PET/CT scan

A PET/CT scan uses two different forms of medical imaging at the same time.

  • PET (positron emission tomography) is a medical imaging technique in which a small amount of a radioactive tracer given to the patient, normally by injecting it into a vein. The most commonly used tracer in PET is a radioactive form of glucose. The scan shows how the body breaks down and uses glucose. Cancer cells use glucose differently and this will show up on the scan.
  • CT (computerised tomography) uses X-rays to produce images of the body.

By combining PET and CT, we are able to provide important information about many conditions affecting the different organs of the body. This will help your doctor to plan appropriate treatment.

Are there any risks?

The amount of radiation in the tracer is equivalent to the radiation you are exposed to when you have an X-ray. The benefits of the scan far outweigh any potential risk from the radiation. The tracer will not produce any side effects. In particular, it will not make you drowsy and you will be able to drive after your appointment.

Please do not bring anyone who is pregnant or young children to the department. With most nuclear medicine investigations the level of radioactivity will have decreased to a safe level by the time you arrive home after the scan. However, with some investigations, contact with young children may need to be more restricted. These will be explained if they apply to you.

Pregnancy and breast-feeding

As a general rule PET/CT scans are not carried out on pregnant women unless clinically justified. In such cases, the dose of radioactivity administered will probably be reduced.

Preparing for a PET/CT scan

You will be given instructions on how to prepare for your scan.

You should not have anything to eat for six hours before your appointment. During this time you can drink as much water, diet soft drinks, and black unsweetened coffee or tea as you like. You do not need to have a full bladder for your scan. You can continue to take any medication that has been prescribed for you by your doctor and it is also safe for you to take over-the-counter medicines.

Before your scan, you will be asked ask you to change into a hospital gown and remove all your jewellery and any other metallic objects.

Some patients may be prescribed diazepam to relax the muscles round the neck and shoulders to provide clearer images.

During a PET/CT scan

The radioactive tracer is given as an injection. When the tracer has been absorbed by your body you are ready for your scan. Before your scan you will be asked to go to the toilet in order to empty your bladder.

In the scanning room you will be asked to lie on your back on the scanning bed. The bed will move through the scanner and collect images for between 30 and 90 minutes, depending on which parts of your body are being studied. The scan is not particularly noisy although there is a constant background noise caused by the computers and air conditioning which will make it difficult for you to listen to any music during the scan.

After a PET/CT scan?

Once the scan is complete you will be able to leave the hospital or return to your ward immediately. You will be able to eat and drink what you like and go wherever you wish; however, your should avoid prolonged close contact with children for the rest of the day to avoid exposing them to unnecessary radiation.

The radioactive tracer will not produce any side effects. In particular it will not make you drowsy and so will not prevent you from driving a car. However, if you have been given diazepam you must not drive for the rest of the day.

The results of your PET/CT scan will be sent to the consultant who referred you, who will arrange to give you the results.


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www.royalmarsden.nhs.uk/cancer-information/detection-diagnosis/pet-ct-scan

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