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  • Rosalyn Carson-DeWitt, MD
Publication Type:




Positron emission tomography (PET) scans make pictures that show activity in body tissues. Computed tomography (CT) scan uses a computer to take many x-rays of the body. A PET/CT scan is a test that combines PET and CT scans to take pictures of the body.

PET/CT scans can be done on any part of the body.

PET Scan of the Brain.

PET scan head brainhttp://services.epnet.com/getimage.aspx?imageiid=74937493exh56667.jpgexh56667.jpgNULLjpgexh56667.jpgNULL\\hgfiler01a\intellect\images\exh56667.jpgNULL74NULL2008-12-10400291Copyright © Nucleus Medical Media, Inc.

Reasons for Test

PET/CT scans give us details about the structure of a body part and how it is working.

The scans can:

  • Diagnose cancer early
  • Show a tumor and the function of the cells that make up the tumor. This can help tell cancerous and noncancerous growths apart.
  • Show if cancer has spread to other parts of the body

Brain, endocrine, and heart disorders are also studied using PET/CT scans.

Possible Complications

Problems from the procedure are rare, but all procedures have some risk. Your doctor will review potential problems, like:

  • Allergic reactions to the chemicals used
  • Kidney damage from the contrast chemical used
  • Long-term problems from the radiation used

What to Expect

Call Your Doctor

Call your doctor if you have:

  • Signs of allergic reaction, such as flushing, hives , and itching
  • Swollen or itchy eyes
  • Problems breathing or a feeling of tightness in your throat
  • Nausea
  • Less urine than normal

If you think you have an emergency, call for emergency medical services right away.

Prior to Test

Bring a list of the medicines you take to the test. If you have diabetes, ask your doctor if you should take your medicine before the test. An abnormal blood glucose level may cause problems with the test results.

Let your doctor know if you have kidney problems. The doctor may need to take steps to keep your kidneys safe during the test.

If you are breastfeeding, talk to your doctor before you go for your test. Your doctor may tell you to pump breast milk to use until the contrast materials leave your body.

Several hours before the test you may need to:

  • Stop eating after a certain time
  • Avoid drinks with high sugar and calorie content
  • Drink plenty of water

At the test center, the staff will ask if you have or ever have had:





  • PET/CT scan. UPMC website. Available at: http://www.upmc.com/patients-visitors/education/tests/Pages/petct-scan.aspx. Accessed March 14, 2018.
  • Positron emission tomography-computed tomography (PET/CT). Radiological Society of North America Radiology Info website. Available at: https://www.radiologyinfo.org/en/info.cfm?pg=pet. Updated January 23, 2017. Accessed March 14, 2018.
  • Schidt GP, Kramer H, Reiser MF, Glaser C. Whole-body magnetic resonance imaging and positron-emission tomography-computed tomography in oncology. Top Magn Reson Imaging. 2007;18(3):193-202.


  • Marcie L. Sidman, 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.