宫颈癌术后盆腔容积调强弧形治疗与固定野调强放疗计划的剂量学研究

目的 研究宫颈癌术后患者应用固定野调强放疗(FF-IMRT)和容积调强弧形治疗(VIMAT)计划剂量学差异。方法 选择 13例宫颈癌术后调强放疗患者CT模拟定位并勾画靶区及危及器官,对同一CT图像设计FF-IMRT计划和VIMAT计划,评估计划靶体积(PTV)及危及器官的剂量学参数。两种计划参数比较用配对t检验。结果 与FF-IMRT计划相比,VIMAT计划PTV的95%覆盖度增加(t=9.84,P=0.000)、110%覆盖度降低(t=－3.72,P=0.003)、最大剂量(D_max)降低(t=－3.51,P=0.005)、适形指数变差(t=5.93,P=0.000),但PTV105%覆盖度、平均剂量(D_mean)、不均匀指数均相似(t=－0.02、－0.60、1.13,P=0.842、0.560、0.283);膀胱 V₃₀降低约10%(t=－4.99,P=0.000)、D_mean降低1.4 Gy (t=－3.65,P=0.004)、D_max降低1.5 Gy (t=－18.03,P=0.000),直肠 V₄₀降低约10%(t=－2.99,P=0.012),D_mean降低0.6 Gy (t=－2.98,P=0.013)、D_max降低0.8 Gy (t=－4.05,P=0.002),小肠 V₄₀降低最多(10%)(t=－4.74,P=0.001)、D_max降低0.8 Gy (t=－9.45,P=0.000),骨髓 V₅₀降低最多(16%)(t=－4.04,P=0.002)、D_mean降低1.9 Gy (t=－16.21,P=0.000),左、右股骨头 D₅和马尾神经 D_max分别降低1.6、2.7 Gy和1.5 Gy (t=－2.89、－6.22、－4.80,P=0.015、0.000、0.001);机器跳数减少57%(t=－40.54,P=0.000)。结论 宫颈癌患者采用VIMAT技术可获得等同于或优FF-IMRT计划的剂量分布,机器数量明显降低,但其疗效还需进一步临床评估。

Dosimetric study of volumetric intensity-modulated arc therapy and fixed field intensity-modulated radiotherapy for cervix cancer

Objective To compare the dosimetry characteristics of volumetric intensity-modulated arc therapy (VIMAT) and fixed field intensity-modulated radiation therapy (FF-IMRT) for cervix cancer. Methods CT images of 13 patients with cervix uteri cancer were transferred into Eclipse planning system. FF-IMRT and VIMAT plans were optimized on an Eclipse treatment planning system using beam data generated for Varian trilogy linear accelerator. Planning target volume (PTV) and organs at risk were evaluated with dose-volume histogram. To appraise the difference between the techniques, the paired t-test was applied.Results Compared with the FF-IMRT plans, PTV95% coverage of VIMAT plan group increased (t=9.84,P=0.000), PTV110% became lower (t=－3.72,P=0.003), D_max decreased (t=－3.51,P=0.005), and CI became worser (t=5.39,P=0.000). PTV105%, D_mean, and HI had no difference (t=－0.02,－0.60,1.13,P=0.842,0.560,0.283). V₃₀ of the bladder was reduced by about 10%(t=－4.99,P=0.000), and D_mean and D_max were 1.4 Gy and 1.5 Gy lower respectively (t=－3.65,－18.03,P=0.004, 0.000);V₄₀ of the rectum was reduced by about 10%(t=－2.99,P=0.012), and D_mean and D_max were reduced by 0.6 Gy, 0.8 Gy respectively (t=－2.98,－4.05,P=0.013,0.002);V₃₀, V₄₀ and V₅₀ of the small intestine were reduced by 16%, 10% and 11%(t=－10.85,－4.74,－8.66,P=0.000, 0.001, 0.000), and D_max was reduced by 0.8 Gy (t=－9.45,P=0.000);V₃₀, V₄₀ and V₅₀ of the bone marrow were reduced by 26%, 19% and 16%(t=－22.10,－10.19,－4.04,P=0.000, 0.000,0.002),and D_mean reduced by 1.9 Gy (t=－16.21,P=0.000);D₅ of the left and right femoral heads were reduced by 1.6 Gy and 2.7 Gy (t=－2.89,－6.22,P=0.015,0.000). D_max of the caudate equine wasreduced by 1.5 Gy (t=－4.80,P=0.001).V₂₀, V₃₀, V₄₀ and V₅₀ of the body were reduced by 18%, 18%, 4% and 3%(t=－7.52,－11.75,－6.26,－6.94,P=0.000, 0.000, 0.000, 0.000). D_mean and D_max of the body decreased by 1.0 Gy and 0.4 Gy (t=－3.72,－3.51,P=0.000, 0.005). Average machine unit (MU) decreased by 57%(t=－40.54,P=0.000).Conclusions cervical cancer Patients with VIMAT technology can get equivalent or superior dose distribution compared with the FF-IMRT technology. And VIMAT technology could reduce MU. But the efficacy needs further clinical evaluation