Positron emission tomography (PET)

If you're a patient at Great Ormond Street Hospital (GOSH) you may have a PET scan to help us look at what activity is happening inside your body.

For example, PET scans result in pictures that can measure how much oxygen or sugar our bodies use and the rate of the blood flow. 

Glucose (a type of sugar) is most often used in helping experts to measure body activity. By injecting a radioactive sugar substance (usually fluorodeoxyglucose or FDG) the scanner can pick up on areas where there is a lot of activity, as the places where the sugar substance ends up are highlighted on the picture. This is because the sugar is being used to provide energy for the cells.

What the image looks like

The PET scan will give a 3D image of any body part. Those areas or parts of internal organs which are using sugar are more active. These parts will be more intense on the picture.

Why a PET scan might help you 

PET scans are great for showing the activity going on in the different areas of the body and are combined with a CT scan to ensure accurate localisation (CT scans are better at showing structure of body parts). The PET scan can show the difference between normal tissues and abnormal tissues. For example, cancer cells will use up more sugar than normal cells and will be highlighted on the image.

Though PET scans can be used to show up many things, they are sometimes used to show which areas of the brain are being used during different tasks. They can also give us valuable information about the heart. The whole process may take around two hours, though you will only have to spend an hour or less in the scanner.

Is it safe?

The radioactive sugar substance used in the scan decays after a really short period of time, so it does not cause you any problems.

Many of the studies we perform involve the use of x-rays. All girls aged 12 years or older are tested to make sure they are not pregnant on the day of their scan. If they are found to be pregnant the Radiology team will decide if the scan should be delayed or cancelled.

Compiled by:
Great Ormond Street Hospital
Last review date:
March 2012