LuYAP/LSO phoswich detectors for high resolution positron emission tomography

A way to improve the spatial resolution in positron emission tomography (PET) is to determine the depth-of-interaction (DOI) in the detector which can be achieved by using the phoswich approach. The depth identification is done by using differences in scintillation decay time and pulse shape discrimination techniques. The advantages of the concept have been demonstrated in the HRRT high resolution PET system using a LSO/LYSO combination giving a high spatial resolution uniformity of around 2.5 mm. In this paper we have looked at a phoswich combination used by the Crystal Clear Collaboration in their animal PET system, LuAP/LSO or LuYAP/LSO. This phoswich combination for use in PET is patented. The combination of scintillators is especially interesting since LuAP and LuYAP have emission in the excitation band of LSO. As will be indicated in this paper, however, these potential difficulties can be understood and the phoswich concept can be utilized without complications but with some limitations.