Analytic reconstruction for improved spatial resolution with the RatCAP PET tomograph

The RatCAP is a miniaturized, high resolution PET scanner worn by the subject on its head for conscious rat brain imaging. Image reconstruction by Filtered Back Projection (FBP) is complicated by a number of factors including, but not limited to gaps between detectors, the size of the field of view relative to the size of the scanner and the depth of the interaction in the detector crystal. Spatial resolution in PET is also degraded by random coincidences, photon scatter and intrinsic detector inefficiencies. Novel techniques to optimize spatial resolution that take advantage of our highly accurate Monte Carlo scanner model have been described in this paper. Initial results show an FWHM resolution of <1.6 mm at the center. Transaxial and radial resolution FWHM values will be reported for a point source placed at different radial distances from the center of the field of view (FOV).