St. Luke's Hospital
Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
Find a Physician Payment Options Locations & Directions
Follow us on: facebook twitter Mobile Email Page Email Page Print Page Print Page Increase Font Size Decrease Font Size Font Size
America's 50 Best Hospitals
Meet the Doctor
Spirit of Women
Community Health Needs Assessment
Home > Health Information

Multimedia Encyclopedia

    Print-Friendly
    Bookmarks

    MRI

    Magnetic resonance imaging; Nuclear magnetic resonance (NMR) imaging

    An MRI (magnetic resonance imaging) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not use radiation (x-rays).

    Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of images.

    For more information, see the specific MRI topics:

    • Abdominal MRI
    • Chest MRI
    • Cranial MRI
    • Heart MRI
    • Spine MRI

    How the Test is Performed

    You may be asked to wear a hospital gown or clothing without zippers or snaps (such as sweatpants and a t-shirt). Certain types of metal can cause blurry images.

    You will lie on a narrow table, which slides into a large tunnel-shaped scanner.

    Some exams require a special dye (contrast). Most of the time, the dye be given through a vein (IV) in your hand or forearm before the test. The dye helps the radiologist see certain areas more clearly.

    Small devices, called coils, may be placed around the head, arm, or leg, or other areas to be studied. These help send and receive the radio waves, andhelp thequality of the images.

    During the MRI, the person who operates the machine will watch you from another room. The testlasts about 30-60 minutes, but may take longer.

    How to Prepare for the Test

    You may be asked not to eat or drink anything for 4 - 6 hours before the scan.

    Tell your doctor if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious, or your doctor may suggest an "open" MRI, in which the machine is not as close to the body.

    Before the test, tell your health care provider if you have:

    • Artificial heart valves
    • Brain aneurysm clips
    • Heart defibrillator or pacemaker
    • Inner ear (cochlear) implants
    • Kidney disease or dialysis (you may not be able to receive contrast)
    • Recently placed artificial joints
    • Vascular stents
    • Worked with sheet metal in the past (you may need tests to check for metal pieces in your eyes)

    Because the MRI contains strong magnets, metal objects are not allowed into the room with the MRI scanner:

    • Items such as jewelry, watches, credit cards, and hearing aids can be damaged.
    • Pens, pocketknives, and eyeglasses may fly across the room.
    • Pins, hairpins, metal zippers, and similar metallic items can distort the images.
    • Removable dental work should be taken out just before the scan.

    How the Test Will Feel

    An MRI exam causes no pain. If you have difficulty lying still or are very nervous, you may be given a medicine to relax you. Too much movement can blur MRI images and cause errors.

    The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises when turned on. You can wear ear plugs to help reduce the noise.

    An intercom in the room allows you to speak to someone at any time. Some MRIs have televisions and special headphones that you can use to help the time pass.

    There is no recovery time, unless you were given a medicine to relax. After an MRI scan, you can resume your normal diet, activity, and medications.

    Why the Test is Performed

    Having MRIs with other imaging methods can often help your doctor make adiagnosis.

    MRI images taken after a special dye (contrast) is delivered intoyour body may provide extra information about the blood vessels.

    An MRA, or magnetic resonance angiogram, is a form of magnetic resonance imaging, that creates three-dimensional pictures of blood vessels. It is often used when traditional angiography cannot be done.

    Normal Results

    A normal result means the body area being studied looks normal.

    What Abnormal Results Mean

    Results depend on the part of the body being examined and the nature of the problem. Different types of tissues send back different MRI signals. For example, healthy tissue sends back a slightly different signal than cancerous tissue. Consult your health care provider with any questions and concerns.

    Risks

    MRI oes not use ionizing radiation. No side effects from the magnetic fields and radio waves have been reported.

    The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions rarely occur. However, gadolinium can be harmful topeople with kidney problems whoare ondialysis. Tell your health care provider before the test ifyou have kidney problems.

    The strong magnetic fields created during an MRI can cause heart pacemakers and other implants not to work as well.The magnets can also cause apiece of metal inside your body to move or shift.

    References

    Wilkinson ID, Paley MNJ. Magnetic resonance imaging: basic principles. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 5.

    BACK TO TOP

    • MRI scans

      illustration

      • MRI scans

        illustration

      A Closer Look

        Self Care

          Tests for MRI

          Review Date: 11/9/2012

          Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.

          The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
          adam.com

          A.D.A.M. content is best viewed in IE9 or above, Fire Fox and chrome browser.


          Back  |  Top
          About Us
          Contact Us
          History
          Mission
          Locations & Directions
          Quality Reports
          Annual Reports
          Honors & Awards
          Community Health Needs
          Assessment

          Newsroom
          Services
          Brain & Spine
          Cancer
          Heart
          Maternity
          Orthopedics
          Pulmonary
          Sleep Medicine
          Urgent Care
          Women's Services
          All Services
          Patients & Visitors
          Locations & Directions
          Find a Physician
          Tour St. Luke's
          Patient & Visitor Information
          Contact Us
          Payment Options
          Financial Assistance
          Send a Card
          Mammogram Appointments
          Health Tools
          My Personal Health
          mystlukes
          Spirit of Women
          Health Information & Tools
          Clinical Trials
          Health Risk Assessments
          Employer Programs -
          Passport to Wellness

          Classes & Events
          Classes & Events
          Spirit of Women
          Donate & Volunteer
          Giving Opportunities
          Volunteer
          Physicians & Employees
          For Physicians
          Remote Access
          Medical Residency Information
          Pharmacy Residency Information
          Physician CPOE Training
          Careers
          Careers
          St. Luke's Hospital - 232 South Woods Mill Road - Chesterfield, MO 63017 Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
          Copyright © St. Luke's Hospital Website Terms and Conditions  |  Privacy Policy  |  Patient Notice of Privacy Policies PDF Sitemap St. Luke's Mobile