Multi-electrode stimulation and measurement patterns versus prior information of fast 3D EIT

Abdi, M. (2015). Multi-electrode stimulation and measurement patterns versus prior information of fast 3D EIT. (Unpublished Masters thesis, City, University of London)

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Abstract

Electrical Impedance Tomography or as referred to as EIT, is a typical inverse problem of estimating the unknown interior material impedance properties inside a conductive medium through measurements performed at the periphery of the containing medium. Due to its inverse nature, EIT’s poor spatial resolution is still one of its biggest downfalls since meaningful images are hard to obtain without incorporating some sort of prior information about the material distribution characteristics.

Given the ill-posedness of the EIT problem coupled with the limited number of collectable boundary voltage measurements, the resulted discrete system is heavily underdetermined and ill-conditioned. Therefore, a sensible step to overcome this problem is to collect as many measurements as the number of the finite elements composing the medium. From one hand, this is not practically possible, on the other, an increased number of measurements will contribute towards unrealistically high computational overheads both for the assembly and the inversion of the resulted dense system matrix.

For any given EIT configuration, the discrete Picard’s stability criterion can be deployed as a practical measure of the system performance against noise contaminated measurements. Herein, this study includes extensive use of this measure to quantify the performance of impedance imaging systems for various injection patterns. In effect, it is numerically demonstrated that by varying electrode distributions and numbers, little improvement, if any, in the performance of the impedance imaging system is recorded. In contrast, by using groups of electrodes in the 3D current injection process, a step increase in performance is obtained. Numerical results reveal that the performance measure of the imaging system is 29% for a conventional combination of stimulation and prior information, 97% for groups of electrodes and the same prior and 98% for groups of electrodes and a more accurate prior. Finally, since a smaller number of electrodes are involved in the measurement process, a smaller number of measurements are acquired. However, no compromise in the quality of the reconstructed images is observed.

Item Type: Thesis (Masters)
Subjects: Q Science > QA Mathematics
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: School of Engineering & Mathematical Sciences > Engineering
URI: http://openaccess.city.ac.uk/id/eprint/16089

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