- Magnetic resonance imaging (MRI): This test combines a powerful magnet with an advanced computer system and radio waves to produce accurate, detailed pictures of organs and tissues. During the scan, the subject lies on a table in a narrow cylinder containing a magnetic field, wearing ear plugs to muffle loud noises that occur with electrical switching of the magnetic fields. He or she can speak with a staff member via an intercom system at all times during the procedure. In addition to standard MRI, subjects may have newer MRI tests, such as diffusion tensor MRI and magnetic resonance spectroscopy.