Efficient particle transport simulation through beam modulating devices for Monte Carlo treatment planning

Area of Science:

• Medical Physics
• Computational Physics
• Radiotherapy Physics

Background:

• Accurate modeling of patient-specific beam modifying devices, such as Multi-Leaf Collimators (MLC), is crucial for Monte Carlo (MC) treatment planning.
• Efficient simulation of photon and electron transport through MLCs is essential to reduce calculation time in radiotherapy.

Purpose of the Study:

• To present a novel Monte Carlo geometry tracking procedure for efficient simulation of photon and electron transport through MLCs.
• To develop and integrate advanced MLC models, including tongue-and-groove effects and curved leaf ends, into an MC dose calculation engine.

Main Methods:

• A geometry tracking procedure based on elemental regions, surfaces, bit patterns, and bit masks was developed.
• Photon cross sections and electron stopping powers/ranges from NIST Physical Reference Data were utilized.
• The procedure was implemented in C++ using object-oriented design and integrated into the XVMC dose calculation engine.

Main Results:

• The developed geometry technique allows for efficient simulation of photon and electron transport through MLCs.
• Several MLC models, accounting for complex features like tongue-and-groove effects and curved leaf ends, were successfully constructed and integrated.
• The system demonstrated efficient calculation times and was validated through comparisons of different MLC implementations and experimental measurements.

Conclusions:

• The presented Monte Carlo geometry tracking procedure enables efficient and accurate simulation of patient-dependent beam modifying devices like MLCs.
• This advancement facilitates faster and more precise Monte Carlo treatment planning in radiotherapy.
• The integration of detailed MLC models enhances the fidelity of radiation dose calculations.