Model refinement increases confidence levels and clinical agreement when commissioning a three-dimensional secondary...

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Accurate dose calculation is critical for radiation therapy efficacy and patient safety.
• Second check dose calculation systems require rigorous validation against established benchmarks.
• The AAPM-TG119 protocol provides a standardized method for evaluating treatment planning systems.

Purpose of the Study:

• To evaluate custom beam models for the Sun Nuclear Dose Calculator (SDC) system.
• To assess the SDC system's performance using statistically verifiable passing criteria for film analysis, dose-volume histogram (DVH) metrics, and 3D gamma analysis.
• To ensure the SDC system meets clinical requirements for a second check dose calculation.

Main Methods:

• Custom beam models for nine linear accelerators were developed for the SDC algorithm.
• The AAPM-TG119 test suite, including Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) plans, was used for evaluation.
• Comparisons were made against the Analytic Anisotropic Algorithm (AAA) and gafchromic film measurements.
• Dose distributions were analyzed using DVH metrics and 3D gamma analysis with criteria of 3%/3 mm or 3%/1 mm.

Main Results:

• SDC demonstrated high agreement with film measurements across different machine types and beam energies (e.g., 98.76% ± 2.30% for HD MLC SRS beams).
• Comparisons between SDC and AAA showed excellent agreement for both DVH point metrics and 3D gamma analysis across various LINAC configurations.
• All evaluated models met or exceeded the TG119 confidence limits (CLs), indicating robust performance.

Conclusions:

• The SDC system, with custom beam models, shows strong agreement within TG119 confidence limits for both film and AAA comparisons.
• The study validates the SDC system as a reliable tool for second check dose calculations in radiation therapy.
• TG119 plans are effective for guiding model adjustments and establishing clinical baselines for DVH and 3D gamma criteria.