(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: investigated the physical dose enhancement effect caused by the direct application of gold nanospheres and gold-silicon nanoshells in brachytherapy using Monte Carlo simulations. In particular, we studied the dependence of dose enhancement on the nanoparticles’ size, structure, and concentration.
Methods: to our previous study?¹?, gold nanoparticles were built in a hierarchical structure into the Geant4 application. A certain number of nanoparticles (N³) was uniformly distributed in 3-dimensions into a tally with dimensions of 0.1 × 0.1 × 0.1 mm³. Gold nanoparticle concentrations of 1.0%, 5.6%, and 13.6% were investigated. The center of the cubic nanosphere-containing region was located 15 mm directly above the Ir-192 brachytherapy source, as shown in Figure 1. We also simulated gold-silicon nanoshells, which were modeled in the water phantom as silicon nanospheres coated with a layer of gold (Figure 2). A BEBIG Ir-192 HDR application from Geant4.8.1.p0119-20 Monte Carlo simulation toolkits was constructed. AIDA and JAS3 were used for analysis of the Geant4 application.
Results: 3 shows the dose enhancement effect due to gold nanospheres with a radius of r = 50 nm at different concentrations in the region from Y = 10 mm to Y = 20 mm directly above the Ir-192 brachytherapy source. The maximum dose enhancement was about 43%, and the average dose enhancement was about 35%. From the simulation results, we conclude that the dose enhancement effect increases linearly with nanosphere concentration. We also found the average dose enhancements caused by gold nanospheres and gold-silicon nanoshells were almost identical under the same concentration.
Conclusion: We found the dose enhancement existed in the close vicinity of gold nanoparticles with Ir-192 brachytherapy source, and the dose enhancement is strongly dependent on the gold nanoparticle concentration in the medium.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by grants from the DOD (W81XWH-06-1-0672).
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