不同射野数目在宫颈癌调强放疗中的剂量学研究

A dosimetric study of different field numbers in intensity-modulated radiotherapy for cervical cancer

目的比较不同射野数目对宫颈癌调强放疗计划的剂量学特点。方法选取我院2020年8月至12月20例接受调强放疗的宫颈癌患者,每个病例分别设计5野和7野两组调强放疗治疗计划,5野入射度为45°、115°、180°、245°、315°(PlanA);7野入射角度为0°、50°、100°、150°、210°、260°、310°(PlanB),采用等效均匀剂量优化法,在膀胱、直肠以及小肠罚分值≠0时,尽量使骨盆剂量降低,使100%等剂量线刚好覆盖95%靶体积,比较其靶区和危及器官的剂量学差异。结果两组放疗计划靶区的适形度指数CI和均匀性指数HI,PlanB优于PlanA,且均具有统计学意义(P<0.001)。危及器官直肠V_(10)、V_(50)以及膀胱V_(10)、V_(50)无统计学意义(P>0.05);直肠V_(20)、V_(30)、V_(40)、D_(mean)、膀胱V_(20)、V_(30)、V_(40)、D_(mean)、小肠V_(30)、V_(40)、V_(50)、D_(mean)、骨盆V_(20)、V_(30)、V_(40)、V_(50)、D_(mean),PlanB优于PlanA;对于小肠V_(10)、V_(20)以及骨盆V_(10),PlanA优于PlanB,且均具有统计学意义(P<0.05);机器跳数和出束时间PlanA略少于PlanB,且具有统计学意义(P<0.001)。结论两组计划均能满足临床需要,小肠及骨盆在高低剂量区各自具有其优势,但是综合考虑发生放射损伤相关性研究结果以及剂量学结果PlanB更适合于临床应用。

Objective To investigate the dosimetric characteristics of different field numbers in intensity-modulated radiotherapy for cervical cancer.Methods A total of 20 patients with cervical cancer who received intensity-modulated radiotherapy in our hospital from August to December 2020 were enrolled;and two intensity-modulated radiotherapy plans with 5 and 7 fields were designed for each patient.The incidence angles were 45°,115°,180°,245°,and 315°in the plan with 5 fields(Plan A)and were 0°,50°,100°,150°,210°,260°,and 310°in the plan with 7 fields(Plan B).The equivalent uniform dose optimization method was used;and when the cost values of the bladder;the rectum;and the small intestine were not equal to zero and the dose of the pelvis was minimized so that the 100%isodose contour covered 95%of the target volume;the target area and the organs at risk were compared in terms of dosimetry.Results Plan B had significantly better conformity index and homogeneity index of the planning target than Plan A(P<0.001).There were no significant differences in V_(10)and V_(50)of the organs at risk(rectum and bladder)between the two plans(P>0.05).Compared with Plan A,Plan B had significantly better V_(20),V_(30),V_(40),and Dmean of the rectum;V_(20),V_(30),V_(40),and Dmean of the bladder,V_(30),V_(40),V_(50),and Dmean of the small intestine and V_(20),V_(30),V_(40),V_(50),and Dmean of the pelvis;while Plan A had significantly better V_(10)and V_(20)of the small intestine and V_(10)of the pelvis than Plan B(P<0.05).Compared with Plan B;Plan A had a significantly lower number of monitor units and a significantly shorter beam-on time than Plan B(P<0.001).Conclusion Both plans can meet clinical needs and have their own advantages in the high-and low-dose areas of the small intestine and the pelvis;however,considering the association with radiation injury and the results of dosimetric analysis,Plan B is more suitable for clinical application.