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Positron Emission Tomography (PET)

How It Feels

You will not feel pain during the test. The table you lie on may be hard and the room may be cool. It may be difficult to lie still during the test.

You may feel a quick sting or pinch when the IV is put in your arm. The tracer is unlikely to cause any side effects. If you don't feel well during or after the test, tell the person who is doing the test.

You may feel nervous inside the PET scanner.

Risks

There is always a slight chance of damage to cells or tissue from radiation, including the low levels of radiation used for this test. But the chance of damage is usually very low compared with the benefits of the test.

Most of the tracer will be flushed from your body within 6 to 24 hours. Allergic reactions to the tracer are very rare.

In rare cases, some soreness or swelling may develop at the IV site where the radioactive tracer was put in. Apply a moist, warm compress to your arm.

Results

Positron emission tomography (PET) is a test that uses a special type of camera and a tracer (radioactive chemical) to look at organs in the body.

The radiologist may discuss preliminary results of the PET scan with you right after the test. Complete results are usually available in 1 to 2 days.

Positron emission tomography (PET)
Normal:

Blood flow is normal and organs are working well. The flow and pattern of the tracer shows normal distribution in the body.

Abnormal: Heart:
  • Decreased blood flow and increased glucose metabolism may show that the blood vessels are blocked. This may mean coronary artery disease (CAD) is present.
  • Decreased blood flow and glucose metabolism may mean that heart tissue is scarred and damaged, such as from a heart attack.
Brain:
  • Areas of increased glucose metabolism or lower oxygen use and blood flow may mean you have epilepsy.
  • Decreased oxygen use and blood flow may mean a stroke has occurred.
  • Decreased glucose metabolism may mean a form of dementia. Dementia may be caused by Parkinson's disease, Huntington's disease, or mental illness, such as schizophrenia.
  • Patterns of blood flow and oxygen use that are not normal may mean a brain tumor is present.
  • A special test (called amyloid imaging) may show signs of Alzheimer's disease.
Tumor detection:

Areas of increased glucose metabolism may mean a tumor is present.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Being pregnant. A PET scan is not usually done during pregnancy because the radiation could harm the unborn baby (fetus).
  • Using caffeine, tobacco, or alcohol in the past 24 hours.
  • Not being able to lie still for the test.
  • Using sedatives.
  • Taking medicines, such as insulin, that change your metabolism.
  • Having recently had surgery, a biopsy, chemotherapy, or radiation therapy.

WebMD Medical Reference from Healthwise

Last Updated: January 28, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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