准直器角度对容积调强计划执行精度的影响  

Effect of collimator angle on accuracy of volumetric modulated arc therapy(VMAT)plan

作　　者：杨旭[1] 葛超 王利波[1] 时颖华[1] 夏文明[1] 陈坤志[1] 李钰[1] 董丽华[1,2] 孙无忌 王辉东 YANG Xu;GE Chao;WANG Li-bo;SHI Ying-hua;XIA Wen-ming;CHEN Kun-zhi;LI Yu;DONG Li-hua;SUN Wu-ji;WANG Hui-dong(Department of Radiation Therapy,the First Hospital of Jilin University,Changchun 130021,China;Jilin Key Laboratory of Radiation Oncology Therapy,Changchun 130021,China)

机构地区：[1]吉林大学第一医院放疗科,长春130021 [2]吉林省放射肿瘤治疗重点实验室,长春130021

出　　处：《医疗卫生装备》2020年第12期58-62,共5页Chinese Medical Equipment Journal

摘　　要：目的:研究准直器角度对宫颈癌患者容积调强放疗(volumetric modulated arc therapy,VMAT)计划的剂量验证结果,分析VMAT计划执行的精度。方法:随机选取2018年5月1日至2019年5月1日收治的宫颈癌根治术后患者12例,对每例患者重新设计两弧VMAT计划,弧1机架角从181°到179°(顺时针方向旋转),准直器角度为10°;弧2机架角从179°到181°(逆时针方向旋转),准直器角度为350°。采用Varian TrueBeam加速器的PD(Portal Dosimetry)系统进行验证,验证时将弧1的准直器角度分别设置为10°、20°、30°、40°、45°、50°、60°、70°、80°,将弧2的准直器角度分别设置为350°、340°、330°、320°、315°、310°、300°、290°、280°。将每个准直器角度验证后实际得到的剂量分布与对应的计划系统计算出的剂量分布进行Gamma分析,分析参数为3%/3 mm、3%/2 mm、2%/2 mm,统计同一弧、不同准直器角度的Gamma通过率。使用SPSS 20.0软件,以准直器角度为10°时的验证结果为基准,其他角度的验证结果与其做配对t检验。结果:Gamma分析参数为3%/3 mm、3%/2 mm、2%/2 mm,准直器角度为10°时的Gamma通过率最高,分别为(98.48±0.83)%、(96.77±1.58)%、(94.81±2.03)%;准直器角度为45°时的Gamma通过率最低,分别为(98.03±1.08)%、(95.88±2.08)%、(93.57±2.75)%(P=0.002、0.003、0.002)。准直器角度从10°到45°的过程中,Gamma通过率逐渐下降,而从50°到70°则是逐渐上升,70°后略有下降。结论:以宫颈癌为例的研究表明,VMAT的计划执行精度随准直器角度变化,准直器角度在10°附近的Gamma通过率最高,45°附近最低,在设计放疗计划时应结合实际情况合理选择准直器角度。Objective To study the dosimetric verification results of the multi-leaf collimator angle on cervical cancer patients with VMAT plan,and analyze the accuracy of volume modulation plan execution.Methods Twelve postoperative cervical carcinoma patients admitted from May 1,2018 to May 1,2019 were randomly selected,and for each patient,a two-arc VMAT plan was redesigned,with an arc 1 rack angle from 181°to 179°(clockwise rotation)and a collimator angle of 10°,and an arc 2 rack angle from 179°to 181°(counterclockwise rotation)and a collimator angle of 350°.Portal Dosimetry(PD)system of Varian TrueBeam Accelerator was used for verification,the collimator angle for arc 1 was set to 10°,20°,30°,40°,45°,50°,60°,70°and 80°,and the collimator angle for arc 2 was set to 350°,340°,330°,320°,315°,310°,300°,290°and 280°.Gamma analysis was performed on the dose distribution actually obtained after the verification of each collimator angle with the dose distribution calculated by the corresponding planning system,with the analysis parameters of 3%/3 mm,3%/2 mm and 2%/2 mm,and on the Gamma pass rates for the same arc and different collimator angles.SPSS 20.0 software was used to benchmark the validation results for the collimator angle of 10°,and paired t-tests were performed for other angles.Results The Gamma analysis parameters were 3%/3 mm,3%/2 mm and 2%/2 mm.The highest Gamma pass rates were(98.48±0.83)%,(96.77±1.58)%and(94.81±2.03)%respectively when the collimator angle was 10°;the lowest pass rates were(98.03±1.08)%,(95.88±2.08)%and(93.57±2.75)%respectively when the collimator angle was 45°(P=0.002,0.003 and 0.002).The collimator angle decreased progressively from 10°to 45°,while the Gamma passage rate increased gradually from 50°to 70°and decreased slightly after 70°.Conclusion Studies using cervical cancer as an example show that the planning accuracy of VMAT varies with the collimator angle,with the highest Gamma pass rates occurring around 10°and the lowest around 45°,and that the

关 键 词：宫颈癌 容积调强放疗 准直器角度 多叶准直器 剂量验证 

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