The goal of this proposed project is to develop an ultrahigh sensitivity, broadband X-ray fluorescence emission tomography (XFET) system. This system combines advanced CdTe X-ray imaging spectrometers assembled in a customized SPECT-like detection system design, and optimized source/filtering configurations to achieve a dramatically improved sensitivity to a broad range of metal elements that emit fluorescence x-rays of 5-100 keV. This system would be ideally suited for imaging heavier elements, such as Hf, Gd, Au and Pt with adequate tissue penetration for in vivo small animal studies. As a design target, we seek to construct an XFET system that is capable of imaging these heavy metals at a concentration of the order of 10 g/ml in tissue equivalent, mouse-sized objects irradiated with X-ray sources of ~10 mA tube current and up to 150 kVp, and with an imaging time of around 1-2 hours and at a spatial resolution of a few hundred microns. This system would offer a unique imaging tool for guiding and monitoring the delivery of radiation-induced and nanoparticle-mediated radiation therapy.
Metal-based compounds play a large role in medicine as imaging probes, chemotherapeutic agents, and,increasingly, as radiosensitizing nanoparticles. In recent years, nanoparticles containing metals (such as Au, Pt and Hf) have gained substantial attention for their potential use in cancer therapy, which could improve the efficacy of radiation therapy by enhancing X-ray absorption and generating low-energy photoelectrons and Auger electrons, as well as reactive oxygen species (ROS). We are pursuing an approach to metal mapping based on X-ray fluorescence, which allows specific imaging of a broad range of non-radioactive, non- paramagnetic metals through the use of external X-ray beams to induce emission of characteristic X-rays.