A positron emission tomography (PET) brain scan is a test used by medical professionals to take pictures of your brain. It's natural to feel slightly apprehensive about this test, but it's actually a relatively simple process. A radioactive substance is injected into the body and then you wait a while for it to be absorbed. Next you lie down on a table that slides into the imaging scanner and stay still while it records images of the brain; the radioactive substance highlights areas where there is metabolic activity. The images that result can help with diagnosis and evaluation of a variety of conditions including brain cancer.
When the PET brain scan is scheduled, your doctor will give you pretest instructions to follow. These include not eating or drinking anything but water for four to six hours before the scan, and no caffeine for at least 12 hours prior. It's important to tell the doctor about your medical history because some prescriptions may interfere with the scan. You may also want to leave any jewelry or metal objects at home since they will need to be removed during the test. It's a good idea to bring a book or other activity for the time you will spend waiting.
When you arrive for the PET brain scan, a small amount of radioactive material will be injected into the body usually through an intravenous line. The radioactive material is attached to a substance that the brain uses during metabolic processes, most often glucose. The resulting compound is called a radionuclide. You will probably feel the needle from the radionuclide injection; this is often the most uncomfortable part of the test.
The next step in a PET brain scan is waiting approximately one hour for the radionuclide to be absorbed and reach the brain. Usually there is a quiet area available where you can relax. You will be instructed to remove any jewelry or metal items and lie down on a table that slides into the PET scanning machine shaped like a round tunnel. It's important to lie still while the scanner records images; the length of the scan can last from 30 minutes to two hours. You won't feel the scanning process, although some people do complain of discomfort from the close quarters.
The PET brain scan results are a series of images of the brain. Areas where there is additional or unusual metabolic activity will be highlighted on the image results due to the presence of higher concentrations of the radioactive material. This can help doctors diagnose and evaluate a number of conditions including the extent of tumor growth associated with brain cancer or other brain disorders like Alzheimer's disease.