宫颈癌术后螺旋断层放疗与常规加速器调强放疗的剂量学比较

Dosimetric comparison between helical tomotherapy and step-and-shoot intensity modulated radiation therapy for cervix carcinoma

目的 研究宫颈癌术后螺旋断层放疗（helical tomotherapy,HT）与常规静态调强放疗（IMRT）的剂量学特点.方法 采用10例宫颈癌术后患者CT图像,统一勾画靶区及危及器官（膀胱、直肠、小肠及双侧股骨头）,分别传输至HT计划系统和IMRT计划系统,比较两组计划剂量体积直方图、适形度指数（CI）、均匀指数（HI）和危及器官所接受的照射剂量和体积,统一给予阴道残端60 Gy/25次,亚临床病灶50 Gy/25次,同时限定膀胱、直肠、小肠、股骨头等危及器官受照射剂量与体积.统一应用50 Gy处方剂量评价和比较CI和HI.结果 HT组适形指数（0.94±0.03）和均匀指数（1.28±0.02）均明显好于IMRT组（0.85±0.01和1.36±0.03）（t=5.12和-6.34,P〈0.01）;HT组PTV平均剂量为51.77 Gy显著低于IMRT组54.53 Gy（t=-8.01,P〈0.05）;HT组膀胱、直肠和小肠最大剂量、平均剂量、V30、V40和V50照射体积均显著低于IMRT组;HT组左、右侧股骨头最大剂量、平均剂量、V30和V40照射体积均显著低于IMRT组.结论 HT与IMRT计划均有较好的靶区剂量分布,但HT组在适形指数、均匀指数及对周围危及器官的保护均比IMRT组有明显优势.

Objective To compare the dosimetric characteristics of helical tomotherapy（HT）and step-and-shoot intensity modulated radiotherapy（IMRT）for post-operative cervix cancer patients. Methods Ten patients with post-operative cervix cancer were enrolled in this study.HT and IMRT plans were developed for each patient.The dose distributions of the targets,organs at risk（OARs）,CI and HI were analyzed and compared.The prescribed dose was 60 Gy/25 f for CTV1,50 Gy/25 f for CTV2.The iso-dose line of 50 Gy was used.Results The homogeneity indexes（HI）（0.94±0.03）,conformity index（C1）（1.28±0.02）in HT group were better than in IMRT group（0.85±0.01 and 1.36±0.03）,respectively（t=5.12,-6.34,P〈0.001）.The Dmean of PTV in HT group（51.77 Gy）was lower than that in IMRT group（54.53 Gy）（t=-8.01,P〈0.05）.The Dmax ,Dmean,V30,V40 and V50 of bladder、rectum and small bowel were lower in HT group than those in IM RT group.The Dmax,Dmean,V30 and V40 of right and left femoral head were lower in HT group than those in IMRT group.Conclusion Helical tomotherapy treatment plan has a better homogeneity,steeper dose gradient,and a better protection for organs at risk.