Super-harmonic ultrasonic imaging of the coronary artery

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The increase in cardiovascular disease in the United States has created a need for methods that can screen high-risk patients for life-threatening plaques and assess the effectiveness of new cardiovascular drugs. Abnormal proliferation of the vasa vasorum in diseased vessels may promote the progression of atherosclerosis and increase the propensity of plaque rupture. Consequently, we and others are actively developing methods for visualizing the vasa vasorum. Contrast-enhanced ultrasound (CEU) imaging is frequently used to visualize the vasa vasorum within the carotid artery; however, the lack of sensitive high frequency broadband catheters has prevented researchers from advancing CEU to the smaller coronary artery. To overcome this technological challenge, we plan to use the principle of optomechanical transduction to develop high-performance (sensitive and broadband) tunable ultrasound catheters. Specifically, we will design and fabricate a novel high quality optomechanical resonator from silicon carbide (Aim 1). This optomechanical resonator will form the backbone of a tunable ultrasound transducer that we plan to develop (Aim 2). We will use the optomechanical resonator to detect harmonic signals (subharmonic, fundamental, second harmonic, ultra-harmonic, and super-harmonic) emitted when microbubble ultrasound contrast agents are excited with a 20 MHz piezoelectric transducer. We plan to perform phantom studies to evaluate the performance of the integrated optomechanical/piezoelectric transducer. We will use an embryonic chick model to assess the sensitivity of harmonic images created with the proposed integrated optomechanical/piezoelectric transducer and dual frequency transducers (a competing technology) to changes in vessel size and density. If successful, the proposed technology could revolutionize ultrasonic imaging by providing a novel approach for fabricating reliable broadband transducers desired by several clinical applications. Additionally, the proposed research represents a critical step towards establishing vasa vasorum imaging as a technique for evaluating the efficacy of new cardiovascular drugs.