Monte Carlo simulation of small electron fields collimated by the integrated photon MLC

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Accurate modeling of electron beams from linear accelerators is crucial for precise radiation therapy.
• Existing models may require refinement for specific accelerator configurations and beam types.

Purpose of the Study:

• To develop and validate a Monte Carlo (MC) based beam model for an ELEKTA linear accelerator using the EGSnrc code.
• To investigate the impact of air density and BEAMnrc 'skin depth' parameter on electron beam modeling.

Main Methods:

• Established an MC beam model using EGSnrc for 10, 12, and 15 MeV electron beams.
• Derived source parameters from water phantom measurements (depth-dose, lateral profiles).
• Investigated air density effects and optimized the 'skin depth' parameter for small fields.

Main Results:

• Achieved agreement within 1%/1 mm for depth-dose curves and within 3%/3 mm for overall validation.
• Identified air density and 'skin depth' as critical parameters for accurate electron beam modeling.
• Successfully modeled electron beams using only integrated photon multi-leaf-collimators (MLCs).

Conclusions:

• The developed MC beam model provides accurate simulation of ELEKTA linear accelerator electron beams.
• Proper consideration of environmental factors (air density) and algorithm parameters ('skin depth') is essential for precise dosimetry.
• The model is suitable for clinical applications requiring accurate electron beam dose calculations.