The impact of electrode area, contact impedance and boundary shape on EIT images

Abstract

Abstract. Electrical Impedance Tomography (EIT) measures the conductivity distribution within an object based on the current applied and voltage measured at surface electrodes. Thus, EIT images are sensitive to electrode properties (i.e. contact impedance, electrode area, and boundary shape under the electrode). While some of these electrode properties have been investigated individually, this paper investigates these properties and their interaction using Finite Element Method (FEM) simulations and the Complete Electrode Model (CEM). The effect of conformal deformations on image reconstruction when using the CEM was of specific interest. Observed artifacts were quantified using a measure that compared an ideal image to the reconstructed image, in this case a nonoise reconstruction that isolated the electrodes' effects. For electrode contact impedance and electrode area, uniform reductions to all electrodes resulted in ringing artifacts in the reconstructed images when the CEM was used, while parameter variations that were not correlated amongst electrodes resulted in artifacts distributed throughout the image. When the boundary shape changed under the electrode, as with non-symmetric conformal deformations, using the CEM resulted in structured distortions within the reconstructed image. Mean electrode contact impedance increases, independent of inter-electrode variation, did not result in artifacts in the reconstructed image.

Shape Deformation in Two-Dimensional Electrical Impedance Tomography

“…This observation clarifies one source of the artifacts observed due to movement of the boundary [12].…”

“…This provides an adequate and necessary correction for acceptable reconstruction of the conductivity. We also observe the effect of the size of the electrodes and note that the area (or length in two dimensions) of the electrodes is not preserved by conformal mappings [12]. In order to validate these results experimentally, we develop a deformable phantom from which we test the theoretical and simulated results.…”

Improving the performance of primal--dual interior-point method in inverse conductivity problems

“…The 32 electrodes are equally divided into 2 planes. The placement of the electrodes as well as the measurement protocol was conducted based on the planar strategy discussed in Graham and Adler [32]. The model has a background conductivity of 1 Sm −1 .…”

An instrumental electrode model for solving EIT forward problems

“…The BCs we used to obtain the results in section 4 are very similar to the Gap electrode model (Boyle and Adler 2011) and errors introduced by the quasi-static approximation (or the full Maxwell effect, as we named it in the previous sections) can therefore be estimated independently and separately from any errors caused by electrode models.…”