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Authors
W. Wang; L. Wang; B. Tunstall; M. Brien; D-W. Gu

Identifier
10.3182/20060920-3-FR-2912.00030

Index Terms
biomedical,contact resistance,electrodes,repeatability,variance

Abstract
The paper investigates three sources of potential error in measurements that may be taken as part of a clinical protocol using Electrical Impedance Tomography (EIT). The findings of an investigation show that the error of two types of electrode used (Stainless Steel and ECG) could produce 13.5-44.5%, 1.5-34.8% and 9.9-83.7% errors in repeatability, contact drift and electrode mismatching studies, respectively. Such widely varying errors challenge EIT imaging both when measurements are taken at different clinical visits and even at the same visit. The paper discusses the consequence of such measurement inaccuracies and proposes a "best practice" showing how to reduce these errors.

References

[1] Asfaw Y, and Adler A 2005 Automatic detection of
    detached and erroneous electrodes in electrical
    impedance tomography. Physio. Meas, 26
    S175-S183.
[2] Brown B H, Barber D C, Wang W, Lu L, Leathard A
    D, Smallwood R H, Hampshire A R, Mackay R
    and Hatzigalanis 1994 Multi-frequency imaging
    and modelling of respiratory related electrical
    impedance changes. Physiol Meas, 15(2A)
    A1-A12.
[3] Gonzalez-Correa C A, Brown B H, Smallwood R H,
    Walker D C and Bardhan K D 2005 Electrical
    bioimpedance readings increase with higher
    pressure applied to the measuring probe. Physiol.
    Meas, 26 S39-S47.
[4] Jossinet J, Tourtel C and Jarry R 1994 Active
    current electrodes for in vivo electrical
    impedance tomography. Physiol Meas 15
    A83-A90.
[5] Kerner T. E., Paulsen K. D., Hartov A., Soho S. K.,
    Poplack S. P. (2002): Electrical Impedance
    Spectroscopy of the Breast: Clinical Imaging
    Results in 26 Subjects. IEEE Trans. Med.
    Imaging, 21(6): 638-645.
[6] McAdams E T, McLaughlin J A and J McC Anderson,
    1994 Multi-electrode systems for electrical
    impedance tomography. Physiol Meas, 15
    A101-AI06.
[7] Smit H J, Handoko M L, Noordegraaf A V, Faes T J
    C, Postmus P E, de Vries P and Boonstra A
    (2003): Electrical impedance tomography to
    measure pulmonary perfusion: is the
    reproducibility high enough for clinical practice?
    Physiol. Meas, 24 491-9.
[8] Wang W, Brown B H and Leathard A D 1994 Noise
    equalisation within EIT images Physiol Meas
    15(2A) 211-16.
[9] Wang W, Brown B H and Barber D C 1995a System
    errors, noise and artefacts in Sheffield MK3
    electrical impedance tomographic spectroscope
    (EITS) system In: Proceedings of the IX ICEBI
    (E Gersing and H Schaffer (Ed)).
[10] Wang W, Barber D C and Brown B H 1995b
     Recovery of cardiac related changes in Sheffield
     EIT images by advanced signal processing
     techniques, In: Proceedings of the IX ICEBI
     (E Gersing and H Schaffer (Ed)).
[11] Wang W, Tunstall B, Chauhan D and McCormick M
     1998 The design of De Montfort Mk2 electrical
     impedance mammography system, In:
     Proceedings of the 20th IEEE, EMBS (H K
     Chang and Y T Zhang (Ed)).