Investigation of the dose enhancement factor of high intensity low mono-energetic X-ray radiation with labeled tissues by gold nanoparticles

Abstract

The aim of radiotherapy is to maximize the dose applied to the tumor while keeping the dose to the sur- rounding healthy tissue as low as possible. To further enhance dose to a tumor, techniques to radiosensitization of the tumor, using high atomic number elements, have been proposed. The aim of this study was to investigate the influence of using gold nanoparticles as a contrast agent on tumor dose enhancement when the tissue is irradiated by a typical mono energy X-ray beam. To improve the conventional radiotherapy enhancement of the absorbed dose in a tumor tissue and to spare the skin and normal tissues during irradiation in the presence of concentration agent, a model based on a Monte Carlo N-Particle eXtended (MCNPX) computer code has been designed to simulate the depth dose in a phantom containing an assumed tumor. Test was carried out in two phases. In phase 1, verification of this model using the MCNPX was evaluated by comparing the obtained results with those of the published reports. In phase 2, gold was introduced into assumed tumor inside the phantom at different depths in the simulation program. Simulation was per- formed for four different concentrations of gold nanoparticles using a low mono-energetic parallel beam of synchrotron radiation. The obtained results show that the optimum energy for dose enhancement is found to be around 83-90 keV for all gold concentrations. The dose enhancement factor is increased linearly with concentration and diminished in depth along the central beam in the tumor. This approach of introducing contrast agents in conventional radiotherapy could hopefully prepare new treatment planning and improve the efficiency of tumor therapy.