Heterogeneous multiscale Monte Carlo simulations for gold nanoparticle radiosensitization

Area of Science:

• Medical Physics
• Computational Biology
• Radiotherapy Research

Background:

• Gold nanoparticle radiation therapy (GNPT) offers potential for enhanced cancer treatment.
• Accurate dose calculations in GNPT require models that account for effects on multiple length scales.
• Existing simulation methods may struggle to efficiently incorporate these multiscale effects.

Purpose of the Study:

• Introduce the heterogeneous multiscale (HetMS) model for Monte Carlo simulations in GNPT.
• Apply and validate the HetMS model in two distinct GNPT-relevant scenarios.
• Compare simulation results, including dose enhancement factors (DEFs), with published data.

Main Methods:

• Implemented the HetMS model using an extended EGSnrc user-code (egs_chamber).
• Validated the model against independent gold nanoparticle (GNP) simulations.
• Simulated two scenarios: photon beams on a cylinder and a brachytherapy source in a sphere with diffusing GNPs.

Main Results:

• The HetMS model effectively captures competing effects of photon fluence perturbation and local energy deposition from discrete GNPs.
• Dose enhancement factors (DEFs) are sensitive to source energy and depth, with DEFs below unity observed in brachytherapy-relevant energies.
• Simulation efficiency improved up to 122-fold compared to discrete GNP modeling, enabling complex calculations.

Conclusions:

• The HetMS model accurately computes energy deposition and DEFs for GNPT by integrating multiscale geometric models.
• Significant efficiency gains allow for previously prohibitive calculations.
• The HetMS model provides a versatile platform for diverse GNPT research and development scenarios.