Nuclear medicine is a specialized area of radiology that uses very small amounts of radioactive substances to evaluate organs, bones, or tissues. Unlike X-rays where external radiation is used, nuclear medicine scans involve the patient taking a dose of radiopharmaceuticals internally.

There are several types of nuclear medicine diagnostic techniques. Scintigraphy creates two-dimensional images to evaluate areas such as bone, myocardial perfusion, and parathyroid. SPECT is a 3D technique that helps doctors evaluate functional processes of the body. There are also hybrid techniques that superimpose nuclear medicine scans onto CT images, for example.

Nuclear medicine differs from imaging such as CT and MRI, in that it reveals the physiological function of the system being evaluated, rather than showing traditional anatomical images.