Scanning equipment consists of a detector and a collimator. The former is usually sodium iodide containing thalium iodide as activator. The radiation emitted by the radioactive isotope, introduced into the patient strikes the detector. The radiation from the source only is recorded whereas rest is absorbed by lead eolli mator. A more sensitive device called position camera which records particulate (positron) radiation. Radioisotopic scanning has an additional significance in the investigations of intracranial lesions, liver diseases, jaundice biliary excretion of 125-Rose Bengal, kidney complications and infections, lungs (Pulmonary embolism), thyroid and pancreas diseases (placentography).