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Dose Enhancement Using Gold Nanoparticles as a Function of Tumor Size, Depth and Gold Concentration

F Cifter

F Cifter1*, B Zhang1 , E Sajo2 , N Lamichhane1 , (1) University of Maryland, Baltimore, MD, (2) Univ Massachusetts Lowell, Lowell, MA


SU-I-GPD-T-424 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Application of gold nanoparticles (GNP) as radiosensitizer requires detailed characterization of energy deposition in sub-millimeter resolution. The purpose of this study is to investigate the behavior of GNP dose enhancement ratios (DER) and the dosimetric properties of GNP-laden tumor regions in homogeneous and heterogeneous phantoms as a function of GNP concentration, tumor volume, and depth.

Methods: Radiation transport calculations were performed using the CEPXS/ONEDANT deterministic computer code. Clinical 6 MV source photons were normally incident on a water phantom with a GNP-laden embedded tumor layer followed by either water or bone layer. Two tumor volumes, 1 and 5 cm thick respectively, were placed at two different depths, 1 and 5 cm, to represent the typical superficial and deep-seated tumors. In each case, normalized GNP concentrations of c=0.3, 0.64 and 1 (limiting case) were used.

Results: Our study shows that the maximum value of DER on the proximal border of the tumor increases with increasing GNP concentration (lower maxima were observed on distal edge due to the attenuation of the beam). For the same tumor volume, better dose uniformity is achieved with smaller GNP concentrations inside the tumor volume, regardless of the tumor depth or the material of the end layer (water or bone). Lastly, the maximum DER values increase with the concentrations of c=0.64 and 0.3 but stay almost the same with c=1, for all cases. There is not a significant difference on DER values between the water end layer and the bone end layer.

Conclusion: GNP concentration, target volume and depth have a strong impact on the magnitude of DER values and dose uniformity inside the target volume. But the material (water or bone) at the distal end of the phantom does not change DER significantly.

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