PET Scans Printer Friendly Format [DOC]

Other Common Names:

  • Positron Emission Tomography
  • FDG-PET Scan
  • PET/CT Scan

Description: PET is a nuclear medicine medical imaging technique that produces a 3-D image of functional processes in the body. A PET scan uses a small amount of a radioactive drug, or tracer, to show differences between healthy tissue and diseased tissue. The most commonly used tracer is called FDG (fluorodeoxyglucose), so the test is sometimes called an FDG-PET scan. Before the PET scan, a small amount of FDG is injected into the patient. Because cancer grows at a faster rate than healthy tissue, cancer cells absorb more of the FDG. The PET scanner detects the radiation given off by the FDG and produces color-coded images of the body that show both normal and cancerous tissue.

Currently, many PET scanners also include a conventional computed tomography (CT) scanner. This allows images of both anatomy (CT) and function (PET) to be taken during the same examination.

Example of uses: PET scans can be used to view, monitor, or diagnose

  • tumors
  • blood flow to the heart
  • brain disorders

Preparation: Your doctor will give you detailed instructions on how to prepare for your scan. A general rule is to not eat anything for at least 6 hours before the scan. You will be encouraged to drink water. Wear comfortable clothes.

During the Exam: A nurse or technologist will take you to a special room where you will receive an intravenous (IV) injection of the radioactive drug. Sometimes, you will be asked to inhale the drug instead. Then you will wait 30 to 90 minutes for the drug to travel through your body and accumulate in the tissues being studied. During this time, you will rest quietly and avoid movement. You won’t be able to feel the drug in your body.

The PET scanner is a large machine with a hole in the middle. It looks like a donut with a table in the middle. You will lie on the table. The table will slide into the machine. You will be asked to remain still during the scan.

Time Required: 30 to 45 minutes.

Noise During Exam: Buzzing or clicking sounds.

Space During Exam: You will lie on a narrow table that slides into a circular opening of the scanner. The size of the opening is 27 to 30 inches. How much space you feel you have around you will depend on your body size and the scanner used. A mild sedative may be used to help you feel more comfortable during the exam. If you feel any anxiety over being in enclosed spaces, let your doctor know.


  • The functional information obtained by a PET scan is unique and unavailable using other types of imaging. For many diseases, PET provides the most useful information required to make a diagnosis and determine the most appropriate treatment.


Although a radioactive tracer is used during a PET scan, the amount of radiation that you are exposed to is low and it is short-lived. It is not enough to affect the normal body processes. However, there are risks due to the tracer:

  • The radioactive substance may expose radiation to the fetus of a pregnant woman or to the infant of a woman who is breastfeeding. If you are pregnant or nursing, please discuss this with your doctor.
  • There is a rare risk of a major allergic reaction to the tracer.


A radiologist, who is a physician with specialized training in PET and other imaging tests, will analyze and interpret the results of your PET scan and then send a report to your personal physician. It usually takes a day or so to interpret, report, and deliver the results. Contact your personal physician for information on the results of your exam.

For further info: http://www.radiologyinfo.org/


A PET Scanner

A PET Image


The development of lay imaging descriptions is a project of the 
American College of Radiology Imaging Network
Patient Advocacy Committee.