Geant4 track structure simulation of electron beam interaction with a gold nanoparticle

Abstract

Application of nanoparticles as radiosensitizer in various radiation therapy modalities have recently attracted considerable interest. Although experimental findings have shown radiosensitization effect of gold nanoparticles (GNPs) when combining with electron irradiations, observing the recent literature reveals the lack of a standard analysis regarding the modification effects caused by the presence of GNP on physical energy deposition pattern in electron fields. The aim of the current study is to evaluate and verify radioenhancement effects of GNPs under electron beams. Monte Carlo track structure simulation that is the generally accepted approach for investigation of radiation effects in the nanometer scale was conducted by the use of Geant4-DNA code to track electrons down to the 7.4 eV energy. Macroscopic megavoltage energy electron spectrum from an intraoperative electron radiation source was used to irradiate a water phantom while particles were tracked to score the microscopic (nanometer) beam spectrum. Then, a single 50 nm gold nanoparticle was irradiated with the nanobeam where secondary electrons and energy deposition were scored. The results reveal a non-negligible dose escalation of up to 12% at close vicinities of the nanoparticle gradually decreasing at further distances that is caused by low energy electrons originated in the NP. Although, the amount of calculated dose enhancement show dependence on the parameters of the microscopic simulation, the current result provides a theoretical evidence in support of the physical dose enhancement in GNP aided electron radiotherapy.