Abstract-Lack of spatial resolution is a major drawback in small-animal SPECT imaging, particularly when parallel hole collimators are employed. This work evaluates the feasibility of enhancing the spatial resolution of a small-animal SPECT scanner by applying an approach based on a super-resolution technique combined with dedicated hardware. The detectors are based on PS-PMTs (Hamamatsu, H8500), NaI(TI) crystal arrays and parallel hole collimators. The system enables the mechanical shifting of the gamma-cameras and the object under study during the acquisition in steps smaller than the detector intrinsic sampling pitch. This fact allows using a super-resolution technique without the necessity of blind movement estimators between projections. In the absence of noise the algorithm converged to the original image, and with real noisy data it achieved improvements in resolution between 28% (tomographic) and 42% (planar) in phantom studies.
Abstract-This work compares two different X-ray flat-panel detectors for its use in high-speed, cone-beam CT applied to small-animal imaging. The main differences between these two devices are the scintillators and the achievable frame rate. Both devices have been tested in terms of system linearity, sensitivity, resolution, stability and noise properties, taking into account the different timing schemes for each one of them and the mandatory corrections on the raw data. Tomographic scans have been carried out using both detectors to evaluate its final performance as well as the delivered dose needed to achieve similar quality scans. An experimental cone-beam CT test-bench has been designed and implemented to perform the different measurements. It uses a micro-focus X-ray source and a rotating stage where the samples are placed. A modified FDK algorithm has been used to reconstruct the acquired data. Both detectors show similar results for pixel linearity and stability measurements, and their noise levels are comparable. The resolution and sensitivity features are better for the direct grown scintillator detector (9 Ipmm vs. 6 Ipmm, and -4 times more sensitive for similar delivered dose). Since tomographic reconstructed images for the higher frame-rate detector show acceptable quality, it can be used to implement a faster system for high-speed acquisition techniques like, for example, dynamic imaging or gated protocols.
Abstract-In this work we characterized a recently developed gamma imager for small animal SPECT applications. The Hamamatsu C9177 is a mini-gamma camera that integrates the detector and all the electronics, including the acquisition system, in a compact and portable housing. The detector is based on a high resolution parallel hole collimator, a CsI(NaI) crystal array and a PS-PMT (flat panel type). The active field of view is 41.9 x 41.9 mm 2 and the assembly is optimized for 60 to 200 keV. The electronics in the housing includes the high voltage divider, an ASIC which converts the 64 anodes into Anger-like signals, ADCs which are fed with these signals and position and energy lookup tables which allow digital information for each detected photon to be obtained directly from the imager. In order to be able to obtain tomographic data and to improve the measurement protocols, we mounted the detector in a custom-built motorized gantry. We evaluated detector uniformity and energy resolution using a flood field image. Planar intrinsic spatial resolution and spatial linearity were assessed by stepping a capillary source across the detector surface and plotting the count profile for each individual crystal of the array. We additionally performed phantom studies to preliminarily characterize the tomographic performance. Energy resolution is 11.6% (mean), sensitivity is 2.54 cps/μCi and planar spatial resolution is 2.4 mm (CFOV 20% energy window) when the source is placed on the detector surface.
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