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Positron Emission Tomography

  • Editorial Staff and Contributors
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Positron Emission Tomography



This test makes images that show areas of active disease. It uses a substance that is radioactive and is attracted to areas of disease. When the scan takes images, the areas of disease will be highlighted.

PET Scans of the Brain.

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Reasons for Test

A PET scan may be done for a number of reasons, including:

  • Looking for tumors or assessing tumor level of activity after treatment
  • Assessing causes of memory disorders
  • Finding the cause of seizures and helping to find treatments
  • Assessing brain metabolism in those with chronic fatigue syndrome
  • Looking for heart disease

Possible Complications

Problems are rare. The doctor will go over some problems such as:

  • A bad reaction to the substance. In some people, it can cause allergic reactions or kidney problems.
  • Radiation exposure. A PET scan may not be advised for people who are pregnant.

Risks should be discussed with the doctor before the test.

What to Expect


The images will show disease activity levels. It will show as different colors or brightness. A radiologist will review the images and send the results to your doctor. It may take a few days for your doctor to receive the report.

Problems to Look Out For

Call your doctor if you have any unusual symptoms such as a rash, itching, or problems breathing. These may be signs of an allergic reaction to the radioactive substance.





  • Kwon DH, Velazquez AI, de Kouchkovsky I. PSMA PET Scan. JAMA Oncol. 2022;8(12):1860.
  • PET scan. NHS Choices website. Available at:https://www.nhs.uk/conditions/pet-scan.
  • Positron emission tomography—computed tomography (PET/CT). Radiology Info—Radiological Society of North America website. Available at:https://www.radiologyinfo.org/en/info/pet.
  • Positron emission tomography (PET scan). Cleveland Clinic website. Available at: https://my.clevelandclinic.org/health/diagnostics/10123-pet-scan.
  • Positron emission tomography (PET scan). Johns Hopkins Medicine website. Available at: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/positron-emission-tomography-pet.


  • Mark Arredondo, MD
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.