MRI Test Procedures

Magnetic resonance imaging, or MRI, is a medical imaging technique used to diagnose and follow the progress of numerous conditions, such as stroke, Alzheimer’s or tumors. MRI provides highly refined pictures of different body parts from various angles. It can see through the bones and presents a clear picture of the brain's soft tissue structures. MRI is safe, noninvasive method that does not use radiation like many other imaging methods, but applies strong magnets instead.

Preparation

Prior to coming to the scan, a patient is asked to wash her hair and remove all makeup. No hair sprays, gels or cosmetics can be worn during the MRI scan. The patient is typically asked to wear a medical gown, but she may also be allowed to wear her own clothing if it has no metal fasteners. Before entering the room with the scanner, a patient must remove all the metal objects such as jewelry or eyeglasses. For some types of MRI scanners, the patients may be asked to fast for eight to 12 hours, but in most cases, the patient can follow her regular diet. A radiologist may also give the patient a chemical that increases the quality of the image before the scan. Although the use of this chemical has some benefits, it is rarely used. This contrast material may be swallowed or received through an injection. Another type of chemical that is sometimes given to patients before an MRI scan is a sedative. Their use is sometimes necessary if a patient is not able to stay still during the scanning or if she suffers from claustrophobia.

Procedure

In most MRI exams, a patient lies on his back on a narrow table and is moved into a long tube. This open-ended tube houses the magnet used to render the scan. Once the patient is inside the device and the radiologist and technician have left the room, the scanning can begin. Depending on the type of scanning performed, the procedure lasts between 15 and 45 minutes. When the scan is in progress, a patient will hear loud sounds and will have to remain as still as possible, but can move once more when the sounds disappear. Any movement during the scan results in unclear images that may be so poor, they cannot be used at all. For some type of exams, the patient may be asked to hold his breath for a while. After a typical MRI exam, no recovery time is necessary and the patient may resume his usual activities right away.

Precautions

MRI is safe to use with most patients but some groups may do well to avoid it. MRI scanning should not be used if there are any metal objects in the patient’s body. A patient should let the doctor know if she has, for example, cardiac pacemakers, cochlear implants, bullet fragments or broken bones fixed with screws or metal pins. Dyes used in tattoos may contain iron and heat up during the scan, and tooth fillings may distort images taken from the head, so the patient should let the doctor know about these prior to the scan. Some patients may also be allergic to the contrast material and may experience hives or itchy eyes as a result.