Clinical dosimetry commissioning of 1.5 T MR-linac
Li Minghui, Tian Yuan, Zhang Ke, Niu Chuanmeng, Wang Hongkai, Men Kuo, Dai Jianrong
Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
摘要目的 介绍1.5 T MR加速器的临床剂量调试方法和结果。方法 中国医学科学院肿瘤医院于2019年5月安装1台医科达Unity型1.5 T MR加速器,使用磁场兼容测量设备对其进行剂量调试。调试项目包括绝对剂量校准、数据采集和计划系统模型验证。结果 磁场下绝对剂量校准需要使用磁场修正因子修正,参考条件下的绝对剂量为87cGy。将采集的射束数据和计划系统计算结果进行γ分析(3%/2mm),标准野测试例剂量验证平均通过率为96.41%,TG119测试例为98.24%,美国休斯敦肿瘤放疗和成像质控中心(IROC)端对端测试例为97.5%(7%/4mm)。结论 计划系统模型和射束采集数据具有良好的一致性;标准野和TG119测试例剂量验证结果达到AAPM TG218号报告的通用容差限值要求,端对端测试例验证结果满足IROC中心标准。
Abstract：Objective To introduce the clinical dosimetry commissioning methods and results of the 1.5 T MR-linac. Methods In May, 2019, an Elekta Unity 1.5 T MR-linac was installed in Cancer Hospital, Chinese Academy of Medical Sciences and dosimetry commissioning was performed with magnetic field compatible measuring instruments. Commissioning items include absolute dose calibration, data acquisition and planning system model verification. Results Absolute dose calibration in magnetic field should be corrected by magnetic field correction factor. The standard output dose of Unity was 87 cGy. Gamma analysis (3%/2mm) was performed on the beam collection data and the planning system calculation data. The average pass rate of dose verification of standard field test cases was 96.41%, and the TG119 test case was 98.24%. The IROC end to end test case was 97.5%(7%/4mm). Conclusions The planning system model and the beam collection data have good consistency. The dose verification results of the standard field and TG119 test cases meet the general tolerance limit requirements of the AAPM TG218 report, and the verification results of the IROC end-to-end test cases meet the IROC center standards.
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2022, Vol. 31 
