Initial beam size study for passive scatter proton therapy. I. Monte Carlo verification

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Modeling

Background:

• Accurate modeling of proton therapy beam delivery is crucial for precise radiation treatments.
• Monte Carlo (MC) simulations are powerful tools for simulating radiation transport and dose deposition.
• Validation of these models against experimental data is essential for their reliable application.

Purpose of the Study:

• To perform an initial validation of a Monte Carlo (MC) model simulating the passive scattering treatment nozzle at a major proton therapy center.
• To compare MC-calculated dose and fluence profiles with measured data for clinical proton beam energies.
• To establish the reliability of the MC model for future investigations into proton beam characteristics.

Main Methods:

• Development of a detailed MC model of the passive scattering nozzle, including beam-modifying elements.
• Inclusion of interactions with the rotating modulator wheel for spread-out Bragg peak generation in MC simulations.
• Comparison of calculated dose and fluence profiles with experimental measurements at 250 and 180 MeV beam energies.

Main Results:

• MC calculations demonstrated agreement within 1.5 mm of measured dose and fluence profiles across both 250 and 180 MeV beam energies.
• The study confirmed the model's ability to accurately represent the physical processes within the treatment nozzle.
• High fidelity between simulated and measured data was achieved, indicating successful model calibration.

Conclusions:

• The validated MC model provides a reliable tool for simulating proton beam characteristics at the nozzle entrance.
• This validated model can be used to investigate the dosimetric effects of proton beam size and shape.
• The findings support the use of this MC model for quality assurance and treatment planning optimization in proton therapy.