Dose Enhancement Due to Injection of 79Au, 64Ga, 26Fe and 22Ti Nanoparticles into Tumor During HDR- 192Ir Brachytherapy Treatment: Monte Carlo Study

On the base of photon interactions with material، increase of atomic number and decrease of emitted photon energy increases photoelectric absorption. In the current study، the dose enhancement factor (DEF) of loaded tumor with nanoparticles (NPs) was studied using 192Ir HDR brachytherapy source. Subjects and Monte Carlo calculations were performed with MCNP4C code to determine the DEF from 192Ir source. The NPs-water mixture model was simulated. Uniform distribution of NPs into the tumor volume located 1. 5 cm from center of source centered in the water phantom with 7، 18 and 30 mgr/gr concentrations of 79Au، 64Ga، 26Fe and 22Ti، was considered. DEF of 1. 049، 1. 122، 1. 201 and 1. 033، 1. 083 and 1. 136 were estimated for 79Au and 64Gd with concentrations of 7، 18 and 30 mgr/gr، respectively. Increasing of tumor doses was not significant due to loading of 26Fe and 22Ti. Increase the radial distance of source from the tumor (from 1. 5 to 5 cm) increases the DEF (up to 22. 3%). Our data predicate that loading of tumor with high-Z NPs such as gold NPs increase the absorbed dose of tumor irradiated to 192Ir HDR brachytherapy source due to increase of photoelectric interactions. Increase of atomic number and concentration of NPs and radial distance of tumor from the source increase DEF. Loading of the tumor volume with NPs during radiation therapy improves therapeutic ratio.