MR image‐guided radiotherapy has the potential to improve patient care, but integration of an MRI scanner with a linear accelerator adds complexity to the commissioning process. This work describes a single institution experience of commissioning an Elekta Unity MR‐linac, including mechanical testing, MRI scanner commissioning, and dosimetric validation. Mechanical testing included multileaf collimator (MLC) positional accuracy, measurement of radiation isocenter diameter, and MR‐to‐MV coincidence. Key MRI tests included magnetic field homogeneity, geometric accuracy, image quality, and the accuracy of navigator‐triggered imaging for motion management. Dosimetric validation consisted of comparison between measured and calculated PDDs and profiles, IMRT measurements, and end‐to‐end testing. Multileaf collimator positional accuracy was within 1.0 mm, the measured radiation isocenter walkout was 0.20 mm, and the coincidence between MR and MV isocenter was 1.06 mm, which is accounted for in the treatment planning system (TPS). For a 350‐mm‐diameter spherical volume, the peak‐to‐peak deviation of the magnetic field homogeneity was 4.44 ppm and the geometric distortion was 0.8 mm. All image quality metrics were within ACR recommendations. Navigator‐triggered images showed a maximum deviation of 0.42, 0.75, and 3.0 mm in the target centroid location compared to the stationary target for a 20 mm motion at 10, 15, and 20 breaths per minute, respectively. TPS‐calculated PDDs and profiles showed excellent agreement with measurement. The gamma passing rate for IMRT plans was 98.4 ± 1.1% (3%/ 2 mm) and end‐to‐end testing of adapted plans showed agreement within 0.4% between ion‐chamber measurement and TPS calculation. All credentialing criteria were satisfied in an independent end‐to‐end test using an IROC MRgRT phantom.

中文翻译：

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1.5T Elekta Unity MR-直线加速器的调试：具有单一机构经验。

MR图像引导放射疗法有可能改善患者护理水平，但是将MRI扫描仪与线性加速器集成在一起会增加调试过程的复杂性。这项工作描述了Elekta Unity MR-linac调试的单一机构经验，包括机械测试，MRI扫描仪调试和剂量学验证。机械测试包括多叶准直器（MLC）的位置精度，辐射等中心线直径的测量以及MR与MV的重合。MRI的关键测试包括磁场均匀性，几何精度，图像质量以及导航仪触发的用于运动管理的成像的精度。剂量学验证包括测量的和计算的PDD和配置文件之间的比较，IMRT测量以及端到端测试。多叶准直仪的位置精度在1.0毫米以内，测得的辐射等中心点走线为0.20 mm，MR和MV等中心点的重合为1.06 mm，这在治疗计划系统（TPS）中得到了说明。对于直径为350毫米的球形体积，磁场均匀性的峰峰值偏差为4.44 ppm，几何变形为0.8毫米。所有图像质量指标均在ACR建议之内。导航器触发的图像显示，与静止目标相比，以每分钟10、15和20次呼吸进行20 mm运动时，目标质心位置的最大偏差为0.42、0.75和3.0 mm。TPS计算得出的PDD和分布图与测量结果非常吻合。IMRT计划的伽玛通过率是98.4±1.1％（3％/ 2 mm），适应计划的端到端测试显示一致性在0以内。离子室测量和TPS计算之间为4％。使用IROC MRgRT体模的独立端到端测试满足了所有认证标准。