Single-Ended Readout PET Detector Based on Pixelated Crystals With TOF and DOI Capabilities

Abstract

Traditional PET detectors based on pixelated scintillation crystals with single-ended readout do not provide depth of interaction (DOI) information in an easy and cost-effective way. In this work, we propose a PET detector with single-ended readout and 1:1 coupling, based on arrays of naked pixelated crystals that are glued in one direction, and optically separated in the other one. We have named this approach as pseudo-slab. In this configuration, some of the optical photons will propagate in the glued direction, generating a light distribution from which DOI information can be retrieved. We have characterized four different detector configurations, all of them consisting of a linear array of $1\times 8$ LYSO crystals of $3\times 3\times 20~{\mathrm { mm}}^{3}$ each, with an optical glue of approximately $70~\mu $ m in between them. The top and bottom faces are polished, and with a different number of unpolished lateral surfaces (2 versus 4) and different wrappings (Enhanced Specular Reflector versus BaSO4). The results obtained for the four detector configurations show energy resolutions ranging from 8.5% to 9.8% and coincidence time resolutions (with a reference pixel) below 290 ps for all cases using only the fastest timestamp and close to 230 ps when energy-weighted averaging of multiple timestamps is applied (corresponding to 182 ps detector time resolution). Regarding DOI performance, all configurations provide DOI information, showing a better performance with more number of unpolished faces and also when using ${\mathrm { BaSO}}_{4}$ as a reflector.