Evaluation of cerium doped lutetium oxyorthosilicate (LSO) scintillation crystals for PET

A new scintillation crystal, cerium doped lutetium oxyorthosilicate (LSO), is discussed. It has light intensity which is 75% of NaI(Tl), scintillation decay time of 12 ns (30%) and 42 ns (70%), effective Z of 66, and density of 7.4 g/cm/sup 3/. The fast decay time and scintillation light output of LSO are superior to those of bismuth germanate (BGO) for positron emission tomography (PET) and the stopping power of LSO for 511-keV photons is only slightly lower than BGO. The detection characteristics relevant to PET applications of small crystals of LSO (2*2*10 mm) are compared with those of BGO. The energy resolution at 511 keV is 12% full width half maximum (FWHM) for LSO and two to three times wider for BGO. The coincidence timing of two opposing crystals, using a position sensitive photomultiplier tube (PMT), is 1.4 ns FWHM for LSO and more than three times higher for BGO. Using a fast PMT, coincidence timing for LSO yields 0.46 ns FWHM. These crystals are being used to simulate a small-scale PET scanner and to investigate its imaging performance.<
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