ABSTRACT
This paper presents the construction of a probe for immittance spectroscopy. The probe is based on the four-electrode technique. The current application electrodes are long parallel strips and have been partitioned into three segments to measure the immittance of relatively small volumes. The probe constant has been calculated assuming anisotropy of the materials examined. The experiments, based on the measurements of KCl solutions and numerical simulations (finite element method--FEM), have shown a high degree of consistency with the theoretical value. Experimental in vivo measurements on swine gluteal tissue were performed and the conductivity and permittivity reconstructed from these measurements are presented.
Subject(s)
Electric Conductivity , Electrodes , Spectrum Analysis/methods , Anisotropy , Electrophysiology , HumansABSTRACT
The construction of the cell for measurement of complex electric conductivity is described. Two-chamber and four-electrode system with temperature stabilisation is developed. Guarding chamber and electrodes are used to minimise the leakage of current from the measurement chamber. The cell construction is examined by use of Finite Element Method. The model of the measurement cell is examined in order to improve the accuracy of measurements. The calibration procedure based on measurement of reference materials is presented. The frequency range of the cell is extended to 10 MHz with acceptable level of error. The examples of results from measurement breast normal and cancerous tissues are presented.
Subject(s)
Breast Neoplasms/diagnosis , Electric Conductivity , Electric Impedance , Finite Element Analysis , Models, Biological , Signal Processing, Computer-Assisted , Bias , Calibration , Electrodes , Female , Humans , Reproducibility of ResultsABSTRACT
A FEM has been used to examine influence of tissues' conductivities and electrodes' array configurations on the results obtained by Impedance Cardiography. A Geselowitz's relationship has been applied to estimate partial contributions from each region of thorax. The obtained results have indicated the strong dependence of ICG signal on factors mentioned above. It seems that additional measurements and more advanced ICG waveform processing must be done to minimise errors in estimating parameters of mechanical work of heart by means of ICG.
