Room: Exhibit Hall
Purpose: To quantify the theoretical dose enhancement effects of using different gold concentrations, sizes, and spacing of gold nanoparticles in high dose rate (HDR) brachytherapy and external beam radiotherapy.
Methods: A microSelectron HDR Ir-192 brachytherapy source and a 6MV photon beam were modeled using Monte Carlo N-Particle radiation transport software (MCNP 6.1.1b). The Ir-192 source was modeled according to published source dimensions and encapsulation. Modeling for the 6MV beam was tailored to match measured beam profiles and percent depth doses from a Varian 600C linear accelerator. The repeating structures capability of MCNP6.1.1b was utilized to simulate different sizes and spacing of gold nanospheres as well as the total concentration of gold inside a theoretical tumor, with a diameter of 4 cm. Dose enhancements were also evaluated in the case of increasing distance from the HDR Ir-192 brachytherapy source to the tumor. Dose delivered to the tumor from the Ir-192 source and the 6MV beam were calculated both with and without the presence of gold nanospheres. Dose enhancement factors were computed as the ratio of dose to the tumor containing gold nanospheres relative to that without.
Results: Dose enhancement factors of 1.158 and 1.006 were observed for the Ir-192 source and the 6MV beam, respectively, at low gold concentrations. The highest dose enhancement factors were observed in the case of HDR brachytherapy for a total gold concentration of 173.4 nM and a nanosphere spacing of 0.002 cm. It was observed that increasing gold concentration and decreasing the size of the nanospheres produced the greatest dose enhancement for both HDR brachytherapy and external beam radiotherapy cases.
Conclusion: This work indicates the potential for significant dose enhancement using external beam radiation therapy and Ir-192 HDR brachytherapy in practice. Dose enhancements using gold nanoparticles are expected in future follow-up experiments.
Funding Support, Disclosures, and Conflict of Interest: Research supported by the San Antonio Medical Foundation