Evaluation of Cerium Doped Lutetium Oxyorthosilicate ( LSO ) Scintillation Crystal for PET

A new scintillation crystal, cerium-doped lutetium oxyorthosilicate &SO) was recently discovered a, with light intensity 75 % of NaI(Tl), scintillation decay time of 12 ns (30%) and 42 ns (70%), effective Z of 66, and density of 7.4 glcc. The fast decay time and scintillation light output of LSO are superior to those of BGO for PET and the stopping power of LSO for 511 keV photons is only slightly lower than BGO. In this study we directly compared the detection characteristics relevent to PET applications of small crystals of LSO (2 x 2 x 10 mm) with those of BGO. The energy resolution at 511 keV was 12% FWHM for LSO and 2 to 3 times wider for BGO. The coincidence timing of two opposing crystals, using a position sensitive PMT (Hamamatsu R2486), were 1.4 ns FWHM for LSO and more than 3 times higher for BGO. Using a fast PMT (Hamamatsu R3177) coincidence timing for LSO yielded 0.46 ns FWHM. These crystals are being used to simulate a small scale PET scanner and to investigate its imaging performance.