How the PET scan works
A PET scan involves the painless injection of a small amount of a ‘positron emitting’ radioactive material (called a radiopharmaceutical). Images of the body are then taken using a PET scanner. The camera detects emissions coming from the injected radiopharmaceutical, and the computer attached to the camera creates two- and three-dimensional images of the area being examined.
Areas where the particular injected radiopharmaceutical accumulates (for example, fast-growing cancer cells) appear ‘brighter’ than normal tissues on the images.
Almost all PET scanners today are combined with a CT scanner in such a way that the PET images can be combined or fused with the CT images. This allows the nuclear medicine specialist to combine the structural information from the CT scan with the PET’s functional information and improve the accuracy of the test. In these scanners the patient passes through both scanners on the one bed and in the same position.
When the PET scan is used
Some of the uses of the PET scan include:
Medical issues to consider with a PET scan
Medical considerations prior to the PET scan may include:
PET scan procedure
Before the scan you will be given a small injection of radioactive material. The injection is painless and it does not make you feel any different at all. The PET scanner then takes a series of images. For some tests, the procedure begins as soon as you have the injection. In other cases, you may have to wait at least 60 minutes after the injection before the scan is taken.
In most cases you will need to rest before and after the injection of the radioactive material. For example, if you are having a brain PET scan, you will lie quietly in a darkened room before and after the injection to ensure your brain remains relaxed and is not stimulated by light, or noise or reading.
Once the appropriate amount of time has passed, you will be asked to lie on the imaging bed. This bed has special rests for your legs, arms and head to help keep them still and comfortable.
You must lie quietly and still as the scanning table moves through the scanner ‘ring’. The scanner detects the gamma rays released by the radioactive material that has localised in the area of your body being investigated, and uses it to create images of your internal body structures.
Imaging generally takes around 30 minutes. The nuclear medicine scientist who performs the test will tell you exactly how long your procedure will take. They will be there to look after you during the procedure. A PET scan is completely painless and you will not feel any different after the injection, during imaging or after the scan.
Immediately after the PET scan
After your PET scan, you can go on with 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. Before you leave, the nuclear medicine scientist will tell you when your doctor will have the results. You will need to make a follow-up appointment with your doctor to discuss the results of your PET scan.
Possible complications of a PET scan
A PET scan is considered to be a safe procedure. It exposes you to around the same amount of radiation that you would receive from the general environment over about three years. The injected radioactive chemicals have a very short lifespan and are removed from the body fairly quickly. Sometimes you will be advised to avoid close contact with babies or pregnant women in the few hours after your scan. The nuclear medicine scientist will tell you if this is necessary, after your scan.
Taking care of yourself at home after a PET scan
The PET scan is a safe, painless and non-invasive procedure that does not require any ‘recovery time’. Generally, there are no special aftercare instructions. However, drinking plenty of fluids will help your body to flush out the injected radioactive substances. The nuclear medicine scientist who performs your scan will tell you of any special requirements.
Long-term outlook of a PET scan
A lot of research has been done to check the safety and long-term side effects of nuclear medicine examinations. Up to now, there are no known issues – the radiation dose you receive from a PET examination is considered to be safe and justified.
Alternatives to the PET scan
The PET scan is a unique diagnostic imaging study because it detects how your organs and body systems are working, as well as their structure. PET imaging however, requires expensive and sophisticated equipment. It is currently only available in a few specialised centres in Australia.
Alternatives to the PET scan depend on the condition under investigation, but could include: