A depth-encoding PET detector module with improved spatial sampling

Detector modules in small ring diameter PET scanners must possess depth-of-interaction (DOI) encoding, increased spatial sampling, high sensitivity and the ability to handle high photon input rates without excessive pulse pileup or random coincidences. We created such a module by optically coupling an entrance array of individual LGSO crystals to an exit array of individual GSO (and other) crystals that was, in turn, optically and directly coupled to a miniature PSPMT. DOI was determined for each event by delayed charge integration (DCI), a technique that exploits differences in light decay time between GSO and LGSO. Spatial sampling in 3D was increased by introducing a half crystal pitch spatial offset between the entrance and exit arrays in both the X and Y directions. Position detection accuracy in both the LGSO and GSO layers, and the accuracy of DOI assignment of events to either layer was high. These results suggest that this combination of scintillators and acquisition/processing methods may be particularly useful in the design of high performance, small ring diameter PET scanners for small animal imaging