DOI- and TOF-Capable PET Array Detectors Using Double-Ended Light Readout and Stripline-Based Row and Column Electronics Readout

We investigated a highly multiplexing PET detector design capable of depth-of-interaction (DOI) and time-of-flight (TOF) detection by use of double-ended light readout of the scintillator and stripline (SL) based row- and column-wise electronic readout of the SiPMs [1]. We developed 4x4 and 8x8 evaluation modules consisting of 3.0x3.0x20 mm
³
LYSO crystals that were coupled to SiPM pixels at both the front and back ends. For each LYSO crystal, its 4 long surfaces were grounded (9 μm) and covered with BaSO4 for light reflection. The SiPM outputs at the front-end of the crystal array were read by a single SL that was designed to resolve the row position of the detected signal. Likewise, the SiPMs at the back-end were read by a column-resolving SL. As a result, a module had a total of 4 output signals and they were sampled at 2 GHz by use of the DRS4 evaluation board. Using these modules, we reported successful discrimination of individual detector pixels. For the 4x4 module, we obtained an average pixel-level energy resolution (ER) of 14.1% (ranging from 11.3% to 19.3%), a DOI resolution of about 2.7 mm, and a best coincidence time resolution (CTR) of about 391 ps with a reference detector. For the 8x8 module, the average pixel-level ER and DOI resolutions were slightly inferior to those measured for 4x4 module, yielding 13.9% (ranging from 11.7%-17.6%) and about 3.5 mm respectively. However, the best CTR deteriorates considerably to about 584 ps. Our preliminary data suggests that the CTR degradation may be due to intercrystal scattering of the gamma-ray photon.