瓦里安Halcyon加速器的安装验收测试

Installation product acceptance of Varian Halcyon accelerator

目的通过安装验收测试(IPA)了解掌握瓦里安新型Halcyon加速器的构造、性能、验收测试和质控方法。方法参考瓦里安提供的IPA手册,AAPM TG-142 C形臂加速器质控和TG-148 tomotherapy质控标准,测试并验收Halcyon的软件授权、安全联锁、机械精度、射束性能、成像系统等,并与传统TrueBeam加速器相关性能进行比较。结果本次IPA测试软件授权完整,安全联锁正常。几何精度:机架旋转过程中束流稳定性最大偏差1.13%,等中心>0.59mm,兆伏成像系统偏差0.09mm,准直系统旋转误差-0.21°,机架旋转绝对误差0.11°,治疗床最大误差(垂直方向)0.15mm,虚拟-实际等中心误差最大值(垂直方向)-0.04mm。射束性能:最大剂量点深度偏差0.1cm,10cm百分深度剂量偏差0.5%,离轴强度偏差最大值0.9%,对称性偏差最大值0.94%,剂量可重复性最大偏差-0.44%。成像系统:探测器本底值614,噪声4.4,坏点数3626,坏线数0,探测器灵敏度19177,线性度好于0.47%,均位于可接受范围内。对比度分辨率和细小物体识别能力均达标。结论在缺乏有针对性的TG报告和成熟指南情况下,厂家公布的IPA手册有助于建立Halcyon新型加速器的验收和质控方法。Halcyon加速器在北京大学肿瘤医院装机验收测试全部合格,其智能集成系统大大简化了实验操作,提高了工作效率。

Objective To understand the components,performance,acceptance test and quality assurance(QA)protocols of the new Varian Halcyon accelerator through the procedures of installation product acceptance(IPA).Methods Per Varian IPA protocol,TG-142 for LINAC and TG-148 for tomotherapy QA protocols,the software license,safety interlock,mechanical accuracy,dosimetric performance and imager system were checked thoroughly.Some parameters were benchmarked to the conventional TrueBeam system.Results The system has been fully licensed.Safety interlock was normal.Mechanical accuracy:The maximum deviation of beam stability per gantry rotation was 1.13%.The size of isocenter was>0.59mm.The offsets of MV imager,collimation rotation and absolute gantry rotation were 0.09mm,-0.21°and 0.11°,respectively.The maximum offsets of couch,virtual-to-isocenter were 0.15mm(vertical)and-0.04mm(vertical),respectively.Beam performance:The depth deviation of maximum dose was 0.1cm.The offset of percentage depth dose at 10cm was 0.5%.The maximum deviations of off-axis-intensity,symmetry,and repeatability were 0.9%,0.94%and-0.44%,respectively.MV imager:The dark field mean pixel value,noise,corrected pixels,defective lines,sensitivity and linearity disparity of dose were 614,4.4,3626,0,19177,and 0.47%,respectively.All values were within the range of tolerance.Visual check of contrast resolution and small object detection was all satisfactory.Conclusions Without Halcyon-specific TG report or guidelines,manufacture-provided IPA manual can be helpful with the installation of acceptance and QA protocols.IPA has been successfully performed for Halcyon at Peking University Cancer Hospital.The automated workflow improves the clinical efficiency by simplifying the operations.