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Performance Evaluation of Five Types of Ag/AgCl Bio-Electrodes for Cerebral Electrical Impedance Tomography

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Abstract

Electrical impedance tomography (EIT) is an emerging medical imaging technique, which has already been investigated in several clinical applications due to its low-cost, non-invasiveness, non-radioactivity, high temporal resolution, and great sensitivity to impedance changes. One potential use of EIT is to perform long-term continuous imaging monitoring of brain for patients who suffer from severe cerebral diseases. However, this application requires a demanding performance of electrodes because of the characteristics of cerebral EIT measurements. Although Ag/AgCl bio-electrodes are widely used for clinical practices or EIT research at the moment, influences of different types of Ag/AgCl electrodes on cerebral EIT measurements have not been investigated. In this study, five common types of Ag/AgCl bio-electrodes were put into comparison by measuring the forearm and the brain of 10 healthy adult volunteers and evaluating those data in frequency or time domain in terms of contact impedance, uniformity, signal-to-noise ratio, and stability. Results show that Ag/AgCl powder electrode has an overall best performance with as low contact impedance as commercial ECG electrodes (p > 0.05), high SNR (60.3 ± 4.5 dB), better uniformity (coefficient of correlation 0.95 ± 0.03), and greater stability (slope 0.68 ± 0.03). After further improvement in design and instrumentation, Ag/AgCl powder electrode is likely to become the optimal choice for cerebral EIT measurements and provide feasible technical support for further research or application in cerebral EIT.

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Acknowledgments

The authors would like to gratefully acknowledge Prof. Yanwen Duan with College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, China, for providing several types of electrode system for cerebral EIT. This study was partially supported by the PNSF of China under Grants 50937005 and 61071033, and the KPNSTPP of China under Grants 2009BAI79B03.

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Authors and Affiliations

  1. Department of Bioengineering, Fourth Military Medical University, Xi’an, 710032, People’s Republic of China

    Shiwei Xu, Meng Dai, Canhua Xu, Chaoshuang Chen, Xuetao Shi & Xiuzhen Dong

  2. Department of Bioengineering, Imperial College London, London, SW7 2AZ, United Kingdom

    Mengxing Tang

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  1. Shiwei Xu
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  2. Meng Dai
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  3. Canhua Xu
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Correspondence to Xuetao Shi or Xiuzhen Dong.

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Associate Editor James Tunnell oversaw the review of this article.

Shiwei Xu and Meng Dai contributed equally to this work.

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Xu, S., Dai, M., Xu, C. et al. Performance Evaluation of Five Types of Ag/AgCl Bio-Electrodes for Cerebral Electrical Impedance Tomography. Ann Biomed Eng 39, 2059–2067 (2011). https://doi.org/10.1007/s10439-011-0302-9

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