Magnetic Resonance Imaging (MRI)
What is it?
Magnetic resonance imaging (MRI) is a painless
diagnostic test that uses a strong magnetic field to
produce extremely detailed images of the structures inside
the body. MRI technology can “see” inside of the bones, as
well as provide a clear picture of the tissues beyond the
bones.
Who needs this procedure?
An MRI is a very effective tool for detecting brain
tumors, signs of a previous stroke, bleeding,
abnormalities in the brain and spinal cord, bone cancer,
and injuries to the bones, joints, and soft tissues. It is
also used to diagnose neurological diseases such as
multiple sclerosis, as well as heart disease and eye,
nose, and ear disorders. MRI is needed when x-rays cannot
provide adequate pictures of the structure being studied,
or when repeated scans are needed and there is concern
over excessive exposure to radiation.
How do I prepare for this procedure?
While there are no special preparations for this
procedure, there are some cases in which MRI may not be
recommended. You cannot have MRI if you have any metal in
your body, such as metal plates, pins, or fragments, which
will attract the magnet. You also cannot have MRI if you
have a pacemaker because the MRI may damage it. The
effects of magnetic waves on an unborn child have not been
determined. For this reason, you should let your doctor
know if you are pregnant before having this procedure.
Also tell your doctor know if you have difficulty being in
small spaces (claustrophobia).
How is this procedure performed?
Before the procedure begins, you will be asked to
remove any clothes that have any metal fasteners, such as
zippers, snaps, or hooks, and put on a gown. You will also
need to remove any metal jewelry. Small transmitters,
which send and receive radio waves, are placed on the area
being studied. If you are having MRI of the head or neck
area, you may wear a small helmet-like hat. You may also
be monitored for vital signs, such as respiration and
heart rate. An MRI machine looks like a large, hollow tube
with a padded table sticking out of it. As you lie on the
table, it moves slowly into the tube. It is very important
that you lie very still during the test or the pictures
will be blurry. You may be gently strapped to the table to
help you lie still. Right outside of the MRI room is a
smaller room with a window in it. The radiologist sits in
this room and controls the MRI equipment. A microphone
allows the radiologist to talk to you throughout the
procedure. During the MRI test, the machine directs
magnetic and radio waves at the part of your body that is
being studied. You cannot feel these waves, but as they
pass through your body they create a picture that is seen
on a computer monitor. Many pictures are taken, and each
one provides a view of a different layer of your body. An
MRI machine is noisy. You will be given earphones to wear
so you can listen to music during the procedure. If you
are claustrophobic, your doctor may give you a mild
sedative before the test. Or, you may be able to have an
open MRI, which does not require you to be inside a tube.
Some patients are injected with a dye, called a contrast
agent, that makes the part of the body being studied show
up better. Tell your doctor if you have any known
allergies to this type of dye. In most cases, MRI takes
between 30 and 90 minutes.
What can I expect after the procedure?
MRI has no side effects. Your healthcare provider will
notify you when he or she has received the results.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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