对偶弧功能在宫颈癌VMAT计划中的应用

Application of Dual Arc Function in VMAT Plan for Cervical Cancer

目的利用Raystation计划系统的对偶弧功能,比较双弧与对偶弧计划对宫颈癌放疗患者危及器官的保护作用。方法选取2020年12月至2021年5月于柳州市工人医院肿瘤科接受放疗的宫颈癌术后患者20例作为研究对象,设计双弧与对偶弧计划,比较2种计划的靶区剂量分布、适形度指数(Conformity Index,CI)、均匀性指数(Homogeneity Index,HI)、子野形状以及危及器官受照剂量。结果2种治疗方案均符合临床治疗要求,对偶弧计划的计划靶体积(Planning Target Volume,PTV)D50%高于双弧计划,而V_(50.4,Body)(处方剂量为50.4 Gy时覆盖正常组织的体积)低于双弧计划,差异均有统计学意义(P<0.05)。对偶弧计划的CI优于双弧计划,总跳数(Monitor Units,MU)高于双弧计划,差异均有统计学意义(P<0.05),而2种计划的PTV D2%、D98%和HI无统计学差异(P>0.05)。在危及器官方面,对偶弧计划的直肠、膀胱和小肠的Dmean、V_(30)和V_(40)均低于双弧计划,股骨头的V_(30)和V_(40)低于双弧计划,差异均有统计学意义(P<0.05)。双弧计划A1与A2子野之间形状相似;对偶弧计划的A1子野开口偏X1侧,A2子野开口偏X2侧,A1与A2之间呈左右互补的形状。结论对于宫颈癌容积旋转强调放疗计划设计,双弧计划和对偶弧计划均能实现较好的靶区覆盖,对偶弧计划适形度更优,且使用对偶弧功能可以进一步降低多数危及器官的受照剂量,在临床设计宫颈癌容积旋转强调放疗计划时可优先使用对偶弧功能。

Objective To compare the protection of the organs at risk between two arc and dual arc plans for patients during radiotherapy for cervical cancer by using dual arc function of Raystation treatment planning system.Methods A total of 20 patients with cervical cancer who received radiotherapy in the Department of Oncology,Liuzhou Worker’s Hospital from December 2020 to May 2021 were selected as the research subjects.The two arc plan and dual arc plan were designed to compare the target dose distribution,conformity index(CI),homogeneity index(HI),subfield shape and exposure dose of organs at risk.Results Both treatment plans met the requirements of clinical treatments.The planning target volume(PTV)D50%of dual arc plan was higher than those of two arc plan,while the V50.4,Body(the volume of normal tissue was covered when the prescription dose was 50.4 Gy)was lower than of two arc plan,the difference was statistically significant(P<0.05).The CI of dual arc plan was better than that of two arc plan,and the total number of monitor units(MU)increased compared with two arc plans,the difference was statistically significant(P<0.05).There was no statistically difference in PTV D2%,D98%and HI between the two plans(P>0.05).As to organs at risk,the Dmean,V_(30)and V_(40)of rectum,bladder and small intestine in dual arc plan were all lower than those of two arc plan,the femoral head V_(30)and V_(40)of dual arc plan were lower than those of two arc plan,the difference was statistically significant(P<0.05).The shapes of A1 and A2 segments in two arc plan were similar.The opening of A1 segments of dual arc plans was biased to the X1 side,while the opening of A2 segments was biased to X2 side,A1 and A2 were complementary to each other.Conclusion For the volumetric intensity modulated arc therapy plan design of cervical cancer,both the dual arc plan and the two arc plan can achieve better target coverage,and the dual arc plan has better conformality,and the use of dual arc function can further reduce the radiation dose of most organs at risk,so the dual arc function can be given priority in the clinical design of volumetric intensity modulated arc therapy plan for cervical cancer.