Effect of depth of interaction decoding on resolution in PET: A simulation study

Information about the (gamma) depth of interaction (DOI) in the crystal can help to improve the resolution uniformity in positron emission tomography cameras by reducing the blurring due to the parallax error. The parallax error is particularly severe for tomographs with small detector-to-detector distance, which is by itself a desirable feature, since it maximizes the detection solid angle and thus sensitivity. In this study we have developed simulations to determine the effect of a particular DOI correction method on resolution for some tomograph and crystal geometries. The considered DOI correction method relies on a double layer crystal configuration where the two crystals have different scintillation decay times. Round and octagonal PET camera geometries were considered. For each geometry two different crystal configurations were simulated: LSO/LSO and LSO/GSO. Empirical data were used to include scintillation decay time into the simulation. For specific configurations examined DOI correction was found to improve the Sresolution uniformity up to 37%.