Emission Imaging

In this Article

PET scans, or emission imaging tests, use a radioactive tracer to look for diseases or structures within the organs and tissues of your body. The tracer is put into your body with an IV, and then lights up areas on the test results.

What is emission imaging?

PET scans, or positron emission tomography [toh-MUH-gruh-fee] scans, use a radioactive [rey-dee-oh-AK-tiv] tracer to look for disease in your body. The tracer is put into your body through an IV. The tracer collects in organs and tissues to help the radiologist [rey-dee-OL-uh-jist] see those areas clearly.

Once the tracer is in your body, you will need to wait for a period of time while it is absorbed. During the test, you will be on a narrow table and inside of a large, tunnel-shaped scanner that will move above your body. Your doctor will ask you to remain still during the test.

Emission imaging is not the same as an MRI or CT scan. Those tests check blood flow and structure in organs.

Emission imaging can be used to look at a variety of conditions, including:

  • The spread or lessening of cancer
  • Brain function
  • Epilepsy (seizure) activity in the brain
  • Blood flow in the heart
  • Masses in the lung

Normal results from a PET scan mean that the test did not show abnormalities in your organs or tissues.

Abnormal results mean that there may be:

  • Changes in the size, position, or shape of organs
  • Cancer
  • Infection
  • Other problems with your organs

What are the risks and/or side effects?

The amount of radioactive material used in a PET scan is low, and leaves the body completely between 2 and 10 hours after the test.

If you have lots of emission imaging tests over time, your risk for cancer may go up. The risk for a single test is low. You and your doctor should weigh the benefits of having a test against the risks.

Few people have allergic reactions to tracer materials, but it is a possibility. Some people have pain, redness, or swelling at the spot where the IV is put in.

Tell your doctor if you have allergies to latex, are pregnant, or if you’re nursing. Unborn children are more sensitive to radiation since they have not finished growing.

What are the benefits?

PET scans help to figure out what’s going on in structures of your body that cannot be seen with the naked eye. They provide checks for:

  • The progress of cancer
  • Lumps in the lungs
  • Organ health
  • Brain function
  • How well cancer treatment is working

The test is one of the main tools used to check cancer.

How do I prepare?

Some preparation may be needed before the test. You may need to fast for four to six hours before the scan. You can drink water, but avoid any other drinks like coffee. Don’t take diabetes medicine if you have diabetes.

Tell your healthcare provider if:

  • You are afraid of small spaces
  • You are pregnant
  • You have any allergies
  • You are taking any medicines

How is it done or administered?

If you have an emission imaging test, you will first have the tracer injected into your body with an IV. You may feel a sting when the needle is placed in your arm. Then you’ll wait about one hour for the tracer to spread through your system.

The test takes place inside of a tunnel-shaped scanner and causes no pain. You can ask for a blanket or a pillow for comfort. There is a microphone inside the test area so you can ask for help if you need it.

The length of the test depends on what part of the body is being checked. It is important to stay as still as possible. Movement can damage the test results.

When will I know the results?

The results of the test will likely be interpreted by a radiologist. Your doctor will let you know the result of the test.

What are follow-up requirements and options?

Many PET scans are also performed with a CT scan for a complete picture of what’s going on inside your body.