Diagnostic nuclear medicine involves the use of radioactive tracers to image and/or measure the global or regional function of an organ.

The radioactive tracer (radiopharmaceutical) is given to the patient by intravenous injection, orally or by other routes depending on the organ and the function to be studied. The uptake, turnover and/or excretion of the tracer substance is then studied with a gamma camera, positron emission tomography (PET) camera or another instrument, such as a simple stationary radiation detector. The uptake of the tracer is generally a measure of the organ function or metabolism or the organ blood flow.?