magnetic resonance imaging

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Related to Nuclear magnetic resonance imaging: Nuclear magnetic resonance spectroscopy

magnetic resonance imaging

(MRI), noninvasive diagnostic technique that uses nuclear magnetic resonancemagnetic resonance,
in physics and chemistry, phenomenon produced by simultaneously applying a steady magnetic field and electromagnetic radiation (usually radio waves) to a sample of atoms and then adjusting the frequency of the radiation and the strength of the magnetic field
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 to produce cross-sectional images of organs and other internal body structures. The patient lies inside a large, hollow cylinder containing a strong electromagnet, which causes the nuclei of certain atoms in the body (especially those of hydrogen) to align magnetically. The patient is then subjected to radio waves, which cause the aligned nuclei to "flip"; when the radio waves are withdrawn the nuclei return to their original positions, emitting radio waves that are then detected by a receiver and translated into a two-dimensional picture by computer. Unhampered by bone and capable of producing images in a variety of planes, MRI is used in the diagnosis of brain tumors and disorders, spinal disorders, multiple sclerosis, and cardiovascular disease. The procedure is considered to be without risk, but the scanner may interfere with pacemakers, hearing aids, or other mechanical devices. Although the images are similar in many ways to those of CAT scansCAT scan
[computerized axial tomography], X-ray technique that allows relatively safe, painless, and rapid diagnosis in previously inaccessible areas of the body; also called CT scan.
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, they are obtained without X rays or other radiation, and generally provide more contrast between normal and abnormal tissue.

magnetic resonance imaging

[mag′ned·ik ′rez·ən·əns ′im·ij·iŋ]
(engineering)
A technique in which an object placed in a spatially varying magnetic field is subjected to a pulse of radio-frequency radiation, and the resulting nuclear magnetic resonance spectra are combined to give cross-sectional images. Abbreviated MRI.
References in periodicals archive ?
They began eyeing the other helium isotope, helium-3, whose atomic nuclei spin in such a way that the substance is readily visible to nuclear magnetic resonance imaging instru- ments.
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Nuclear magnetic resonance imaging, the technology that allows physicians to look at cancer cells and brain lesions, has for the first time been used to examine core samples taken from the ocean floor.

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