SIMULATING THE PERFORMANCES OF AN LSO BASED POSITION ENCODING DETECTOR FOR PET

We investigated the impact of replacing BGO by lutetium oxyorthosilica te (LSO) in the fabrication of the EXACT HR PLUS position encoding det ector for PET. A detailed Monte Carlo simulation was used to track the interactions of energetic photons in the volume of the block as well as to treat the generation and propagation of scintillation light thro ugh its geometry. The simulation also accounts for LSO's non-proportio nal scintillation response, the bulk attenuation to its own scintillat ion and the noise contribution from the amplification of photoelectron s in the readout units. The model predicts that the increased photosta tistics available in LSO compared to BGO leads to improvements by up t o a factor five in the peak-to-valley ratios of the position response of the block to a uniform flood of 511 keV photons. For the crystals l ocated along the diagonal, and considering events in a window of 350 t o 650 keV, the position encoding accuracy is found to vary from 69% to 88% representing an absolute gain of at most 8% over its BGO precurso r. With peak photoelectron counts of 678 to 2024, the energy resolutio n of the same crystals is found to vary from 14% to 9%.