Novel Photosensor for Scintillation Cameras

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DESCRIPTION (provided by applicant): We will develop a prototype 19-channel Anger Camera, for nuclear medicine applications, that will be based on a new solid-state photodetetor that replaces the currently used photomultiplier tubes (PMTs). The use of PMTs in the construction of gamma cameras for nuclear medicine has been largely unchanged since the 1950's. Recently there has been an intensive effort by several groups including ourselves to develop various types of solid state gamma cameras because they offer vast improvements in performance, size and weight, and cost. To date, gamma cameras based on solid-state detectors have not achieved all of these goals because of the basic limitations of the solid-state detector technologies explored so far. The performance of solid-state photodetectors is limited by noise due to their capacitance and leakage current. In Phase I, we have made significant progress on the development of avalanche silicon drift photodetectors (A+SDPs) for direct replacement of the PMT's in Anger cameras. The main advantage of these new detectors is their extremely small capacitance (independent of detector size) and low noise. During the Phase I effort we developed a significant innovation in detector design that adds internal gain to the drift photodetector. This mitigates leakage current noise, so that the new devices do not have to be cooled. In Phase I, we designed and fabricated test structures showing the feasibility of the proposed approach. In Phase II, the new avalanche drift photodetector design will be optimized and a prototype 19-channel Anger camera module will be constructed. Full electronics readout, mechanical packaging, and DAQ software for the prototype camera will be developed in Phase II. The prototype detector module will be characterized with respect to energy resolution, spatial resolution and sensitivity using radioisotope sources and radioisotope-filled phantoms in collaboration with Dr. Edward Hoffman at the UCLA School of Medicine. The Phase II development will lead directly to the Phase III commercialization of a small field-of-view Anger camera for single organ imaging in nuclear medicine applications.