During a magnetic resonance imaging scan (or MRI), powerful magnets and radio waves are used to create detailed images of your body.

An MRI is used to help detect injuries or abnormalities in many parts of your body.

It's a noninvasive procedure, and an MRI does not use x-rays.

How to Prepare for an MRI

To prepare for an MRI:

  • Depending on the type of study being performed, you may be able to eat and drink normally, or you may be asked not to eat or drink anything for up to six hours prior to your test.
  • You may be given a gown to wear, or asked to wear loose fitting clothing with no metallic snaps, clasps, or zippers.
  • Remove all jewelry, including metal piercings.
  • Make sure your pockets are empty, and remove all hairpins from your hair.
  • Let your doctor know if you are claustrophobic. He or she may prescribe a sedative to make the test more comfortable for you.
  • You may have dye (contrast) injected into your veins intravenously to make it easier for the MRI to be read.
  • Be sure to tell your doctor if you have any allergies to radiology contrasts, or if you have kidney or liver problems.
  • Let your doctor and MRI technician know if you have any metal in your body (pacemakers, shrapnel, implants, surgical plates or screws, etc.), or if you have any tattoos

What Happens During an MRI?

The MRI room will likely be cold; this ensures a proper working environment for the machine's magnets. 

During the MRI, you'll lie completely still on a narrow table inside a large, tunnel-shaped scanner that's open at both ends.

You'll be alone while the technician operates the MRI scanner from a nearby room, but you can communicate with one another via a microphone.

You may be given earplugs to cancel out the loud "drumming" noise of the machine.

An MRI scan generally lasts between 45 and 90 minutes.

How Does the MRI Work?

During a scan, the MRI machine's magnetic field forces the protons in your body's hydrogen atoms to line up.

Radio waves delivered by the machine knock the protons out of line with each other. When the radio waves are turned off, the protons line back up, sending out radio waves in the process.

These radio waves are picked up by receivers, and processed by a computer to produce images of the body's tissues.

The images created by MRI can be cross-sectional "slices" or 3-D images.

Who Should Have an MRI?

Your doctor will request an MRI to look for:

  • Tumors or other abnormalities in your liver, pancreas, spleen, kidneys, uterus and ovaries (in women), or prostate and testicles (in men)
  • Aneurysms, strokes, multiple sclerosis, spinal cord injuries, or disorders of the eye and inner ear
  • Joint disorders, including arthritis, bone infections, joint problems caused by traumatic or repetitive injuries, or disk abnormalities in the spine
  • Heart health, including the size and function of its chambers, thickness and movement of its walls, inflammation or blockages of blood vessels, or to assess damage from heart attack or heart disease

Results of an MRI

A radiologist will review your MRI and report the results to your doctor.

Your doctor will follow up with you and determine what, if any, next steps are needed.