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

We investigate a highly multiplexing readout for depth-of-interaction (DOI) and time-of-flight PET detector consisting of an N x N crystals whose light outputs at the front and back ends are detected by using silicon photomultipliers (SiPMs). The front NxN SiPM array is read by using a stripline (SL) configured to support discrimination of the row position of the signal-producing crystal. The back N x N SiPM array is similarly read by an SL for column discrimination. Hence, the detector has only four outputs. We built 4 x 4 and 8 x 8 detector modules (DMs) by using 3.0-mm(3) x 3.0-mm3 x 20-mm(3) lutetium-yttrium oxyorthosilicates. The outputs were sampled and processed offline. For both DMs, crystal discrimination was successful. For the 4x4 DM, we obtained an average energy resolution (ER) of 14.1%, an average DOI resolution of 2.5 mm, a non DOI-corrected coincidence resolving time (CRT), measured in coincidence with a single-pixel reference detector (refDet), of about 495 ps. For the 8x8 DM, the average ER, average DOI resolution and average CRT were 16.4%, 2.9 mm, and 641 ps, respectively. We identified the intercrystal scattering as a probable cause for the CRT deterioration when the DM was increased from 4x4 to 8x8.