Megavoltage dose enhancement of gold nanoparticles for different geometric set-ups: Measurements and Monte Carlo simulation

Gold nanoparticles (GNPs) have been shown as a good radiosensitizer. In combination with radiotherapy, several studies with orthovoltage X-rays have shown considerable dose enhancement effects. This paper reports the dose enhancement factor (DEF) due to GNPs in 18 megavoltage (MV) beams. Different geometrical 50-nm GNPs configurations at a concentration of 5 mg/ml were used by both experimental and Monte Carlo (MC) simulation in a deep-seated tumor-like insertion within a phantom. Using MCNP repeated structure capability; a large number of gold nanospheres with a semi-random distribution were applied to simulate this phantom based study. Thermoluminescence dosimetries were used to verify the process of irradiation and MC simulation. Under geometries with different probable combinations of water and GNPs distribution in the tumor, the percentage depth dose and DEF were calculated. Incorporation of GNPs into the radiation field in our set-ups showed a 12% DEF. We show that the method of nanoparticles, distribution, and orientation can effectively change the DEF value.