What Is a PET Scan?
A positron emission tomography (PET) scan is a type of imaging study that can help doctors see what’s happening inside your body and how it’s working. This can help them understand how a disease is unfolding. A PET scan is different from an X-ray, CT, or MRI, which only show images of the body.
When you get a PET scan, your doctor will give you a radioactive substance called a radiotracer (or just “tracer”). The PET scanner can see where this tracer goes in your body. If it builds up in certain areas, that could be a sign of disease.
What does a PET scan machine look like?
A PET scan machine has a large, doughnut-shaped ring with a bed or table in the middle. When you have the scan, you lie down on the table, which slides into the hole of the machine. The scanner is big, but open, so it doesn’t completely enclose you the way many MRI machines do.
What does a PET scan show?
A PET scan shows how the organs and tissues in your body are working, including how well your heart is pumping blood, or if there’s unusual activity in certain areas that might be caused by disease, like cancer. This can help doctors understand if there’s a problem, even if it doesn’t show up on another type of scan.
What Is a PET Scan Used For?
A PET scan can help doctors test for diseases, prepare for surgery, and see how well treatments are working. You might get one for several reasons, but they’re most often used with cancer, heart disease, and brain conditions.
PET scan for cancer
PET scans can show how much energy different cells in your body are using. Since cancer cells are more active than normal cells, the scan can pick up on their activity. Areas with cancer cells light up as bright spots on the images. A PET scan can often detect cancer before most other tests.
Besides cancer detection, your doctor may also use a PET scan to see if cancer has spread, check if cancer treatment is working, or determine if cancer came back after treatment.
Pet scan for the heart
A PET scan can check for heart disease by showing how well your heart is working. After you’re given the radioactive substance (tracer), it travels through your bloodstream. The scan then shows how much blood is flowing to different parts of your heart. If certain areas aren’t getting enough blood, it could mean there’s a problem. Your doctor might also use a PET scan to help decide the best treatment for clogged arteries or to look at the effects of a heart attack.
Doctor also use PET scans to check for brain conditions, such as:
- Alzheimer’s disease
- Parkinson’s disease
- Huntington’s disease
- Seizures
- Strokes
- Tumors
PET Scan vs. CT Scan
CT scans use X-rays to take images of the inside of your body, including your bones, blood vessels, and soft tissues. These are more detailed than a standard X-ray because the machine that captures them scans your body from several angles.
A PET scan, on the other hand, does more than just take images – it shows what’s actually happening inside your body using a combination of nuclear medicine (which uses a small amount of a radioactive substance to highlight activity) and biochemical analysis (which measures how your cells use energy).
PET Scan vs. MRI
MRI scans also create detailed images of the inside of your body, but they do this using strong magnets and radio waves. MRIs show the structure of your organs, tissues, blood vessels, spine, and lymph nodes, and they can help doctors find tumors, injuries, and other problems.
Since PET scans show how well your organs are working, they can pick up changes in their cells earlier than most other types of scans.
Many doctors use MRI/PET or CT/PET hybrid scanners, which combine the two tools into a single scan for more detailed results.
How Do I Prepare for a PET Scan?
First, you’ll need to tell your doctor about any of the following:
- Allergies, especially to contrast dye, iodine, or seafood
- Health conditions, like diabetes, or any illnesses you’ve had recently
- Medicines, herbs, and supplements you take
If you’re a woman or were assigned female at birth, tell your doctor if you’re:
- Breastfeeding – you may need to pump milk because you can’t breastfeed until the tracer is out of your body. Check with your doctor to see how long you should wait.
- Pregnant or think you might be – the tracer can harm your baby, so talk to your doctor about the best options for you.
Your doctor will give you specific directions to prepare for your scan. Be sure to follow them closely. Often you’ll need to:
- Avoid intense physical activity for 24 hours before the scan.
- Drink only water and avoid eating for several hours before the scan.
- Remove all piercings, jewelry, and metal objects from your body.
PET scan cost
The cost of a PET scan can depend on where you live, your health care provider, and whether you have insurance. Without insurance, a PET scan can cost between $1,500 and $7,000. If you have insurance, it will likely cost much less.
