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

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

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-CT图像设计FF—IMRT计划和VIMAT计划，评估计划靶体积（HIV）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（Dmax）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（Dmean）、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）、Dmean降低1．4Gy（t=-3．65，P=0．004）、Dmax降低1．5Gy（t=-18．03，P=0．000），直肠V40降低约10％（t=-2．99，P=0．012），Dmean降低0．6Gy（t=-2．98，P=0．013）、Dmax降低0．8Gy（t=-4．05，P=0．002），小肠V40降低最多（10％）（t=-4．74，P=0．001）、Dmax降低0．8Gy（t=-9．45，P=0．000），骨髓V50降低最多（16％）（t=-4．04，P=0．002）、Dmean降低1．9Gy（t=-16．21，P=0．000），左、右股骨头D，和马尾神经Dmax分别降低1．6、2．7Gy和1．5Gy（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。

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） , Dmax decreased （t = -3.51,P=0.005）, and CI became worser （t=5.39,P=0. 000）. PTV105% , D and HI had no difference （t = -0. 02, -0. 60,1.13,P = 0. 842,0. 560,0. 283 ）. V3o of the bladder was reduced by about 10% （t = -4. 99,P =0. 000）, and D and Dmax 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 and Dmax were reduced by 0.6 Gy, O. 8 Gy respectively （t = -2.98, -4.05 ,P =0. 013,0. 002） ;V30, V4o and Vso 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 Dmax 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 reduced by 1. 9 Gy （ t = - 16.21, P = 0. 0 0 0 ） ; 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）. Dmax of the caudate equine was reduced by 1.5 Gy （t = -4. 80, P = 0. 001 ）. V2o, V30, V4o and Vs0 of the body were reduced by 18% , 18%,4% and3%（t= -7.52, -11.75, -6.26,-6.94,P=0.000,0.000, 0.000,0.000）. D and Dmax 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