螺旋断层调强技术在宫颈癌患者放疗中的剂量学研究

Dosimetric Study of Helical Tomotherapy in Patients with Cervical Cancer

目的探讨TOMO螺旋断层调强技术在宫颈癌患者放疗中的剂量学优势,为临床选择理想的放疗技术提供依据。方法随机选取20例宫颈癌放疗患者,经CT模拟定位机扫描后将图像传至瓦里安Eclipse13.5三维治疗计划系统由同一高年资放疗医生进行靶区勾画。处方剂量为50 Gy/25 F,针对每例患者PTV肿瘤靶区分别设计TOMO和VMAT和固定角度7野调强放疗计划。在满足PTV达到95%处方剂量的前提下,应用剂量体积直方图(DVH)评价三种调强照射方法的靶区和适形指数(CI)及剂量不均匀性指数(HI)、最大剂量(D_(max))、平均剂量(D_(mean))、最小剂量(D_(min))和各危及器官的受照剂量(OARs)。结果三种方式的所有计划都符合临床规定的剂量限制。TOMO计划方式的靶区均匀性指数(HI)及靶区适形度指数(CI)均显著优于VMAT和IMRT计划方式,差异具有统计学意义(P<0.05)。危及器官保护方面:患者膀胱受照体积V_(20)~V_(50)、直肠V_(30)和V_(40)、双侧股骨头的V_(30)和平均剂量、脊髓的最大受量等方面TOMO计划方式显著优于VMAT和IMRT计划方式,差异具有统计学意义(P<0.05)。在双侧肾脏和小肠肠管等器官吸收剂量方面,三者间均无明显差异,无统计学意义(P>0.05)。结论与IMRT和VMAT照射方式相比,TOMO照射技术具有显著的剂量学优势,其可大幅提高患者PTV肿瘤靶区剂量分布的适形度和均匀性,同时大幅降低靶区周围膀胱、直肠、脊髓等危及器官的照射剂量和照射体积,进而减少放射性损伤的发生率,具有重要的现实意义和临床推广应用价值。

Objective To evaluate the dosimetric advantage of helical tomotherapy technique in radiotherapy treatment planning for patients with cervical cancer.Methods 20 patients with cervical cancer were chosen randomly.After CT images were inputted into the Varian Eclipse13.5 treatment planning system,the same radiation therapy physician was invited to outline the tumor target volume.The prescribed dose was 50 Gy/25 fractions.Three seven-field IMRT plans(7F IMRT),volumetric modulated are therapy(VMAT)plans and helical tomotherapy plans(TOMO)were designed for each patient.Under the premise that the 95%isodose curve covers the PTV,dose-volume histogram was applied to evaluate the PTV,conformal index(CI),heterogeneity index(HI),maximum dose(D_(max)),mean dose(D_(mean)),minimum dose(D_(min))and absorbed doses of organs at risk(OARs)in three plans.Results All plans of the three radiotherapy plan design methods meet the clinically prescribed dose limit requirements for organs at risk.The heterogeneity index(HI)and conformity index(CI)of the target region in TOMO plan were significantly better than those of VMAT and IMRT plans,and the difference was statistically significant(P<0.05).The TOMO plan was significantly superior to the VMAT plan and IMRT plan in terms of the absorbed doses volume from V_(20) to V_(50) of bladder,the V_(30) and V_(40) of rectum,V_(30) and mean dose of bilateral femoral head,max dose of spinal cord,showing statistically significant difference(P<0.05).However,the three plans showed no obvious differences in terms of the absorbed doses of the kidney and bowel,without statistical significance.Conclusion Compared with the IMRT and VMAT plan for patients with cervical cancer,TOMO technology has significant dosimetric advantages.TOMO plans significantly decreased the radiation dose and radiation volume of OARs surrounding the target area(e.g.,bladder,rectum and spinal cord)while increasing the CI and HI of PTV dose greatly,thus enabling the decrease in the incidence rate of radiation negative reaction damage.