加速器多叶准直器叶片到位精度在不同机架角度下的稳定性评价  

Evaluation on the stability of positioning precision of the leaves of accelerator MLC under different gantry angles

作　　者：刘帅蓬 马阳光[1] 郭跃信[1] LIU Shuai-peng;MA Yang-guang;GUO Yue-xing(Department of Radiotherapy,The First Affiliated Hospital of Zhengzhou University,Henan Zhengzhou 450001,China;不详)

机构地区：[1]郑州大学第一附属医院放射治疗部,河南郑州450001

出　　处：《中国医学装备》2023年第12期33-36,共4页China Medical Equipment

基　　金：河南省医学科技攻关计划(SBGJ202102102)“基于深度学习由患者单角度X线投影预测其多维CT建立影像引导放疗系统的研究”。

摘　　要：目的:评价加速器多叶准直器(MLC)叶片到位精度在不同机架角度下的稳定性,以确定叶片到位精度是否受机架角度影响。方法:选用美国瓦里安Edge医用直线加速器的HD 120型MLC,利用Varian Eclipse放射治疗计划系统设计测试例。设计1个含有5个动态子野的测试计划(PMLCE测试计划),射线量为100 MU,小机头保持0°位置,各控制点对应叶片位置数目分别为-20 cm、-15 cm、-10 cm、-5 cm、0 cm、5 cm、10 cm和12 cm,共计8个,剂量率设定为500 MU/min。测试中所有叶片从一侧极限位匀速滑动至对侧极限位置,相邻控制点间叶片运动距离为5 cm。采用IEC1217坐标系在Edge直线加速器上执行PMLCE测试计划,每次均在8个不同的机架角度(0°、45°、90°、135°、180°、225°、270°和315°)下测试,得到8个加速器治疗日志文件。利用Matlab2016a软件编写程序,读取加速器日志文件,提取出叶片位置数据,并计算所有叶片实际位置与计划位置的偏差,记录每个文件包含120个叶片在8个叶片位置的到位偏差共960个数据。间隔3 d执行以上数据获取方案10次,取平均值,共8组HD 120型MLC在不同机架角度的到位偏差数据。对以上8组数据进行统计分析。结果:在各个角度下,叶片到位偏差≤10μm的百分比为45.7%~58.3%;叶片到位偏差≤30μm的百分比为95.6%~99.2%。机架角度为0°和180°时,叶片到位精度相对较高,叶片到位偏差≤10μm的百分比分别为58.3%和57.9%。HD 120型MLC的最大到位误差均≤43.3μm。单因素方差分析显示,在机架角度为0°、45°、90°、135°、180°、225°、270°和325°的8个叶片位置的到位精度观测值的情况下,0°分别与45°、90°、135°、225°、270°和315°;90°与180°;135°与180°;180°分别与225°、270°和315°机架角度下的平均到位精度之间比较,差异均有统计学意义(F=4.32,F=5.67,F=3.98,F=3.85,F=6.14,F=2.87,F=4.89,F=4.56,F=4.12,F=5.01,F=6.77;P<0.05),其余机架角度�Objective:To evaluate the stability of the positioning precisions of the leaves of accelerator multi-leaf collimator(MLC)at different gantry angles,so as to determine whether the positioning precision of leaf is affected by the gantry angle.Methods:The HD 120 MLC of American Varian Edge medical linear accelerator at our hospital was selected,and the Varian Eclipse radiotherapy planning system was used to design test cases.One test plan included 5 dynamic subfields(named PMLCE)was designed,which ray amount was 100MU,and small machine head was kept at 0°position,and the numbers of the positions of corresponding leaves of each control point were respectively-20,-15,-10,-5,0,5,10 and 12 that were 8 in total,and the dose rate was set at 500MU/min.In test,all leaves slid as uniform velocity from one extreme position to the opposite extreme position,and the movement distance of leaves between the adjacent control points was 5 cm.The PMLCE test plan was executed on the EDGE linear accelerator by using the IEC1217 coordinate system,and each test was conducted at eight different gantry angles(0°,45°,90°,135°,180°,225°,270°and 315°),and a total of 8 treatment log files of accelerator were obtained.A program was written by using Matlab2016a(MathWorks,USA)software to read the log files of accelerator,and extract out leaf position data,and calculate the deviation between the actual position and planned position of all leaves,and record a total of 960 data of positioning deviations of 120 leaves at 8 leaves positions which included in each file.The above acquisition scheme of data was performed per three days for 10 times,and then the average value was obtained.There were the data of positioning deviations of a total of 8 groups of HD 120 MLC at different gantry angles.The above 8 groups of data were analyzed as statistical method.Results:Under various angles,the range of the percentage of“leaf positioning deviations≤10μm”was between 45.7%and 58.3%,and that of“leaf positioning deviations≤30μm”was between

关 键 词：多叶准直器 机架角度 到位精度 医用直线加速器 

分 类 号：R197.39[医药卫生—卫生事业管理]