A Basic Study of Electrical Impedance Spectroscopy for Intravascular Diagnosis and Therapy Monitoring of Atherosclerosis

The goal of this thesis is the conception, development and evaluation of an electrical impedance-based method for the diagnosis and therapy monitoring of arthrosclerosis. To understand basically how the change of tissue parameters on the cellular level can be characterized electrically by impedance spectroscopy, theoretical and experimental investigations based on a single cell/micro hole model were performed. The results indicate that changes in the tissue parameters on the cellular level like cellular shape and membrane integrity affect the electrical characteristics of tissues, and that impedance spectroscopy can be used to characterize electrically the effects of atherosclerosis related to these parameters. In vitro experiments based on adipogenic stem cell differentiation and virus infection showed that the cellular alterations in cell assemblies on atherosclerotic pathology (e.g. disruption of cell layer by virus infection, accumulation of fat cells) are well reflected in the measured impedance data. A balloon impedance catheter with integrated flexible microelectrodes was developed and used for experimental investigation in vitro and in situ and considered for theoretical investigations respectively. For the first time, it was successfully demonstrated that the aortas containing fatty plaques can be distinguished from normal aortas by intravascular impedance measurement with the developed balloon impedance catheter system.