PET (Positron Emission Tomography)

“PET” is short for positron (POZ-ih-tron) emission tomography (tuh-MOG-ruff-ee). PET creates an image of the chemical activity in your body. The PET scan shows the level of activity in the cells and blood flow in tissues and organs. PET is often used to detect brain disease, blood vessel disease, and cancer.

How does PET work?

When you have a PET exam, a small amount of radioactive material is injected into your blood stream. This small amount is not harmful to you. The radioactive material joins with natural chemicals in your body and then gives off (emits) tiny invisible particles called positrons. A computer detects them and then creates an image on the computer screen. The image is color coded — different colors show various levels of cell activity.



If you are pregnant or think you might be, or if you are breast-feeding, tell your doctor or technologist before the test.

How do I prepare for the test?

  • Do not eat or drink anything for at least 6 hours before the test. If your doctor tells you to take your regular medicine, take it only with a small sip of water.
  • Before the day of your test, tell your doctor all the medicines you take. Do as your doctor tells you about taking your regular medicines. If you have diabetes, ask your doctor about any special instructions for
     taking insulin and other diabetes medicines.
  • Wear loose-fitting, comfortable clothes to the test. Leave all jewelry and other valuables at home.
  • Empty your bladder before going to the test.
  • Your doctor or testing center may give you added instructions, based on the reason for your PET exam.
  • Do not schedule any other test that uses radioactive material for the same day as your PET exam.

What happens during the test?

You will change into a hospital gown. You’ll receive the radioactive material by an intravenous line (IV) inserted in your arm. You will then sit quietly while the radioactive material moves throughout your body. Before going to the scanning room, you will be asked to empty your bladder.


The PET scanner is shaped like a large ring. The scanning table will move slowly through the ring. You will need to lie very still for the entire test. The scan is painless; you should not feel anything.

The technologist will go into a room on the other side of a glass window. During the scan, the technologist may give you some added instructions. You’ll be able to talk to the staff during the scan if you need to. You should lie as quietly as possible. The test usually lasts about 2 hours.

What happens after the test?

Most of the radioactive material will collect in your bladder. After the test, you should drink plenty of fluids to flush it out of your body. You may resume your normal diet.

How do I get my results?

Your doctor will discuss the results of the test with you. Check with your doctor or the testing center about how and when to get your results.

Questions and concerns

It’s normal to feel some anxiety before and during a test. But a PET scan should not be a frightening experience. Feel free to express concerns about your test. Please ask the medical staff any questions you may have.

My test appointment

Date: ____________ Time: ____________

Place: _______________________________

Report to: ____________________________

Phone number: _______________________

Special instructions: _______________________________________________________


UPMC | Affiliated with the University of Pittsburgh Schools of the Health Sciences | Supplemental content provided by Healthwise, Incorporated. To learn more, visit

For help in finding a doctor or health service that suits your needs, call the UPMC Referral Service at 412-647-UPMC (8762) or 1-800-533-UPMC (8762). Select option 1.

UPMC is an equal opportunity employer. UPMC policy prohibits discrimination or harassment on the basis of race, color, religion, ancestry, national origin, age, sex, genetics, sexual orientation, gender identity, marital status, familial status, disability, veteran status, or any other legally protected group status. Further, UPMC will continue to support and promote equal employment opportunity, human dignity, and racial, ethnic, and cultural diversity. This policy applies to admissions, employment, and access to and treatment in UPMC programs and activities. This commitment is made by UPMC in accordance with federal, state, and/or local laws and regulations.

Medical information made available on is not intended to be used as a substitute for professional medical advice, diagnosis, or treatment. You should not rely entirely on this information for your health care needs. Ask your own doctor or health care provider any specific medical questions that you have. Further, is not a tool to be used in the case of an emergency. If an emergency arises, you should seek appropriate emergency medical services.

Pittsburgh, PA, USA |