The passive DC conductivity of human tissues described by cells in solution

The electrical conductivity of human tissue at low frequencies is discussed when a uniform electric field is applied to some tissue containing many ce lls. Human tissue is described as a suspension of particles in a conducting solution. Relations are derived for the apparent conductivity of a cell su rrounded by a membrane. These relations can he used to estimate the accurac y of a model that considers the cell as a non-conducting particle. Usually, a tissue is composed of several types of particles. A relationship that expresses the effective conductivity of a suspension of one type of e llipsoidal particles could be found in the literature. The orientation of t he particles could be uniform or they could be randomly distributed. For no n-conducting particles, this expression is known as Archie's law. The expre ssion is extended such that also the effective conductivity of a suspension of various types of particles can be calculated. The result is evaluated f or the cortex of the brain using experimental data given in the literature. (C) 2001 Elsevier Science B.V. All rights reserved.