Heterogeneity model for photon beams incorporating electron transport

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Accurate photon dose calculation in heterogeneous media is crucial for effective radiation therapy.
• Existing methods often struggle with electron transport effects at medium interfaces.
• Electron disequilibrium significantly impacts dose deposition, especially in complex geometries.

Purpose of the Study:

• To develop and validate a novel method for calculating photon doses in heterogeneous media.
• To incorporate electron transport phenomena into dose calculation algorithms.
• To improve the accuracy of dose predictions in regions of electron disequilibrium.

Main Methods:

• The study employs a convolution method, combining primary photon kerma with an exponential longitudinal electron spread function.
• Electron penetration across medium interfaces is modeled to account for transport effects.
• The proposed method is validated against Monte Carlo simulations and experimental measurements for a 15-MV photon beam.

Main Results:

• The method accurately predicts photon doses in heterogeneous media, achieving agreement within 2% in most regions of electron disequilibrium.
• It demonstrates significant improvements over existing techniques in scenarios with extreme electron disequilibrium, such as low-density materials.
• The dose calculations approach an asymptotic value at larger distances from interfaces, consistent with scaling theorems.

Conclusions:

• The developed convolution method provides a robust and accurate approach for photon dose calculation in heterogeneous media.
• This technique offers enhanced precision for radiation therapy planning, particularly in challenging clinical scenarios.
• The findings represent a significant advancement in computational dosimetry, addressing limitations of current dose calculation algorithms.