Evaluation of the impact of energy, radiation type, and concentration on dose enhancement by Gold Nanoparticles

Abstract

This study aimed to investigate the radiosensitization effects of Gold Nanoparticles (GNPs) on microscopic and macroscopic Dose Enhancement Ratios (DER) across various radiation energies and types, as well as different GNP concentrations. We utilized the OncoSeed ¹²⁵I model with 6711 spectra, simulating linac megavoltage beams to irradiate GNP-loaded cells. Ten-nanometer GNPs filled small water cells (30 cm per side) in a cubic phantom, while additional 10 nm GNPs were placed in cubic voxels (0.1 × 0.1 × 0.1 µm³) centered in a 1 cm diameter cell, with concentrations ranging from 0 to 30 mg/g of Au were used to study the Dose Enhancement Factor (DEF). Both elastic and inelastic scattering mechanisms were included to accurately model low- and high-energy radiations. A monoenergetic beam of 50 keV targeted the GNP-loaded tumors, with interaction physics managed using data from the ENDF/BIII.1 file. Our findings revealed significant radiosensitization effects, particularly with low-energy and short-range electrons (<1 µm). DEF values ranged from 1 to 30 mg/g of gold under a 50 keV photon beam, resulting in dose increases of up to 2.29 for photons and 1.22 for electrons. We observed a 100 % reduction in DEF for electrons at the same energy and concentration, while higher ratios were noted for the linac photon beam. The modeled ¹²⁵I seed produced a dose rate of 0.965 ± 0.002 cGy h^-1 U^-1, consistent with findings from the TG-43 report and existing literature. Increasing radiation energy significantly decreased DER, while higher GNP concentrations resulted in a dramatic increase. Further research on this topic is strongly encouraged.