Abstract
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Objectives: Multi-Pinhole SPECT has become a proven modality in small-animal molecular imaging. Although the spatial-resolution capabilities of SPECT are greater than those of PET, the latter is generally considered the gold-standard nuclear imaging modality due to high-sensitivities. In this work, we present a high-throughput SPECT system that achieves submillimeter reconstructed resolutions while simultaneously approaching the sensitivity of PET. This increase in sensitivity combined with existing advantages of SPECT, e.g. tracer chemistry, cost and dual isotope capabilities, improves the standing of SPECT as a molecular imager.
Methods: This camera, the NanoSPECT, consists of four detectors (215x230mm NaI, 33 PMTs, 2mm intrinsic resolution at 140keV) mounted on a high-precision gantry. Each detector is outfitted with an interchangeable 9-pinhole aperture for a total of 36 pinholes surrounding the field of view (FOV). Pinhole diameter and FOV are chosen in accordance with the prescribed application, e.g., mouse or rat imaging. The axial FOV is extended using helical scanning (user-selectable range from 20 to 290mm). Additionally, helical orbits provide an increase in the angular sampling. All told, this increase in sensitivity and sampling greatly improves image quality both for detection and estimation (quantification) as compared to standard SPECT acquisition techniques.
Results: We will present a detailed description of the NanoSPECT along with numerous phantom studies and small-animal scans performed with an array of Tc-99m, I-123 and In-111 tracers. The results will address resolution, sensitivity, imaging times, injected dose and quantification results as well as multi-isotope and dynamic SPECT capabilities.
Conclusions: We have developed a system with high resolution (submillimeter), high sensitivity (> 2000cps/MBq) and fast acquisition times (down to 1 minute) with quantification and dynamic scanning capabilities.
- Society of Nuclear Medicine, Inc.