A PET/CT scan uses two different forms of medical imaging at the same time.
Positron Emission Tomography (PET) 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.
A CT (Computerised Tomography) scan 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.
The amount of radiation in the tracer and 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.
Pregnancy and breastfeeding
As a general rule these investigations are not carried out on pregnant women unless clinically justified. In such cases, the dose of radioactivity administered will probably be reduced. If the patient is pregnant or breastfeeding the department should be advised as soon as possible to determine if the investigation should proceed and to give appropriate advice.
What will happened when I have my 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, black unsweetened coffee or tea and diet soft drinks 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.
When you arrive for your scan you will be taken to a preparation room. We will ask you to change into a hospital gown and remove all your jewellery and any other metallic objects. A member of our staff will explain the procedure and will also ask a few questions about your health. If you have any questions this is a good opportunity to ask them.
Some patients may be prescribed diazepam. The diazepam will relax the muscles around your neck and shoulders to provide clearer images. If diazepam has been requested we will give it to you soon after arrival.
The tracer is given as an injection. We will usually insert a cannula into one of your veins about 15 minutes before we want to give you the radioactive tracer. We will ask you to lie down to have the cannula inserted, while the radioactive tracer is given and for at least one hour following this. When the radioactive 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, 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 we need to look at. The scan is not particularly noisy although there is a constant background noise caused by the computers and air conditioning and this will make it difficult for you to listen to any music during the scan. There is a two-way microphone between the scanner and the control room and we will be able to hear you and respond if you have any queries.
What happens after my PET/CT scan?
Once the scan is completed you will be able to leave the department immediately. You will be able to eat and drink what you like. You may go anywhere you wish but we ask you to avoid prolonged close contact with children for the rest of the day. This is to avoid exposing children to unnecessary radiation.
The tracer that we inject will not produce any side effects. In particular it will not make you drowsy and so will not prevent you from driving a car. 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 posted the following day to the consultant who referred you, who will arrange to give you the results.
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.