Enhancing patient-specific quality assurance in MR-guided radiation therapy: A fluence-based method using log files

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Patient-specific quality assurance (PSQA) is essential for safe and accurate radiation therapy.
• The Elekta Unity MR-Linac system presents unique PSQA challenges due to its adaptive nature and magnetic field.

Purpose of the Study:

• To introduce a novel PSQA method for the Elekta Unity MR-Linac.
• To develop a more efficient alternative to traditional measurement-based QA techniques.

Main Methods:

• Analysis of treatment log files (MU, MLC, jaw positions) against TPS values.
• Generation and gamma analysis of fluence maps for each gantry angle.
• Development of a user-friendly interface for streamlined QA process.

Main Results:

• Strong concordance between planned and delivered parameters in nine SBRT cases.
• MU deviations within 0.5 MU and positional deviations under 1 mm.
• Fluence map gamma analysis passing rates exceeding 98% across all gantry angles.

Conclusions:

• The log file-based PSQA method significantly reduces QA time compared to traditional approaches.
• Provides direct assessment of delivered plans and comprehensive evaluation of treatment parameters.
• Offers an efficient and accurate PSQA solution for MR-guided adaptive radiotherapy.