Quantitative Image Reconstruction for the RatCAP PET Tomograph

The RatCAP is a miniaturized, head-mounted PET scanner designed to image the brain of conscious rats. This eliminates the need for anesthesia which is known to severely depress brain function. The small field of view of the RatCAP allows a highly accurate Monte Carlo based system matrix for fully 3D maximum likelihood image reconstruction. A number of issues have been addressed in an attempt to realize the full potential of quantitative imaging with RatCAP, including corrections for detector efficiencies, random coincidences, photon scatter and attenuation. In particular, a new method to correct for scatter originating outside the field of view is presented, which takes advantage of the RatCAP iterative reconstruction framework. Preliminary results show significant qualitative and quantitative improvements in the bias and variance of the data.