A positron emission tomography (PET) scan is a type of nuclear medicine imaging test. It's used to examine various body tissues to identify certain conditions by looking at blood flow, metabolism, and oxygen use. PET scans may also be used to see how well the treatment of certain diseases is working.
For a PET scan, a tiny amount of a radioactive substance, called a radioactive tracer, is used to show the metabolism of a particular organ or tissue. This test gives the healthcare provider information about the function and structure of the organ or tissue. It also gives information about its biochemical properties. A PET scan may detect biochemical changes in an organ or tissue that are signs of a disease process before physical changes related to the disease can be seen with other imaging tests. These include computed tomography (CT) or magnetic resonance imaging (MRI).
PET scans are often done along with CT scans (called a PET/CT scan) to give more definitive information about metabolism changes and exactly where they are happening in the body.
A PET/CT scan produces a highly detailed three dimensional image of functional processes in the body. It creates these intricate images using X-rays of cross-sections, or "slices," of the body. This process allows earlier and more accurate detection of diseases.