Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Patent
1996-08-26
1998-09-15
Kamm, William E.
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
600547, A61B 505
Patent
active
058072519
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/GB95/00520filed Mar. 10, 1995.
This invention relates to electrical impedance tomography (EIT), which has been known for some time in clinical applications and has recently gained acceptance as a useful technique for rapidly delineating the resistivity distribution of materials inside a process vessel or pipeline.
In the clinical use of EIT, it is known to provide a set of electrodes spaced around, say, the thorax of a patient in electrical contact with the skin, and to apply a constant current or constant voltage input electrical signal between each in turn of all the possible mutually adjacent pairs of electrodes. While the input signal is being applied to any one pair of mutually adjacent electrodes, the currents or voltages between each mutually adjacent pair of the remainder of the electrodes are measured and the resulting measured-data are processed in known manner to yield, and display on a screen, a representation of the distribution of the electrical resistivity across a cross section of the patient which is bounded by the ring of electrodes.
It is also known from U.S. Pat. 5,272,624 to employ a medical electrical impedance imaging technique using set current patterns, in which electrical current is simultaneously injected to each of an array of spaced electrodes around the periphery of the body under investigation, the amplitude of the current varying according to, say, a cosinusoidal distribution around the periphery. The pattern of injected current is then successively altered around the electrode array, and the amplitude of the input signal is adapted to give the optimum distinguishability for the particular application of interest.
The technique of U.S. Pat. No. 5,272,624 involves the measurement of the voltages developed at or near each electrode with respect to a common point, or earth reference. However, the currents are injected independently of this earth reference.
It has also become known to apply EIT to vessels and pipelines made of electrically non-conductive material, such as acrylic or other plastics materials, in order to determine the resistivity distribution, over a cross-section of the vessel or pipeline, of its contents, notably when these are or may be a suspension of solids in a liquid of different resistivity, or a plurality of mutually immiscible liquids of different resistivities. In this application of EIT, it is known to provide that the electrodes are mounted in and project through the vessel or pipeline wall so as to be directly in electrical contact with the contents within. Only a minor modification of the data processing algorithm is required to take account of the fact that the pairs of electrodes between which an input signal is applied or an output signal is measured may now be actually or effectively within (though usually only slightly within) the body of material of which the resistivity distribution is to be determined.
It has also been proposed to employ EIT in connection with vessels and pipelines made of electrically conductive materials. Clearly, since most industrial pipelines and process vessels are constructed from electrically conductive metallic materials, there is a practical need to modify existing EIT techniques as may be necessary to accommodate such materials. Since it is necessary to keep the electrodes insulated from one another, it is necessary to insulate them from the conductive containing wall and to arrange that they project through the wall into direct electrical contact with the contents within. Even when that is done, however, it is found that, when an input signal is applied between one pair of adjacent electrodes, output signals measured between other pairs of mutually adjacent electrodes are of low amplitude and consequently have a poor signal-to-noise ratio leading, after signal processing in known manner, to a resistivity-distribution determination of unsatisfactorily poor quality.
A useful summary of the applications of EIT to fluid mixtures in process reactors and
REFERENCES:
patent: 4709704 (1987-12-01), Lukasiewicz
patent: 4974598 (1990-12-01), John
patent: 5020541 (1991-06-01), Marriott
patent: 5184624 (1993-02-01), Brown et al.
patent: 5284142 (1994-02-01), Goble et al.
patent: 5311878 (1994-05-01), Brown et al.
patent: 5351697 (1994-10-01), Cheney et al.
patent: 5353802 (1994-10-01), Ollmar
patent: 5381333 (1995-01-01), Isaacson et al.
patent: 5390110 (1995-02-01), Cheney et al.
patent: 5421345 (1995-06-01), Lekholm et al.
patent: 5465730 (1995-11-01), Zadehkoochak et al.
patent: 5544662 (1996-08-01), Saulnier et al.
patent: 5560372 (1996-10-01), Cory
patent: 5575292 (1996-11-01), Brown et al.
patent: 5626146 (1997-05-01), Barber et al.
patent: 5657552 (1997-08-01), Reineck et al.
Ping Hua et al, "Using Compound Electrodes in Electrical Impedance Tomography", IEEE Transactions on Biomedical Engineering, vol. 40 No. 1, Jan. 1993.
F.J. Dickin et al "Determination of Composition and Motion of . . . ", Chemical Engineering Science, vol. 48 No. 10 pp. 1883-1897, 1993.
C J Kotre, "A Sensitivity coefficient method for the reconstruction of . . . ", Clin. Phys. Physiol Meas., 1989 vol. 10 No. 3, pp. 275-281.
Dickin Fraser John
Wang Mi
Williams Richard Andrew
British Technology Group Limited
Kamm William E.
Shaw Shawna J.
LandOfFree
Electrical impedance tomography does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrical impedance tomography, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrical impedance tomography will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-82329