Spatial Mesh-Based Surface Source Model for the Electron Contamination of an 18 MV Photon Beams

Area of Science:

• Medical Physics
• Computational Dosimetry
• Radiation Oncology

Background:

• Monte Carlo simulations are computationally intensive.
• Source modeling reduces computational burden but can decrease accuracy.
• Electron contamination significantly impacts skin and shallow dose calculations.

Purpose of the Study:

• To enhance the accuracy of electron contamination modeling in Monte Carlo simulations.
• To develop a spatial mesh-based surface source model for improved accuracy.
• To address a key challenge in accurate radiation dosimetry.

Main Methods:

• A spatial mesh-based surface source model was generated.
• The model is positioned downstream from the flattening filter and mirror, upstream from the movable jaws.
• Simplified particle parameterization (5 components) using electron distance, angles, and energy.

Main Results:

• The simplified source model maintains high accuracy for electron contamination.
• Electron contamination is modeled with an accuracy of 1.5%.
• Significant reduction in computational time and disk space required.

Conclusions:

• The spatial mesh-based surface source model effectively improves electron contamination accuracy.
• This method offers a balance between computational efficiency and accuracy in Monte Carlo simulations.
• The findings are crucial for precise skin and shallow dose assessment in radiotherapy.