A Preclinical Positron Emission Tomography (PET) and Electron-Paramagnetic-Resonance-Imaging (EPRI) Hybrid System: PET Detector Module

We report the design and experimental validation of a compact positron emission tomography (PET) detector module (DM) intended for building a preclinical PET and electron paramagnetic-resonance-imaging hybrid system that supports submillimeter image resolution and high-sensitivity, whole-body animal imaging. The DM is eight detector units (DUs) in a row. Each DU contains 12x12 lutetium-yttrium oxyorthosilicate (LYSO) crystals having a 1.05-mm pitch read by 4x4 silicon photomultipliers (SiPMs) having a 3.2-mm pitch. A small-footprint, highly multiplexing readout employing only passive electronics is devised to produce six outputs for the DM, including two outputs derived from SiPM cathodes for determining event time and active DU and four outputs derived from SiPM anodes for determining energy and active crystal. Presently, we have developed two DMs that are 1.28x10.4 cm(2) in extent and approximately 1.8 cm in thickness, with their outputs sampled at 0.7 GS/s and analyzed offline. For both DMs, our results show successfully discriminated DUs and crystals. With no correction for SiPM nonlinearity, the average energy resolution for crystals in a DU ranges from 14% to 16%. While not needed for pre clinical imaging, the DM may support 300-400-ps time-of-flight resolution.