Commissioning of a Commercial Secondary Dose Check Software and Clinical Implementation for the Magnetic...

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Magnetic resonance-guided linear accelerators (MR-linacs) offer advanced precision in radiation therapy.
• Accurate secondary dose calculation software is crucial for ensuring treatment efficacy and patient safety with MR-linacs.
• Commissioning new software requires rigorous validation against established guidelines and clinical data.

Purpose of the Study:

• To commission the ThinkQA (TQA) software as a secondary dose calculation engine for an MR-linac.
• To validate TQA's performance against Medical Physics Practice Guideline 5.a. (MPPG5a) and clinical measurements.
• To establish appropriate gamma criteria for clinical implementation in adaptive radiotherapy workflows.

Main Methods:

• MPPG5a tests, including dose in inhomogeneities, beam profiles, and depth dose curves, were performed and compared between Monaco and TQA.
• Five intensity-modulated radiotherapy (IMRT) plans were evaluated using varying gamma criteria.
• Clinical data from 17 patients and measurements from five patients using ArcCheck were analyzed and compared with TQA calculations.

Main Results:

• Most MPPG5a tests met tolerances, with exceptions in dose profiles and fields with extensive blocking.
• A 3%/2 mm gamma criterion was found suitable for IMRT plans with high-to-low-density interfaces, unlike tighter criteria.
• Clinical case calculations showed high agreement between TQA and ArcCheck, with minor discrepancies in a specific prostate case.

Conclusions:

• ThinkQA (TQA) is successfully commissioned as a secondary dose calculation software for MR-linac.
• TQA is clinically implemented for adaptive treatment workflows using a 3%/2 mm gamma criterion (95% tolerance, 90% action limit).
• The chosen criteria maintain treatment quality, even with complex density interfaces.