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Study On the Dependence of Dose Enhancement On the Cluster Morphology of Gold Nano Particles in Radiation Therapy Using Body Centered Cubic Model

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S Ahn

S Ahn1*, K Chung2, Y Han2*, H Park2, D Choi2, D Lim2, (1) Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan, Seoul, (2) Samsung Medical Center, Sungkyunkwan University School of Medicine Radiation Oncology, Seoul


SU-I-GPD-T-638 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Injected gold nano particles (GNPs) to an animal body for dose enhancement in radiation therapy are known to form cluster morphology in a tumor. To better understand the dose enhancement mechanism, We investigated the dependence of dose enhancement on the morphology characteristic with an approximated morphology model by using Monte Carlo simulations and verified with experiments.

Methods: For Monte Carlo simulation, TOPAS was used. GNP cluster morphology was approximated as a body centered cubic(BCC) model by placing GNPs at the corners and one at the center of from 1.03 x 1.03 x 1.03 μm³ to 0.22 x 0.22 x 0.22 μm³ cubes located in a 4 x 4 x 4 μm³ water filled cube phantom. To verify the BCC model, a random distribution (NRD) of GNPs were also simulated. Poly-energetic 50, 260 kVp photons were irradiated to the water phantom with GNPs in it. We computed the dose enhancement ratio (DER) as a function of distance from the surface of the GNP at the cube center for 12 different cube geometries. For scoring particles, 10 nm width of concentric shell shaped detector was constructed up to 100 nm from the center of the cube. The validity of models was accessed in comparisons with experimental data which quantitatively measured increased relative biological effect (RBE) due to radio-sensitization of GNPs in PC-3 cells.

Results: DER increases as the distance between the GNPs reduces. The largest DER was obtained for 0.22 x 0.22 x 0.22 μm³ BCC which are 1.97, 1.80 for 50 kVp, 260 kVp photons, respectively. The cell survival parameter predicted by BCC model shows better agreement with experiments than NRD model.

Conclusion: DER with GNPs was larger when they are closely packed in the phantom and BCC model can provide an effective method in nanoparticle dosimetry.

Funding Support, Disclosures, and Conflict of Interest: Acknowledgement This research was supported by the NRF funded by the Ministry of Science, ICT & Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081]

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