PET (positron emission tomography) scan and cancer diagnosis

PDF download is not available for Arabic and Urdu languages at this time. Please use the browser print function instead

A PET scan is a diagnostic test that shows where cancer cells are in the body. Find out how PET scans are done, what to expect during the scan and when you get your results.

Key points

  • A PET scan shows parts of the body where cells are burning a lot of energy because they are dividing quickly, which usually means they are cancerous.
  • You may be asked not to eat or drink for 6 hours before the PET scan; 1 hour before you will be given glucose by IV.
  • The PET scan takes between 1-2 hours and you will need to lie very still while the computer takes the pictures.
  • Your doctor will review the results of the scan with you.

What is a PET scan?

PET (positron emission tomography) scans take a picture that shows parts of the body where cells are burning lots of energy. Cancer cells use lots of energy to divide very fast, so they will show up easily on a PET scan.

Many times, you will have a CT scan on the same day as your PET scan. A computer puts the pictures from the two scans together to make a very detailed picture that shows both the inside of your body and where the cells are most active.

The amount of radioactivity injected for a PET scan is very small. It is gone from your body in a few hours. If you or your family have questions or are worried about the radioactivity from a PET scan, talk to your doctor or nurse.

How are PET scans done?

Before the scan, you may be asked not to eat or drink anything for six hours. About an hour before the PET scan, you will be given a sugar called glucose (cells burn glucose for energy) through an IV.

You will need to lie still for an hour as the sugar travels to the parts of your body where the cells are very active. The glucose will have a radioactive tag attached to it. The sugar takes the radioactivity with it as it travels through your body. The scanner senses the radioactivity. The computer uses the radioactivity to make a picture that shows where in your body the cells are active and burning lots of energy.

The PET scanner looks like a big box with a tunnel in the middle. When it is time, you may be asked to change into a hospital gown. Then you will lie on a narrow bed that slides into the scanner. You will need to lie very still as the computer takes the pictures. You may be able to listen to music to help you relax. If you are worried about lying still inside the tunnel, talk to your doctor or nurse before the day of the scan. They can give you suggestions to help you through it or may be able to give you some medicine that will help you relax.

A PET scan usually takes between one and two hours.

PET scan results

Your doctor will let you know how long you will need to wait for the PET scan pictures to be ready.

A specialist will look at the pictures from the PET scan and will then talk to your doctor. Your doctor will tell you and your family what the pictures show.

Last updated: September 3rd 2019