Tabulated square-shaped source model for linear accelerator electron beam simulation.

Area of Science:

• Medical Physics
• Computational Dosimetry
• Radiation Oncology

Background:

• Monte Carlo (MC) simulations are crucial for accurate radiation therapy planning.
• Simulating electron beams from medical linear accelerators (LINACs) can be computationally intensive.
• Existing models often require complex geometry and material definitions, increasing simulation time.

Purpose of the Study:

• To develop a simplified source model for LINAC electron beam simulations.
• To reduce the complexity of electron beam geometry simulation.
• To accelerate MC computation for electron beams.

Main Methods:

• Investigated a tabulated square-shaped source with specific distribution biasing and a semi-Gaussian spectrum.
• Incorporated a low-energy photon spectrum to mitigate bremsstrahlung X-ray contamination.
• Optimized spectral parameters for four electron energies across three LINAC models (Elekta, Siemens, Varian).
• Validated simulated beam characteristics against measured percentage depth doses and dose profiles.

Main Results:

• Achieved excellent agreement between simulated and measured data (max difference of 1.8% for depth dose, 4% for dose profiles).
• Determined optimal spectral parameters and distribution weightings for various electron beams.
• Demonstrated a significant reduction in computation time, up to 702 times faster than full head simulations.

Conclusions:

• The proposed source model shows excellent agreement with experimental measurements.
• The simplified model eliminates the need for detailed LINAC head geometry and material definition.
• This approach significantly optimizes calculation speed for MC simulations of electron beams.