28 March 2007 Photon-counting gamma camera based on columnar CsI(Tl) optically coupled to a back-illuminated CCD
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Recent advances have been made in a new class of CCD-based, single-photon-counting gamma-ray detectors which offer sub-100 μm intrinsic resolutions.1-7 These detectors show great promise in small-animal SPECT and molecular imaging and exist in a variety of cofigurations. Typically, a columnar CsI(Tl) scintillator or a radiography screen (Gd2O2S:Tb) is imaged onto the CCD. Gamma-ray interactions are seen as clusters of signal spread over multiple pixels. When the detector is operated in a charge-integration mode, signal spread across pixels results in spatial-resolution degradation. However, if the detector is operated in photon-counting mode, the gamma-ray interaction position can be estimated using either Anger (centroid) estimation or maximum-likelihood position estimation resulting in a substantial improvement in spatial resolution.2 Due to the low-light-level nature of the scintillation process, CCD-based gamma cameras implement an amplfication stage in the CCD via electron multiplying (EMCCDs)8-10 or via an image intensfier prior to the optical path.1 We have applied ideas and techniques from previous systems to our high-resolution LumiSPECT detector.11, 12 LumiSPECT is a dual-modality optical/SPECT small-animal imaging system which was originally designed to operate in charge-integration mode. It employs a cryogenically cooled, high-quantum-efficiency, back-illuminated large-format CCD and operates in single-photon-counting mode without any intermediate amplfication process. Operating in photon-counting mode, the detector has an intrinsic spatial resolution of 64 μm compared to 134 μm in integrating mode.
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Brian W. Miller, Brian W. Miller, H. Bradford Barber, H. Bradford Barber, Harrison H. Barrett, Harrison H. Barrett, Liying Chen, Liying Chen, Sean J. Taylor, Sean J. Taylor, } "Photon-counting gamma camera based on columnar CsI(Tl) optically coupled to a back-illuminated CCD", Proc. SPIE 6510, Medical Imaging 2007: Physics of Medical Imaging, 65100N (28 March 2007); doi: 10.1117/12.710109; https://doi.org/10.1117/12.710109

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