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Radionuclide scanning
Last reviewed: 07.07.2025

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A radionuclide is an unstable isotope that becomes more stable when it releases energy as radiation (nuclear decay). This radiation may include the emission of a particulate or gamma-ray photons. Radiation produced by radionuclides can be used in imaging and in certain situations to treat disorders (such as thyroid disorders).
A radionuclide may also be combined with various stable compounds to form a radiopharmaceutical that localizes a specific anatomical or cellular structure. For example, a radionuclide combined with a diphosphonate is used to image the skeleton and test for bone metastasis or infection; radionuclide-labeled white blood cells are used to identify inflammation; and radionuclide-labeled red blood cells are used to localize lower gastrointestinal bleeding. Radionuclide-labeled sulfur colloid is taken up by the liver, spleen, and bone marrow. Radionuclide-labeled iminodiacetic acid derivatives are used to image the biliary system and test for biliary obstruction and gallbladder disorders. Other clinical nuclear medicine techniques are used to image the cerebrovascular system, thyroid, cardiovascular system, respiratory system, genitourinary system, and tumors.
Various types of cameras are used to produce images. An Anger (gamma) camera uses a crystal to convert photons emitted by the radionuclide into an image. Whole-body cameras are used to take pictures of bone; portable cameras are also available. Single-photon emission computed tomography uses a rotating camera and computer algorithms to produce images that allow three-dimensional localization of the radionuclide delivery, similar to a CT scan.
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