- Magnetic resonance imaging (MRI). This test uses a magnetic field and radio waves to obtain images of body tissues and organs. The patient lies on a table that can slide in and out of the scanner, wearing earplugs to muffle loud knocking and thumping sounds that occur during the scanning process. The procedure lasts about 45 minutes, during which time the patient will be asked to lie still for up to 15 minutes at a time.