Getting a PET scan? What to expect
April 27, 2015
Medically Reviewed | Last reviewed by an MD Anderson Cancer Center medical professional on April 27, 2015
Scheduled to get a PET scan? Also known as a positron emission tomography scan, these screening exams cause anxiety for many patients. But knowing what to expect and following the recommended PET scan prep can make a big difference.
What is a PET scan?
A PET scan uses a radiotracer to measure things like blood flow, oxygen use and sugar metabolism.
A PET scan shows how your tissues and organs are functioning. It also can let you and your doctors know if cancer treatment is working.
Follow your PET scan prep for best results
To make sure your doctor gets the information he or she needs, it's important to prepare for your PET scan. Unless your doctor tells you otherwise, don't eat or drink anything, except for water or prescribed medicines for six hours before a PET scan.
Your last meal before the scan should include high protein foods and plenty of water. Avoid carbohydrates and foods with sugar. Because PET scans read your sugar metabolism, eating sugar could affect the results of your scan.
It's also important that you don't exercise for 24 hours before your PET scan. That's because exercise affects the radiotracer's reading and could cause the results to be inaccurate.
Tell the nurse if you are:
- Diabetic
- Pregnant or breastfeeding
- Taking steroid medication
- Over 400 pounds
- Claustrophobic
- Unable to lie on your back
- Receiving a high density contrast
If any of these apply to you, the nurse can make adjustments to keep you comfortable and ensure accurate PET scan results.
What happens during a PET scan?
When you arrive at MD Anderson for your PET scan, your care team will check your blood sugar. Then, an IV line will be started and a radiotracer will be injected into your body. This allows the PET scan to show where the sugar metabolizes in your body so your doctors can see if your cancer is growing. The radiotracer does not cause any side effects or pain.
How long does a PET scan take?
A PET scan will take about 60 to 90 minutes for the radiotracer to start working, depending on what type of information your doctor is looking for.
Once you're ready to start the scan, you'll be asked to lie on your back on a platform. The platform will enter a long tube where the PET scan is performed. The scan will take 20 to 40 minutes. It's very important to remain still during the test. That's because movement could affect the results of the PET scan.
What happens after the PET scan?
After your PET scan, a very small amount of radioactive sugar will remain in your body. So, be sure to drink plenty of water to help flush it out your system. You don't need to follow any special dietary restrictions or guidelines after your PET scan.
Your doctor will receive your PET scan results afterwards, and will share them at your next appointment.