Two Tests in One: The PET/CT Scan
- A PET scan uses a radioactive tracer to find cancer in your body
- CT scans take a series of x-rays from different angles and combine them into a cross-sectional image
- The PET/CT scan combines both tests in one machine
"Imaging plays a very important role in management of patients with lymphoma," Dr. Jakub Svoboda, medical oncologist at Penn Medicine, tells SurvivorNet. "And the most advanced technology we’ve been using for the past 10-plus years is PET/CT scans."
Read MoreWhat is a PET/CT Scan?
PET stands for "positron emission tomography." It's a type of nuclear imaging scan that uses small (and safe) amounts of a radioactive material called a radiotracer and a computer to look for cancer inside your body. One commonly used radiotracer is F-18 fluorodeoxyglucose, or FDG, which is similar to glucose (sugar). The tracer collects in the cancer, making it show up on a computer screen. Because a PET scan can identify changes in your body at the molecular level, it can find cancer that's not visible on other types of imaging tests. That gives PET scans "advantages over traditional anatomic imaging like CT scans, x-rays, or ultrasounds," Dr. Svoboda says.CT is short for "computed tomography." It takes a series of x-rays from different angles and combines them using a computer into three-dimensional cross-sectional images of your bones and other tissues inside your body.
A PET/CT scan combines both of these tests into one machine to streamline the process. "Basically you're getting two scans two for one," Dr. Svoboda says.
What to Expect During the Test
Your doctor will probably tell you to fast for several hours before the scan. Eating can affect the distribution of the PET tracer around your body, and it could compromise the quality of the scan. You'll also want to avoid sugary drinks, but you can have water. If you have diabetes, ask your doctor for special instructions about eating and drinking.
Metal objects, such as jewelry, eyeglasses, hearing aids, and hairpins could interfere with the scan. The technician might ask you to remove them before the test.
A technician will first give you an injection of the radioactive tracer. It takes about 60 minutes for the tracer to travel throughout your body and collect in the cancer. Then you'll be ready to start the scan.
You'll lie on a table, which slides into a donut-shaped hole in the center of a large machine. The technologist will sit in a separate room. They will be able to hear and talk to you throughout the procedure.
The scan shouldn't cause you any pain, with the exception of the prick needed to inject the radiotracer. If you're claustrophobic, you might feel a little uncomfortable in the tube. Ask your doctor ahead of time if there’s anything you can do to relax during the test. You’ll need to stay still during the 30-minute test to get a clear image.
Expect to be at the imaging center for about two hours in total.
What the Scan Will Show
The advantage to a PET/CT scan is that your doctor will not only be able to see your organs and tissues, for example whether your spleen or lymph nodes are enlarged, but also areas of cancer, Dr. Svoboda says. Cancer cells are more metabolically active hungrier than healthy cells — so they gobble up glucose and light up on the scan.
A radiologist or other nuclear medicine specialist will read your scan and send a report to your doctor. Once your results are in, ask your doctor what they mean, how your treatment might change, and what outlook you can expect.
Learn more about SurvivorNet's rigorous medical review process.
