Understanding Brain MRIs

Magnetic resonance imaging, or MRI, is a noninvasive technique used to identify abnormalities in the body. By using magnetic fields and radio frequencies, an image is produced that shows detailed pictures of internal body structures. By using an MRI to scan the brain, damage to the brain can located and properly treated.

Creating the Image

• MRIs rely on powerful magnets, stored in the MRI scanner, and radio waves to create an image of the brain. The magnetic field, which is 10,000 times stronger than the earth's magnetic field, forces the hydrogen atoms within the body to line up. Then, when the radio waves are emitted toward the body, the radio waves bounce against the lined-up hydrogen atoms and are sent back. The computer that is connected to the MRI scanner records the signal, which produces the image. Each type of tissue in the body sends back a unique signal, allowing the computer-generated image to differentiate between the different types of tissue.
  An individual MRI image is called a slice. More than one image is taken of the brain when scanned; the number of pictures taken with the MRI scanner can range from a few to hundreds. The benefit of multiple images is that they are taken from different angles, which can reveal the full scope of an injury. In addition, a tumor may not be seen from a frontal image, but is visible when the image is taken from the side of the head.

What Is Shown

• A MRI of the brain can show a variety of abnormalities that can lead to a proper diagnosis. MRIs can reveal the location of a brain injury, such as those caused by a stroke or a traumatic injury. In addition, the brain MRI images can show anomalies: those that were developmental or vascular, like an aneurysm.
  Disorders and diseases can also be identified using a MRI. Brain tumor diagnoses rely heavily on MRIs to pinpoint the tumor's location. Disorders of the eyes and the inner ear and diseases in the pituitary gland can also be recognized through the use of a brain MRI. Figuring out the cause of chronic headaches is also possible with an MRI, as scanning the brain can help identify any changes in it.

Difficulties

• No metal objects can be on a patient's person while an MRI scanner is in use. This means that people with brain aneurysm clips, inner ear implants, some older types of vascular stents, some kinds of artificial heart valves and recently placed artificial joints may not be able to undergo an MRI.
  While an MRI provides very good images of the brain, it may not always distinguish between cancerous tissue and edema fluid from brain swelling, which can lead to a misdiagnosis.