The FE-lspd model for electron beam dosimetry

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Accurate dose calculation is crucial for effective radiation therapy.
• Small-angle transport theory has limitations in describing electron beam scattering.
• Existing models like Fermi-Eyges may not fully capture lateral electron scatter.

Purpose of the Study:

• To introduce and validate the two-component FE-lspd electron beam model.
• To assess the accuracy of the FE-lspd model in calculating dose distributions, particularly in blocked fields.
• To compare the FE-lspd model's performance against the Fermi-Eyges model and EGS4 Monte Carlo simulations.

Main Methods:

• Developed a two-component model (FE-lspd) separating primary electrons and laterally scattered primary distribution (lspd).
• Incorporated a simplified Fermi-Eyges model for the primary beam component.
• Validated the model by comparing calculated dose profiles and central-axis depth dose distributions with EGS4 Monte Carlo simulations and experimental measurements for a 10 MeV electron beam in water.

Main Results:

• The FE-lspd model demonstrated high accuracy, with dose differences of <2% compared to EGS4 Monte Carlo for field sizes >3 cm.
• The FE-lspd model achieved <6% difference at 1 cm field diameter, significantly outperforming the Fermi-Eyges model which showed ~18% difference at 2.5 cm.
• Experimental validation showed <2% error for FE-lspd in central-axis depth dose distribution, compared to ~18% error for the Fermi-Eyges model.

Conclusions:

• The FE-lspd model provides a more accurate method for calculating electron beam dose distributions, especially in complex geometries like blocked fields.
• The model's ability to account for lateral electron scatter enhances its predictive power over traditional models.
• FE-lspd offers a significant improvement in dosimetric accuracy for clinical electron beam therapy.