title: Photon-counting gamma camera based on columnar CsI(Tl) optically coupled to a back-illuminated CCD.
abstract: 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 configurations. Typically, a columnar CsI(Tl) scintillator or a radiography screen (Gd(2)O(2)S: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 amplification stage in the CCD via electron multiplying (EMCCDs)8-10 or via an image intensifier prior to the optical path.1We 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 amplification process. Operating in photon-counting mode, the detector has an intrinsic spatial resolution of 64 μm compared to 134 μm in integrating mode.
authors.affiliation: College of Optical Sciences and Department of Radiology, University of Arizona, Tucson, AZ 85721.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Miller
authors.forename: H Bradford
authors.initials: HB
authors.lastname: Barber
authors.forename: Harrison H
authors.initials: HH
authors.lastname: Barrett
authors.forename: Liying
authors.initials: L
authors.lastname: Chen
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Taylor