(MRI)
a diagnostic technique based on analysis of the absorption and transmission of high-frequency radio waves by the hydrogen in water molecules and other components of tissues placed in a strong magnetic field (see nuclear magnetic resonance). Using modern high-speed computers, this analysis can be used to 'map out' the variation in tissue signals in any plane and thus produce images of the tissues in most parts of the body. MRI can be used for the noninvasive diagnosis and treatment planning of a wide range of diseases, including cancer, and is increasingly used to guide interventional radiological procedures. It has the advantage that it does not use potentially harmful ionizing radiation, such as X-rays. However, MRI should not be undertaken in patients with pacemakers, metal clips, or metal heart valves because the strong magnetic field may cause damage. See interventional radiology, minimally invasive surgery.
Medical dictionary. 2011.