Time and Energy Characterization of Semi-Monolithic Detectors With Different Treatments and SiPMs Suitable for Clinical Imaging

The use of detectors based on semi-monolithic crystals can be of interest to clinical positron emission tomography scanners due to their time of flight (TOF) and depth of interaction (DOI) capabilities. In this work, timing and energy characterization of four different detector configurations based on arrays of eight lutetium yttrium oxyorthosilicate slabs of $25.4\times 3.1\times 20$ mm3 each coupled to silicon photomultipliers (SiPMs) have been carried out. On the one hand, two different surface treatments have been studied. In one configuration, all the slab surfaces were treated with enhanced specular reflector (named ESR). In the other configuration, a retroreflector layer was added to the entrance face and the pixelated external faces were painted black (named ESR+B+RR). On the other hand, two different SiPM array models belonging to the series S13 and S14 from Hamamatsu Photonics were also compared. In all cases, the readout was performed by the TOFPET2 application specific integrated circuit. The results show an energy resolution and a detector time resolution (DTR) as good as 12.5% and 193 ps, respectively, for the ESR treatment and the S13 photosensor. For the ESR+B+RR treatment and S13, the energy resolution and DTR are 14.6% and 238 ps, respectively. When using the S14, the energy resolutions and DTRs are, respectively, 11.6% and 219 ps for the ESR treatment, and 14.2% and 339 ps for the ESR+B+RR treatment.