How It Is Done
A magnetic resonance imaging (MRI) test is usually done by an MRI
technologist. The pictures are usually interpreted by a
radiologist. But some other types of doctors can also
interpret an MRI scan.
You will need to remove all metal objects (such as hearing aids,
dentures, jewellery, watches, and bobby pins) from your body, because these
objects may be attracted to the powerful magnet used for the test.
You will need to take off all or most of your clothes, depending on
which area is examined (you may be allowed to keep on your underwear if it is
not in the way). You will be given a gown to use during the test. If you are
allowed to keep some of your clothes on, you should empty your pockets of any
coins and cards (such as credit cards or ATM cards) with scanner strips on
them, because the MRI magnet may erase the information on the cards.
During the test you will lie on your back on a table that is part
of the MRI scanner. Your head, chest, and arms may be held with straps to help
you remain still. The table will slide into the space that contains the magnet.
A device called a coil may be placed over or wrapped around the area to be
scanned. A special belt strap may be used to sense your breathing or heartbeat.
This triggers the machine to take the scan at the right time.
You may wear cloth straps (harness) that can be pulled during the
test to see how your spine moves in response to tension or weight.
Some people feel nervous (claustrophobic) inside the MRI magnet. If
this keeps you from lying still, you can be given a medicine (sedative) to help
you relax. Some MRI machines (called open MRI) are now made so that the magnet
does not enclose your entire body. Open MRI machines may be helpful if you are
claustrophobic, but are not available everywhere. The pictures from an open MRI
may not be as good as those from a standard MRI machine. See pictures of a
standard
MRI machine
and an
open MRI
machine
.
Inside the scanner you will hear a fan and feel air moving. You may
also hear tapping or snapping noises as the MRI scans are taken. You may be
given earplugs or headphones with music to reduce the noise. It is very
important to hold completely still while the scan is being done. You may be
asked to hold your breath for short periods of time.
During the test, you may be alone in the scanner room. But the
technologist will watch you through a window. You will be able to talk with the
technologist through a two-way intercom.
If contrast material is needed, the technologist will inject it,
usually through an
intravenous (IV) line in your arm. The material may be
given over 1 to 2 minutes. Then more MRI scans are done.
An MRI test usually takes 30 to 60 minutes but can take as long as
2 hours.