Hollow gold nanoparticle interaction with kilovoltage and megavoltage photons: Shell size dependence of absorbed dose enhancement
The absorbed dose enhancement of a hollow gold nanoparticle (GNPs) at varying shell sizes were determined using Geant4, a Monte Carlo simulation toolkit for particle-matter interactions. The set-up was composed of a GNP at varying shell sizes submerged in a water volume and irradiated with 200 keV and 6 MeV photon energies. The energy deposition in the water volume from these interactions were then obtained to acquire the corresponding absorbed dose for each GNP at different shell sizes. The results showed that the GNPs irradiated with 200 keV produced higher absorbed doses than GNPs irradiated with 6 MeV. This may be attributed to the higher cross section of lower energy photons with the GNP compared to the higher energy photons. On the other hand, for both incident photon energies, the absorbed dose in the water volume decreases as a function of decreasing GNP shell size. This is attributed to the fewer secondary particle production at decreasing shell size which means that the total energy deposition from these secondary particles also decreases with decreasing shell size.