Bi-frequency symmetry difference electrical impedance tomography—a novel technique for perturbation detection in static scenes

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Title: Bi-frequency symmetry difference electrical impedance tomography—a novel technique for perturbation detection in static scenes
Authors: McDermott, BJ
Avery, J
O'Halloran, M
Aristovich, KY
Porter, E
Item 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.
Issue Date: 26-Apr-2019
Date of Acceptance: 20-Feb-2019
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
Sponsor/Funder: Imperial College Healthcare NHS Trust- BRC Funding
Funder's Grant Number: RDB04
Keywords: Science & Technology
Life Sciences & Biomedicine
Engineering, Biomedical
Biomedical imaging
electrical impedance tomography
reconstruction algorithm
Biomedical Imaging
Electrical Impedance Tomography
Reconstruction Algorithm
Biomedical Engineering
0903 Biomedical Engineering
1116 Medical Physiology
0906 Electrical and Electronic Engineering
Publication Status: Published
Conference Place: England
Embargo Date: 2020-02-20
Article Number: 044005
Online Publication Date: 2019-02-20
Appears in Collections:Division of Surgery
Faculty of Medicine

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