The Four-Electrode Resistivity Technique as Applied to Cardiac Muscle

Design of a multi-electrode array to measure cardiac conductivities

“…The array is aligned with the longitudinal and transverse fibre directions. The dimensions of the array given in Figure 2 were chosen because the potential measurements required to obtain the conductivities need to be made at distances less than or equal to the space constant of the tissue (referred to as closely spaced), as well as at distances greater than the space constant (referred to as widely spaced) [19]. Johnston et al [12] found that that a two pass protocol is required to find the desired parameters accurately.…”

“…Johnston et al [12] found that that a two pass protocol is required to find the desired parameters accurately. On the first pass, potentials are stimulated and measured on a subset of electrodes that are closely spaced (0.5 mm) to give the extracellular conductivities [19]. These closely spaced electrodes are shown in plan view in Figure 3(a), along with the source and sink electrodes.…”

“…Many techniques for finding the bidomain conductivities are based on the so-called four electrode technique [26,19], which uses four collinear equispaced electrodes. Current is applied to the outer pair of electrodes and measurements are made on the inner pair.…”

“…This technique is used in two ways to obtain the four conductivities. In the first method, measurements are made with the array aligned in both the longitudinal and transverse directions, while also varying the distance between electrodes to be both less than and greater than the space constant of the tissue [19]. The second approach is to use electrode spacings of the order of the space constant and apply ac current with variable frequency [16].…”

Model of electrical conductivity of skeletal muscle based on tissue structure

“…Recently PLONSEY and BARR (1982) analysed the fourelectrode method for homogeneous bidomain media. In this approach it was supposed that current is redistributed between intra-and extracellular space, thought to be continuously mixed.…”