- Magnetic resonance imaging (MRI) of the brain - a test that uses strong magnetic fields and radio waves to generate images of the brain. The patient lies still on a stretcher inside a cylinder containing a magnetic field. The patient's head is stabilized with a plastic strap and foam pads. During the imaging, a substance called gadolinium-DTPA is injected into an arm vein through a catheter (thin plastic tube). This substance is used to enhance the images.