Nuclear medicine imaging involves the administration of a radiolabelled chemical called a radiopharmaceutical.
This radiopharmaceutical is administered internally, via injection, swallowing or inhalation. Once taken, the chemical moves through the body to the specific organ or tissue it is attracted to, before being metabolized and excreted from the body. As the chemical moves through the body, external detectors are used to detect the radiation it emits, which is used to generate images of the area of interest.
Nuclear medicine imaging can be performed using several different techniques. One example is scintigraphy, where the radiation captured creates two-dimensional images. Another example is single photon emission computed tomography (SPECT), where the emitted radiation is used to form three dimensional images, although gamma cameras are also used to capture internal radiation. Positron emission tomography (PET) is another example of a medical imaging procedure that generates three-dimensional images rather than two dimensional ones.
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 iodobenzylguanidine (MIBG) scan, the octreotide scans, the indium white blood cell scan, and the gallium scan.