SUMMARY

Gold nanoparticles function as an ideal radiosensitizer for radiation therapy due to the high-atomic-number nature and increased tumor specificity. The degree of radiosensitization is highly dependent on both the gold nanoparticle concentration within the tumor and the radiation quality incident on the tumor. Previous Monte Carlo simulations have demonstrated that the gamma-ray energy spectrum of Ytterbium-169 is an appropriate candidate for a high dose rate brachytherapy implementation of gold nanoparticle-aided radiation therapy.

The current study is aimed at the design of a new high dose rate Ytterbium-169 source that would maximize the dose enhancement during gold nanoparticle radiation therapy while meeting the practical constraints for the manufacture of a clinically-relevant brachytherapy source. Different encapsulation materials are studied in order to determine how the dosimetric characteristics of the source are affected. The photon spectra, secondary electron spectra, and dose enhancement factors are obtained via Monte Carlo simulations to investigate the effects of source encapsulation on radiosensitization. The project also involves a study into a modified beam from a Philips RT-250 orthovoltage x-ray machine in an attempt to match the dosimetric characteristics of the Ytterbium-169 brachytherapy source. The photon beam from the orthovoltage machine is modified using a variety of filtering materials and beam-mixing techniques in order to replicate the characteristics of the Ytterbium-169 brachytherapy source. A photon beam of this type would be an essential tool in the pre-clinical investigation of the Ytterbium-169 brachytherapy source for gold nanoparticle radiation therapy.