Commissioning of a Commercial Secondary Dose Check Software and Clinical Implementation for the Magnetic Resonance-guided Linear Accelerator Adaptive Workflow.

Purpose: The purpose of this study was to report the commissioning the secondary dose calculation software ThinkQA (TQA) for an magnetic resonance-guided linear accelerator (MR-linac).

Methods: The Medical Physics Practice Guideline 5.a. (MPPG5a) tests, and dose in inhomogeneities, beam profiles, and depth dose curves were calculated and compared between Monaco and TQA. Five intensity modulated radiotherapy (IMRT) plans (anal, abdominal, head and neck, prostate, and lung), based on TG-244 guidelines were evaluated varying the gamma criteria. Furthermore, the initial and adapted plans for the first session for 17 patients in different anatomical regions were calculated in TQA using different gamma criteria. For five patients, six measurements were made at different fractions using ArcCheck and compared with TQA.

Results: The majority of tests met the tolerances defined in the MPPG5a with the exception of dose profiles (>10%), and large multileaf collimator-shaped fields with extensive blocking (>2%). For the IMRT plans, tight criteria such as 2%/2 mm may not be suitable for all scenarios. Thus, we adopt a reasonable 3%/2 mm without compromising the quality of the plan that included significant high-to-low-density interfaces. It is observed that, the values obtained for clinical cases are in the range from 94.6% to 99.8% (TQA), 97.0% to 99.6% (ArcCheck), except in a prostate case with 87.8% (TQA) and 99.3% (ArcCheck).

Conclusion: We commissioned TQA as a secondary dose calculation for MR-linac and we introduced it clinically for adaptive treatment workflow using 3%/2 mm with 95% as tolerance limit and 90% as action limit.