Positron Emission Tomography (PET)
PET is a very uselful procedure in assessing brain function after brain injury. When procedure results are compared to neuropsychological findings, treatment can be specified to enhance recovery.
Definition
Positron emission tomography (PET) is an imaging test that uses a radioactive substance (called a tracer) to look for disease in the body. Unlike magnetic resonance imaging (MRI) and computed tomography (CT) scans, which reveal the structure of organs, a PET scan shows how the organs and tissues are functioning.
PET scans use a small amount of a radioactive substance injected into a vein, usually on the inside of the elbow. The substance travels through the blood and collects in organs or tissues.
The scan begins approximately 60 minutes after receiving the radioactive substance. The individual then lies on a table that slides into a tunnel-shaped hole in the center of the PET scanner.
The PET machine detects energy given off by the radioactive substance and converts it into 3-dimensional pictures. The images are sent to a computer, where they are displayed on a monitor for the physician to read.
The test takes about 30 minutes.
How to Prepare for the Test
You must sign a consent form before having this test. You will be told not to eat anything for 4 - 6 hours before the PET scan, although you will be able to drink water.
Tell your doctor if you are pregnant or think you might be pregnant.
Also tell your doctor about any prescription and over-the-counter medicines that you are taking, because they may interfere with the test.
Be sure to mention if you have any allergies, or if you've had any recent imaging studies using injected dye (contrast).
During the test, you may need to wear a hospital gown. Take off any jewelry, dentures, and other metal objects because they could affect the scan results.
Why the Test is Performed
A PET scan can reveal the size, shape, position, and function of the brain and other organs. It is used to diagnose cancer, heart problems, and brain disorders. It can see how far cancer has spread, reveal areas of poor blood flow to the heart, and check brain function.
Normal Results
A normal scan reveals no problems in the size, shape, or position of an organ. An abnormal scan reveals areas in which the radiotracer has abnormally collected.
Risks
The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation doesn't last for very long in your body.
However, women who are pregnant or are breastfeeding should let their doctor know before having this test. Infants and fetuses are more sensitive to the effects of radiation because their organs are still growing.
It is possible, although very unlikely, to have an allergic reaction to the radioactive tracer. Some people have pain, redness, or swelling at the injection site.
