蒙特卡罗模拟机架和多叶准直器误差对旋转放疗剂量的影响  

Monte Carlo simulation of errors in gantry angle and multi-leaf collimators on intensity modulated arc therapy radiation dose

作　　者：张若辉 郜玉兰[2] 白文文[1] 孟慧鹏 王克强 迟子锋[1] ZHANG Ruohui;GAO Yulan;BAI Wenwen;MENG Huipeng;WANG Keqiang;CHI Zifeng(Department of Radiation Oncology,The Fourth Hospital of Hebei Medical University,Shijiazhuang 050011,China;Department of Endoscopy,Hebei General Hospital,Shijiazhuang 050051,China;Radiotherapy Center,Tianjin First Central Hospital,Tianjin 300384,China;Biomedical Engineering Department,Tianjin University,Tianjin 300072,China)

机构地区：[1]河北医科大学第四医院放射治疗科,石家庄050011 [2]河北省人民医院内镜诊疗科,石家庄050051 [3]天津市第一中心医院放疗中心,天津300384 [4]天津大学精仪学院生物医学工程,天津300072

出　　处：《辐射研究与辐射工艺学报》2024年第2期68-77,共10页Journal of Radiation Research and Radiation Processing

基　　金：“河北省精准医学联合基金培育项目”(H 2021206174)资助。

摘　　要：研究在常规直线加速器实施快速旋转调强放疗(IMAT)治疗过程中,内置多叶准直器(MLCs)和机架旋转误差对放疗剂量的影响。随机选择7例脑胶质瘤患者,并在常规直线加速器Varian 23EX上设计IMAT计划,对MLCs和机架分别引入不同大小误差。通过不一致指数和剂量体积直方图(DVH)评估引入误差对IMAT放疗临床剂量的影响。对于单侧MLCs随机误差,当MLCs随机误差达2 mm时计划靶体积平均剂量(PTV-Dmean)增加了约2.7%。当MLCs一侧外扩MLC-1 mm、MLC-2 mm、MLC-rnd时导致其PTV-Dmean平均偏差分别为1.12%、2.15%和1.15%,晶体的平均剂量偏差分别为5.25%、9.97%和5.49%。对于MLC两组叶片分别偏移±2 mm时导致PTV平均剂量的最大偏差为0.8%,晶体和脑干的最大剂量和平均剂量分别增加了11.4%、15.8%和1.99%、1.07%。引入机架角度误差,计划靶体积最小剂量(PTV-Dmin)和PTV-Dmean最大剂量分别降低了2.75%和0.35%。导致危及器官(OAR)的DVH的剂量学偏差变化较大,尤其对于晶体当机架偏差为(−2°)时晶体的最大剂量和平均剂量分别偏高达16.9%和38.5%。机架和MLCs误差对OAR的受量均产生较大剂量偏差。随机误差导致的MLCs剂量偏差受叶片位移误差的大小以及在特定弧段处的射束子野权重影响,MLCs误差(−2 mm或+2 mm)时产生的剂量偏差最大。机架旋转误差对靶区PTV剂量分布的影响不大,但是对于OAR会产生较大的剂量偏差。This study aimed to investigate the impact of conventional linear accelerator errors in the gantry angle and multi-leaf collimators(MLCs)on the intensity-modulated arc therapy(IMAT)radiation dose for brain tumors.Seven typical planning datasets of patients with brain tumors were randomly selected and retreated using the IMAT conventional linear accelerator Varian 23EX.Random and system errors were introduced to modify these plans while maintaining the remaining treatment information.The dose-volume parameters of the target and critical organs were compared and analyzed.The results showed that for random single-sided MLCs errors,if a group of errors was moved outward by 2 mm,the planning target volume(PTV)-Dmean increased by approximately 2.7%.If one side of the MLCs expanded outward with MLC-1,MLC-2,and MLC-rnd,the mean deviations of PTV-Dmean were 1.12%,2.15%,and 1.15%,respectively,and the Dmean deviations of the lenses were 5.25%,9.97%,and 5.49%,respectively.The maximum deviation of PTV-Dmean because of the deviation of two sets of leaves caused by system errors(±2 mm)was 0.8%,and maximum dose and Dmean of the lens and brainstem increased by 11.4%,15.8%and 1.99%,1.07%,respectively.By introducing a gantry angle error,the maximum doses of PTV-Dmin and-Dmean reduced by 2.75%and 0.35%,respectively.An incorrect gantry position results in significant changes in the dosimetric deviation of the OAR dose-volume histogram,especially for the lens.Note that the maximum and mean dose deviations of a patient’s lens if the gantry deviation(–2°)were 16.9%and 38.5%higher than those of the reference plan,respectively.The dose deviation caused by random errors of the MLCs leaves was influenced by the actual size of the random displacement errors of the leaves and weight of the beam subfield at a specific arc segment.The maximum dose deviation occurs if MLCs move to the maximum simulation error(±2 mm).The gantry rotation error had no significant impact on the target area PTV dose distribution;however,it had a significant do

关 键 词：旋转调强放射治疗 多叶准直器(MLC)误差 机架误差 剂量偏差 

分 类 号：R815.6[医药卫生—放射医学] R734.2[医药卫生—临床医学]