What you can expect

By Mayo Clinic Staff

The PET scanner is a large machine that looks a little like a giant doughnut standing upright, similar to a computerized tomography (CT) machine.

During the test

Depending upon the organ being studied, you may inhale or swallow the radioactive substance or receive it intravenously. If the substance is injected intravenously, you might briefly feel a cold sensation moving up your arm.

You must wait 30 to 60 minutes for the radioactive substance to be absorbed by the organ or tissue to be imaged. After the specified time has passed, you'll lie on a narrow table that slides into the PET scanner's opening. The test itself is painless, but you must lie very still or the images will be blurred. It takes about 30 minutes to complete the test, during which time you'll hear buzzing and clicking sounds.

If you're claustrophobic, you may feel some anxiety while positioned in the scanner. Be sure to tell the nurse or technologist about any discomfort. Medications can help you feel more relaxed.

After the test

In general, there are no restrictions on your daily routine after the test. However, drink plenty of fluids to help flush the radioactive substance from your body.

May. 07, 2011