The principles of nuclear medicine studies are based on the assessment of radionuclidic distribution in a given organ after in vivo administration of a radiopharmaceutical to distinguish between the normal and abnormal tissues. Such assessment of radionuclide distribution is performed by gamma cameras that primarily comprise NaI(Tl) detectors and the associated electronics described in the previous chapter. The gamma cameras permit the acquisition of both static and dynamic images with better spatial resolution and can be oriented in any direction around the patient. Various aspects of gamma cameras are discussed below.