两种宫颈癌调强放射治疗计划对多叶准直器位置误差灵敏度研究  

Sensitivity study of two cervical cancer intensity-modulated radiotherapy plans for position error of multi-leaf collimator

作　　者：王猛 杨树松[1] 孙维凯[1] 王凡[1] WANG Meng;YANG Shu-song;SUN Wei-kai;WANG Fan(Department of Radiation Therapy,Shanghai Tongji Hospital,Shanghai 200065,China)

机构地区：[1]同济大学附属同济医院放疗科,上海200065

出　　处：《生物医学工程与临床》2020年第4期398-403,共6页Biomedical Engineering and Clinical Medicine

基　　金：国家自然科学基金资助项目(61201067)。

摘　　要：目的分析不同多叶准直器(MLC)位置误差对宫颈癌患者适形调强放射治疗(IMRT)和容积旋转调强放射治疗(VMAT)计划剂量分布的影响。方法选择10例宫颈癌术后患者,年龄41~55岁,平均年龄47.8岁。为每例患者设计IMRT计划,并重新设计VMAT计划。利用MATLAB修改这些计划中的MLC源文件,分别植入0.5 mm、1.0 mm、1.5 mm、2.0 mm 4种大小的位置误差,模拟放射治疗过程中可能出现的MLC移位误差情况。根据两边MLC误差方向的不同,可分为3种类型,同向移位误差MLC(S)、反向移位误差MLC(E)、对向移位误差MLC(I)。对引入MLC误差后计划的剂量分布数据进行线性回归分析。每毫米引起的剂量变化百分率定义为灵敏度。分析并比较IMRT与VMAT计划对MLC位置误差的灵敏度差异,剂量参数评价指标采用PTV D98%、D2%、Dmean,正常组织中直肠Dmax和V50,小肠Dmax和V50,膀胱Dmean。结果对于PTV D2%和小肠Dmax,两种计划中均有MLC(E)<MLC(S)<MLC(I);对于PTV D98%、Dmean、直肠Dmax、直肠V50、小肠V50、膀胱Dmean来说,两种计划中均有MLC(S)小于MLC(I)和MLC(E)。IMRT计划剂量灵敏度变化范围为(-18.11~15.41)%/mm,VMAT计划剂量灵敏度变化范围为(-20.25~18.56)%/mm。在剂量分布的各项评价指标中,VMAT计划对MLC位置误差的灵敏度大于IMRT计划。结论在宫颈癌的VMAT计划的质控中,应制定比IMRT计划更加严格的MLC误差标准。Objective To analyze the effects of different multi-leaf collimator(MLC)position errors on the dose distribution of intensity modulated radiation therapy(IMRT)and volume modulated arc therapy(VMAT)in cervical cancer patients.Methods A total of 10 patients with cervical cancer surgery were enrolled,which aged 41-55 years old with mean age of 47.8 years old.The IMRT plan for each patient was designed,and redesigned VMAT plan.The planned MLC source files were modified by MATLAB,and 4 position errors of 0.5 mm,1.0 mm,1.5 mm,and 2.0 mm were implanted to simulate possible MLC errors in radiotherapy.By the different error directions of MLC,which were divided into co-rotating displacement error MLC(S),reverse displacement error MLC(E)and opposite displacement error MLC(I).The linear regression analysis was performed on the dose distribution data of MLC error plans.The percentage change in dose per millimeter was defined as sensitivity.The sensitivity difference of MLC position error between IMRT and VMAT were analyzed and compared.The PTV D98%,D2%and Dmean of target,Dmax and V50 of rectum,Dmax and V50 of intestine and Dmeanof bladder were used to evaluate dose parameters.Results For PTV D2%and intestine Dmax,2 plans were MLC(E)<MLC(S)<MLC(I).For PTV D98%,Dmean,rectal Dmax,rectal V50,intestine V50 and bladder Dmean,2 plans were MLC(S)<MLC(I)and MLC(E).The dose sensitivity range of IMRT plan was(-18.11-15.41)%/mm and that of VMAT plan was(-20.25-18.56)%/mm.In evaluation indexes of dose distribution,the sensitivity of VMAT plan for MLC position error was bigger than that of IMRT plan.Conclusion It is demonstrated that vertical cancer MLC error standards in VMAT plan are more stricter than that in IMRT plan.

关 键 词：宫颈癌 适形调强放射治疗(IMRT) 容积旋转调强放射治疗(VMAT) 多叶准直器 计划剂量设计 误差标准 质量控制 

分 类 号：R730.55[医药卫生—肿瘤] R737.33[医药卫生—临床医学]