PET scan

Patient having a PET-CT scan

During a positron emission tomography (PET) scan, a small amount of radioactive tracer is injected into one of your veins. This give off a type of radiation that the PET scanner can pick up as the tracer moves through your body. This provides information about how your organs and tissues are functioning.

A CT (Computed Tomography) scan uses X-rays to produce detailed 3D images of the inside of your body.

A PET-CT scan combines these two types of imaging into one scan, to help identify organs or tissues that are not working normally.

What is it used for?

A PET-CT scan is usually used to help diagnose a range of different cancers, to find out how far they have spread and to decide the best ways of treating them. It gives detailed information about how well parts of your body are working as well as showing the areas that have been affected by disease.

Do I need to prepare?

For 6 hours before your appointment time:

  • do not eat eat or drink – except plain water
  • do not chew gum.

Failure to fast in this way can cause inaccurate scan results and your scan will have to be rescheduled.

Avoid any strenuous physical activity for 24 hours before to your appointment time. This includes running, cycling and exercising in a gym.

Take any prescribed medications as usual, unless instructed otherwise in your appointment letter.

If you are diabetic, contact the department before your appointment, for specific instructions on preparing for your scan.

A member of the team providing your care will explain what to do if you do need to prepare further.

What happens during the procedure?

A small amount of a radioactive substance, known as a radiotracer, will be injected into a vein in your arm or hand. This has no side effects and you will not feel any different from this injection.

Next, you will need to rest for an hour before having your scan. This is known as the ‘uptake period’ - when your body takes up the radioactive tracer. During this time it is important that you lie still and relax quietly. You should not read, use a mobile phone or listen to music.

After the uptake period you will be directed to the scanner room and asked to lie on your back on the scanner couch. The scan will take about 30 minutes and you will need to lie still with your arms placed above your head. If you think this may be a problem for you, let us know before starting your scan.

The scanner couch will move you through the large circular scanner. It is safe and should not be painful. Our medical staff will be able to see you throughout your scan.

Some people feel slightly claustrophobic ('closed in') when they are inside the scanner. If you are worried this may happen, please tell us beforehand.

Drink plenty of fluids after the scan to help flush the radioactive medication from your body. It should leave your body naturally through the course of the day.

You can go home after the scan.

Go to www.nhs.uk for more information about PET scans and CT scans.