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Magnetic Resonance Imaging (MRI)


A magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body.

The radiologist may discuss initial results of the MRI with you right after the test. Complete results are usually ready for your doctor in 1 to 2 days.

An MRI can sometimes find a problem in a tissue or organ even when the size and shape of the tissue or organ looks normal.

Magnetic resonance imaging (MRI)

The organs, blood vessels, bones, and joints are normal in size, shape, appearance, and location.

No abnormal growths, such as tumors, are present.

No bleeding, abnormal fluid, blockage in the flow of blood, or bulges in the blood vessels (aneurysms) are present.

No signs of inflammation or infection are present.


An organ is too large, too small, damaged, or absent.

Abnormal growths (such as tumors) are present.

Abnormal fluid from a cause such as bleeding or an infection is present. Fluid is found around the lungs or heart. Fluid is found around the liver, bowel, or other organ in the abdomen.

A blood vessel is narrowed or blocked. An aneurysm is present.

Blockage in the gallbladder bile ducts or in the tubes (ureters) that lead out of the kidneys is present.

Damage to joints, ligaments, or cartilage camera.gif is seen. Bones are broken or show infection or disease.

Problems of the nervous system are present, such as multiple sclerosis (MS), dementia, Alzheimer's disease, or herniated disc camera.gif.

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.

WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
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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