Towards implementation of independent calculation-based dose verification in proton therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Proton therapy offers precise tumor targeting with minimal healthy tissue damage.
• Independent dose calculation, utilizing Monte Carlo simulations, serves as a crucial secondary validation tool for patient-specific quality assurance (PSQA).

Purpose of the Study:

• To implement independent dose calculation for PSQA in proton therapy.
• To establish confidence, tolerance, and action limits for this validation method.

Main Methods:

• Point dose validation was performed using ionization chambers.
• Dose distributions were compared between independent and treatment planning calculations for single and multiple energy plans.
• Gamma analysis (3%/3mm and 5%/3mm) was applied to 50 clinical plans across five anatomical regions.

Main Results:

• Dose differences between measurement and independent calculation were within 1.0%.
• Gamma passing rates exceeded 98.0% for multiple energy plans and averaged 95.9% (3%/3mm) and 97.9% (5%/3mm) across all sites.
• Established confidence, tolerance, and action limits ranged from 85.4% to 94.3% depending on gamma criteria.

Conclusions:

• Independent dose calculation is a viable secondary dose validation method for PSQA in proton therapy.
• This approach can enhance efficiency in busy clinics.
• Careful consideration of confidence, tolerance, and action limits is essential for reliable proton therapy treatments.