Silicon avalanche photodiodes (APDs) have offered high sensitivity solid state photodetection for many years, but have not been available at low cost due to their labor-intensive production process. In Phase 1, we have shown that a new APD design can offer high performance, photodetection while avoiding the problematic production processes that have been limiting their general availability. One obvious application for the new low cut sensors is in the field of scintillator based gamma detectors. Current generation detectors use photomultiplier tubes which are large and require heavy shielding. APD based detectors, however, may be produced at a much smaller size and weight. In Phase 2, we propose to make a small, lightweight prototype gamma camera for use in clinical 'bedside imaging' applications. This camera would assist in emergency room or operating room situations where immediate, convenient imaging is important. Cardiac nuclear imaging, for example, would particular benefit from the availability of such an instrument. In Phase 2 work will entail the construction of a camera 4 inches by 4 inches in size, which will have square APD array pixels with a 3.5 mm pitch. A 'segmented' CsI(TI) scintillator will be used, approximately 6 mm in thickness, which will offer excellent light output to each APD pixel. Existing commercially available miniaturized multichannel analog readout electronics and digital/analog conversion hardware will be utilized to obtain radiographic images. Our collaborators at the University of California at San Francisco will simulate and test the prototype camera, and a clinical cardiologists will be consulted in order to determine how our new camera can best satisfy practical needs in the field.
Gamma cameras are used extensively in hospital settings to assess function, metabolism and morphological change sin patients. Our research offers a miniaturized version of these cameras which would allow their use in environments where they are not presently used, such as in the operating room or emergency room. Because of the acknowledged need for such an imaging instrument, the potential market within the medical industry is quite large.
