GOALI: Development of an Ultrasound-Based System for Dynamic Intra-Coronary Plaque Characterization

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9902011IlegbusiAlthough all segments of the coronary artery tree are exposed to the same systemic risk factors (high LDL cholesterol, hypertension, nicotine metabolites, etc.), all the clinically important aspects of coronary heart disease are manifest as local phenomena at specific locations within the coronary tree. Most notably: The initial atherosclerotic lesions appear eccentrically at bends and near bifurcations of the coronary arteries. Lesion progression is most commonly eccentric and localized, at least until the most advanced stages of the disease. Myocardial infarction (i.e. heart attack) occurs as a result of rupture of a specific lesion, often one that does not occlude more than 50% of the artery, followed by the formation of a lumen occluding thrombus (blood clot) over the lesion.Extensive study of the post-mortem coronary arteries has made it clear that all of these phenomena are intimately dependent on the detailed blood flow pattern, primarily the shear stress exerted by the blood on the endothelial lining of the artery. Low shear stress promotes initial atheroma formation and growth while high shear stress and (probably) shear stress gradient promote plaque rupture with subsequent thrombus formation on potential artery occlusion.To date, it has been impossible to investigate local blood flow and shear stress patterns in vivo, either in humans or experimental animals, because the insertion of a measuring catheter into the coronary artery completely distorts the flow-field being measured, while current magnetic resonance imaging techniques (MRI) do not have adequate resolution. We propose developing an ultrasound-based system for determining hemodynamic characteristics and atherosclerotic plaque growth in real time. First, the three-dimensional anatomy of the artery will be determined by reconstructing the image data obtained after directional atherectomy ultrasound and biplane coronary angiography. This luminal geometry will then be processed into a grid structure suitable for use in computation. The detailed intravascular flow characteristics will be obtained from numerical solution of the transport equations governing the conservation of mass and momentum. The image processing and numerical models will be verified independently and the final results will be recorded in a database and displayed on the computer to follow the progression of atherosclerotic plaque. The long-term objective of the proposal is to provide a tool with which the relationship between hemodynamics and atherosclerotic plaque can be further investigated. We envisage that an award will provide leveraging to seek additional funds to test the system thus developed through animal studies. This proposal is a collaborative program between Northeastern University, with expertise in numerical modeling and image analysis, two Harvard affiliated hospitals, with expertise in cardiology, ICUS and biplane angiography, and Quinton Instruments Co. with expertise in medical instrumentation. Quinton will closely advise the project on the practical aspects of integrating our system with both hemodynamic and imaging systems. This will accelerate the time-to-market of our system and ensure that it is compatible with the needs of a broad spectrum of catheterization laboratories worldwide. If the project is successful, it will be a logical addition to the Quinton product line. Our collaborators at the hospitals will perform simultaneous ICUS and biplane angiography to provide image data. The project is expected to be completed in 36 months.