Nuclear medicine is the branch of medicine that involves the administration of radioactive substances in order to diagnose and treat disease. The scans performed in nuclear medicine are carried out by a radiographer. This speciality of nuclear medicine is sometimes referred to as endoradiology because the radiation emitted from inside the body is detected rather than being applied externally, as with an X-ray procedure, for example. For nuclear medicine scans, radionuclides are combined with other chemical compounds to form the radiopharmaceuticals that are widely used in this field. When administered to the patient, these radiopharmaceuticals target specific organs or cellular receptors and bind to them selectively. External detectors are used to capture the radiation emitted from the radiopharmaceutical as it moves through the body and this is used to generate an image. Diagnosis is based on the way the body is known to handle substances in the health state and disease state. The radionuclide used is usually bound to a specific complex (tracer) that is known to act in a particular way in the body. When disease is present, the tracer may be distributed or processed in a different way to when no disease is present. Increased physiological function that may occur as a result of disease or injury usually results in an increased concentration of the tracer, which can often be detected as a “hot spot.” Sometimes, the disease process leads to exclusion of the tracer and a “cold spot” is detected instead.  A large variety of tracer complexes are used in nuclear medicine to visualize and treat the different organs, tissues and physiological systems in the body. The main difference between nuclear medicine diagnostic tests and other imaging modalities is that nuclear imaging techniques show the physiological function of the tissue or organ being investigated, while traditional imaging systems such as computed tomography (CT scan) and magnetic resonance imaging (MRI scans) show only the anatomy or structure. Nuclear medicine imaging techniques are also organ- or tissue-specific. While a CT or MRI scan can be used to visualize the whole of the chest cavity or abdominal cavity, for example, nuclear imaging techniques are used to view specific organs such as the lungs, heart or brain. Nuclear medicine studies can also be whole-body based, if the agent used targets specific cellular receptors or functions. Examples of these techniques include the whole-body PET scan or PET/CT scan, the meta iodobenzy lguanidine (MIBG) scan, the octreotide scans, the indium white blood cell scan, and the gallium scan. Nuclear medicine procedures are used in diagnosing and treating certain illnesses. These procedures use radioactive materials called radiopharmaceuticals. Examples of diseases treated with nuclear medicine procedures are hyperthyroidism, thyroid cancer, lymphomas, and bone pain from some types of cancer. The amount of radioactive materials used in diagnosing illnesses depends on the needs of the person and range from a small amount to a large amount. These materials flow through different body organs and in some cases are taken up by specific organs or tissue. The radiation that comes from the radiopharmaceutical is used for treatment or is detected by a camera to take pictures of the corresponding body organ, region or tissue. Radioactive materials are chemicals that release radiation (energy). Radioactive materials can be natural or they can be man-made. They can be solids (like some rocks on earth) or liquids or they can also be gases that people can breathe (like radon). Each radioactive material has a unique half-life, which tells how quickly it stops being radioactive. The Nuclear Regulatory Commission (NRC), the U.S. Food and Drug Administration (FDA) and states regulate the use of radioactive materials for nuclear medicine to make sure patients, medical personnel, and the public are safe. Before any type of nuclear medicine procedure is used, it must be justified to ensure the benefits of the procedures outweigh risks to the patient. However, exposure to too much radiation can quickly damage organs or tissues, while exposure to any amount of radiation might lead to an increase in the risk of cancer years after the exposure occurs. Image Gently externalicon is a campaign that encourages medical facilities to use a “child size” amount of radioactive material when a child has a nuclear medicine procedure.