Real Time Implementation of a Wiener Filter Based Crystal Identification Algorithm for Photon Counting CT Imaging

The recently launched LabPETtrade, a small animal avalanche photodiode (APD)-based PET scanner with quasi-individual readout and massively parallel processing, makes it possible to acquire both computed tomography (CT) and positron emission tomography (PET) images using the same detection system. However, since each APD is coupled to an LYSO/LGSO phoswich scintillator pair, an efficient crystal identification algorithm must be developed to meet the stringent requirements of CT data acquisition in single photon counting mode. We propose a new ultra-fast crystal identification algorithm based on a Wiener filter. This filter instantly recovers crystal parameters by minimizing a linear cost function. A simple one-dimension projection based discrimination is used to identify the scintillating crystal. The algorithm achieves a discrimination rate of 88% for low-energy X-ray photons (~60 keV) at a high count rate >1 M events/sec/channel when implemented in a field programmable gate array.