PET Scan
Reviewed
A PET (positron emission tomography) scan is a nuclear imaging test that looks at how well your tissues and organs are working. It also checks for signs of cancer. For the scan, you will get an injection of a small amount of a tracer, which is a safe radioactive substance. The tracer settles in areas of your body that have high levels of chemical activity. This activity can be a sign of cancer or other diseases. The tracer can also help measure blood flow, oxygen use, and changes in the metabolism of a particular tissue or organ. Chemical changes in your body can show up before you even have symptoms of a disease. Since a PET scan can see how your organs are working in real-time, it can find signs of disease at an early stage, often before the disease can be seen on other imaging tests.
Preparation and collection
Talk to your provider about how to prepare for the test. You may be asked to fast (not eat or drink) for four to six hours before the test. You may be asked to avoid tobacco products and food or drinks with caffeine or alcohol for 24 hours before the test. If you have diabetes and use insulin, you may need to change the timing of your regular dose. Your provider will give you specific instructions about adjusting your insulin since people with diabetes may not absorb the sugar in the tracer. This may affect the results of your scan. You may need to stop taking other medicines or supplements before the test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to. Also, tell your provider if you have claustrophobia (fear of enclosed spaces). Your provider may decide to give you a medicine to help you relax during the test.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Some cancers may not show up on a PET scan, so your provider may order additional tests based on your symptoms and medical history.
- The scan cannot diagnose a specific condition on its own; results are interpreted by a radiologist and correlated with other clinical information.
What to do next
Talk to your provider about your results. They will explain what the findings mean and whether any follow-up tests are needed.