Yuan Kai, Man-Hin Cheung Matthew, Lee Louis
Medical Physics Division, Department of Medical Innovation & Technology, CUHK Medical Centre, Hong Kong SAR, China.
Department of Clinical Oncology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China.
J Appl Clin Med Phys. 2025 Sep;26(9):e70238. doi: 10.1002/acm2.70238.
Patient-specific quality assurance (PSQA) is crucial in radiation therapy to ensure accurate and safe dose delivery. The Elekta Unity MR-Linac system, which combines MRI with a linear accelerator, presents unique challenges for conventional PSQA methods due to its adaptive capabilities and the presence of a magnetic field.
This study introduced a novel PSQA method for the Elekta Unity MR-Linac system, utilizing treatment log files and fluence map verification to provide a more efficient alternative to traditional measurement-based techniques.
The proposed method analyzed log file data, including monitor units (MU), multi-leaf collimator (MLC) positions, and jaw positions, comparing them with treatment planning system (TPS) values. Fluence maps were generated for each gantry angle and evaluated using gamma analysis. A user-friendly interface was developed to streamline the process.
The method was tested on nine stereotactic body radiation therapy (SBRT) cases, showing strong concordance between planned and delivered parameters. MU deviations were within 0.5 MU, X-jaw and MLC leaf position deviations were under 1 mm, and gamma analysis of fluence maps achieved passing rates above 98% for all gantry angles.
This log file-based PSQA method offered distinct advantages over traditional measurement-based approaches, including reduced QA time, direct assessment of the delivered plan, and comprehensive evaluation of treatment parameters. This method provided an efficient and accurate alternative PSQA solution for MR-guided adaptive radiotherapy.
患者特异性质量保证（PSQA）在放射治疗中对于确保准确且安全的剂量输送至关重要。Elekta Unity MR直线加速器系统将MRI与直线加速器相结合，由于其自适应能力和磁场的存在，给传统的PSQA方法带来了独特的挑战。
本研究为Elekta Unity MR直线加速器系统引入了一种新颖的PSQA方法，利用治疗日志文件和注量图验证，为基于传统测量的技术提供一种更高效的替代方法。
所提出的方法分析日志文件数据，包括监测单位（MU）、多叶准直器（MLC）位置和射野挡块位置，并将它们与治疗计划系统（TPS）值进行比较。为每个机架角度生成注量图，并使用伽马分析进行评估。开发了一个用户友好的界面来简化流程。
该方法在9例立体定向体部放射治疗（SBRT）病例上进行了测试，显示计划参数与实际输送参数之间具有高度一致性。MU偏差在0.5 MU以内，X射野挡块和MLC叶片位置偏差在1毫米以内，所有机架角度的注量图伽马分析通过率均高于98%。
这种基于日志文件的PSQA方法相对于传统的基于测量的方法具有明显优势，包括减少QA时间、直接评估实际输送的计划以及全面评估治疗参数。该方法为MR引导的自适应放射治疗提供了一种高效且准确的替代PSQA解决方案。
