A non-invasive procedure that uses powerful magnets and radio waves to construct pictures of the body. Unlike conventional radiography and Computed Tomographic (CT) imaging which make use of ionizing, and hence, potentially harmful, radiation (X-rays) passing through a patient to generate images, MRI imaging is based on the magnetic properties of atoms. A powerful magnet generates a magnetic field roughly 10,000 times stronger than the Earth's. A very small percentage of hydrogen atoms within the body will align with this field. The "nuclear" in the original, and now seldom used, name refers to the proton in the nucleus of the hydrogen atom and does not imply radioactivity. When focused, short radio wave pulses are broadcast towards the aligned hydrogen atoms in tissues of interest, they will return a signal of their own. The subtle differing characteristics of that signal from dissimilar tissues combined with complex mathematical formulas solved on modern computers is what enables MRI to differentiate between various organs, and potentially, provide contrast between benign and malignant tissue. Any imaging plane, or "slice", can be projected, and then stored in a computer or printed on film. MRI can easily be performed through clothing and bones, however, certain types of metal in or around the area of interest can cause significant errors in the reconstructed images (artifact).

Alternative Names

Nuclear magnetic resonance - chest; Magnetic resonance imaging - chest; NMR - chest; MRI of the thorax