Dedicated small field of view SPECT system based on a 5" PSPMT and crystal scintillator array for high resolution small animal cardiac imaging

We have developed and evaluated a high resolution small animal single photon emission computed tomography (SPECT) imaging system using a small field-of-view gamma camera based on a 10 cm diameter Hamamatsu R3292 position sensitive PMT and NaI(Tl) crystal array. The instrument was designed primarily to image myocardial perfusion as well as heart and lung uptake of molecular-targeted tracers in rodent models. In the present study, we evaluated the system performance by imaging a stationary micro SPECT phantom and a variety of in vivo small animal models. Using a magnification factor of 1.57 and a 0.5 mm pinhole collimator, the reconstructed phantom images showed a spatial separation of individual rods as small as 1.6 mm. A myocardial perfusion study which was performed on a rat yielded high quality tomographic slices of the heart which clearly revealed both left and right ventricular walls and chambers. Such high resolution cardiac imaging was made possible due to the high intrinsic spatial resolution of the detector combined with pinhole collimation and OSEM reconstruction methodology. The system proved to be a very useful tool for use in molecular imaging of targeted probes.