PET Scan

What is a PET scan?

A positron emission tomography (PET) scan is an imaging test that creates images of your organs and tissues at work. The test uses a safe, injectable radioactive chemical called a radiotracer and a device called a PET scanner. The scanner detects cells that absorb large amounts of the radiotracer, which indicates a potential health problem. A PET scan can measure vital functions, such as blood flow, oxygen use and metabolism.

A healthcare provider may order a PET scan to check for signs of:

• Cancer, including breast cancer, lung cancer and thyroid cancer
• Coronary artery disease, heart attack or other heart problems
• Brain disorders, such as brain tumors, epilepsy, dementia and Alzheimer’s disease

They can also use it to:

• Determine if cancer has spread, evaluate if cancer treatment is working or see if cancer has returned
• Evaluate damage from a heart attack or stroke and identify areas of your heart that need treatment

How does a PET scan work?

A PET scan is a type of nuclear medicine imaging that uses a small, safe amount of radioactive material (radiotracer) given through an IV. Unlike other imaging techniques, PET scans focus on processes and molecular activity within your body. This gives them the potential to find disease in its earliest stages.

Diseased cells in your body absorb different amounts of the radiotracer than healthy ones do. These are called “hot spots.” The PET scanner detects this radiation and produces images of the affected tissue. Your provider may perform a PET/CT scan, which combines images from a CT scan with PET scan images.

How do I prepare?

PET scans are an outpatient procedure, which means you go home the same day. Your healthcare provider will give you detailed instructions on how to prepare for the scan. In general, you should:

• Make sure your provider has a current list of all medications, vitamins and supplements you take, as well as any allergies you have.
• Alert your provider if you think you could be pregnant or if you’re breastfeeding.
• Not eat anything for six hours before the test. Your healthcare provider may change this direction if you have diabetes. Follow up with your provider about diabetes medications or insulin use before the test.
• Drink only water.
• Avoid caffeine for 24 hours before the test if you’re being tested for a heart problem.
• Wear comfortable clothes and leave metal accessories, such as jewelry, eyeglasses and dentures, at home.
• Tell your healthcare provider if being in an enclosed space makes you anxious. You may be able to take a mild sedative to help you relax during the procedure.

What should I expect during a PET scan?

You can expect the following during a PET scan:

1. You’ll receive an IV injection of a radiotracer that contains a safe amount of a radioactive drug.
2. You’ll sit in a chair for about an hour while the radiotracer moves through your bloodstream and gets absorbed by your organs and tissues. Too much activity can send the radiotracer to areas of your body that your healthcare provider isn’t testing. You won’t be able to feel the radiotracer.
3. If you’re getting a PET/CT scan, you may also get an IV injection of a contrast dye. This dye helps irregularities stand out.
4. You’ll lie on an exam table that slides in and out of the PET/CT scanner. This scanner is shaped like a doughnut.
5. You must remain still during the scan. Movement can blur the images.
6. You’ll hear buzzing and clicking sounds as the scanner takes images.
7. A technologist will review the scans before you leave to ensure the images are in focus.

How long does a PET scan take?

The entire PET scan process takes about two hours.

It can take up to 60 minutes for your body to absorb the injected radiotracer. During this time, you’ll need to sit quietly and limit your movements. The actual PET scan takes about 30 minutes. After the test, you’ll need to wait while the technologist reviews the scans to ensure the images are clear.

What are the risks and side effects of a PET scan?

In general, PET scans are safe and rarely cause problems. The amount of radiation in the radioactive tracer is very low. It doesn’t stay in your body for long. You should drink lots of water after a PET scan to help flush the radioactive drug from your body.

PET scans generally only pose risks in the following situations:

• If you’re pregnant or breastfeeding. The radiation may be harmful to a fetus and can pass to your infant through breast milk.
• You have an allergic reaction to PET scan radioactive tracers or CT scan contrast dyes. These allergic reactions are extremely rare and usually mild.
• People with diabetes may not absorb the sugar in the radiotracer, which can affect scan results. Your healthcare provider will offer suggestions to modify your diet and medications before the test.

What can I expect after a PET scan?

After the scan, you can go back to your usual activities. The tracer leaves your body within a few hours. Drinking plenty of liquids can help flush it out faster. Side effects are rare, but it’s possible to have discomfort at the injection site.

When should I get my results?

A radiologist with specialized training in PET scans will review the images, write a report and send it to your healthcare provider. This process usually takes 24 to 48 hours.

What type of results do I get with a PET scan?

A PET scan will tell your provider how your organs and tissues are functioning. You can get the following results:

• Normal: There are no signs of diseases or irregularities.
• Abnormal: There was something unusual that suggests infection, inflammation or cancer.

The scan can also tell your provider how a disease is progressing or how well treatment for a condition is working.

Your provider will tell you what your results mean for you and if any follow-up tests are necessary.

When should I call my healthcare provider?

Contact your healthcare provider if you have any of the symptoms after the scan:

• Dizziness
• Nausea
• Difficulty breathing
• Worsening pain at the injection site