MRI: Magnetic Resonance Imaging

MRI stands for "magnetic resonance imaging." An MRI is a type of medical imaging technology that uses magnetic fields. To produce an MRI image, the patient's body is placed in a strong magnetic field. This makes certain atoms in the body produce signals that can be detected by special radio equipment in the MRI machine. A computer then creates an image of the part of the body under study. Since the powerful magnetic fields used can cause problems with hip implants or heart pacemakers, people with these or other metallic objects in the body should not have MRIs performed without special precautions.

MRIs are primarily used in medical imaging to visualize the structure and function of the body. It provides detailed images of the body in any plane. MRI has much greater soft tissue contrast than computed tomography (CT) making it especially useful in neurological, musculoskeletal, cardiovascular, and oncological imaging. Unlike CT it uses no ionizing radiation, but uses a powerful magnetic field to align the magnetation of hydrogen atoms in the body. Radio waves are used to systematically alter the alignment of hydrogen atoms to produce a rotating magnetic field detectable by the scanner. Scientists sill use the term NMRI when discussing non-medical devises operation on the same principals.

One of the contributors to modern MRI technology, Paul Lauterbur, originally named the technique zeugmatography, a Greek term meaning "that which is used for joining." The term referred to the interaction between the static and the gradient magnetic fields necessary to create an image, but no surprisingly this term was not adopted.

This signal can be manipulated by additional magnetic fields to build up enough information to reconstruct an image of the body. Magnetic Resonance spectroscopy is used to measure the levels of different metabolites in the body tissue. The MR signal produces a spectrum of resonances that correspond to different molecular arrangements of the isotope being "excited." This signature is used to diagnose certain metabolic disorders, especially those affecting the brain as well as providing information on tumor metabolism. Magnetic resonance imaging was developed from knowledge gained in the study of nuclear magnetic resonance. In its early years the technique was referred to as nuclear magnetic resonance imaging (NMRI). However, as the work nuclear was associated with ionizing radiation exposure, it is generally now referred to simply as MRI.