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Magnetic Resonance Imaging (MRI)

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Pregnancy. An MRI test usually is not done during pregnancy. But MRI may be done to get more information about a possible problem that cannot be seen clearly with ultrasound.
  • Medical devices that use electronics, such as a pacemaker or medicine infusion pump. The MRI magnet may cause problems with these devices, and that may keep you from having an MRI.
  • Medical devices that have metal in them. The metal might make some of the detailed MRI pictures blurry. This may prevent your doctor from seeing the organ that is being looked at. For example, an intrauterine device (IUD) with metal may prevent your doctor from seeing the uterus clearly.
  • Inability to remain still during the test.
  • Obesity. A person who is very overweight may not fit into standard MRI machines.

Many modern medical devices that do not use electronics—such as heart valves, stents, or clips—can be safely placed in most MRI machines. But some newer MRI machines have stronger magnets. The safety of MRI scans with these stronger MRI magnets in people with medical devices is not known.

What To Think About

  • Sometimes your MRI test results may be different from the results of CT, ultrasound, or X-ray tests, because the MRI scan shows tissue differently.
  • MRI is a safe test for looking at structures and organs inside the body. It costs more than other methods and may not be available in your area.
  • Open MRI machines are now made so that the magnet does not completely surround you. But these machines may not be available in all medical centers. Open MRI is useful for people who are claustrophobic or obese.
  • Magnetic resonance angiogram (MRA) is a special MRI method that studies blood vessels and blood flow. To learn more, see the topic Magnetic Resonance Angiogram (MRA).
  • MRI spectroscopy is a special MRI method that identifies certain medical problems by looking for specific chemicals in body tissues.
  • Contrast material that contains gadolinium may cause a serious skin problem (called nephrogenic fibrosing dermopathy) in people with kidney failure. Before having an MRI scan, tell your doctor if you have serious kidney disease or if you have had a kidney transplant.

MRI can be used to check different parts of the body, such as the head, belly, breast, spine, shoulder, and knee.

Other Works Consulted

  • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

WebMD Medical Reference from Healthwise

Last Updated: May 24, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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