Magnetic Resonance Imaging (MRI)

Your Care Explained > Tests and Procedures : Magnetic Resonance Imaging (MRI)

MRI is a noninvasive technology that produces detailed images of organs and structures within the body. It allows doctors to see the heart as it beats, providing information about both its structure and its function.

However, it is not recommended for pregnant women, because the magnetic energy can raise the temperature of the amniotic fluid.

What is MRI?

MRI is used to clarify the results from other tests, such as echocardiograms or CT scans, to evaluate a variety of heart conditions. It uses radio waves, magnets and computers to create images of organs and tissues. Because MRI imaging doesn’t use ionizing radiation, it doesn’t raise the risk of cancer. However, it is not safe for people who have metal implants, which may be affected by the force of the magnet, or for pregnant women, because the magnetic energy can raise the temperature of the amniotic fluid.

The dye that is injected into a vein to help highlight the heart or blood vessels on the images doesn’t contain iodine, so it is safe for those with iodine allergies or kidney disease. However, there is a slight risk that it may cause an allergic reaction.

What to Expect:

  • The IV injection of contrast dye may sting.
  • A sedative can help you relax in the confined space.
  • The scanner makes a clanging noise as it works.
  • You can wear earplugs or listen to music.
  • The test will last about an hour.
  • You may need a ride home.

Preparing for MRI

You will be asked to fill out a questionnaire asking whether you have any metal implants that might interfere with the exam, and sign a consent form acknowledging and accepting the slight risk posed by the contrast dye. The staff will review your questionnaire to determine whether an MRI is appropriate for you.

Having an MRI

You will be asked to remove any clothing, jewelry, glasses, removable dental work or other objects that may interfere with the procedure, and will be given a gown to wear. You will be helped onto a padded table and may be belted down to prevent movement during the procedure. If your MRI is to be done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast dye. If you have claustrophobia or difficulty lying still for several minutes, you may need a sedative to relax you during the test.

The table will slide into the scanner. The technologist will be in another room where the scanner controls are located, but will be able to see you through a window. He or she will be able to talk to you through speakers inside the scanner. You will have a call button so that you can let the technologist know if you have any problems during the procedure. Because the magnet makes a clanging noise as it works, you can wear earplugs or a headset to listen to music or audio during the examination. If you have a condition that makes lying still uncomfortable, you may be given a pain reliever before the procedure. If contrast dye is used for your procedure, you may feel coolness or discomfort when the dye is injected into the IV line, but only for a few moments.

It will be important for you to remain very still during the examination, as any movement could cause distortion and affect the quality of the scan. At intervals, you may be instructed to hold your breath for a few seconds. You will then be told when you can breathe.

The test will last about an hour. Once the scan has been completed, the table will slide out of the scanner and you will be assisted off the table. You should move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying flat for the length of the procedure. If an IV line was inserted for contrast administration, it will be removed. You may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash or difficulty breathing. If you took a sedative for the MRI, you may need to rest until you are alert, and will need to avoid driving until the effects have worn off. Otherwise, you won’t need any special care.

Learning Your Results

A cardiac MRI specialist will review the images and report the results to your doctor or cardiologist, who will discuss them with you. It might take up to a week before you know.

Date Last Modified: January 21, 2011

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