Cardiovascular disease is the number one killer of Americans, claiming over 500,000 lives annually. These deaths occur when the fibrous cap of an atherosclerotic plaque ruptures in the later stages of the disease. Current screening tests for the diagnosis of coronary atherosclerosis is limited. Coronary angiography, the "gold standard" employed to assess the severity of coronary disease in symptomatic patients, reveals only the degree of luminal narrowing, and fails to visualize the arterial wall. Additionally, arterial remodeling prevents many plaques from being detected by coronary angiography. The overall goal of this proposal is to develop two pragmatic ultrasound-imaging techniques (neovascular imaging, and elastography imaging) to identify life threatening atherosclerotic plaques. The microvascular networks or vasa vasorum of developing atherosclerotic plaques may function as a conduit for the migration of leukocytes and plasma components into the arterial wall or into the endothelium on the arterial surface. These inflammatory cells, if allowed to accumulate, will weaken the fibrous cap. The resolution of intravascular ultrasound (IVUS) is not sufficiently high to visualize plaque neovasculature;therefore, we propose to develop a microbubble ultrasound contrast that binds preferentially to newly formed blood vessels. More specifically, we propose to conjugate a microbubble contrast agent to a peptide with the NGR-homing sequence that binds to CD13, and a monoclonal antibody, DC101, that binds to the VEGF receptor-2. The conjugated microbubbles will be visualized by employing the second harmonic contrast imaging mode, which we propose to implement on a commercial ultrasound IVUS scanner. The mechanical behavior of stable plaques is noticeably different from those of stable plaques. Circumferential stress will accumulate at the junction between the normal intima, and the fibrous cap overlaying the lipid pool in unstable plaques;whereas this does not occur in stable plaques. To differentiate between stable and unstable plaques based on their mechanical behavior we propose to visualize the stress distribution within vascular tissue using a novel prototype system for intravascular ultrasonic elastographic imaging. An atherosclerotic animal model will be employed to assess a) the sensitivity and specificity of detecting life-threatening plaques with both imaging approaches as standalone methods will be assessed relative to a combined microvascular-elastography imaging approach, and b) the feasibility of predicting the propensity of plaque to rupture based on the three imaging approaches. A successful out come of the proposed may prove to be beneficial to the over 50 million Americans who are unaware that they may be suffering from advance coronary atherosclerosis and should be placed on a lipid-lowering dietary and pharmacological treatment.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Biomedical Imaging Technology Study Section (BMIT)
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Buxton, Denis B
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University of Rochester
Engineering (All Types)
Schools of Engineering
United States
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Doyley, M M; Parker, K J (2014) Elastography: general principles and clincial applications. Ultrasound Clin 9:1-11
Shekhar, Himanshu; Awuor, Ivy; Thomas, Keri et al. (2014) The delayed onset of subharmonic and ultraharmonic emissions from a phospholipid-shelled microbubble contrast agent. Ultrasound Med Biol 40:727-38
Richards, Michael S; Doyley, Marvin M (2013) Non-rigid image registration based strain estimator for intravascular ultrasound elastography. Ultrasound Med Biol 39:515-33
Shekhar, Himanshu; Doyley, Marvin M (2013) The response of phospholipid-encapsulated microbubbles to chirp-coded excitation: implications for high-frequency nonlinear imaging. J Acoust Soc Am 133:3145-58
Shekhar, Himanshu; Rychak, Joshua J; Doyley, Marvin M (2013) Modifying the size distribution of microbubble contrast agents for high-frequency subharmonic imaging. Med Phys 40:082903
Sridharan, Anush; Eisenbrey, John R; Machado, Priscilla et al. (2013) Delineation of atherosclerotic plaque using subharmonic imaging filtering techniques and a commercial intravascular ultrasound system. Ultrason Imaging 35:30-44
Hansen, Hendrik H G; Richards, Michael S; Doyley, Marvin M et al. (2013) Noninvasive vascular displacement estimation for relative elastic modulus reconstruction in transversal imaging planes. Sensors (Basel) 13:3341-57
Shekhar, Himanshu; Doyley, Marvin M (2012) Improving the sensitivity of high-frequency subharmonic imaging with coded excitation: a feasibility study. Med Phys 39:2049-60
Doyley, M M (2012) Model-based elastography: a survey of approaches to the inverse elasticity problem. Phys Med Biol 57:R35-73
Eisenbrey, John R; Sridharan, Anush; deMuinck, Ebo D et al. (2012) Parametric subharmonic imaging using a commercial intravascular ultrasound scanner: an in vivo feasibility study. J Ultrasound Med 31:361-71

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