乳腺癌保乳术后螺旋断层治疗技术的剂量学研究

目的 研究乳腺癌保乳术后患者应用固定野调强放疗(FF-IMRT)和螺旋断层治疗(HT)计划的剂量学差异。方法 选择10例左侧乳腺癌保乳术后IMRT患者，CT模拟定位、勾画靶区及危及器官，对同一CT图像设计FF-IMRT计划和HT计划。配对t检验两种计划靶区及危及器官剂量分布及照射时间差异。结果 与FF-IMRT计划相比，HT计划的100%PTV覆盖度增加(P=0.000)，105%PTV覆盖度降低(P=0.000)，平均剂量(D_mean)降低(P=0.002)，均匀指数(HI)、适形指数(CI)增加(P=0.001、0.023)。HT计划的患侧肺剂量体积V₅、V₁₀、V₂₀、V₃₀、V₄₀、D_mean分别降低28%、30%、35%、46%、61%、32%(P=0.000)，双肺的分别降低30%、28%、34%、46%、62%、26%(P=0.000)，心脏的和最大剂量(D_max)分别降低57%、59%、71%、82%、91%、45%和12%(P=0.000~0.002)，健侧乳腺D_mean、D_max分别增加0.9、3.0 Gy (P=0.000、0.000)，健侧肺的分别增加0.42、2.70 Gy (P=0.000、0.000)。HT计划照射时间明显高于FF-IMRT计划(11.98 min:5.96 min，P=0.000)。结论 左侧如乳腺癌HT计划的靶区均匀性和适形度均优于FF-IMRT计划，危及器官可获得等同于或优于FF-IMRT计划的剂量分布，可作为新照射方式用于乳腺癌保乳术后患者。

Study the dosimetric for whole breast irradiation with fixed field IMRT and helical tomotherapy

Objective To compare the dosimetry difference between helical tomotherapy and fixed field IMRT for breast cancer radiotherapy after breast-conserving surgery. Methods Ten patients received radiotherapy after breast-conserving surgery were selected. For each patient, two treatment plans (FF-IMRT plan and HT plan) were designed with Eclipse and TomoTherapy. Same institutional dose-volume constraints for breast cancer were used in both techniques. Targets and organs at risk were compared with paired t-test for two planning. Results In comparison with the FF-IMRT planning, PTV coverage of HT plan group increased, D_mean became lower (P=0.000,0.002). the HI and CI were significantly higher for HT (P=0.001,0.023).Compared with the FF-IMRT plans, V₅,V₁₀,V₂₀,V₃₀,V₄₀ and D_mean of the ipsilateral lung were reduced by about 28%,30%,35%,46%,61% and 32%(P=0.000),those of full lung were reduced by about 30%,28%,34%,46%,62% and 26%(P=0.000), those and D_max of heart were reduced by about 57%,59%,71%,82%,91%,45% and 12%(P=0.000-0.002).The D_mean and D_max of contralateral breast were higher by 0.9 Gy and 3.0 Gy (P=0.000,0.000) respectively, those of contralateral lung were higher by 0.42 Gy and 2.70 Gy (P=0.000,0.000) respectively. It takes significantly long time for the HT plans designed than FF-IMRT plan (11.98 min:5.96 min,P=0.000). Conclusions The HT planning improve the HI and CI of PTV, organs at risk can get equivalent or superior dose distribution compared with the FF-IMRT technology, but it is feasible for clinical applications in breast-conserving surgery as a new method.