A PET scan shows metabolic activity in the body

A positron emission tomography (PET) scan is a type of nuclear medicine imaging test. It is 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.

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.

How PET scans work and what’s involved

PET works by using a special camera that detects positrons emitted by the radioactive tracer in the organ or tissue being examined.

The radioactive tracers are attached to a chemical substance that a particular organ or tissue uses during metabolism. These substances include glucose, carbon, or oxygen. Other substances may be used for PET scanning, depending on the purpose of the scan.

The radioactive tracer/sugar is put into a vein through an intravenous (IV) line. It moves through the blood and collects in areas with a lot of cell activity. During this time, the PET scanner slowly moves over the body. A computer creates a map of the body. The amount of the radionuclide collected in the tissue affects how brightly the tissue appears on the image. It also indicates the level of sugar uptake or cell activity in that organ or tissue.

When a PET scan might be needed

In general, PET scans are used to evaluate organs and/or tissues for the presence of disease or other conditions. More specific reasons for PET scans include:

  • To diagnose neurological conditions such as:
    • Alzheimer disease and other dementias
    • Parkinson disease (a progressive disease of the nervous system in which a fine tremor, muscle weakness, and a peculiar type of gait are seen)
    • Huntington disease (a hereditary disease of the nervous system which causes increasing dementia, bizarre involuntary movements, and abnormal posture)
    • Epilepsy (a brain disorder involving recurrent seizures)
    • Stroke
  • To locate the specific area to be reached during brain surgery
  • To evaluate the brain after injury to look for a blood clot or bleeding in, or blood and oxygen flow to the brain tissue
  • To detect the spread of cancer to other parts of the body from the original cancer site
  • To see how well cancer treatment is working
  • To evaluate blood flow heart muscle to determine if treatment is needed to improve blood flow to the heart  and to determine the effects of a heart attack
  • To further identify lung lesions or masses seen on chest X-ray and/or chest CT
  • To look for cancers that have come back after treatment and find them earlier than can be done with other diagnostic tests

There may be other reasons for your health care provider to recommend a PET scan.

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