Room: Exhibit Hall | Forum 2
Purpose: The radiosensitization by gold nanoparticles (GNPs) has already been demonstrated in numerous early experiments. However, there was a discrepancy between macroscopically predicted levels of radiosensitization and the experimental observations. By calculating dose distributions in sub-cellular scale, the local effective model (LEM) was developed to assess the biological effectiveness of GNPs. However, the microscopic dose distributions in the cell are not measurable. Instead, the microdosimetric kinetic model (MKM) uses the lineal energy, which is a measurable quantity in hadrontherapy. The aim of this study is to calculate lineal energy distributions for electrons emitting from photon interactions with GNPs.
Methods: In the first step, a single GNP was irradiated by photon beams of different energies and Monte Carlo physics was set to Geant4-Penelope. The ejecting electrons at the surface of GNP were scored in phase space files. In the second step, the recorded phase space files were used as a point source near a nucleus-size water phantom. The deposited energies per each event in the nucleus region were calculated by using Geant4-DNA. The lineal energy was calculated as deposited energies per event divided by a mean chord length of nucleus phantom.
Results: The lineal energy distributions in the cell nucleus region somewhat varied with the energy of incident photon beam. The dose-mean lineal energy had a maximum of 3.10 keV/Âµm at 81 keV incident photon energy.
Conclusion: The lineal energy distributions were calculated for radiations from GNPs. The dose-mean lineal energy distribution vs. photon energy were similar to the photon attenuation coefficients of gold. A full MKM is under development to calculate the biological effectiveness of GNPs with radiation.