During Magnetic Resonance Imaging the patient is placed inside a giant magnet and is exposed to radio waves. Hydrogen nuclei in the body behave as tiny magnets and orient themselves with the external magnetic field. They are forced out of alignment by radio waves and the time it takes for them to realign gives clues to disease processes. The term “nuclear” referred to the nucleus of hydrogen atoms and had nothing to do with radioactivity. Public fear of radiation forced the name change from “Nuclear Magnetic Resonance Imaging” to “Magnetic Resonance Imaging (MRI).”
