A model of the electromechanical behavior of a myocardial region is presented. The model combines an electrophysiological, a force development and an excitation propagation model. All of these models incorporate the effects of deformation of the myocardium. An extension of the traditional bidomain model for excitation propagation is proposed. The extension describes the stretch dependency of the conductivity tensor of the intra- and extracellular space and is constructed outgoing from physically motivated assumptions, which simplify the behavior of the conductivity tensor. The extension makes usage of the deformation gradient tensor, which is a foundation in the theory of continuums mechanics. The performed simulations illustrate some effects of myocardial electromechanical behavior.
The contact free conductivity measurement is a noninvasive method to find electrical characteristics of tissue that can be used e.g. for monitoring. The system consists of an excitation coil and two sensing coils coupled together as a gradiometer. The excitation coil is driven by an alternating current. Due to this alternating magnetic field eddy currents are generated in the tissue that create a secondary magnetic field. Because of the geometrical arrangement, the induced voltage of the secondary field in the upper and the lower coil is different. The presented sensor can be used e.g. for detection of ischemic areas, monitoring wound healing or detection of hematoma beneath the skull. To demonstrate this sensor, two measurements are carried out to detect post mortem changes in a pig liver. The known characteristics from literature can be reproduced using a noncontact method. For this purpose frequencies between 50 kHz and 400 kHz are used. At a frequency of 350 kHz a phase shift of 0.3 degrees is observed post mortem after 2 to 4 hours corresponding to a conductivity change of approximately 0.4 S/m.
C. H. Riedel, M. A. Golombeck, and O. Dössel. Simulation study for the non-contact measurement of the impedance of biological tissue using an axial gradiometer. In Proc. IEEE EMBS and BMES, pp. 1748-1749, 2002
Simulation of the forward problem in Magnetic Induction Tomography (MIT) is one of the key issues in development of the technology of MIT. We simulate the process of measurement in MIT using an edge based finite element technique. We also present the simulation of this forward problem by a program, MAFIA based on finite integration technique. In both methods the same geometrical arrangements are simulated and results are compared.
M. A. Golombeck, C. H. Riedel, and O. Dössel. Calculation of the Dielectric Properties of Biological Tissue using simple Models of Cell Patches. In Biomedizinische Technik, vol. 47-1, pp. 253-256, 2002
C. H. Riedel. Planare induktive Impedanzmessverfahren in der Medizintechnik. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Dissertation. 2004
Student Theses (1)
C. H. Riedel. Modellierung der Kopplung von elektrischer Erregung und mechanischer Kontraktion von Zellen des Myocardiums. Universität Karlsruhe (TH), Institut für Biomedizinische Technik. Diplomarbeit. 2000