Design and calibration of a compact multi-frequency EIT system for acute stroke imaging

McEwan, Alistair; Romsauerova, A; Yerworth, Rebecca J.; Horesh, Lior; Bayford, Richard; Holder, David

doi:10.1088/0967-3334/27/5/s17

Cited by 110 publications

(88 citation statements)

References 21 publications

(31 reference statements)

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“…Boundary voltage data are processed and used for reconstructing the spatial distribution of the brain impedance. The brain EIT has been applied for a number of application such as: imaging brain function [86,87,111], imaging brain tumours [178], imaging arteriovenous malformations [178], imaging stroke [149,178], detection of cerebral ischaemia [86,87], physiological brain activity [199], fast neural activity [74], imaging of physiologically evoked responses [90], identifying and studying the regional conductivity changes in human brain during epileptic seizures [63], imaging brain function in ambulant human subjects ) and so on.…”

Section: Eit For Brain Imagingmentioning

confidence: 99%

Noninvasive Electromagnetic Methods for Brain Monitoring: A Technical Review

Bera

2014

Brain-Computer Interfaces

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Section: Eit For Brain Imagingmentioning

confidence: 99%

Noninvasive Electromagnetic Methods for Brain Monitoring: A Technical Review

Bera

2014

Brain-Computer Interfaces

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“…Tuning the discrete components of the NIC to make L comply with (11), the capacitive part of Zeq in Figure 5(B) can be cancelled at any specific frequency, ω S . This yields at ω S an output impedance only real and significantly large, in the order of GΩ .…”

Section: Negative Impedance Convertersmentioning

confidence: 99%

Electrical Bioimpedance Cerebral Monitoring

Seoane

Lindecrantz

2008

Encyclopedia of Healthcare Information Systems

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-i - A B S T R A C TNeurologically related injuries cause a similar number of deaths as cancer, and brain damage is the second commonest cause of death in the world and probably the leading cause of permanent disability. The devastating effects of most cases of brain damage could be avoided if it were detected and medical treatment initiated in time. The passive electrical properties of biological tissue have been investigated for almost a century and electrical bioimpedance studies in neurology have been performed for more than 50 years. Even considering the extensive efforts dedicated to investigating potential applications of electrical bioimpedance for brain monitoring, especially in the last 20 years, and the specifically acute need for such non-invasive and efficient diagnosis support tools, Electrical Bioimpedance technology has not made the expected breakthrough into clinical application yet. In order to reach this stage in the age of evidence-based medicine, the first essential step is to demonstrate the biophysical basis of the method under study. The present research work confirms that the cell swelling accompanying the hypoxic/ischemic injury mechanism modifies the electrical properties of brain tissue, and shows that by measuring the complex electrical bioimpedance it is possible to detect the changes resulting from brain damage. For the development of a successful monitoring method, after the vital biophysical validation it is critical to have available the proper electrical bioimpedance technology and to implement an efficient protocol of use. Electronic instrumentation is needed for broadband spectroscopy measurements of complex electrical bioimpedance; the selection of the electrode setup is crucial to obtain clinically relevant measurements, and the proper biosignal analysis and processing is the core of the diagnosis support system. This work has focused on all these aspects since they are fundamental for providing the solid medico-technological background necessary to enable the clinical usage of Electrical Bioimpedance for cerebral monitoring.Keywords: Electrical Bioimpedance Spectroscopy, Hypoxia, Ischemia, Stroke, Brain Monitoring, Impedance Measurements, Biomedical Instrumentation, Non-invasive Monitoring.-iiPreface -iii - P R E F A C EThis research work has been performed mainly in collaboration between the following research and academic institutions: the School of Engineering at University College of Borås, the Department of Signals and Systems at Chalmers University of Technology, the Sahlgrenska University Hospital, and the Sahlgrenska Academy at Göteborg University.Specific activities of this research work have been carried out in collaboration with the Department of Electronic Engineering at the Polytechnic University of Catalonia, Spain.This research work has been mainly funded by the Swedish Research Council (Vetenskapsrådet) through a research grant (No. 2002-5487). The research activity performed has also been part of the following European Network of Excellence: "Comp...

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“…In regard to the advantages of the current source topologies i.e. predictability of constant current with the noise advantages, the current source are commonly employed on EIS systems as is utilized by Kyung Hee (IIRC & Mk1); Oxford Brookes (OXBACT5); Rensselaer (ACT4); Sheffield (Mk3.5); UCL (Mk2.5&1b) and also the Leicester group (Mk3) [1][2][3][4][5][6][7] . The enhancement of the EIS system focuses on developing electrical and electronic instrumentations to improve the accuracy of the transfer impedance measurements to make them operate up to high frequency for the purpose of measuring impedivity and conductivity of different tissues types [8][9][10] .…”

Section: Introductionmentioning

confidence: 99%

Current source enhancements in Electrical Impedance Spectroscopy (EIS) to cancel unwanted capacitive effects

Zarafshani

Bach

Chatwin

et al. 2017

Medical Imaging 2017: Biomedical Applications in Molecular, Structural, and Functional Imaging

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Electrical Impedance Spectroscopy (EIS) has emerged as a non-invasive imaging modality to detect and quantify functional or electrical properties related to the suspicious tumors in cancer screening, diagnosis and prognosis assessment. A constraint on EIS systems is that the current excitation system suffers from the effects of stray capacitance having a major impact on the hardware subsystem as the EIS is an ill-posed inverse problem which depends on the noise level in EIS measured data and regularization parameter in the reconstruction algorithm. There is high complexity in the design of stable current sources, with stray capacitance reducing the output impedance and bandwidth of the system. To confront this, we have designed an EIS current source which eliminates the effect of stray capacitance and other impacts of the capacitance via a variable inductance. In this paper, we present a combination of operational CCII based on a generalized impedance converter (OCCII-GIC) with a current source. The aim of this study is to use the EIS system as a biomedical imaging technique, which is effective in the early detection of breast cancer. This article begins with the theoretical description of the EIS structure, current source topologies and proposes a current conveyor in application of a Gyrator to eliminate the current source limitations and its development followed by simulation and experimental results. We demonstrated that the new design could achieve a high output impedance over a 3MHz frequency bandwidth when compared to other types of GIC circuits combined with an improved Howland topology.

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Design and calibration of a compact multi-frequency EIT system for acute stroke imaging

Cited by 110 publications

References 21 publications

Noninvasive Electromagnetic Methods for Brain Monitoring: A Technical Review

Noninvasive Electromagnetic Methods for Brain Monitoring: A Technical Review

Electrical Bioimpedance Cerebral Monitoring

Current source enhancements in Electrical Impedance Spectroscopy (EIS) to cancel unwanted capacitive effects

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