PET scan

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A positron emission tomography (PET) scan is an imaging test that uses a radioactive substance (called a tracer) to look for disease in the body.

Unlike magnetic resonance imaging (MRI) and computed tomography (CT) scans, which reveal the structure of and blood flow to and from organs, a PET scan shows how organs and tissues are working.

See also:

• Brain PET scan
• Breast PET scan
• Heart PET scan
• Lung PET scan

Positron emission tomography

The health care provider will inject a small amount of a radioactive material into one of your veins, usually on the inside of the elbow. The substance travels through the blood and collects in organs and tissues.

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You'll be asked to wait nearby as the radioactive substance is absorbed by your body. This usually takes about 1 hour.

Then, you will lie down on a table that slides into a tunnel-shaped hole in the center of the PET scanner.

The PET machine detects energy given off by the radioactive substance and a computer changes the results into 3-dimensional pictures. The images are displayed on a monitor for the health care provider to read.

You must lie still during the PET scan so that the machine can produce clear images. How long the test takes depends on what part of the body is being scanned. Today, most PET scans are done with CT scanning.

You must sign a consent form before having this test. You will be told not to eat anything for 4 - 6 hours before the PET scan, although you will be able to drink water.

Tell your health care provider if you are pregnant or think you might be pregnant.

Also tell your health care provider about any prescription and over-the-counter medicines that you are taking, because they may interfere with the test.

Be sure to mention if you have any allergies, or if you've had any recent imaging studies using injected dye (contrast).

During the test, you may need to wear a hospital gown. Take off any jewelry, dentures, and other metal objects because they could affect the scan results.