How do PET scans work?

If you have a PET scan, you’ll be given a substance that allows doctors to see if there’s anything abnormal with your tissues or organs. This substance is known as a tracer, and is radioactive.

The tracer may be injected, inhaled or swallowed, depending on what part of your body is being scanned.

After you’re given the tracer, you’ll be asked to lie very still in the PET scanner, which looks like a huge donut.

The scanner picks up energy, in the form of gamma rays, from the tracer and converts the rays into pictures. The tracer collects in areas of your body which have higher chemical activity possibly because they are diseased. These areas show up as bright spots on the scan.

A specialist examines the scans and gives a report to your doctor, who will explain the results to you.

A PET scan is sometimes used with other scans, such as a CT (computed tomography) scan, to get a more accurate view of your condition.

What should I know?

The scan takes about 15 to 20 minutes but you can expect to be in the PET imaging department for between 2 and 3 hours.

Before the scan, you should:

• let the person scanning you know if you’re breastfeeding, or if you are (or might be) pregnant
• tell them if you are likely to feel anxious about being in a closed space
• ask about any food and drink restrictions before your scan