean and PGTV Dmean of TOMO plan were significantly lower than that of coplanar VMAT group and non-coplanar VMAT group, respectively （F=6.500, F=12.755, P〈0.05）, and it was more closer to the requirement of prescription. Conclusion： For different parts of the glioma, all of the coplanar VMAT, non-coplanar VMAT and TOMO under radiotherapy planning system of Varian Eclipse can meet the requirement of dose coverage, homogeneity and conformity in target area. And TOMO has better protective effect for endangered organ than other two plans.