Impedance-based diagnostic system for in vivo atherosclerotic plaque characterization

Transmural Angioplasty Balloon (TAB) is a procedure used in modern medicine to treat arteries clogged by atherosclerotic plaque. Unfortunately, not all types of plaque are good candidates for this kind of operation. If treated by TAB, plaque with a lipid pool underneath (i.e. unstable plaque) can cause complications and lead to patients' re-hospitalization or even death.; The principles for the development of a novel impedance-based technique to characterize unstable plaque are described in this work. The proposed system consists of two components: an array of active miniaturized piezoelectric sensors (PZT) surface-mounted on an angioplasty balloon, and the computer and software. During an operation, the balloon is inserted in the artery and inflated at low pressure to make contact with the plaque. An automatic diagnostic test generates a special narrow band signal and feeds it to the sensors. After the analysis of the sensors' response by the software, the information on acoustic impedance of plaque is displayed on a computer screen in real time thus aiding a correct interpretation of the plaque type prior to full inflation.; This work develops the theoretical framework needed to use impedance for plaque type characterization. Both numerical and experimental tests were performed to verify the validity of the proposed impedance approach. Results indicate that it is possible to differentiate between materials of various acoustic properties. Furthermore, both experimental and numerical data proved that by monitoring the variation of impedance through depth, the existence of a lipid pool underneath the fibrous cap (i.e., unstable plaque) can be predicted.