Comparison of event positioning algorithms for PEM imaging

The objective of this work is to investigate the effect of both multilayer perceptron based and Gaussian maximum likelihood event positioning algorithms on the spatial resolution of a positron emission mammography (PEM) dectector, which use a continuous LSO crystal and a multianode photomultiplier tube, using Monte Carlo simulations. Moreover, the effect of crystal thickness on spatial resolution is explored. An energy threshold of 350 keV is applied to overcome Compton scatters. The aim was to achieve a high sensitivity and a low system cost using a continuous detector and increase the crystal thickness without sacrificing spatial resolution. The multilayer perceptron-based positioning algorithm is found to be less sensitive to the crystal thickness in the center of the crystal, whereas the maximum likelihood-based algorithm gives better results in the center of the first quadrant in terms of insensitivity to the crystal thickness. As a result, it has been observed that the insensitivity of algorithms to crystal thickness makes the usage of thick scintillation crystals possible for PEM designs.