A performance comparison of LFS and LYSO scintillators for TOF PET

Scintillator is an important component which determines the overall performances of PET detectors, and scintillators with fast timing in addition to high light yield are required to achieve better performances, especially for TOF PET scanners. Recently, there have been several reports [1] [2] [3] on Lutetium Fine Silicate (LFS) [4] scintillator showing its improved timing and energy resolution than LYSO (LSO), which has been commonly used for TOF PET. In addition to the superior timing performance of LFS, excellent time resolution, e.g., 96 and 148 ps fwhm, were reported in [2] and [3], respectively, by using 15 mm LFS scintillator. We have carried out a performance comparison between LFS and LYSO scintillator to check the reported results experimentally. In our study, a high-speed waveform sampling digitizer, DRS4 [5], is used for signal readout to measure the event time of the detectors precisely; the electronic time resolution of the DRS4 readout is measured to be ~5 ps fwhm [6]. To investigate the effects on the timing performances, scintillators with three different length are tested in our study. Some preliminary results on decay time, time and energy resolution at 511 keV are presented here.