Because of scarcity of photons emitted from the heart, clinical cardiac SPECT imaging is mainly limited by photon statistics. The sub-optimal detection efficiency of current SPECT systems not only limits the quality of clinical cardiac SPECT imaging but also makes more advanced potential applications difficult to be realized. We propose a high-performance system platform - C-SPECT, which has its sampling geometry optimized for detection of emitted photons in quality and quantity. The C-SPECT has a stationary C-shaped gantry that surrounds the left-front side of a patient’s thorax. The stationary C-shaped collimator and detector systems in the gantry provide effective and efficient detection and sampling of photon emission. For cardiac imaging, the C-SPECT platform could achieve 2 to 4 times the system geometric efficiency of conventional SPECT systems at the same sampling resolution. This platform also includes an integrated transmission CT for attenuation correction. The ability of C-SPECT systems to perform sequential high-quality emission and transmission imaging could bring cost-effective high-performance to clinical imaging. In addition, a C-SPECT system could provide high detection efficiency to accommodate fast acquisition rate for gated and dynamic cardiac imaging. This paper describes the design concepts and performance potential of C-SPECT, and illustrates how these concepts can be implemented in a basic system.

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We have developed a modular cylindrical SPECT system (McSPECT-II) for clinical brain imaging. This system features a stationary cylindrical detector and a rotating collimator. The cylindrical detector is comprised of 120 NaI(T1) crystal bars coupled to a circular array of PMT's. The output signal from each PMT is digitized by an ADC! The position calculation and corrections are performed using software and precalculated lookup tables on a Pentium-based PC. The collimator has four quadrants, and each quadrant consists of a parallel array of 25 collimator units. The four corner wedges between adjacent quadrants are utilized to accommodate line sources for system calibrations. This paper reports the calibration and correction procedures developed for the McSPECT-I1 system. These procedures include: 1) PMT gain normalization, 2) azimuth bar identification, 3) energy correction, 4) axial linearity correction, and 5) uniformity correction. Results of these calibrations and corrections on data acquired by imaging various phantoms are presented.

A new detector module has been developed for a prototype system, McSPECT 11, which is being constructed for highresolution clinical brain imaging. The detector module is the building block of the cylindrical detector system of the McSPECT 11. Each detector module contains 5 NaI(Tl) bars and is backed by a glass window in an aluminum housing. Each detector module is associated with 6 PMTs to form a functional unit for position estimation. Bench-top tests performed on a sample unit demonstrated an average of 10.5% local energy resolution (ER) at 140 keV. Centroid calculations were applied in both orthogonal directions of the module for position estimation. In the longitudinal direction, a two-step centroid method yields a 1 3 cm UFOV (useful field-of-view) along the bar and an 11 cm CFOV (center FOV), with intrinsic spatial resolution of <5.5 and 3.8k0.3 mm F' WHM, respectively. In the transverse direction, the task of identifying the bar detector involved in an event is simplified, with an accuracy better than 99% when photons are incident normally.