A light sharing, charge multiplexed time-of-flight depth-of-interaction PET detector

Time-of-flight (TOF) and depth of interaction (DOI) measurements are both important capabilities to improve clinical PET imaging. The combination of these two measurements has been shown to improve image quality and uniformity. Current high performance TOF DOI detectors have a high level of complexity, requiring cooling, pulse shape information or increased numbers of photosensors. This works describes and characterizes an approach to TOF DOI using a two layer, 20mm thick, lutetium-yttrium oxyorthosilicate (LYSO) light sharing crystal array. The crystal array was coupled to a single ended SiPM readout with a novel binary encoded multiplexing scheme that has a 4:1 timing channel multiplexing ratio, and two position channels. Flood maps show show excellent crystal separation with a minimum ratio of distance between crystal peaks to standard deviation of crystal peaks of 9.2. The detector achieves 10mm DOI resolution with 180 +/-2ps FWHM coincident time resolution. The top and bottom layers had 170 +/- 2ps, and 185 +/-3ps FWHM coincident timing resolutions respectively. The simplicity of the readout scheme makes it a good candidate for scaling to a practical TOF DOI PET system. The detector presented in this work has single ended readout, no active cooling, a 4:1 timing channel multiplexing ratio, and requires no pulse shape information.