3. Magnetic resonance imaging (MRI) of the carotid arteries-The patient lies on a table in a narrow cylinder (the MRI machine) containing a magnetic field. A flexible padded sensor called a MRI coil is placed over the neck area. Earplugs are placed in the ear to muffle the loud thumping sounds the machine makes when the magnetic fields are switched. During the second half of the exam, a contrast agent (gadolinium) is injected through an intravenous catheter (flexible tube placed in a vein) to brighten the images. The heart is monitored during the procedure with an electrocardiogram.