What is a PET-CT scan?
A positron emission tomography and computed tomography (PET-CT) scan is an imaging test used to learn more about the cancer’s stage and where it has spread to. It is also used to:
Find the right place to do a biopsy
Find out how well treatment is working or has worked
Plan radiation therapy
Sometimes, your doctor may refer to a PET-CT scan as a PET scan or PET imaging.
A PET-CT scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.
A PET-CT scan is done by a nuclear medicine technologist or radiologic technologist. These are trained health care professionals. A doctor, either a nuclear medicine physician or a radiologist, will read the scan and decide what it means.
You will need to go to your hospital’s radiology or nuclear medicine department or to an outpatient imaging center to have a PET-CT scan.
Preparing for your PET-CT scan
When you are scheduling your PET-CT scan, be sure to discuss the following topics with your health care team:
Your current medications. Bring a list of all the medications you take, including any vitamins or supplements. Ask if you should keep taking them before the scan.
Any allergies or other medical conditions you may have.
If you have diabetes. You may need special preparation if you have diabetes.
If you are breastfeeding or may be pregnant.
If you are claustrophobic and don’t like to be in small spaces.
Some people feel more relaxed when they listen to music. If this applies to you, ask if you can listen to music during the scan. That way, you can prepare your music and device in advance.
The staff will ask you to sign a form that says you understand the risks and benefits of a PET-CT scan. It also says you agree to have the test. This is called a consent form. If you have concerns, talk with your doctor before you sign.
Meanwhile, contact your insurance company to learn if it will pay for the scan. Ask if you will need to pay for any or all of the cost of the procedure. Find out if you need any approval or pre-authorization before this test is done, based on your specific health insurance policy.
You will need to take specific steps, or preparations, before the scan. These may be different, depending on the specific scan you receive, but preparations often include:
Avoid exercising 24 hours before the scan.
Follow a special diet for 12 to 24 hours before the scan.
Don’t drink or eat anything, except water, for 6 hours before the scan.
Ask your health care team when you can expect to learn about the test results and who will explain the results to you.
Before the PET-CT scan
Wear comfortable clothing for the scan. You may also need to change from your regular clothing into a hospital gown. Leave valuables at home, such as jewelry or a watch, so they don’t get misplaced. You may need to remove anything that contains metal, such as eyeglasses, dentures, or hearing aids, during the test.
An intravenous (IV) line will be placed into a vein. You will then receive an injection of a radioactive substance, called a radiotracer or tracer. It enters your body through the IV line. It takes 30 to 90 minutes for the substance to travel all over the body. During that time, you’ll need to remain still and stay relaxed.
You may also receive a special dye called a contrast medium before the scan. Contrast medium can make the images from a PET-CT scan easier to interpret. You might drink the contrast medium, or the technologist or a nurse may put it in your IV.
When the substance has traveled all over your body, it will be time to start the scan. Most people are asked to lie on their back on the exam table. But your position depends on where in the body the doctor wants to scan.
During the PET-CT scan
The scanning device is a large machine with a donut-shaped hole in the middle. When the exam starts, the table slides quickly through the hole. This first pass shows the technologist if you’re in the right body position to get the needed images. Then, the table slides slowly back and forth. You will need to stay still. Sometimes, the technologist may ask you to hold your breath. This prevents blurry pictures from the movement of your body breathing. The technologist might raise, lower, or tilt the table during the scan. This helps get pictures from different angles.
The scan can take from 30 minutes to 1 hour.
During the exam, you’ll be able to talk with the technologist, who will be in a nearby room monitoring your test through a window.
After a PET-CT scan
After the PET-CT scan, you can return to your usual diet and activities. This includes driving. Drink lots of water. It helps wash any leftover radioactive substance and dye out of your body.
The scan results will be interpreted by the nuclear medicine physician and/or a radiologist, and that report will be sent to your doctor.