Choosing $FUDGEMS in EGS4 Monte Carlo

Area of Science:

• Medical Physics
• Computational Physics

Background:

• The EGS4 Monte Carlo program is widely used for simulating electron transport in materials.
• Accurate modeling of electron scattering is crucial for precise dose calculations in radiation therapy and imaging.

Purpose of the Study:

• To identify and address a significant overestimation of electron scattering power in the EGS4 Monte Carlo program.
• To propose a consistent method for combining scattering models within EGS4.

Main Methods:

• Analysis of the EGS4 Monte Carlo program's electron scattering algorithms.
• Modification of the FUDGEMS parameter to reconcile two different scattering models.
• Comparison of dose calculations with the original and modified EGS4 models for 10 MeV electron beams in water.

Main Results:

• EGS4 was found to overestimate electron scattering power due to redundant accounting of atomic orbital electron scattering.
• Setting the FUDGEMS parameter to a fractional value allows for consistent combination of the two scattering models.
• Inconsistent scattering power in EGS4 can lead to dose calculation discrepancies of approximately +/-1.5% in maximum broad beam dose for 10 MeV electron beams in water.

Conclusions:

• A minor adjustment to the FUDGEMS parameter in EGS4 significantly improves the accuracy of electron scattering calculations.
• Consistent electron scattering modeling is essential for reliable Monte Carlo-based dose estimations in various applications.