Nanocrystalline Phosphors for Medical Imaging Applications

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DESCRIPTION (provided by applicant): A new class of high-performance X-ray phosphor screens will be developed based on nanocrystal quantum dots (QDs), with applications to protein crystallography, digital radiography and mammography applications, as well as a host of other important imaging and lighting applications. The goal in this project is to maximize X-ray conversion efficiency, spatial resolution, and time response, which will minimize afterglow. Nano-composite phosphor screens will be tested in state-of- the-art crystallographic CCD detectors, and compared with "standard" micro-crystalline ZnSe:Cu,Cl and Gd2O2S:Tb phosphor screens. Although phosphor screens made from micron-sized phosphors are efficient, bright X-ray converters, their large particle size produces a great deal of scatter, which limits their spatial resolution. Preliminary theoretical and experimental studies show that quantum dot phosphors in a transparent polymer-matrix screen exhibit significantly higher spatial resolution than micron-sized phosphor particles. In addition, their pico- to nano-seconds decay times and low afterglow characteristics will ensure response times orders of magnitude faster than existing phosphors. Moreover, QD phosphors can be made from high-Z materials to increase X-ray absorption and their spectral characteristic tuned to match the spectral sensitivity of CCD sensors. Specifically in Phase I, we will prepare QD phosphors and related screening techniques, and quantify their X-ray photoluminescence performance. Success in Phase I will be proven if we can show that nanometer-sized crystalline phosphors are significantly better than existing micron-sized crystalline phosphors, in terms of spatial resolution and time resolution. In Phase II, we will develop the techniques to synthesize large quantities of high quality nanocrystals, and optimize large screen characteristics for protein crystallography and medical imaging CCD detectors. QD-based X-ray converting films will have significant applications in digital radiography, crystallography, mammography, and various other biomedical imaging applications, enhancing their value to the NIH and to the molecular biology and medical communities as a whole. Key Words: Xray phosphor, nano-phosphor, nanocrystals, quantum dots, protein crystallography, digital radiography, mammography, biomedical imaging. PUBLIC HEALTH RELEVANCE: The proposed nanocrystalline phosphor materials will have significant applications in digital radiography, crystallography, and various medical imaging applications, enhancing its value to the NIH and to the molecular biology and medical communities as a whole.