Program Information
An Investigation of Radiation Dose Enhancement at the Water-Gold Interface and Its Correlation with Free Radical Generation
K Xie*, C Liu , E Parsai , D Shvydka , University of Toledo Medical Center,Department of Radiation Oncology, Toledo, OH
Presentations
SU-I-GPD-T-354 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: Radiation dose enhancement in treatments with nanoparticles of high Z materials such as gold, may lead to free radical production augmented by the nanoparticle surface. Since the direct method of free radical detection, electron spin resonance (ESR) is not suitable for use with metal nanoparticles we designed an experiment mimicking the effect with thin gold wires placed in capillaries filled with water and spin-trap agent. The wires can be taken out after sample irradiation. We use Monte Carlo (MC) simulations to model the experimental setup, and correlate dose deposition data with our previous experiments on hydroxyl free radical generation.
Methods: MCNP6 was used to model the experimental setup for gold wires with diameters ranging from 1 to 500 microns, irradiated by Ir-192 clinical brachytherapy source. The dose enhancement values in the presence of wires were calculated based on the energy deposition in surrounding aqueous media within capillaries. Calculations were done for different wire placements (middle vs. along the walls) within capillaries to find the associated uncertainty in the dose deposition.
Results: MC simulations showed that the dose enhancement region is generally limited to <0.5mm from the surface of gold wires at 0.38MV photon energies of Ir-192 source. It is expected that the hydroxyl radical generation is limited to a similarly narrow area. Consequently, the geometry selected for the experiment is suitable for free radical measurement with ESR spectroscopy.
Conclusion: MCNP6 was used to model the experimental setup for gold wires with diameters ranging from 1 to 500 microns, irradiated by Ir-192 clinical brachytherapy source. The dose enhancement values in the presence of wires were calculated based on the energy deposition in surrounding aqueous media within capillaries. Calculations were done for different wire placements (middle vs. along the walls) within capillaries to find the associated uncertainty in the dose deposition.
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