Alternate Names : MRI, Head, MRI, Cranial, Cranial Magnetic Resonance Imaging, Magnetic Resonance Imaging, Cranial, Magnetic Resonance Imaging, Head
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.
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:
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
How is the test performed?
Before the test, the doctor will ask if the person:
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.