From SPECT and PET to dual head coincidence γ-camera

Both SPECT and PET techniques are described. The main differences in the used methodology (positron annihilation physics, interaction photons with matter, intrinsic energy and space resolution of different types of detectors, as well as the timing properties of these detectors), are analyzed and the results, concerning both the overall efficiency and the space resolution, are presented. The improvements made by passing from one head - camera to the dual head - camera are discussed and especially focused on the possibility of implementation of the coincidence technique in such systems