Advantages using pulse shape discrimination to assign the depth of interaction information (DOI) from a multi-layer phoswich detector

Recently new high resolution brain PET and PET/SPECT tomographs have been discussed using phoswich detectors. The detector design with two layers of scintillator crystals in the z-axis with different physical properties as light decay time or light yield makes it feasible to assign the depth of interaction (DOI) information in order to be able to correct for spatial degradation in PET or to operate the detector in PET or SPECT mode. In this work we discuss the possibility separating events from the two different layers in the time domain using pulse shape discrimination or in the energy domain using pulse height discrimination. Further we investigated the feasibility of inter detector scatter suppression using pulse shape discrimination. The measurements have been done using a LSO/LSO high resolution PET detector, a LSO and GSO crystal in coincidence and a NaI(Tl)/LSO combined PET/SPECT detector