<qa>  What is the time required in the scanner?- Magnetic resonance imaging MRI: This test uses a strong magnetic field and radio waves to show structural and chemical changes in the brain. During the scan, the subject lies on a table in a narrow cylinder the scanner. The time required in the scanner is about 1 hour, during which the subject is asked to lie very still for 10 to 15 minutes at a time. He or she can speak with a staff member via an intercom system at all times during the procedure. 