Diffusing alpha-emitters radiation therapy dosimetry: Geant4 multi-stage Monte Carlo modeling of sources

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Modeling

Background:

• Diffusing alpha-emitters Radiation Therapy (DaRT) uses ${}^{224}Ra$ progeny for solid tumor treatment.
• Accurate dosimetry requires complex modeling of the ${}^{224}Ra$ decay chain, diffusion, and energy transfer.

Purpose of the Study:

• To develop and validate a 3D Monte Carlo (MC) model for temporal DaRT dosimetry.
• The model integrates the complete ${}^{224}Ra$ decay chain, diffusion, and energy transfer physics.

Main Methods:

• A multi-stage Monte Carlo model (MSMCM) was developed using the Geant4 toolkit.
• Simulations incorporated radioactive decay, Brownian motion, and particle energy transfer.
• Dose distributions were validated against analytical models for point, single, and multi-source configurations.

Main Results:

• The MSMCM successfully generated spatial and temporal dose distributions for all source types.
• Dosimetry, dose-buildup, and dose-rate curves were produced for clinically relevant timeframes.
• Model predictions showed good agreement (within 5%) with benchmark analytical models.

Conclusions:

• The MSMCM offers a flexible particle-by-particle simulation for DaRT dosimetry.
• The model is suitable for micro/nanodosimetry, multi-source in-vivo dosimetry, and detector analysis.
• It provides a robust framework for complex DaRT treatment planning and research.