Evaluation of the effect of gold and iron oxide nanoparticles dispersed on the bolus in radiation therapy by using Monte Carlo simulation

Objective(s): The aim of this study was to determine the entrance skin dose distribution for breast cancer patients who undergo radiotherapy in the presence of bolus containing gold and Fe3O4 nanoparticles to evaluate and compare the changes in dose distribution. Materials and Methods: Gold and Fe3O4 nanoparticles can increase the rate of photoelectric, Compton, and pair production absorption of x-ray photons. Nanoparticles were simulated in the bolus, over the skin of a breast phantom, by the exertion of MCNPX Monte Carlo code. The skin dose was also experimentally measured by using a bolus that contained homogeneously distributed Fe3O4 nanoparticles on the surface of a slab phantom and an advanced Markus chamber. Results: A significant skin dose enhancement was obtained for the case that 25 nm gold and Fe3O4 nanoparticles with 3% concentration were uniformly distributed in the bolus. However, increased concentration of nanoparticles in the bolus will increase the skin dose. Conclusion: It is concluded that using nanoparticles in the bolus leads to a significant skin dose enhancement for 6 MV x-ray photons. Furthermore, this study suggested that, less thick blouses may provide the same dose distribution.