Vascular ultrasound allows for the evaluation of blood circulation within the arms and legs via a painless and completely noninvasive imaging test. The test works by directing invisible sound waves at the blood vessels, where blood cells reflect them back to create a picture on a computer monitor. All that is required of the patient is for him or her to lie down on an exam table where a special gel is applied and a transducer device controlled by the physician or radiologist is moved across the area to be examined. This test may be used to determine the location and severity of a narrowed artery and/or to determine how well blood is flowing to a newly transplanted organ. It is also sometimes used to check the arteries within the neck that supply blood to the brain, or for “mapping” purposes to identify blood vessels in the lower part of the body that may be used in a coronary artery bypass graft procedure.