n. the *SI unit of magnetic flux density, equal to a density of 1 weber per square metre. This unit is important in *magnetic resonance imaging (MRI). Most MRI scanners operate between 0.1 and 2.5 T, but some modern research scanners may go up to 7 T. Symbol: T.
(MRI) a diagnostic imaging technique based on the emission of electromagnetic waves from the body when the patient is placed in a strong magnetic field and exposed to radiofrequency radiation (see nuclear magnetic resonance). The strength of the magnetic field is measured in *teslas. Most images rely on the signal from hydrogen in water, which is particularly strong, although other elements with unpaired outer electrons can be used (see magnetic resonance spectroscopy). A major advantage over *computerized tomography is the lack of X-rays, which reduces exposure to ionizing radiation. MRI is used for the noninvasive diagnosis and treatment planning of a wide range of diseases and also to guide interventional radiological procedures. See also functional magnetic resonance imaging.... magnetic resonance imaging
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