Application of measured pencil beam parameters for electron beam model evaluation

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Current electron beam models in treatment planning systems rely on broad beam data and approximations for scatter and heterogeneity.
• Accurate dose calculation is crucial for effective radiation therapy planning.

Purpose of the Study:

• To extend a pencil beam model for calculating doses in heterogeneous media and beyond field edges.
• To evaluate the developed model's performance against commercial treatment planning systems.

Main Methods:

• Developed an algorithm based on the lateral buildup ratio (LBR) for dose calculation in irregular electron fields.
• Incorporated density and mass-angular scattering power into broad beam data to derive LBR ratios.
• Inferred depth-dependent radial spread parameters to model arbitrary fields.
• Validated the model by comparing calculated fractional depth doses with measurements and commercial system outputs for small fields incident on aluminum and cork.

Main Results:

• The developed pencil beam model accurately calculates doses at any point in irregular electron fields, including off-axis points.
• The model effectively handles heterogeneous media and accounts for radial scatter.
• Calculations using the LBR-based model showed good agreement with experimental data and commercial planning systems.

Conclusions:

• The extended pencil beam model offers a robust method for accurate electron beam dose calculation in complex scenarios.
• This model serves as a valuable tool for evaluating and potentially improving commercial electron beam treatment planning systems.