Positron Emission Tomography (PET) Scans use radioactive tracers to show the workings of bodily tissues. This gives much more information than scans such as MRI or X-rays that simply reveal the structure.

PET Scans are painless and can be done on an out-patient basis, and you will be allowed home the same day. There are very few risks or side effects to the scan process and the results can be very useful in tracking the progress of a disease and planning treatment. However, since the scanning equipment (and each individual scan) is very expensive there is limited availability within the UK.

This article on PET scans is written by Jackie Griffiths, a freelance journalist who writes health, medical, biological, and pharmaceutical articles for national and international journals, newsletters and web sites.

Why would you have it?

PET Scans are primarily used in the diagnosis of cancer. They can be used to detect:

  • The presence of cancer
  • What stage the cancer is at
  • The extent to which cancer has spread
  • The progress of treatment, such as chemotherapy or radiotherapy

PET Scans can also help determine whether a lump or scar tissue is cancerous or not.

Because they show the workings of the body, as well as the structure, PET Scans can also be used to analyse:

  • Damage to heart muscle after a heart attack
  • Blood flow to the heart and any blockages
  • Brain tumours and problems with the nervous system
  • Epilepsy and other seizures
  • Alzheimer’s Disease

The results of a PET Scan can help your consultant assess the extent of damage or disease, as well as precisely identify the location of the problem, helping him or her decide the best course of treatment.

How it works

The PET Scanner detects positrons produced in the decay of radioactive material. This material is introduced into the body via an injection, a drink, or a vapour spray, depending on which organs or areas the scan will be looking at.

The most commonly used tracer is Fluorine 18, which is a radioactive version of glucose. This is used because it shows the way the tissues are using glucose. Cancers and damaged tissue will use glucose in a different way to normal tissue. Glucose is also an ideal tracer for brain activity.

Because of the importance of glucose, you will be advised what to eat before your scan. You may also be advised not to eat for 4 – 6 hours beforehand as this may affect the results.

It usually takes an hour or more for the tracer to reach the target area, so it’s important you arrive on time for your scan as the process is not flexible.

Once the tracer is in place, you’ll be asked to lie on a trolley which will then be wheeled into the PET Scanner. The machine is similar to an MRI scanner and consists of a narrow tube surrounded by the detection equipment. You may need to stay in the scanner for an hour or more for the tests to be done.

After your PET scan, you are safe to go home and continue your normal activities. The tracer will pass out of your body naturally in due course. You should receive your results in around two weeks, although this can be speeded up in urgent cases.

While there is little risk to children or adults from a PET Scan, the risks to infants could be higher. Therefore, you should not have a PET Scan if you’re pregnant, or think you could be. Nursing mothers are advised to express milk in advance of their scan and to avoid contact with their baby for at least six hours afterwards.


While PET Scans are an important diagnostic tool, they are also a very expensive one. Each scanner costs over £4million and takes two years to set up and calibrate. It then costs a further £1million a year to run, making the cost of each scan around £1,000.

Understandably, there are only twelve NHS PET Scanners in England, none in Wales, and only one each in Scotland and Northern Ireland. There are also three mobile scanners, which travel around the UK.

As a result, you may need to travel to your nearest scanner for tests. These are located in Birmingham, Cambridge, Cheltenham, Guildford, Manchester, Nottingham, and Oxford, as well as five in London.

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