  Simulation studies are presented regarding the performance of algorithms that
localize point-like radioactive sources detected by a position sensitive
portable radiation instrument (COCAE). The source direction is estimated by
using the List Mode Maximum Likelihood Expectation Maximization (LM-ML-EM)
imaging algorithm. Furthermore, the source-to-detector distance is evaluated by
three different algorithms based on the photo-peak count information of each
detecting layer, on the quality of the reconstructed source image as well as on
the triangulation method. These algorithms have been tested on a large number
of simulated photons in a wide energy range (from 200keV up to 2MeV) emitted by
point-like radioactive sources located at different orientation and
source-to-detector distances.
