A New Method for Electric Impedance Imaging Using an Eddy Current With a Tetrapolar Circuit

A new contactless technique for electrical impedance imaging, using an eddy current managed along with the tetrapolar circuit method, is proposed. The eddy current produced by a magnetic field is superimposed on a constant current that is normally used in the tetrapolar circuit method, and thus is used to control the current distribution in the body. By changing the current distribution, a set of voltage differences is measured with a pair of electrodes. This set of voltage differences is used in the image reconstruction of the resistivity distribution. The least square error minimization method is used in the reconstruction algorithm. The principle of this method is explained theoretically. A backprojection algorithm was used to get 2-D images. Based on this principle, a measurement system was developed and model experiments were conducted with a saline-filled phantom. The estimated shape of each model in the reconstructed image was similar to that of the corresponding model. From the results of these experiments, it is confirmed that the proposed method is applicable to the realization of electrical conductivity imaging.

[1]  Lawrence K. Forbes,et al.  An analytic simplification for the reconstruction problem of electrical impedance tomography , 2002, Int. J. Imaging Syst. Technol..

[2]  Mustafa Kuzuoglu,et al.  Electrical impedance tomography using induced currents , 1994, IEEE Trans. Medical Imaging.

[3]  H. Griffiths.  Magnetic induction tomography , 2001 .

[4]  Willis J. Tompkins,et al.  Comparing Reconstruction Algorithms for Electrical Impedance Tomography , 1987, IEEE Transactions on Biomedical Engineering.

[5]  H Griffiths,et al.  A primary field compensation scheme for planar array magnetic induction tomography. , 2004, Physiological measurement.

[6]  David Isaacson,et al.  NOSER: An algorithm for solving the inverse conductivity problem , 1990, Int. J. Imaging Syst. Technol..

[7]  J. Ikebe,et al.  New tetrapolar circuit method using magnetic field for measurement of local impedance change in biological substances , 1990, IEEE Transactions on Biomedical Engineering.

[8]  Patricia Brunner,et al.  Solution of the inverse problem of magnetic induction tomography (MIT) , 2005, Physiological measurement.

[9]  Nevzat G. Gencer,et al.  Electrical conductivity imaging via contactless measurements: an experimental study , 2003, IEEE Transactions on Medical Imaging.

[10]  Hermann Scharfetter,et al.  Magnetic induction tomography: evaluation of the point spread function and analysis of resolution and image distortion. , 2007, Physiological measurement.

[11]  Hermann Scharfetter,et al.  Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations , 2003, IEEE Transactions on Biomedical Engineering.

[12]  John G. Webster,et al.  Electrical Impedance Tomography , 1991 .

[13]  N.G. Gencer,et al.  Electrical impedance tomography: induced-current imaging achieved with a multiple coil system , 1996, IEEE Transactions on Biomedical Engineering.

[14]  Hermann Scharfetter,et al.  Single-Step 3-D Image Reconstruction in Magnetic Induction Tomography: Theoretical Limits of Spatial Resolution and Contrast to Noise Ratio , 2006, Annals of Biomedical Engineering.

[15]  H. Lackner,et al.  Magnetic induction tomography: hardware for multi-frequency measurements in biological tissues. , 2001, Physiological measurement.

[16]  H Griffiths,et al.  Magnetic Induction Tomography: A Measuring System for Biological Tissues , 1999, Annals of the New York Academy of Sciences.