Research Article | Open Access
Yair Granot, Antoni Ivorra, Boris Rubinsky, "Frequency-Division Multiplexing for Electrical Impedance Tomography in Biomedical Applications", International Journal of Biomedical Imaging, vol. 2007, Article ID 054798, 9 pages, 2007. https://doi.org/10.1155/2007/54798
Frequency-Division Multiplexing for Electrical Impedance Tomography in Biomedical Applications
Electrical impedance tomography (EIT) produces an image of the electrical impedance distribution of tissues in the body, using electrodes that are placed on the periphery of the imaged area. These electrodes inject currents and measure voltages and from these data, the impedance can be computed. Traditional EIT systems usually inject current patterns in a serial manner which means that the impedance is computed from data collected at slightly different times. It is usually also a time-consuming process. In this paper, we propose a method for collecting data concurrently from all of the current patterns in biomedical applications of EIT. This is achieved by injecting current through all of the current injecting electrodes simultaneously, and measuring all of the resulting voltages at once. The signals from various current injecting electrodes are separated by injecting different frequencies through each electrode. This is called frequency-division multiplexing (FDM). At the voltage measurement electrodes, the voltage related to each current injecting electrode is isolated by using Fourier decomposition. In biomedical applications, using different frequencies has important implications due to dispersions as the tissue's electrical properties change with frequency. Another significant issue arises when we are recording data in a dynamic environment where the properties change very fast. This method allows simultaneous measurements of all the current patterns, which may be important in applications where the tissue changes occur in the same time scale as the measurement. We discuss the FDM EIT method from the biomedical point of view and show results obtained with a simple experimental system.
- K. Boone, D. Barber, and B. Brown, “Imaging with electricity: report of the European Concerted Action on Impedance Tomography,” Journal of Medical Engineering and Technology, vol. 21, no. 6, pp. 201–232, 1997.
- N. Polydorides and W. R. B. Lionheart, “A Matlab toolkit for three-dimensional electrical impedance tomography: a contribution to the Electrical Impedance and Diffuse Optical Reconstruction Software project,” Measurement Science and Technology, vol. 13, no. 12, pp. 1871–1883, 2002.
- R. H. Bayford, “Bioimpedance tomography (electrical impedance tomography),” Annual Review of Biomedical Engineering, vol. 8, no. 1, pp. 63–91, 2006.
- M. Tang, W. Wang, J. Wheeler, M. McCormick, and X. Dong, “The number of electrodes and basis functions in EIT image reconstruction,” Physiological Measurement, vol. 23, no. 1, pp. 129–140, 2002.
- M. Vauhkonen, P. A. Karjalainen, and J. P. Kaipio, “A Kalman filter approach to track fast impedance changes in electrical impedance tomography,” IEEE Transactions on Biomedical Engineering, vol. 45, no. 4, pp. 486–493, 1998.
- F. C. Trigo, R. Gonzalez-Lima, and M. B. P. Amato, “Electrical impedance tomography using the extended Kalman filter,” IEEE Transactions on Biomedical Engineering, vol. 51, no. 1, pp. 72–81, 2004.
- K. Y. Kim, B. S. Kim, M. C. Kim, S. Kim, D. Isaacson, and J. C. Newell, “Dynamic electrical impedance imaging with the interacting multiple model scheme,” Physiological Measurement, vol. 26, no. 2, pp. S217–S233, 2005.
- T. York, “Status of electrical tomography in industrial applications,” Journal of Electronic Imaging, vol. 10, no. 3, pp. 608–619, 2001.
- Q. S. Zhu, C. N. McLeod, C. W. Denyer, F. J. Lidgey, and W. R. B. Lionheart, “Development of a real-time adaptive current tomography,” Physiological Measurement, vol. 15, 2A, pp. A37–A43, 1994.
- G. Teague, Mass flow measurement of multi-phase mixtures by means of tomographic techniques, Ph.D. thesis, Electrical Engineering, University of Cape Town, Cape Town, South Africa, 2002.
