Room: Exhibit Hall
Purpose: To improve the efficacy of radiation therapy on tumors while reducing the risk that normal tissue is irradiated, we have computationally studied novel X-ray sources and their interactions with varying nanoparticles. The goal is to determine which combinations of sources and nanoparticles show the largest increase in tumor X-ray absorption and DNA single or double strand breaks.
Methods: We used the Monte Carlo simulation code GEANT4 to simulate spectra from quasi-monochromatic, monochromatic, and traditional broadband medical X-ray sources interacting with heavy element nanoparticles. Nanoparticles were composed of gold, platinum, or gadolinium, were varied in size from 2-20 nm, and were varied in shape including rods, spheres, and cubes.
Results: Unfiltered broadband sources show a large flux of low-energy Auger electrons that do not escape the nanoparticle. Quasi-monochromatic and monochromatic sources show the highest enhancement in X-ray absorption compared to traditional broadband sources. In combination with heavy element nanovehicles, they produce a high flux of ionized and Auger electrons capable of inducing DNA single and double strand breaks. We have also made progress in studying a novel physical process, pumping KÎ± resonance fluorescence, that can further reduce the dose needed to kill malignant cancer cells.
Conclusion: Quasi-monochromatic and monochromatic sources perform similarly efficiently and show markedly improved efficacy over broadband sources when interacting with heavy element nanoparticles.