Log file-based patient-specific quality assurance for MR-guided radiation therapy with comprehensive motion management.

BACKGROUND

Patient-Specific Quality Assurance (PSQA) for Elekta Unity MR-Linac treatments delivered under Comprehensive Motion Management (CMM) is challenging because beam gating, unexpected interruptions, and split sub-segments introduce delivery complexities that are not fully addressed by conventional quality assurance workflows.

PURPOSE: This study aimed to develop and evaluate a log file-based PSQA program for Elekta Unity MR-Linac treatments delivered under CMM.

METHODS

Log files were parsed to extract Multileaf Collimator (MLC) positions, jaw positions, and Monitor Units (MU) for each segment, with dedicated handling of CMM-induced beam gating, unexpected beam interruptions, and split sub-segments. Gantry-resolved fluence maps reconstructed from the log files were compared with planned fluence maps using gamma analysis. The system was evaluated for 66 cases, including 3 completion plans and 2 baseline shift plans.

RESULTS

Among the 66 plans, 64 achieved passing gamma results, with a pooled average passing rate of 99.91 ± 0.21%.

CONCLUSIONS

The proposed log file-based PSQA framework demonstrates accuracy and clinical practicality for MR-Linac treatments in CMM mode. It may serve as a reliable post-treatment verification tool and reduce dependence on conventional phantom-based QA.