MEDICAL IMAGING

MRI (Magnetic Resonance Imaging)

Although an MRI scanner may look like a CT scanner, MRI produces images in a very different way. MRI does not use radiation, but rather uses a very strong magnet and pulsed radio waves to image the patient's body. During an MRI, the MRI technologist may place devices called "coils" in contact with the patient's body. The patient then goes into the opening in the magnet. Once inside the magnet, the coils emit radio waves that "excite" atoms inside the patient. When these atoms "relax," they give off radio waves. The coils detect the radio waves coming from the patient and send the information to a computer that produces the images. MRI is very good at seeing differences between soft tissues--especially for the brain, the spine and joints. The MRI scanner makes many loud noises during a scan, so patients wear headphones and listen to music during their scan. Because of the strong magnet used, some patients who have metal in their body may not be able to have an MRI. Patients may have to have X-rays of their eyes (orbits) before their MRI exam to be certain that there are no metal fragments. Nothing metallic should ever enter the MRI scanning room, because it could actually fly across the room, causing injury to anyone in the way.

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