Magnetic Resonance Imaging (MRI) (cont.)
During the Procedure
The study may take place on either an open scanner or a closed scanner. For an open scanner, a person lies on a table face up, and the table slides under the magnet from the side. For a closed scanner, which looks like a tube, a person lies on the table face up and goes in either head-first or feet-first, depending on what part of the body is being scanned.
The MRI scan is performed inside a large magnet, and the person lies on the table in the center. During the procedure, the machine scans the body by turning small magnets on and off. Radio waves are sent into the body. The machine then receives returning radio waves and uses a computer to create pictures of the part of the body being scanned. The radio waves used in the procedure are safe and are similar to the radio waves used in a car radio.
- The scanner can make a loud knocking sound, so people are given either earplugs or music headphones. The knocking sound is due to the small magnets in the machine being turned on and off.
- People have to hold the part of their body being scanned motionless for 30
to 60 minutes, which is the length of a typical MRI scan. If a person moves during the scan, some or all of it often has to be repeated. The scans are done in multiple parts. The technologist talks between each part to let the person know how things are going with the scan and to remind the person to hold still.
- Sedation is sometimes necessary. Infants and young children often require sedation or general anesthesia in order to remain motionless during the scan. Most older children and adults do not require any medication for relaxation or sedation. On occasion, people who are nervous or claustrophobic require oral sedation and, rarely, general anesthesia.
- Claustrophobia is a common concern. Many people wonder how far into the scanner they have to go. To get the best pictures possible, the part of the body being studied has to be in the middle of the scanner. For example, if a person is having a brain MRI, the head has to be in the middle of the scanner. If a person is having an ankle MRI, the ankle is in the scanner, but the head is not.
- Unlike older MRI scanners in which the person was placed in a long tube, many centers now offer new, "short-bore" scanners that are much shorter and more comfortable if a person is claustrophobic. For people with severe claustrophobia, medication can be given to help them relax during the scan. For those people who take medication, someone must drive them home.
Medically Reviewed by a Doctor on 8/3/2012
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