Magnetic Resonance Imaging (MRI)

What is magnetic resonance imaging (MRI?)

Magnetic resonance imaging (MRI) uses a strong magnetic field and radio waves to show detailed pictures of the organs and structures in your body. While an X-ray is very good at showing bones, an MRI can show more than an X-ray, such as muscles, ligaments, cartilage, blood flow, and organs, such as the eyes, brain, and heart.

When is it used?

Healthcare providers use MRI scans to see detailed images of almost any place in the body. For example, they may use them to:

  • Diagnose injuries and diseases of bones and the tissues that connect them to muscles or other bones
  • Diagnose conditions that affect the brain or spinal cord
  • Diagnose cancer

If you have a pacemaker you may or may not be able to have an MRI, depending on the type of pacemaker you have. If you have any metal fragments in or around your eyes, you cannot have an MRI because it may injure your eyes.

How do I prepare for this procedure?

Usually no preparation is needed for an MRI, but in some cases your healthcare provider may give you instructions to follow before the scan. Your instructions may include:

  • Changes to how you take your medicines
  • What you can eat and drink before the MRI
  • Getting other tests or procedures

Metal will interfere with the scan, so take the following precautions:

  • Wear loose, comfortable clothing without metal fastenings such as zippers or clasps.
  • Don’t wear jewelry.
  • If you have any metal in your body, such as plates or screws from a previous surgery, tell your healthcare provider. The metal may cause the MRI pictures to be blurry.
  • Some skin medicine patches contain metals. The patches could overheat during an MRI and burn your skin. If you wear a medicine patch, you may need to remove it before an MRI. Talk with your healthcare provider about this.

Tell your healthcare provider if you are or may be pregnant. Although there is no evidence that an MRI will hurt a baby during the first trimester of pregnancy, the National Radiological Protection Board recommends not using it during the first 3 months of pregnancy. MRI may be used safely later in pregnancy.

Most MRI machines are tunnel shaped, which means you will be in a small space during the scan. Tell your healthcare provider if you have anxiety or fears when you are in small or crowded spaces. Your provider may give you medicine to help you feel less nervous, or you may be able to go to a site with an open MRI scanner.

What happens during the procedure?

With most machines, you will lie on a narrow bed that moves through the MRI machine. Some machines move over the bed. You will need to be very still during the scan so the pictures will not be blurry. Sometimes you will be given IV fluid called contrast before you have the MRI. Contrast can make areas in your body easier to see in the pictures created by the MRI.

Most MRIs take 30 to 60 minutes and some take longer. You will hear knocking and a whirring sound while the pictures are being taken. If you are concerned that the noise will bother you, ask the person doing the scan if you can wear earplugs or listen to music during the scan. You will be able to speak with the person doing the scan so you can let them know if you are having any problems.

When the scan is over you may go home.

Ask your healthcare provider when and how you will get the results.

What are the risks of this procedure?

Every procedure or treatment has risks. Some possible risks of this procedure include:

  • In rare cases you may have an allergic reaction to contrast used during the procedure.

Ask your healthcare provider how the risks apply to you. Be sure to discuss any other questions or concerns that you may have.

Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth.
Last modified: 2013-08-05
Last reviewed: 2013-07-19
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.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.

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