A magnetic resonance imaging or MRI is a test that generates images of the brain and adjacent tissue by use of radio waves and magnetic fields, states MedlinePlus. It's also known as an MRI of the head and is applicable in diagnosing brain conditions such as brain tumors and stroke.
Prior to the test, the doctor sometimes injects the patient with a special dye for image clarity. During a brain MRI, a patient lies on a table, and the table slides into a scanner for the brain images to form. The test usually takes about 30 to 60 minutes to complete, as MedlinePlus explains.