Monte Carlo analysis of dose distribution in tumour and adjacent healthy tissues during <sup>192</sup>Ir HDR brachytherapy in the presence of gold nanoparticles

Abstract

High dose rate (HDR) brachytherapy using 192Ir is an effective modality for cancer treatment; however, its therapeutic efficiency is often constrained by unintended radiation exposure to healthy tissues surrounding the tumour. Fortunately, the incorporation of high atomic number (Z) nanoparticles as radiosensitizers has emerged as a promising strategy to enhance tumour dose while sparing adjacent normal tissues. In this study, the dose distribution in tumour and nearby healthy tissues during 192Ir HDR brachytherapy was investigated in the presence of gold (Au) nanoparticles using Monte Carlo simulations based on the Geant4 toolkit. Radial dose distributions and anisotropy characteristics were analysed for tumours loaded with nanoparticles at equivalent concentrations. The results demonstrate that the presence of nanoparticles significantly modifies the dose distribution, leading to anisotropic dose patterns within the tumour. The presence of Au nanoparticles produced the high radial dose enhancement and the low radial dose function values. These findings suggest that high-Z nanoparticles, particularly Au, can effectively enhance tumour dose deposition while reducing radiation exposure to surrounding healthy tissues. The use of Au nanoparticles in HDR brachytherapy, therefore, shows strong potential for improving treatment efficacy and tumour control.