Bi-frequency symmetry difference electrical impedance tomography—a novel technique for perturbation detection in static scenes
File(s)
Author(s)
McDermott, Barry James
Avery, James
O'Halloran, Martin
Aristovich, Kirill Y
Porter, Emily
Type
Journal Article
Abstract
OBJECTIVE: A novel method for the imaging of static scenes using Electrical Impedance Tomography (EIT) is reported with implementation and validation using numerical and phantom models. The technique is applicable to regions featuring symmetry in the normal case, asymmetry in the presence of a perturbation, and where there is a known, frequency-dependent change in the electrical conductivity of the materials in the region. METHODS: The stroke diagnostic problem is used as a motivating sample application. The head is largely symmetrical across the sagittal plane. A haemorrhagic or ischaemic lesion located away from the sagittal plane will alter this natural symmetry, resulting in a symmetrical imbalance that can be detected using EIT. Specifically, application of EIT stimulation and measurement protocols at two distinct frequencies detects deviations in symmetry if an asymmetrically positioned lesion is present, with subsequent identification and localisation of the perturbation based on known frequency-dependent conductivity changes. Anatomically accurate computational models are used to demonstrate the feasibility of the proposed technique using different types, sizes, and locations of lesions with frequency-dependent (or independent) conductivity. Further, a realistic experimental head phantom is used to validate the technique using frequency-dependent perturbations emulating the key numerical simulations. RESULTS: Lesion presence, type, and location are detectable using this novel technique. Results are presented in the form of images and corresponding robust quantitative metrics. Better detection is achieved for larger lesions, those further from the sagittal plane, and when measurements have a higher signal-to-noise ratio. CONCLUSION: Bi-Frequency Symmetry Difference EIT is an exciting new modality of EIT with the ability to detect deviations in the symmetry of a region that occur due to the presence of a lesion. Notably, this modality does not require a time change in the region and thus may be used in static scenarios such as stroke detection.
Date Issued
2019-04-26
Date Acceptance
2019-02-20
Citation
Physiological Measurement, 2019, 40 (4)
ISSN
0967-3334
Publisher
IOP Publishing
Journal / Book Title
Physiological Measurement
Volume
40
Issue
4
Copyright Statement
© 2018 Institute of Physics and Engineering in Medicine. This is an author-created, un-copyedited version of an article accepted for publication in Physiological Measurement. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at https://dx.doi.org/10.1088/1361-6579/ab08ba.
Sponsor
Imperial College Healthcare NHS Trust- BRC Funding
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/30786267
Grant Number
RDB04
Subjects
Biomedical Imaging
Electrical Impedance Tomography
Reconstruction Algorithm
Publication Status
Published
Coverage Spatial
England
Article Number
044005
Date Publish Online
2019-02-20