Comparative timing measurements of LYSO and LFS-3 to achieve the best time resolution for TOF-PET

Abstract

AbstractThe best Coincidence Time Resolution (CTR) obtained so far – with very short crystals of 3–5mm in length – reach values between 100 and 150ps. Such crystals are not really practical for a TOF PET imaging device, since the sensitivity is quite small for the detection of the 511keV gammas resulting from a positron annihilation. We present our setup and measurements using 15mm length crystals; a length we regard as reasonable for a TOF-PET scanner. We have used a new series of Silicon Photo-Multipliers (SiPM) manufactured by Hamamatsu. These are the High Fill Factor (HFF) and Low Cross-Talk (LCT) Multi-Pixel Photon Counters (MPPC). We have compared three different crystals, LFS-3 (supplied by Zecotek) and two samples of LYSO (manufactured by Saint Gobain and CPI). We have obtained an excellent value of 148 ps for the Coincidence Time Resolution (CTR) with two LFS-3 crystals (15mm long) mounted on each side of a 22Na radioactive source with the HFF-MPPCs at 3.3V over-voltage. Our results are148ps obtained with LFS-3 and 170ps with LYSO crystals using identical SiPMs and electronics