Overview & Description
Magnetic resonance imaging, known as MRI, is a noninvasive imaging technique. It is used to view organs, soft tissue, bone, and other internal body structures. In a cranial MRI, the person's head is exposed to radio waves while in a magnetic field. A cross-sectional picture of the skull and brain is produced by energy emitted from hydrogen atoms in the body's cells. The person is not exposed to radiation during this test.
brain tumors
strokes
neurological diseases such as multiple sclerosis
brain abnormalities in people who have dementia
diseases of the pituitary gland
abnormalities of the vision pathway
inner ear disorders
has any drug allergies or history of allergic reaction to medicines
is allergic to shellfish or to foods with added iodine such as table salt
has experienced claustrophobia, which is a fear of enclosed or small spaces. If this is a problem, mild sedating medicine may be given.
A woman will also be asked if she might be pregnant.
As the test begins, the person lies on a flat platform. The platform then slides into a donut-shaped machine where the scanning takes place. To help keep the final images clear, the person must lie very still during the whole test.
A special substance called a contrast agent is often given before or during the test. The contrast agent is used to enhance internal structures and improve image quality. Typically, this agent is injected into a vein in the arm.
The scanning process is painless. However, the part of the body being imaged may feel a bit warm. This feeling is harmless and is nothing to be concerned about. The person will hear loud banging and knocking noises during many stages of the exam. Earplugs are provided for people who don't like the noises.
After the test, the person is asked to wait until the images are viewed to see if more pictures are needed. If they look OK, the person can leave.
Who is a candidate for the test?
A cranial MRI can be used for several reasons. It is the most sensitive type of exam to identify:How is the test performed?
Before the test, the doctor will ask if the person:A woman will also be asked if she might be pregnant.
As the test begins, the person lies on a flat platform. The platform then slides into a donut-shaped machine where the scanning takes place. To help keep the final images clear, the person must lie very still during the whole test.
A special substance called a contrast agent is often given before or during the test. The contrast agent is used to enhance internal structures and improve image quality. Typically, this agent is injected into a vein in the arm.
The scanning process is painless. However, the part of the body being imaged may feel a bit warm. This feeling is harmless and is nothing to be concerned about. The person will hear loud banging and knocking noises during many stages of the exam. Earplugs are provided for people who don't like the noises.
After the test, the person is asked to wait until the images are viewed to see if more pictures are needed. If they look OK, the person can leave.
Preparation & Expectations
What is involved in preparation for the test?
Before the test, the person is asked to remove all metal objects that might affect imaging. These items include jewelry, hearing aids, hairpins, eyeglasses, and removable dental work. Also, the person should inform the MRI technologist about any previous surgery that required placement of metal, such as a hip pinning. Internal metal objects that cannot be removed may distort the final images. Since the magnetic field can damage watches and credit cards, these objects are not taken into the MRI scanner. Food and fluid do not need to be restricted before an MRI.Results and Values
What do the test results mean?
A special doctor called a radiologist analyzes the MRI images. Cranial MRIs can reveal the size and location of tumors, blood vessel abnormalities, hemorrhages, and other soft-tissue problems. MRI is useful in evaluating bony disorders that affect the skull. The person's doctor and the radiologist will use this information to help guide the next course of action.Attribution
Author:Stephanie Slon, BA
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:06/06/02
Reviewer:Kathleen A. MacNaughton, RN, BSN
Date Reviewed:10/10/02
Pagana, Kathleen D. and Timothy J. Pagana, Mosby's Manual of Diagnstic and Laboratory Tests, St. Louis, 1998.
"MR Imaging (MRI) - Head,"Radiological Society of North America (RSNA), 2000.
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:06/06/02
Reviewer:Kathleen A. MacNaughton, RN, BSN
Date Reviewed:10/10/02
Sources
"MR Imaging (MRI) - Head,"Radiological Society of North America (RSNA), 2000.
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