MR模拟定位机的验收测试-依据指南的实践与结果分析

Acceptance testing for MR simulator:guideline-based practice and result analysis

目的:磁共振模拟定位机(MR Sim)是新类型的放疗模拟定位机。验收测试是MR Sim投入使用前的重要质量保证工作。该文报告一台MR Sim的验收测试实施细节和结果分析。方法:依据新近发布的AAPM TG284报告和NCC/T-RT 002-2023指南,制定验收测试方案。针对MR Sim的磁场屏蔽、成像系统基础功能、图像质量指标、射频线圈验收、图像几何精度、放疗外置激光灯、定位平面床及图像传输等,使用ACR(American College of Radiology)大号模体、几何畸变测量模体等质控设备进行测试。结果:MR Sim验收指标中的屏蔽测试在150 MHz的频率下,屏蔽效能均值为105 dB;8项图像质量指标:几何精度、层位置精度、层厚精度、图像均匀性、伪影比、信噪比、高对比空间分辨率和低对比分辨率,均在容许误差范围内;图像几何精度测量在25 cm感兴趣范围内,最大几何畸变<2 mm;激光灯及床的误差均<1 mm,床水平度<1°;射频线圈测试及图像传输测试满足要求。结论:MR Sim是高精度的复杂设备,为确保其在放疗中的精准应用,投入使用前需结合本单位MR Sim的具体特点,遵循指南规范,进行验收测试具体方案的详细设计和执行。

Objective Magnetic resonance simulator(MR Sim)is a novel type of simulation equipment utilized in radiotherapy.Acceptance testing is an essential quality assurance procedure prior to the clinical use of the MR Sim.The report provides the detailed procedures and result analysis of acceptance testing for an MR Sim.Methods The acceptance testing scheme was developed following the recently published AAPM TG284 report and the NCC/T-RT 002-2023 guidelines.Quality control equipments such as ACR(American College of Radiology)large phantom and geometric distortion measurement phantom were used for evaluating various aspects of the MR Sim,including the effectiveness of shielding,the functionality of imaging system,the image quality,the performance of radio frequency coils,the geometric accuracy of large field imaging,the precision of external laser markings,the couch movement accuracy,and the image transmission accuracy.Results The shielding effectiveness at a frequency of 150 MHz exhibited an average value of 105 dB.All of 8 image quality indices,namely geometric accuracy,slice position accuracy,slice thickness accuracy,image uniformity,artifact ratio,signal-to-noise ratio,high-contrast spatial resolution,and low-contrast resolution,fell within recommended tolerances.The maximum geometric distortion observed across a 25 cm field of view was less than 2 mm.The errors in external laser markings and couch movement accuracy were both less than 1 mm.The couch levelness was less than 1°.Both radio frequency coils and image transmission passed the required tests.Conclusion MR Sim is high-precision and complex.To ensure its precise application in radiotherapy,the acceptance testing for an MR Sim should be meticulously designed and executed following the established guidelines and accounting for its unique performance characteristics.