Detector efficiency and Compton scatter in fully 3D PET

Variations in detector efficiency induce significant artifacts in reconstructed images unless accurate normalization methods are used. Scattered events are detected with significantly different efficiencies than unscattered events because the photons in scattered coincidences arrive at the detector at lower energies and over a wide range of angles of incidence. Current methods work well for septa-extended imaging because the scatter fractions are low. The large scatter fractions encountered in fully 3D imaging, however, require that these differences be accounted for. We propose a normalization technique that accounts for them and show that it yields more uniform images than two other potential methods.>