PET Scan

What is a PET Scan?

Positron emission tomography (PET) is a nuclear medicine, functional imaging technique that is used to observe metabolic processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. Three-dimensional images of tracer concentration within the body are then constructed by computer analysis. In modern PET-CT scanners, three dimensional imaging is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.


What should I expect?

As you are being scheduled for the PET scan, be sure and tell the scheduler if you are:

Pregnant or breastfeeding
Taking steroid medication
Over 400 pounds
Unable to lie on your back
Receiving a high-density contrast, like one you drink for a barium study or for a CT with oral or IV contrast.

Upon arrival and check-in, your blood sugar level will be tested. You should avoid carbohydrates and foods with sugar beforehand, as eating sugar could affect your scan. Usually, an IV with a radioactive tracer will then be injected into a vein. The radiotracer is used to measure the amount of blood flow, oxygen use, and sugar metabolism, and helps the doctor see if your cancer is growing or has spread to other areas. It usually takes from 60 to 90 minutes for the tracer to make its way through the blood.

The scan itself will take 20 to 40 minutes. It is very important to remain still during the test because movement could affect your results. After your PET scan, a very small amount of radioactive sugar will remain in your body, so be sure to drink plenty of water to help flush it out your system. You don’t need to follow any special dietary restrictions or guidelines after your PET scan, and you may resume your regular exercises.

What can I do to prepare?
You should not eat or drink, except for water or prescribed medicines, for six hours before a PET scan. Your last meal before the scan should include high protein foods and plenty of water. It is also important that you don’t exercise for 24 hours before your PET scan. Exercise affects the radiotracer’s reading and could cause the results to be inaccurate.