What is a PET/CT scan?

Positron Emission Tomography (PET) and Computed Tomography (CT) scans are both standard imaging tools that physicians use to pinpoint disease states in the body. A PET scan demonstrates how organs and tissues are functioning at a very early stage in a disease, often before structural changes take place. The CT scan provides information about the body’s anatomy, such as size, shape and location. By combining these two scanning technologies, a PET/CT scan enables physicians to more accurately diagnose and identify cancer, heart disease and brain disorders.1


How does a PET scan differ from CT or MRI scans?

CT and Magnetic Resonance Imaging (MRI) scans are anatomic imaging modalities, which means that they look at the size and shape of organs and body structures. A PET scan looks at how organs and tissues are functioning. The information collected from a PET scan is different from any other test that is available.2


Why is my doctor recommending a PET or PET/CT scan?

A single PET or PET/CT exam can provide information that once would have required several medical studies and possibly surgery. PET scans are most often used to help the physician detect cancer and monitor response to treatment. PET scans are also used to evaluate heart disease and neurological conditions.


What are the benefits?

PET scans provide the physician with valuable information. For cancer patients it may help specialists understand the extent of disease, guide the most effective therapy, and then help evaluate if the treatment is effective. PET scans aid in the diagnosis of heart disease and neurological diseases. This type of imaging may show changes much earlier than other imaging tests like CT or MRI.


Is PET safe?

The risks associated with a PET scan are very slight. The amount of radiation is low and the radiopharmaceutical decays quickly so there is no detectable radioactivity after a few hours. In addition to the radioactive decay, the remaining radiopharmaceutical is eliminated from the body through urine. Family members are not at risk for exposure since most of the radioactivity has left the body or decayed before the patient has left the center. The physician providing you with the PET scan will explain any associated risks and benefits from the PET or PET/CT exam.3


What should I expect?

Upon arrival at the imaging center you will receive an injection of radiopharmaceutical, which will take approximately 60 minutes to distribute throughout your body. You will be asked to empty your bladder and then lie down on the scanner bed. The scan takes approximately 15-35 minutes, depending upon the type of scan you are having and the type of scanner being used. It is important that you lie still during this process. If you need pain medication please bring it with you. You should plan on being at the imaging facility for approximately 2 to 3 hours.


What is a radiopharmaceutical?

Radiopharmaceuticals are used in a wide variety of Nuclear Medicine and PET exams to image and measure how the body functions. In PET imaging the most commonly used PET radiopharmaceutical is a radioactive form of glucose that allows doctors to image and measure how cells in the body use glucose for fuel. Different diseases increase or decrease the amount of glucose used.


What happens after my scan?

Once the PET scan is complete, you will be able to leave the imaging facility. Make sure you drink plenty of water or other fluids throughout the day to help flush the remaining radiopharmaceutical from your body.


Are there any potential side effects to a PET scan?

Ask the physician providing the scan to describe any potential side effects.


When will I get my results?

The PET scan is interpreted by a trained nuclear medicine physician or radiologist and results are usually sent to the referring physician within 24-48 hours. You should contact your doctor to discuss the results.


How often should I have a PET scan?

If you are under a physician’s care, you should follow your physician’s recommendations for frequency of PET scans.


Are there alternatives to PET?

PET scans offer unique information about an organ’s function that can show a physician signs of disease.


Is a PET scan painless?

The only pain involved is the needle prick when you receive the radiopharmaceutical injection, which does not differ from any other type of injection.


Does my insurance cover PET scans?

Many PET scans are covered by private insurance and Medicare; pre-authorization may be needed and is advised.



  1. Society of Nuclear Medicine PET Center of Excellence. PET Professional Resources and Outreach Source PET Scans: Get the Facts. June 2009. http://www.snm.org/docs/PET_PROS/PET.pdf
  2. Cleveland Clinic. Diagnostics and Testing PET Scan. February 2009. http://my.clevelandclinic.org/services/pet_scan/hic_pet_scan.aspx
  3. Radiological Society of North America, Inc. and American College of Radiology. April 2012. http://www.radiologyinfo.org/en/info.cfm?pg=pet


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