Technical Note: An approach to building a Monte Carlo simulation model for a double scattering proton beam system

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Proton therapy offers precise dose delivery.
• Passive scattering systems require accurate modeling for treatment planning.
• Monte Carlo simulations are crucial for detailed dose calculations.

Purpose of the Study:

• Develop a Monte Carlo simulation model for a passive double scattering compact proton therapy system.
• Validate the model using limited mechanical component information.
• Establish a reliable tool for simulating proton beam interactions.

Main Methods:

• Constructed a virtual machine source model (VMSM) with detailed beam-modifying components.
• Simulated beam interactions with range modulation wheels and scatterers.
• Validated the VMSM against measured percent depth dose curves, spread out Bragg peaks (SOBPs), and lateral profiles.

Main Results:

• MC calculations showed excellent agreement with measured beam range (within 1 mm).
• Distal fall-off length agreement was within 1-1.5 mm.
• SOBP widths and lateral profiles showed good agreement (within 2.5 mm and 2 mm, respectively).

Conclusions:

• An acceptable MC source model for passive scattering proton therapy can be developed with limited data.
• Model validation supports its use for investigating dosimetric effects in patient treatments.
• This simulation tool can enhance the accuracy and safety of proton therapy planning.