Magnetic resonance imaging: A special radiology technique designed to image internal structures of the body using magnetism, radio waves, and a computer to produce the images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet. The magnet creates a strong magnetic field that aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal that is detected by the receiver portion of the MRI scanner. A computer processes the receiver information, and an image is produced. The image and resolution is quite detailed and can detect tiny changes of structures within the body.
MRI images tend to be quite clear, particularly those of the soft tissue, brain and spinal cord, abdomen and joints, and they may be superior to routine X-ray images of such structures.
An MRI is painless and has the advantage of avoiding x-ray radiation exposure. There are no known risks of an MRI. The benefits of an MRI relate to its precise accuracy in detecting structural abnormalities of the body.
Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet. Metallic chips, materials, surgical clips, or foreign material (artificial joints, metallic bone plates, or prosthetic devices, etc.) can significantly distort the images obtained by the MRI scanner. Similarly, patients with artificial heart valves, metallic ear implants, bullet fragments, and chemotherapy or insulin pumps should also not have an MRI.
Claustrophobia can be a problem. For an MRI, patients lie in a closed area inside the magnetic tube. Some patients experience a feeling of claustrophobia.
In 2003 the Nobel Prize in Physiology or Medicine was awarded to the American Paul C. Lauterbur (1929-) and the Briton Sir Peter Mansfield (1933-) "for their discoveries concerning magnetic resonance imaging." |
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