An investigation of optimal performance criteria in electrical impedance tomography
An investigation of optimal performance criteria in electrical impedance tomography
In this thesis three main issues are addressed: noise performance, electrode misplacement, and image reconstruction. All of these issues are important for long term monitoring applications of Electrical Impedance Tomography (EIT).
A performance figure of merit for EIT is established based on a model of system noise. It is proposed that the figure of merit be used to characterise the noise performance of a data acquisition unit when attached to either a test object or a human subject. The figure of merit provides a criterion for judging the quality of the data and the sharpness of the image which could be achieved in specific clinical practice.
In long term in vivo EIT monitoring changes in body position affect electrode positioning which introduces artefacts into the images. Also measurement electrodes are difficult to position accurately, particularly on patients in intensive care beds. Two procedures are described to reduce these electrode induced artefacts. The first reduces the sensitivity of the reconstruction to the electrode positions, and provides a rational criterion for regularising the reconstruction. The main consequences are that smoother images are produced, the number of artefacts and their magnitude are generally reduced, and the region of interest measurements are more reliable. The second procedure aims to compensate for electrode movements that occur during data measurement, by utilising the data measured in vivo to estimate modifications to the reconstruction process. Computer simulation tests have shown that this modification produces improved image fidelity.
In most practical EIT systems the imaging algorithms use a reconstruction matrix generated from a uniform conductivity distribution. An assessment is made of the potential gains from incorporating a priori data in the reconstruction process. The results show that in the absence of precise knowledge of anatomy the assumption of uniformity is the least likely to introduce artefacts.
A major part of the thesis develops a new non-linear treatment of image reconstruction, based on the Newton-Raphson iterative procedure. By emphasising the character of the images achieved in the reconstructed solutions this work has not only achieved the best possible EIT images with available hardware, but also holds prospects for future hardware developments.
University of Southampton
1997
Meeson, Stuart
(1997)
An investigation of optimal performance criteria in electrical impedance tomography.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In this thesis three main issues are addressed: noise performance, electrode misplacement, and image reconstruction. All of these issues are important for long term monitoring applications of Electrical Impedance Tomography (EIT).
A performance figure of merit for EIT is established based on a model of system noise. It is proposed that the figure of merit be used to characterise the noise performance of a data acquisition unit when attached to either a test object or a human subject. The figure of merit provides a criterion for judging the quality of the data and the sharpness of the image which could be achieved in specific clinical practice.
In long term in vivo EIT monitoring changes in body position affect electrode positioning which introduces artefacts into the images. Also measurement electrodes are difficult to position accurately, particularly on patients in intensive care beds. Two procedures are described to reduce these electrode induced artefacts. The first reduces the sensitivity of the reconstruction to the electrode positions, and provides a rational criterion for regularising the reconstruction. The main consequences are that smoother images are produced, the number of artefacts and their magnitude are generally reduced, and the region of interest measurements are more reliable. The second procedure aims to compensate for electrode movements that occur during data measurement, by utilising the data measured in vivo to estimate modifications to the reconstruction process. Computer simulation tests have shown that this modification produces improved image fidelity.
In most practical EIT systems the imaging algorithms use a reconstruction matrix generated from a uniform conductivity distribution. An assessment is made of the potential gains from incorporating a priori data in the reconstruction process. The results show that in the absence of precise knowledge of anatomy the assumption of uniformity is the least likely to introduce artefacts.
A major part of the thesis develops a new non-linear treatment of image reconstruction, based on the Newton-Raphson iterative procedure. By emphasising the character of the images achieved in the reconstructed solutions this work has not only achieved the best possible EIT images with available hardware, but also holds prospects for future hardware developments.
This record has no associated files available for download.
More information
Published date: 1997
Identifiers
Local EPrints ID: 463005
URI: http://eprints.soton.ac.uk/id/eprint/463005
PURE UUID: 7e0f8aa1-6a52-435e-a66e-d331b2a200c3
Catalogue record
Date deposited: 04 Jul 2022 20:36
Last modified: 04 Jul 2022 20:36
Export record
Contributors
Author:
Stuart Meeson
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics