Room: Exhibit Hall
Purpose: The purpose of this research is to evaluatie the relative biological effeteness of secondary electrons generated by gold, which is considered as a radiosensitizer, using DNA double strand break (DSB) rate as a biological endpoint. The high Z material like gold is considered to have potential as a radiosensitizer due to its high secondary electron yield under irradiation. This research use Monde Carlo method to evaluate the enhancement of DSB owing to gold.
Methods: The GEANT4 10.02.p02 with GEANT-DNA package is used in this study including, 1) secondary electron spectra within tissue with and without gold; and 2) DSB rate for electrons of different energy in molecular geometry. In the first part, the simulated geometry is a 3 cm multi-shell sphere with ICRU tissue. At the center, there is a 1Î¼m target volume covered by a 200 nm gold. The irradiating beam is in the outer shell (3 cm) focused on center. The second part is simulating the DSB rate for electrons in molecular geometry using GEANT4-DNA. There are 60 energy steps from 1E+1 to 1E+7 keV logarithmly. The results were then weighted by secondary electron spectra to get the RBEDSB.
Results: In the seconfary electron spectra part, there are additional 15 peaks in the tissue with gold than those without gold. And there is a cluster of peaks at 10 keV with intensity close to the K shell emission. Also the DSB rate of these peak is about 8 times higher than the Bremsstrahlung X-ray.
Conclusion: The result shows that gold can increase both radiation quantity and quality. The gold can be a good radiosensitizer if there is specific pharmaceutical possible to send the gold to the target cell.