Magnetic Resonance Imaging (MRI) of the Head

What Affects the Test

• 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:
  • An intrauterine device (IUD) in place.
  • Metal parts or clips in the head or eye.
  • A pacemaker.
  • An implantable cardioverter-defibrillator (ICD).
  • Certain types of artificial limbs.
  • A medicine infusion pump in place.
• 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 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.
• 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.