MRI scanner. View of a woman undergoing a scan in a magnetic resonance imaging (MRI) scanner. MRI, also called Nuclear Magnetic Resonance (NMR), is a diagnostic technique that produces slice" images through the body. The patient lies beneath a powerful magnet which produces a powerful magnetic field. This field makes the nuclei of the hydrogen atoms in the patient's body line up parallel to each other. Radio wave pulses emitted by the scanner knock the hydrogen nuclei out of alignment. As they fall back into alignment they produce a radio signal which can be detected. MRI is useful for studying soft tissues like the brain and spinal cord."