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A PET/CT scan is a type of imaging test that combines positron emission tomography (PET) and computed tomography (CT) techniques. Combined PET/CT scans can be performed on any part of the body.

PET scans use a radioisotope that is introduced into your body to measure the cellular activity of the cell type or body part being scanned. A CT scan takes a large number of x-rays. These are analyzed by a computer to create a 3-dimensional image of the body part being studied. When both tests are performed at the same time, the information about function and structure is integrated through computer models.

The Purpose of a PET/CT    

Because PET/CT scans provide a combination of information about the function and structure of a body part, they are useful for the early diagnosis of cancer. Not only can an abnormal tumor be seen, but the function of the cells that make up the tumor can be analyzed as well. This can help to differentiate between cancerous and noncancerous growths. PET/CT can also be used to see if cancer has spread into other areas of the body.

PET/CT scans are also used to study disorders of the:

  • Brain
  • Endocrine system
  • Heart

Diabetes and PET/CT Scans

If you have diabetes, talk to your doctor about taking your diabetes medications and/or insulin before your test. Abnormal blood glucose levels of higher than 200mg/dl may interfere with test results. 

For any questions about diabetes and PET/CT scans, call our nuclear medicine nurse at 434.982.5240.

Preparing for Your PET/CT Scan

A coordinator will call you the day before your exam to go over your preparation instructions. They'll also review the medications you're currently taking. Call the coordinator with any questions at 434.982.4443.

To prepare for your test, you'll need to:

  • Not eat or drink anything besides water in the six hours before your appointment
  • Drink plenty of water
  • Avoid strenuous exercise 24 hours before your appointment
  • Talk to your doctor if you're anxious about being in enclosed spaces; they can prescribe a light sedative for the scan

If you're breastfeeding, talk to your doctor before you go for your test. Your doctor may recommend that you pump breast milk ahead of time.

You should also know that you'll have to lie flat and still for 15 minutes while the images are taken.

During a PET/CT Scan

  • An IV is placed in your arm.
  • A small quantity of the radioisotope (used for the PET portion of the scan) is injected through the IV. No known allergic reactions have occurred after getting the radioisotope.
  • You'll wait about 60 minutes after this injection.
  • For the imaging, you'll have to lie flat on your back.
  • The table will move slowly through a doughnut-shaped ring. You'll need to lie still for about 15 minutes while the PET/CT images are being taken.

How Long Does a PET/CT Scan Take?   

Most PET/CT appointments take about two hours. The imaging happens one hour after the injection of the radioisotope. Imaging takes about 15 minutes.

Does a PET/CT Scan Hurt?   

The placement of the IV may give you some discomfort, but there should be no other pain involved. 

After a PET/CT Scan    

  • You should continue to drink extra water throughout the day after your scan. This helps to flush the radioisotope from your body.
  • If you've received any sedation, you'll need to have someone drive you home.
  • You can expect to be able to resume your normal activities the same day as your test.
  • A radiologist reviews the images and sends the results to your doctor. It may take a few days for your doctor to receive the report.

Based on the results, your doctor will decide if any further tests or treatments are needed.


Content was created using EBSCO’s Health Library. Edits to original content made by Rector and Visitors of the University of Virginia. This information is not a substitute for professional medical advice.