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
- 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
- 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
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).
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
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 (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.