Electrical Impedance Tomography (EIT), is a medical imaging technique in which an image of the conductivity or permittivity of part of the body is inferred from surface electrical measurements. Typically conducting electrodes are attached to the skin of the subject and small alternating currents applied to some or all of the electrodes. The resulting electrical potentials are measured, and the process repeated for numerous different configurations of applied current. Medical imaging designates the ensemble of techniques and processes used to create images of the human body (or parts thereof) for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). ...

Proposed applications include monitoring of lung function, detection of cancer in the skin and breast and location of epileptic foci. All applications are currently considered experimental. The lungs flank the heart and great vessels in the chest cavity. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue through invasion or by implantation into distant sites by metastasis. ... In zootomy and dermatology, skin is an organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs. ... A pregnant womans breasts. ... Epilepsy (sometimes referred to as a seizure disorder) is a common chronic neurological condition that is characterized by recurrent unprovoked epileptic seizures. ...

In geophysics a similar technique (called electrical resistivity tomography) is used using electrodes on the surface of the earth or in bore holes to locate resistivity anomalies, and in industrial process monitoring the arrays of electrodes are used for example to monitor mixtures of conductive fluids in vessels or pipes. ‹ The template below has been proposed for deletion. ... Electrical resistivity tomography (ERT) is a geophysical technique for imaging sub-surfaces structures from electrical measurements made at the surface, or by electrodes in bore holes. ...

The credit for the invention of EIT as a medical imaging technique is usually attributed to John G. Webster in around 1978, although the first practical realisation of a medical EIT system was due to David C. Barber and Brian H. Brown. In geophysics the idea dates from the 1930s. John G. Webster is an American electrical engineer and a founding pioneer in the field of biomedical engineering. ... 1978 (MCMLXXVIII) was a common year starting on Sunday. ... This article or section does not cite its references or sources. ...

Mathematically the problem of recovering the conductivity from surface measurements of current and potential is a non-linear inverse problem and is severely ill-posed. The mathematical formulation of the problem is due to Alberto Calderón, and in the mathematical literature of inverse problems it is often referred to as the "Calderón Problem". There is extensive mathematical research on the problem of uniqueness of solution and numerial algorithms for this problem. To do: 20th century mathematics chaos theory, fractals Lyapunov stability and non-linear control systems non-linear video editing See also: Aleksandr Mikhailovich Lyapunov Dynamical system External links http://www. ... An inverse problem is the task that often occurs in many branches of science and mathematics where the values of some model parameter(s) must be obtained from the observed data. ... In mathematics, an ill-posed problem is one that is not well-posed, in that it violates one or more of the following conditions: A solution exists. ... Alberto Calderón. ...

Examples

Electrodes on chest

Wires attached

Resulting image

The above images are from the EIT group at Oxford Brookes University and depict an early attempt at three dimensional EIT imaging of the chest using the OXBACT3 EIT system. The reconstructed image is a time average and shows lungs as low conductivity regions. Although an accurate chest shape was used only a 2D reconstruction algorithm was used resulting in a distorted image. The results of a similar chest study were published in N. Kerrouche, CN McLeod, WRB Lionheart, Time series of EIT chest images using singular value decomposition and Fourier transform, Physiol. Meas. 22 No 1, 2001 147-157. Image File history File links EIT_electrodes_on_chest_Oxford_Brookes. ... Image File history File links EIT_electrodes_on_chest_Oxford_Brookes. ... Image File history File links Wires_attached_to_electrodes_for_EIT.jpg‎ Wires attached to electrodes on a human chest for an Electrical Impedance Tomography experiment. ... Image File history File links Wires_attached_to_electrodes_for_EIT.jpg‎ Wires attached to electrodes on a human chest for an Electrical Impedance Tomography experiment. ... Image File history File links EIT_image_of_chest_from_Oxford_Brookes_OXBACT.png‎ A time averaged EIT image of a cross section of a human chest see: N. Kerrouche, CN McLeod, WRB Lionheart, Time series of EIT chest images using singular value decomposition and Fourier transform, Physiol. ... Image File history File links EIT_image_of_chest_from_Oxford_Brookes_OXBACT.png‎ A time averaged EIT image of a cross section of a human chest see: N. Kerrouche, CN McLeod, WRB Lionheart, Time series of EIT chest images using singular value decomposition and Fourier transform, Physiol. ... Oxford Brookes is a public university in Oxfordshire, England. ...

References

• Henderson R.P. and Webster J.G. (1978) An Impedance Camera for Spatially Specific Measurements of the Thorax. IEEE Trans. Biomed. Eng. 25: 250-254.
• Barber D.C. and Brown B.H. (1984) Applied Potential Tomography (Review Article). J. Phys. E:Sci. Instrum 17: 723 - 733.
• Calderón A.P. (1980) On an inverse boundary value problem, in Seminar on Numerical Analysis and its Applications to Continuum Physics, Rio de Janeiro. Scanned copy of paper
• Uhlmann G. (1999) Developments in inverse problems since Calderón's foundational paper, Harmonic Analysis and Partial Differential Equations: Essays in Honor of Alberto P. Calderón, (editors ME Christ and CE Kenig), University of Chicago Press, ISBN 0-226-10455-9
• Holder D.S., Electrical Impedance Tomography: Methods, History and Applications, Institute of Physics, 2004. ISBN 0-7503-0952-0.

• Soleimani M., Gómez-Laberge C., Adler A., Imaging of conductivity changes and electrode movement in EIT, Physio. Meas. 27, S103-S113, May 2006.

External links

• EIT website University College London