To win the battle against heart disease, cardiologists need better ways to identify the composition of plaque most likely to rupture and cause a heart attack. Angiography allows them to examine blood vessels for constricted regions by injecting them with a contrast agent before X-raying them. But because plaque does not always result in constricted vessels, angiography can miss dangerous buildups of plaque. Intravascular ultrasound can penetrate the buildup to identify depth, but lacks the ability to identify some of the finer details about risk of plaque rupture.