Practical comparisons of EIT excitation protocols with applications in high-contrast imaging

In the field of electrical impedance tomography (EIT), numerous studies have aimed at the optimal excitation/measurement strategies for improving conductivity distribution imaging, particularly in the applications involving highly contrasted materials. These studies focus on the conditions to be imposed on the currents fed into the electrodes and on their measurement counterparts, while making use of various quantitative optimal criteria. While most EIT systems rely on a sequential excitation at neighboring electrodes with measurements at the remaining ones, some alternative excitation strategies, or protocols, have also proven to be effective and easy to implement using modern hardware. In this context, the present study aims at confronting some of the predominant EIT excitation protocols on a practical system that is dedicated to the imaging of media with highly contrasted material components, i.e. with large variations of the conductivity field. More specifically, the so-called adjacent, opposite, full-scan and trigonometric excitation strategies are considered here and assessed on a number of criteria, which are: complexity of a practical implementation, number of independent measurements, amplitude of the measured responses, sensitivity distribution and quality of the final reconstructed images. For each of these excitation protocols, numerical simulations and static experiments with test objects placed in the EIT sensor considered are carried out using various conductivity profiles, while reconstructed images are evaluated both qualitatively and qualitatively. Our results highlight the preeminence of the full-scan and trigonometric strategies, which are characterized by high response signals and satisfying overall sensitivities. Moreover, for the studied configurations in both numerical simulations and static experiments, the full scan and trigonometric strategies lead to improved contrasts in the reconstructed images of the phases distribution.