Medications to avoid before a PET scan
In the 24 hours leading up to your scan, avoid any over-the-counter medications that contain caffeine.
If you have diabetes and take pills to help control your blood sugar, don’t take them the morning of the test. Talk to your doctor to see if you need to adjust any other medications before the scan.
PET Scan Procedure
The procedure might be a bit different, depending on where and why you get the scan, but typically, you:
- Change into a hospital gown.
- Go to the bathroom.
- Get the tracer – depending on the type, you’ll either swallow it, breathe it in as a gas, or get it through a needle.
- Wait 30 minutes to an hour for your body to absorb the tracer.
- Lie very still on your back while images are taken. It’s important not to move or talk during the scan, which may last up to an hour.
The PET scan machine is a big, open circle – like a standing doughnut – with a table that moves in and out of it. If you have a fear of tight, closed spaces, you may get a drug to help keep you calm. You’ll hear the machine buzz and click as it takes images.
The scan itself is painless and usually doesn’t have any side effects. For some people, staying still for so long is the hardest part and may cause some aches or discomfort.
After the scan, drink plenty of fluids to help flush the tracer out of your body. Your doctor may suggest you avoid close contact with pregnant people, kids, or babies for a few hours, since you’ll be slightly radioactive for a short time.
How long does a PET scan take?
The scan itself usually takes about 30 minutes, but the entire procedure can take up to an hour, since your body needs time to absorb the tracer.
PET Scan Risks and Side Effects
Certain health conditions may cause discomfort or complications during a PET scan, including:
- A hard time fitting into the PET/CT machine if you're overweight
- Claustrophobia, if you're unable to be in enclosed spaces
- Inaccurate test results among people with diabetes whose blood sugar levels or insulin levels aren’t within the right range during the test
PET scan side effects
While PET scans are generally safe, there are some potential risks, mostly because of the radioactive tracer. These include:
- Pain or redness where a tracer is injected
- Allergic reactions to a tracer, although this rarely happens and reactions are usually mild
- If you’re pregnant or breastfeeding, you shouldn’t get a PET scan because the radiation could harm the baby or pass through your breast milk.
After a PET scan, how long are you radioactive?
Within a few hours of the PET scan, your body will get rid of the radioactive material by passing it through your pee.
PET Scan Follow-Up and Results
A PET scan shows bright areas where there’s heavy activity in your cells, which may be a sign of disease. To get a more complete picture of what’s going on, your doctor may compare your PET scan with results from other imaging you’ve had. Test results are very accurate, but a combined PET/CT tends to be more accurate than the results of either test on its own. You can get results within 24 hours, but it depends on where you have the scan done.
If PET scan is positive, can it be anything but cancer?
A positive PET scan doesn’t always mean cancer. Other conditions, like infections, inflammation, or non-cancerous growths, can also cause areas of your body to light up. If you’ve had a recent surgery, chemotherapy, or radiation treatment, this may also affect your results. And some types of cancer may not show up on a PET scan.
If your PET scan is positive, your doctor might order more tests to confirm whether it’s cancer.
Takeaways
A PET scan can help doctors see how different parts of your body are working and is often used to find cancer, heart disease, and brain conditions. The scan is generally safe, but some people have minor side effects because of the radioactive tracer, so it's important to tell your doctor if you're pregnant, breastfeeding, or taking any medications. After the scan, drink lots of fluids to clear the tracer from your body, and check in with your doctor to go over the results and talk about any further tests that may be needed.
PET Scan FAQs
What is the main reason for a PET scan?
Doctors use PET scans to see how well different parts of your body are working, including your heart and brain.
Is a PET scan only for cancer?
No, a PET scan is not only for cancer. They are also used to find heart problems, brain disorders, and some other conditions.
What are the risks of a PET scan?
The risks of a PET scan are generally low, but some people may have a mild allergic reaction to the radioactive tracer. There are other complications for pregnant or breastfeeding people.
What is the biggest disadvantage of using a PET scan?
The biggest disadvantage of a PET scan is the exposure to a small amount of radiation, which may not be suitable for everyone, especially pregnant people.
What is better than a PET scan?
PET/CT or PET/MRI combines the strengths of both scans, providing detailed images and showing how the body is functioning. This can be more effective than either scan alone.