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Single Cell Geant4-DNA Monte Carlo Model for Gold Nanoparticle Dose Enhancement Estimation

R Liu*, T Zhao , F Reynoso , Washington University, St. Louis, MO


(Tuesday, 7/31/2018) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 4

Purpose: To investigate the radiation dose enhancement characteristics of gold nanoparticle (GNP) aided radiotherapy using a single cell Monte Carlo model.

Methods: A simple Geant4 cell model is built considering a realistic cell geometry and cell organelle formation. The cell is modeled as a water sphere 40 microns in diameter with two cell organelles: the cell nucleus and cytoplasm. The cell nucleus is modeled as a 10 micron water sphere centered on the cell. For the gold nanoparticle geometry, a 30 nm thick gold spherical shell to represent the gold nanoparticle with diameter of 30 nm. This geometry is used to improve efficiency by forcing interactions with gold. The radius of the gold shell is varied to simulate GNP proximity to the cell nucleus from 2, 5 and 10 microns. Geant4-DNA physics is used to model the low energy interactions within the cell, and Livermore physics to model the interactions in the gold spherical shell. DBSCAN (density-based spatial clustering of applications with noise) clustering algorithm to quantify the DNA double strands breaks (DSB) after irradiation. A monoenergetic 100keV photon source was investigated.

Results: The DSB yield/Gy and total dose per cell showed the radiosensitization effects of gold within the cell. For the monoenergetic 100 keV photon the DSB yield increased by 52%, 10% and 2.5% for the gold shell at 2, 5 and 10 microns respectively, showing the strong dependence on GNP localization within the cell. The physical dose enhancement showed an increase of 157%, 155%, and 140% for the gold shell at 2, 5 and 10 micron respectively.

Conclusion: The results show the importance to model the biological effects of GNPs within a cell and not just physical dose enhancement. The DSB yield showed drastically different levels of enhancement when compared to physical dose enhancement.


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