Magnetic resonance imaging (MRI) is a diagnostic test that uses a magnetic field and radio waves to create highly detailed images of your internal organs and tissues. An MRI machine uses a strong magnet to temporarily realign hydrogen atoms in your body. Radio waves then cause these aligned atoms to give off very faint signals, which the machine detects and uses to create cross-sectional images. Some tests require the use of contrast material to show certain organs or structures more clearly.
The high-resolution images obtained during an MRI can help physicians clearly see details that do not show up on an X-ray, ultrasound or computed tomography (CT) scan. Physicians use MRI to help diagnose problems of the brain and spinal cord, as well as conditions of the heart, blood vessels, bones, joints, breasts and other internal organs.
MRI: What to Expect
An MRI test can take anywhere from 15 minutes to an hour. The machine looks like a long, narrow tube that is open at both ends. You will lie down on a movable table, which then slides into the tube.
During the test, a technician will monitor you from an adjoining room. The procedure is completely painless. You will hear loud tapping or thumping noises from the machine, and the technician may ask you to perform small tasks throughout the test.
If your MRI requires a contrast material, the technician will use an IV to inject the dye prior to the start of the test.
After the test, the MRI technician will provide your test results to your doctor.
MRI: How to Prepare
Unless instructed otherwise, you can eat normally and take your usual medications prior to an MRI.
Be sure to tell your doctor if you:
- Are allergic to any medication. The contrast material used for a contrast MRI does not contain iodine, but be sure to tell your doctor if you are allergic to the MRI dye.
- Are or may be pregnant
- Have any metal implanted in your body, including an intrauterine device (IUD), stents, pacemakers, artificial limbs or cochlear implants
- Wear any medicine patches.
- Become nervous in confined spaces. You may require medication to help you relax during the test.
Before your test, the technician will ask you to change into a gown and remove jewelry, hairpins, hearing aids, eyeglasses and other items that may affect the MRI results.