The characteristic features of the magnetic fields used in magnetic resonance imaging (MRI) machines in regards to the biological effects or medical application are discussed. MRI machine employs all three types of fields in order to accomplish three-dimensional imaging for medical diagnostics. The largest of the three types of the MRI magnetic fields is the static magnetic field. The intense static magnetic fields are generally considered safe for the patients and the attending personnel. The powerful MRI magnets can pull all kinds of ferromagnetic objects from the hands of careless workers into the scanner. The U.S. Food and Drug Administration (FDA) also maintains a record of MRI accidents.
