多叶准直器质量保证模体在Truebeam 加速器中的应用研究

Application of multi-leaf collimator quality assurance phantom on Truebeam

目的 利用多叶准直器（MLC）质量保证（QA）模体,对Truebeam加速器执行常规质量保证程序,检验MLC在治疗计划执行过程中的可靠性.方法 MLC QA模体是对MLC进行质量保证的专用模体,呈“L”形,嵌有5颗实心钢珠.模体在Truebeam加速器治疗床上进行摆位.在Eclipse vl0.0治疗计划系统中,创建一个QA计划,包含叶片位置检测、叶片宽度检测、Multi-Port检测和叶片间漏射检测等信息.通过电子射野影像系统（EPID）,获取MLC和模体的影像.按同样的操作对MLC执行每周1次,共6周的检测,并将影像导入PIPSpro软件进行分析.结果 叶片位置检测的误差结果为（0.21±0.02）mm;叶片宽度检测的误差结果为（0.04±0.02）mm;Multi-Port检测的误差结果为（0.26±0.04）mm;叶片透射检测叶片间的漏射结果为1.0％±0.14％.结论 Truebeam加速器的MLC系统运行状态良好,MLC QA模体是一个简单实用的质量保证工具.

Objective To perform a routine quality assurance procedure for Truebeam multi-leaf collimator （MLC） using MLC quality assurance （QA） phantom,verifying the reliability of MLC during the treatment.Methods MLC QA phantom was a specialized phantom for multi-leaf collimator QA,and contained five radio-opaque spheres that were embedded in an L-shape.The phantom was placed isocentrically on the Truebeam treatment couch for the tests.A quality assurance plan was settled up in the Eclipse v10.0 so that the fields for acquiring the necessary images could be created.The images were acquired by the electronic portal imaging device （EPID）,and imported into the PIPSpro software for the analysis.The tests were delivered once a week for six weeks to verify consistency of the delivery,and the images were acquired in the same manner each time.Results For the leaf position test,the average position error was （0.21 ± 0.02） mm.The leaf width was measured at the isocenter,and the average error was （0.04±0.02） mm for the leaf width test.Multi-Port test showed the dynamic leaf shift error,the average error was （0.26 ± 0.04） mm.For the leaf transmission test,the average inter-leaf leakage value was 1.0% ± 0.14%.Conclusions The MLC system of Truebeam could operate very well and the QA phantom is a useful test tool for the MLC QA.