- M. M. Radai, S. Abboud, and B. Rubinsky, “Evaluation of the impedance technique for cryosurgery in a theoretical model of the head,” Cryobiology, vol. 38, no. 1, pp. 51–59, 1999.
- R. V. Davalos, B. Rubinsky, and D. M. Otten, “A feasibility study for electrical impedance tomography as a means to monitor tissue electroporation for molecular medicine,” IEEE Transactions on Biomedical Engineering, vol. 49, no. 4, pp. 400–403, 2002.
- B. Rubinsky and Y. Huang, “Electrical impedance tomography to control electroporation,” May 2002, US patent no. #6,387,671.
- H. P. Schwan and C. F. Kay, “The conductivity of living tissue,” Annals of the New York Academy of Sciences, vol. 65, no. 6, pp. 1007–1013, 1957.
- K. R. Foster and H. P. Schwan, “Dielectric properties of tissues,” in Handbook of Biological Effects of Electromagnetic Fields, C. Polk and E. Postow, Eds., pp. 25–102, CRC Press, Boca Raton, Fla, USA, 1996.
- S. Grimnes and Ø. G. Martinsen, Bioimpedance and Bioelectricity Basics, Academic Press, San Diego, Calif, USA, 2000.
- F. A. Duck, Physical Properties of Tissues: A Comprehensive Reference Book, Academic Press, San Diego, Calif, USA, 1990.
- C. Gabriel, S. Gabriel, and E. Corthout, “The dielectric properties of biological tissues: I. Literature survey,” Physics in Medicine and Biology, vol. 41, no. 11, pp. 2231–2249, 1996.
- J. Schlappa, E. Annese, and H. Griffiths, “Systematic errors in multi-frequency EIT,” Physiological Measurement, vol. 21, no. 1, pp. 111–118, 2000.
- A. McEwan, A. Romsauerova, R. Yerworth, L. Horesh, R. Bayford, and D. Holder, “Design and calibration of a compact multi-frequency EIT system for acute stroke imaging,” Physiological Measurement, vol. 27, no. 5, pp. S199–S210, 2006.
- A. J. Wilson, P. Milnes, A. R. Waterworth, R. H. Smallwood, and B. H. Brown, “Mk3.5: a modular, multi-frequency successor to the Mk3a EIS/EIT system,” Physiological Measurement, vol. 22, no. 1, pp. 49–54, 2001.
- J. H. Li, C. Joppek, and U. Faust, “Fast EIT data acquisition system with active electrodes and its application to cardiac imaging,” Physiological Measurement, vol. 17, no. 4, supplement A, pp. A25–A32, 1996.
- W. R. B. Lionheart, J. Kaipio, and C. N. McLeod, “Generalized optimal current patterns and electrical safety in EIT,” Physiological Measurement, vol. 22, no. 1, pp. 85–90, 2001.
- R. V. Davalos, D. M. Otten, L. M. Mir, and B. Rubinsky, “Electrical impedance tomography for imaging tissue electroporation,” IEEE Transactions on Biomedical Engineering, vol. 51, no. 5, pp. 761–767, 2004.
- V. Kolehmainen, M. Vauhkonen, P. A. Kaijalainen, and J. P. Kaipio, “Assessment of errors in static electrical impedance tomography with adjacent and trigonometric current patterns,” Physiological Measurement, vol. 18, no. 4, pp. 289–303, 1997.
- P. Bertemes-Filho, B. H. Brown, and A. J. Wilson, “A comparison of modified Howland circuits as current generators with current mirror type circuits,” Physiological Measurement, vol. 21, no. 1, pp. 1–6, 2000.
- M. Vauhkonen, W. R. B. Lionheart, L. M. Heikkinen, P. J. Vauhkonen, and J. P. Kaipio, “A Matlab package for the EIDORS project to reconstruct two-dimensional EIT images,” Physiological Measurement, vol. 22, no. 1, pp. 107–111, 2001.
- D. G. Gisser, D. Isaacson, and J. C. Newell, “Current topics in impedance imaging,” Clinical Physics and Physiological Measurement, vol. 8, A, pp. 39–46, 1987.
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