Myocardial contrast echocardiography (MCE) does not use radioactivity. It uses sound waves like standard echocardiography. However, with MCE patients receive an injection of a "contrast agent" directly into the blood stream through a vein. The contrast agent, called Optison, is made of tiny microbubbles smaller than red blood cells. The echocardiogram can detect these microbubbles in the small blood vessels of the heart muscle and allow researchers to find areas of the heart receiving less blood flow than others.