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Monte Carlo study of LSO γ-ray detectors for PET

We have made a detailed study of the response of LSO detectors to 511 keV (gamma) -rays. The LSO, discovered recently, has a density greater than BGO, small decay time, and high light output. As such, it should have an overall behavior better than that of BGO. We have modeled a (gamma) -ray detector using an LSO crystal of rectangular cross-section attached to a photomultiplier tube (PMT). We used our PET simulation package to study the energy resolution, efficiency, and timing resolution for various crystal sizes and various energy thresholds. The simulation takes into account the interactions of (gamma) -rays in the crystal via Compton and photoelectric effects, the production and transport of scintillation photons, the productions of photoelectrons in the PMT and the anode signal formation. We have estimated the efficiency versus energy threshold for various lengths of the LSO crystal and we find the for 400 keV threshold this efficiency is large even for 2 cm crystals and comparable to that of BGO. We also estimated the timing resolution (FWHM) versus crystal length for various energy thresholds. The timing resolution is comparable to that of CeF3 detectors. The energy resolution is about 10% (FWHM), which allows one to set the energy threshold fairly high.