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To win the battle against heart disease, cardiologists need better ways to identify the composition of plaque that is 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 plaque does not always result in constricted vessels. Thus, 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 the risk of plaque rupture.

Professor Laura Marcu's lab in the Department of Biomedical Engineering at University of California - Davis has now combined intravascular ultrasound with fluorescence lifetime imaging (FLIm) in a single catheter probe that can image the tiny arteries of a living heart. The new catheter can simultaneously retrieve structural and biochemical information about arterial plaque that could more reliably predict heart attacks.

An optical fiber in the catheter sends short laser pulses into surrounding tissue, which fluoresces with tiny flashes of light in return. Different kinds of tissue (collagen, proteins, lipids) emit different amounts of fluorescence. At the same time, an ultrasound probe in the catheter records structural information about the blood vessel. The combination FLIm-IVUS imaging catheter provides a comprehensive insight into how atherosclerotic plaque forms, aiding diagnosis and providing a way to measure how plaques shrink in response to therapy.

The new catheter has been tested in living swine hearts and samples of human coronary arteries. The catheter used in the study is flexible enough to access coronary arteries in a living human following standard procedures. It does not require any injected fluorescent tracers or any special modification of the catheterization procedures. Marcu's group is working to obtain FDA approval to test this new intravascular technology on human patients.

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