OSEM-3D reconstruction strategies for the ECAT HRRT

High spatial resolution dynamic brain PET imaging with the ECAT HRRT scanner with short frame durations is characterized by very few counts per sinogram bin due to the small size of the crystal surface. The use of various weighting schemes for OSEM-3D can result in significantly different results. In particular, the correction for random and scattered coincidences prior to the reconstruction can lead to a systematic positive bias in the reconstructed image. We show that the use of Ordinary Poisson OSEM-3D, where all corrections are applied during the iterative steps, allows to avoid this bias without compromising spatial resolution, at a price of a lower convergence rate.