Promising Semiconductor Detector Material for Enhancing PET Performance

Almost all PET systems currently in use or being developed utilize scintillation detector technology to convert the two 511 keV annihilation photons emitted from the subject per event into electronic signals for determining spatial, energy, and temporal information required for PET. The detectors are typically arranged in the shape of a cylinder surrounding the subject. We propose to investigate and develop a high resolution, box-shaped PET detector system built from a new material know as cadmium zinc telluride (CZT). CZT is a high-band gap semiconductor crystal that can be operated at room temperature. CZT has the advantage of a highly efficient, direct conversion of annihilation photons into an electrical signal, without requiring the intermediate steps of creating, collecting, and converting light as is the case for scintillation detectors. The proposed system design incorporates thin CZT detector slabs in a novel “edge-on” configuration designed to exploit all of the benefits of CZT as a photon detector, but at the same time achieving superior photon sensitivity since the incoming photons traverse a minimum of 4 cm thick detector material and there is only ~25 micron dead area between adjacent detectors. Furthermore, unlike scintillation detectors, CZT detectors can localize the three-dimensional coordinates of individual photon interactions in the system. With the use of advanced algorithms this feature enables the accurate estimate of the first interaction coordinate for more uniform spatial resolution and better image contrast resolution throughout the sensitive volume. If successful the proposed enhancements represent a significant leap for PET technology that will advance the ability to detect, visualize and quantify subtle molecular signals associated with disease.

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