Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Brain & Nervous System Health Center

Font Size

Magnetic Resonance Imaging (MRI) of the Head

What Affects the Test

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

  • Being pregnant. An MRI test is not usually done during pregnancy even though the strong magnetic field is not known to be harmful.
  • Having medical devices with metal. The MRI magnet may cause these devices to not work right or to have problems during an MRI scan. This test may not be done if you have:
  • Being unable to lie still during the test.

What To Think About

  • You may be able to have an MRI with an open MRI machine camera.gif that doesn't enclose your entire body. But open MRI machines aren't available everywhere. The pictures from an open MRI may not be as good as those from a standard MRI machine camera.gif.
  • Sometimes your MRI results may be different from earlier test results because you were tested at a different medical center or you had a different kind of test.
  • Several special MRI methods have been developed to look at the brain.
    • Magnetic resonance spectroscopy shows changes in brain chemistry that may occur in certain areas of the brain. These changes may help show diseases that affect the brain.
    • Magnetic resonance angiography (MRA) can be used to study blood vessels. Dye may be injected into the blood vessels so blood flow can be seen clearly. MRA can also be used to show the speed and direction of blood flow. To learn more, see the topic Magnetic Resonance Angiogram (MRA).
    • Diffusion-perfusion imaging shows the water content and character of the brain. This method can give an early diagnosis of a stroke and may help predict the outcome of stroke. It can also be used to find tumors or inflammation of the brain.
    • Functional MRI (fMRI) measures small chemical changes in the brain, which can show the part of the brain being used for functions such as speech, thought, or movement of body parts. Results from fMRI can be used to locate areas of the brain to avoid during brain surgery. These results can also be used to see how well the brain is functioning in people who have certain conditions.

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.

Today on WebMD

nerve damage
Learn how this disease affects the nervous system.
senior woman with lost expression
Know the early warning signs.
woman in art gallery
Tips to stay smart, sharp, and focused.
medical marijuana plant
What is it used for?
senior man
boy hits soccer ball with head
red and white swirl
marijuana plant
brain illustration stroke
nerve damage
Alzheimers Overview
Graphic of number filled head and dna double helix