Positron emission tomography (PET) is a medical 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.
How is a PET scan performed?
PET scans use a small amount of 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. You will be scanned approximately 60 minutes after receiving the radioactive substance.
During the exam, you lie 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 three-dimensional pictures. These images are sent to a computer, where they are displayed on a monitor for your physician to read.
The test takes about 30 minutes, and you must lie still during the PET scan to allow the machine to capture clear images of your organs.
Why is the test performed?
PET is often used to:
- Reveal the size, shape, position and some function of organs
- Diagnose cancer and determine how far cancer has spread
- Diagnose heart problems and identify areas of poor blood flow to the heart
- Diagnose brain disorders and other central nervous system disorders
- Evaluate the effectiveness of a treatment plan
- Check brain function