Basic Problems of the Electrical Measurement of Biological Tissues

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Electrical properties of living tissues have been studied both theoretically and experimentally by many researchers. But even now, there are many problems which remain unsolved.Many researchers have tried to apply the electrical impedance method to clinical measurement and therapy, such as impedance Plethysmography, impedance cardiography, impedance CT, fluid volume measurement, hyperthermia, estimation of the effects of electromagnetic wave and so on. However, we have only a few impedance method which is sufficient and is widely and reliably used in clinical field. There are many causes for this problem. The most important problems is the lack of knowledge about biological tissues, because of the complexity of biological tissues. In this research, we discussed the electrical properties of cell suspension as a model of biological tissues. At first the electrical properties are theoretically discussed. And then the electrical characteristics of blood are experimentally investigated because of the simplicity of blood structure. These theoretical and experimental results could be widely used for the application of electrical method to clinical measurement and therapy. One of the most interesting applications of impedance method is the estimation of fluid distribution in the body. Especially the estimation of intra- and extra-cellular fluid distribution is very important for clinical diagnosis. This measurement method is based on β dispersion phenomenon. Therefore. frequency characteristics of the electrical properties of biological tissues should be well investigated.In this research, we theoretically discussed the electrical properties of cell suspension, and we could accurately measure the intra- and extra-cellular fluid distribution.