An investigation of optimal photomultiplier signal delay method on detector time resolution in positron emission tomography

Cerium doped fast scintillators such as LSO and LaBr3 and fast photomultiplier tubes (PMT) have dramatically improved the timing performance of PET scanners in the last several years. Recent developments in high speed electronics brought new opportunities to understand and process the photosensor signals. In this work, a digital time alignment method is introduced and implemented using fast scintillators and photosensors with the combination of high speed digital electronics. A method was tested on a light sharing 13×13 LSO detector and a 310 ps average crystal time resolution was measured against a single LSO reference detector using optimal signal delays based on a digital leading edge (LE) triggering scheme in a 250 ps sampling interval. The improvement with this method was measured to be about 5.2% compared to the no time alignment case. The crystal time resolution improvements against a single LSO reference detector ranged from 2% to 9% after optimal signal delay implementation.