T Gray¹*, N Bassiri² , S David³ , D Patel⁴ , A Locker⁵ , N Kirby⁶ , K Mayer⁷ , (1) The University of Texas at San Antonio, San Antonio, TX, (2)University of Texas HSC SA, San Antonio, TX (3) University of Texas at San Antonio, San Antonio, TX, (4) University of Texas at San Antonio, San Antonio, TX, (5) University of Texas at San Antonio, San Antonio, TX, (6) University of Texas HSC SA, San Antonio, TX, (7) University of Texas at San Antonio, San Antonio, TX

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  T Gray

(Sunday, 7/14/2019) 4:00 PM - 4:30 PM

Room: Exhibit Hall | Forum 4

Purpose: To develop a method to measure, validate and computationally assess dose enhancement from gold nanoparticles in phantom for different sizes and concentrations of gold nanoparticles in an Ir-192 HDR brachytherapy setup and 18 MV external beam set-up. This data will be utilized to support in vitro experiments to determine the dose enhancing capability of gold nanoparticles.

Methods: Monte Carlo simulations were used to compute dose enhancement in a nanoparticle-containing phantom for Ir-192 HDR brachytherapy and 18 MV external beam radiation therapy. The repeating structures capability of MCNP 6.2 was utilized to accurately model solutions containing gold nanoparticles 30 nm in diameter at concentrations of 8 nM, 16 nM and 22 nM for the Ir-192 set-up and 22 nM, 24 nM and 28 nM concentrations for the 18 MV external beam set-up to match experimental parameters. Experimental validation was carried out on a custom-built acrylic 5x5 cm² phantom, built according to simulation geometry, that houses EBT3 film to measure dose delivered to a volume of 0.075 cm³ surrounding nanoparticle solution. Dose enhancement factors were calculated for each concentration with uncertainties of < 1% for both theoretical and experimental data.

Results: Dose enhancement factors calculated from the Monte Carlo simulations were 1.013, 1.025, and 1.036 for Ir-192 energies at 8 nM, 16 nM, and 22 nM nanoparticle concentrations and 1.012, 1.106 and 1.027 for 18 MV energies at 22 nM, 24 nM, and 28 nM nanoparticle concentrations, respectively. The simulations predicted accurately the experimentally measured dose enhancement factors to the gold nanoparticle containing volume inside the acrylic phantom to within 1%.

Conclusion: This study confirms a method to computationally determine, measure and validate nanoparticle dose enhancement factors in the clinic. This method represents a standard for predicting and measuring dose enhancement from gold nanoparticles in vitro.

Funding Support, Disclosures, and Conflict of Interest: San Antonio Medical Foundation; San Antonio Life Sciences Institute

Keywords

Phantoms, Monte Carlo, Modeling

Taxonomy

TH- Radiation dose measurement devices: General (most aspects)

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