McKesson Clinical Reference Systems: Women's Health Advisor 2002.2
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What is magnetic resonance imaging (MRI?)

Magnetic resonance imaging (MRI) is a special test that produces very clear, detailed pictures of the organs and structures in your body. The test uses a powerful magnetic field, radio waves, and a computer to create images in cross-section. While an x-ray is very good at showing bones, an MRI lets your health care provider see structures made of soft tissue such as ligaments and cartilage and organs such as your eyes, brain, and heart.

When is it used?

Health care providers use MRI to see problems in the brain and spinal cord and to see the size and location of tumors. It can be used to examine joints and soft tissues. MRI is also helpful in diagnosing diseases and disorders of the eyes and ears.

Injuries show up well on an MRI. For example, an MRI may show whether you have torn ligaments or torn cartilage in your knee and help your health care provider decide whether or not you need surgery. It is also useful for injuries involving the shoulder, back, or neck.

How do I prepare for the procedure?

No special preparation is needed. You may eat normally and and take any usual medications. For the test, wear loose, comfortable clothing without metal fastenings such as zippers or clasps because metal will interfere with the test. Do not wear jewelry. If you have any metal in your body (such as plates or screws from a previous surgery) tell your health care provider. If you have a pacemaker you cannot have an MRI because the test may damage it. If you have any metal fragments in your eyes you cannot have an MRI because the test may injure your eyes.

What happens during the procedure?

You lie down on a cushioned bed that moves into a tunnel-shaped magnet that is open on both ends. If you get nervous when you are in small closed spaces you should talk to your health care provider about this before you have your MRI. He or she may be able to give you a medication that will help you feel less nervous. You will have to be very still during the procedure so the pictures will not be blurry.

Most MRIs take between 30 and 60 minutes. You will hear loud knocking and a whirring sound while the pictures are being taken. You will wear earplugs or music will be provided so that the noise doesn't sound so loud.

When the test is over you may go home. Your health care provider will schedule a visit with you to discuss the results.

What are the benefits and risks?

An MRI is painless. There is no radiation and there are no harmful side effects.

Although there is no evidence that MRI will hurt a baby during the first trimester of pregnancy, the National Radiological Protection Board recommends not using it at this time of pregnancy. MRI may be used with safety later in pregnancy.

Reviewed and approved by the Wilmer Eye Institute of The Johns Hopkins Medical Institutions, Baltimore, MD. Web site: http://www.wilmer.jhu.edu

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.