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In Vitro Atherosclerotic Plaque Characterization by Acoustic Impedance Monitoring, Part I: Sensor Modeling, Design, and Fabrication

Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305, USA, rdugnani{at}stanfordalumni.org

F.K. Chang

Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305, USA

This investigation aims at developing a technique to diagnose the presence of plaque in arteries by measuring the variations of the electromechanical impedance of a piezoelectric (PZT) sensor in contact with the arterial surface. The proposed technique makes use of either one or multiple PZT sensors integrated on a balloon and used prior to percutaneous transmural angioplasty interventions. The system we envision consists of two components: the active, miniaturized PZT sensors (surface-mounted on an angioplasty balloon), and the computer and software. In the proposed technique, the angioplasty balloon with the wall-mounted sensor(s) is inflated in the artery to make contact with the plaque. Initially, low pressure is used not to disrupt the plaque. The diagnostic test feeds an electrical signal that excites the sensors; by analyzing the sensors' response, information on features and properties of the plaque is obtained. Doctors will use this information to recognize unstable plaque prior to full pressurization of the angioplasty balloon. The first part of the article describes the procedure used in designing a sensor for the detection of unstable plaque by the impedance method. Both finite element methods and an analytical model — a modified version of the Krimholtz—Leedom—Matthaei model (Krimholtz et al., 1970) — are utilized in the design of the sensor. An appropriate fabrication technique for manufacturing small-scale PZT sensors is also proposed for use in smaller arteries such as the coronary arteries. Experimentation and verification of the proposed technique is presented in the second paper stemmed from this investigation.

Key Words: angioplasty • plaque detection • unstable plaque • percutaneous transmural angioplasty (PTA) • acoustic impedance • atherosclerosis detection • diagnostics technique • piezoelectric sensors • PZT.

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