A Monte Carlo study of the dose enhancement effects of high-z foils in proton therapy

Abstract Background: This investigation quantifies the dose enhancement effect and dose distribution modifications due to the presence of high-z nanospheres in a proton beam. Methods: Various proton pencil beams of therapeutic energies (60–226 MeV) and spatial distribution of 2·7 mm spot size diameter were simulated onto a water phantom utilising the TOPAS Monte Carlo toolkit version 3.6.1. The simulation modelled either water or nanospheres of high-z materials (gold, silver or platinum) at the location of the Bragg Peak (BP) to compare the differences of the resulting dose distributions. Results: The introduction of the nanospheres increases the maximum dose, narrows the BP and shifts the BP location upstream compared to the water phantom with no nanospheres. Conclusions: This work shows that the local dose can be enhanced with the use of high-z nanoparticles in proton therapy, thereby increasing patient safety and decreasing side effects with the same amount of delivered radiation.