Compton Camera Imaging Sensitivity with Improved Event Selection

Besides the noiseless extraction of the energy deposited in the absorber, an ideal event reconstruction in a Compton-Camera system requires the accurate determination of both interaction points in the scatterer and absorber. Limited energy and spatial resolution of the system combined with other misidentification effects leads frequently to the acceptance of faulty events, which affect the quality of the reconstructed image. Based on GEANT4/GATE simulation studies, a filtering procedure to eliminate energy and spatially unbalanced events is proposed in the current work. Attention has been paid to exclude from the coincidence selection procedure events that alternate the normal interaction sequence in the scatterer-absorber subsystems or violate total energy sum rules. Following the proposed filtering approach, volume effects traced back to the angular acceptance of a two-stage Compton-Camera system are systematically investigated and a normalization-correction technique to improve the performance of the system for phantoms with out-of-plane sources is presented.