Initial design of a Large Animal Dynamic SPECT CT imaging system

362 Objectives: Conventional preclinical small-animal SPECT has proven to be very useful in oncological, neurological and translational research. Preclinical SPECT dedicated to large-animal, such as canines, swine, and non-human primate, is limited. In this work, we present the design of a full-ring large-animal SPECT/CT system with an adaptive multi-pinhole collimator. The SPECT acquisition is stationary which facilitates dynamic applications Methods: The designed large-animal SPECT/CT system consists of a 16-slice helical CT and a stationary multi-pinhole SPECT. Six stationary clinical SPECT detectors (585 mm x 470 mm) forms a hexagonal detector ring. The detector intrinsic spatial resolution is 3.4 mm. An adaptive multi-pinhole collimator ring is placed inside the detector ring. It is moveable to allow different multi-pinhole sections aligned to the imaging volume. Three pinhole sections will be designed, which is further extendable, to support different FOV/resolution/sensitivity trade-off (table I). Choice of pinhole section will be determined by CT scout view and imaging applications. Optimal pinhole design is run under FOV size requirement, pinhole projection overlapping minimization criteria and resolution-sensitivity trade-off. Results: In a representative collimator design, the collimator is a 436-mm-diameter cylindrical tungsten ring with 20 mm thickness. 12 (transaxial) x 4 (axial) pinholes are evenly distributed on the collimator ring. The opening angle of the pinholes is 49.3 deg. Such design allows an imaging FOV of 20 cm (transaxial) x 30 cm (axial). When the pinhole diameter is 2.7 mm and 4 mm, achievable spatial resolution and sensitivity are (3 mm, 390 cts/s/MBq) and (4 mm, 770 cts/s/MBq) respectively. Other pinhole designs and full system performance characterization is ongoing. Conclusions: The proposed large-animal SPECT/CT system is capable of performing whole-body, dynamic large animal imaging. Optimal system performance for dedicated applications is realized by adaptive multi-pinhole collimator designs.