Dosimetric study of hippocampal protective whole brain radiotherapy based on Varian accelerator

Objective The purpose of this study is to provide a reference for the selection of clinical radiotherapy plan by comparing the difference of dosimetry between coplanar dynamic intensity modulation dIMRT and coplanar VMAT plan in hippocampal protective whole brain radiotherapy (WBRT). Methods 10 patients were selected whose hippocampal were protected by WBRT, dIMRT and VMAT plans were designed for each patient, the differences of target dose, organ-endangering dose and machine hop count were compared between the two groups. Results The two technical plans PTV V 30 Gy , D 98% and D 2% all meet the standard of RTOG 0933, which is better than the dIMRT group for the PTV HI VMAT group ( P = 0.04), The hippocampal dose of dIMRT group was better than that of VMAT group, but it did not meet the standard of RGOT 0933. The average D max of hippocampus in dIMRT group and VMAT group was 18.44 Gy and 19.30 Gy, respectively ( P = 0.004). The average value of hippocampal D min was 10.03 Gy and 10.77 Gy, respectively ( P = 0.013), and the mean value of hippocampal D mean was 14.20 Gy and 15.12 Gy, respectively ( P = 0.002). The doses of lens, eyeball and optic nerve all met the standard of RTOG0933, and the dose of dIMRT group was significantly better than that of VMAT group ( P = 0.000). The treatment time in VMAT group was significantly lower than that in dIMRT group. The treatment time in VMAT group was significantly lower than that in dIMRT group. Conclusion Varian dIMRT has more advantages in controlling hippocampal dose and protecting lens than VMAT, but PTV HI and treatment efficiency are higher in VMAT group. 摘要： 目的 通过比较 Varian 加速器共面动态调强 dIMRT 与共面 VMAT 计划在海马保护全脑放疗 (WBRT) 中剂量 学差异, 为临床放疗计划选择提供一种依据。 方法 10 例海马保护 WBRT 患者, 每名患者均设计 dIMRT 与 VMAT 计划, 比较两者靶区剂量、危及器官剂量和机器跳数的差异;。 结果 2 种技术计划 PTV V 30 Gy 、 D 98% 和 D 2% 均 符合 RTOG 0933 标准, 对于 PTV HI VMAT 组优于 dIMRT 组 ( P = 0.004)。海马剂量 dIMRT 组优于 VMAT 组, 但均 未达到 RGOT 0933 标准: dIMRT 组与 VMAT 组海马 D max 均值分别为 18.44 Gy 和 19.30 Gy, 有统计学差异 ( P = 0.04); 海马 D min 均值分别为 10.03 Gy 和 10.77 Gy, 有统计学差异 ( P = 0.013); 海马 D mean 均值分别为 14.20 Gy 和 15.12 Gy, 有统计学差异 ( P = 0.002)。晶体、眼球和视神经剂量均符合 RTOG 0933 标准, dIMRT 组也明显优于 VMAT 组, 均 P = 0.000。VMAT 组治疗时间低于 dIMRT 组。 结论 Varian dIMRT 相比 VMAT 控制海马剂量和保护 晶体更有优势, 但 VMAT 组 PTV HI 和治疗效率更高。