Positron Emission Tomography (PET) Scan

Positron Emission Tomography (PET) Scan

Positron emission tomography (PET) is a diagnostic test. It can be used to examine organs such as the heart and brain. It can also look at body tissues such as lymph nodes. Rather than showing the structure of a body part, PET images show the chemical function of an organ or tissue. PET can show changes in how an organ or tissue works. This can help your health care provider diagnose problems and develop a treatment plan for you.

Why a PET Scan Is Done

Man lying on back on scanner table. Healthcare provider is standing next to man preparing to slide table into ring-shaped scanner.

PET scans are often done to help diagnose or manage conditions including:

  • Coronary artery disease

  • Brain tumors

  • Cancer

  • Seizure disorders

  • Memory problems

  • Stroke

  • Brain diseases such as Alzheimer’s, Huntington’s, or Parkinson’s

Preparing for a PET Scan

You will be told how to prepare for your scan. It is important to follow these instructions carefully. If you don't, the test may be inaccurate and need to be repeated. In general:

  • Do not eat for a minimum of 4 to 6 hours before the scan. This includes gum and mints.

  • Drink plenty of water before the scan.

  • Do not drink any liquids that contain sugar. Some examples include soda, juice, energy drinks, sweetened bottled water, and alcohol.

  • Do not participate in strenuous activities or exercise that requires a lot of effort and energy within 24 hours before the test. Strenuous activities or exercises within  24 hours before the test may interfere with results.

  • Tell your health care provider what medications you take and ask if you should take them as usual before the exam.

  • Tell your health care provider if you are, or may be, pregnant, or are breastfeeding.

  • Tell your health care provider if you have diabetes. You will be given special instructions regarding your medications and food intake.

During the Procedure

  • Tell your health care provider if you tend to be claustrophobic. You may be given a sedative to help you relax.

  • You will be given a radioactive compound through an IV (intravenous) line. While your body absorbs the compound, you will rest quietly on a table or in a reclining chair for 30–60 minutes. Once the compound is absorbed, the scan can be done.

  • For the scan, you will lie on a cushioned table. The scan itself takes 30–90 minutes. During that time try to stay as still as possible. Move only when told.

After the Procedure

If you were given a sedative, have an adult friend or family member drive you home. Over the next several hours, drink plenty of clear fluids to help flush the radioactive compound out of your system. Know that the radioactive compound will pose no danger to your loved ones.


Risks of a PET scan are minimal. Ask your doctor to explain them to you.