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Design of a New Yb-169 Source Optimized for Gold Nanoparticle-Aided Radiation Therapy

F Reynoso

F Reynoso1,2*, S Cho1,2, (1) Georgia Tech, Atlanta, GA, (2) The University of Texas MD Anderson Cancer Center, Houston, TX

WE-A-108-3 Wednesday 8:00AM - 9:55AM Room: 108

Purpose: To find an optimum design of a high-dose rate Yb-169 brachytherapy source for gold nanoparticle-aided radiation therapy (GNRT). Previous studies suggested that the gamma-ray energy spectrum of Yb-169 could be almost ideal for a brachytherapy implementation of GNRT. The current study was aimed to design a new Yb-169 source that would maximize dose enhancement during GNRT while meeting practical constraints for manufacturing a clinically-relevant brachytherapy source.

Methods: Monte Carlo simulations were conducted using the MCNP5 code to determine spectral changes caused by four different Yb-169 source designs and associated variations in macroscopic dose enhancement across the tumor/ICRU tissue loaded with gold nanoparticles at 0.7% by weight. The first three source models had a single encapsulation made of aluminum, titanium, or stainless steel, while the last source model adopted a dual encapsulation design with an inner aluminum capsule and an outer titanium capsule.

Results: The results showed spectral changes dependent on source design and their correlation with dose enhancement. The aluminum-encapsulated source showed the lowest intensity-weighted average energy of 108.9 keV, and the greatest dose enhancement of 51.0 % at 1 cm away from the source center. The sources encapsulated by titanium and aluminum/titanium combination showed similar levels of dose enhancement, 49.2 % and 49.3 %, and average energies of 113.3 keV and 112.5 keV respectively. The source encapsulated with stainless steel exhibited the smallest dose enhancement, 43.8 %, and the highest average energy of 126.6 keV.

Conclusion: The current investigation suggests that the attainable macroscopic dose enhancement during GNRT with an Yb-169 source can be further increased by encapsulating the Yb-core with aluminum, titanium or aluminum/titanium combination, instead of stainless steel. Due to its structural integrity and improved safety during manufacturing and clinical uses, the dual encapsulation design would be preferred.

Supported by DOD/PCRP grant W81XWH-12-1-0198

Funding Support, Disclosures, and Conflict of Interest: DOD/PCRP grant W81XWH-12-1-0198

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