The radioactive substance most commonly used in PET scanning is a sugar (like glucose) called FDG, which stands for “fluorodeoxyglucose”. It accumulates in your body wherever sugar is being metabolised at high rates and gives off energy that the scanner can detect. This detected information is then converted into images of your body showing which cells are using the most sugar. Cancer cells tend to use a lot of sugar and therefore show up well on PET images.
PET scanners are combined with computed tomography (CT) scanner, called a PET-CT. CT images are created from multiple x-rays to build up an image of the structures inside your body. The PET or PET-CT scanner looks like a large box with a circular hole in the middle.
If you are claustrophobic or have required sedation for previous scans, please advise us and bring a relative or friend who can drive you home. Please bring prior imaging and inform staff of any previous PET scans.
This will depend on the type of scan you have, but you can expect to be in the PET imaging facility for 2–3 hours. The time on the PET scanner is typically around 20 minutes, but time is also needed for preparation.
When the scan is completed, you will be asked to wait while the images are checked to make sure they are clear. Occasionally, there is a need to obtain more images after this check.
While every PET scan is tailored to the specifics of the individual patient, there are several common factors.
When you come for your PET, you will be seen by the front desk staff who complete the paperwork. One of our technicians will take you into a room where they will ask you a few questions and then place a small needle (a cannula) into a vein in your hand or arm.
The cannula is used to check your blood sugar level before we start and give the FDG. Once given the FDG, you will be asked to sit or lie quietly for around 40 minutes while the material is absorbed. As FDG is basically glucose, it is extremely unlikely you will have any reaction at all. After this time, you will be taken to the camera room and placed on the camera bed. The scanner will move over you a few times as the data is obtained. We typically scan from the top of the head to the mid-thighs. The scan itself will take 30 minutes. After this is complete, you will be free to go home.
Variations include occasionally needing to come back for later images (mainly brain tumour patients) or longer imaging time if we need to scan right down to your toes. For some patients, you will be asked to drink a different contrast material.
This is different from FDG. We will place you on the camera after cannula insertion and then take pictures of your pelvis straight after injection for 20 minutes. Once this is done, we will scan for an additional 30 minutes from head to thighs. You will be on the camera for almost one hour, after which you can go home.
After your PET scan, you can resume your normal activities straight away. The injection of the radioactive material does not make you feel any different or drowsy. There are no sedative drugs or anaesthesia used during this procedure. Your scan results will not be available immediately. The images will be interpreted, and then a report will be sent to your referring doctor, who will provide you with the results.
It is important that you discuss the results with your doctor so that they can explain what the results mean for you.
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