Electrical impedance tomography device and process
First Claim
Patent Images
1. An electrical impedance tomography (EIT) device comprising:
- a plurality of electrodes, which can be placed on a body;
control and measuring circuits to feed alternating current or alternating voltage to said electrodes and to receive voltage or current signals received from said electrodes as measured signals;
a control unit connected to said control and measuring circuits and configured to control a supply of alternating current or with an alternating voltage to an electrode pair as a feeding electrode pair and configured to receive measured voltage signal or measured current signal of each electrode pair from all other electrode pairs as measured signals, and to successively change said feeding electrode pair through said plurality of electrodes and to receive and to process the measured signals (U1, . . . , UM) of a plurality of (M) individual measuring channels (K1, . . . , KM) and to reconstruct therefrom an impedance distribution of the body with a reconstruction algorithm, said control unit further configured to continuously determine at least one property (eα
1, . . . , eα
M) of a set (α
) of properties to determine channel-specific quality parameters (q1, . . . , qM) by a comparison of said at least one property of each channel with predetermined desired values, the properties comprising signal-to-noise ratio of the measured signals, freak value of the measured signals, mean value of the measured signals, phase or real and imaginary part of the measured signals, crosstalk of the measured signals, common mode of the measured signals reciprocity of the measured signals, measured signal drifts, current feed fluctuations, and value and phase of the electrode-skin contact impedances, each from said measured signals (U1, . . . , UM) of all measuring channels and configured to correct measured signals of said measuring channels based on said at least one property by adapting the reconstruction algorithm based on the at least one property by including the channel-specific quality parameters (q1, . . . , qM) among channel-specific properties in the reconstruction algorithm in a matrix that comprises a weighting matrix W(q1, . . . , qM) that comprises the channel-specific quality parameters (q1, . . . , qM), whereinsaid control unit furthermore determines at least another property so as to determine N properties emα
(UM)(α
=1, . . . , N) of the set (α
) of properties in all measuring channels for each measured signal (U1, . . . UM) and compares the N properties with desired values or with desired ranges esollmα
determined in advance or with both the desired values and with the desired ranges determined in advance, to provide results of a comparison, and corrects the measured signals of the measuring channels based on the results of the comparison based on the properties or adapts the reconstruction algorithm based on the properties;
said control unit determines channel-specific quality parameters and property-specific quality parameters qmα
(emα
, esollmα
) from the comparison of the determined properties emα
of each channel m=1, . . . , M with desired values or desired value ranges esollmα
determined in advance, wherein the channel-specific quality parameters are included in the reconstruction algorithm in such a manner that measuring channels with channel-specific quality parameters that are indicative of signals of a lower quality relative to other signals are weighted less strongly than measuring channels with quality parameters that are indicative of signals with a higher quality relative to other signals; and
said control unit forms each of the channel-specific quality parameters from the property-specific quality parameters qmα
(emα
, esollmα
), to provide the channel-specific quality parameters qm(q11, . . . , qmα
, . . . , qMN), by arithmetic or geometric averaging of the property-specific quality parameters qmα
(emα
, esollmα
) for each measuring channel, wherein the channel-specific quality parameters are standardized for an interval, wherein the lowest quality is assigned to the value 0 and the highest quality is assigned to the value 1, and wherein the measuring channels are weighted according to this standardized quality parameter in the reconstruction algorithm.
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Abstract
An EIT device has a plurality of electrodes (4) that can be arranged on a body in order to reconstruct the impedance distribution of the body with a reconstruction algorithm. The control unit (10) of the EIT device is set up by suitable programming to continuously determine at least one property (e1, . . . , eM) each from the measured signals (U1, . . . , UM) of all measuring channels and to correct measured signals of the measuring channels on the basis of the properties or to adapt the reconstruction algorithm on the basis of the properties.
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Citations
13 Claims
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1. An electrical impedance tomography (EIT) device comprising:
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a plurality of electrodes, which can be placed on a body; control and measuring circuits to feed alternating current or alternating voltage to said electrodes and to receive voltage or current signals received from said electrodes as measured signals; a control unit connected to said control and measuring circuits and configured to control a supply of alternating current or with an alternating voltage to an electrode pair as a feeding electrode pair and configured to receive measured voltage signal or measured current signal of each electrode pair from all other electrode pairs as measured signals, and to successively change said feeding electrode pair through said plurality of electrodes and to receive and to process the measured signals (U1, . . . , UM) of a plurality of (M) individual measuring channels (K1, . . . , KM) and to reconstruct therefrom an impedance distribution of the body with a reconstruction algorithm, said control unit further configured to continuously determine at least one property (eα
1, . . . , eα
M) of a set (α
) of properties to determine channel-specific quality parameters (q1, . . . , qM) by a comparison of said at least one property of each channel with predetermined desired values, the properties comprising signal-to-noise ratio of the measured signals, freak value of the measured signals, mean value of the measured signals, phase or real and imaginary part of the measured signals, crosstalk of the measured signals, common mode of the measured signals reciprocity of the measured signals, measured signal drifts, current feed fluctuations, and value and phase of the electrode-skin contact impedances, each from said measured signals (U1, . . . , UM) of all measuring channels and configured to correct measured signals of said measuring channels based on said at least one property by adapting the reconstruction algorithm based on the at least one property by including the channel-specific quality parameters (q1, . . . , qM) among channel-specific properties in the reconstruction algorithm in a matrix that comprises a weighting matrix W(q1, . . . , qM) that comprises the channel-specific quality parameters (q1, . . . , qM), whereinsaid control unit furthermore determines at least another property so as to determine N properties emα
(UM)(α
=1, . . . , N) of the set (α
) of properties in all measuring channels for each measured signal (U1, . . . UM) and compares the N properties with desired values or with desired ranges esollm α
determined in advance or with both the desired values and with the desired ranges determined in advance, to provide results of a comparison, and corrects the measured signals of the measuring channels based on the results of the comparison based on the properties or adapts the reconstruction algorithm based on the properties;said control unit determines channel-specific quality parameters and property-specific quality parameters qmα
(emα
, esollm α
) from the comparison of the determined properties emα
of each channel m=1, . . . , M with desired values or desired value ranges esollm α
determined in advance, wherein the channel-specific quality parameters are included in the reconstruction algorithm in such a manner that measuring channels with channel-specific quality parameters that are indicative of signals of a lower quality relative to other signals are weighted less strongly than measuring channels with quality parameters that are indicative of signals with a higher quality relative to other signals; andsaid control unit forms each of the channel-specific quality parameters from the property-specific quality parameters qmα
(emα
, esollm α
), to provide the channel-specific quality parameters qm(q11, . . . , qmα
, . . . , qMN), by arithmetic or geometric averaging of the property-specific quality parameters qmα
(emα
, esollm α
) for each measuring channel, wherein the channel-specific quality parameters are standardized for an interval, wherein the lowest quality is assigned to the value 0 and the highest quality is assigned to the value 1, and wherein the measuring channels are weighted according to this standardized quality parameter in the reconstruction algorithm. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A process for analyzing measured signals of an electrical impedance tomography (EIT) device, the process comprising:
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providing a plurality of electrodes, which can be applied to a body, control and measuring circuits to feed alternating current or alternating voltage to the electrodes and to receive voltage or current signals received from the electrodes; connecting a control unit to the control and measuring circuits; supplying one electrode pair, as a feeding electrode pair, with an alternating current or with an alternating voltage with the control unit; receiving the measured voltage signal or measured current signal as a measured signal of each electrode pair from all other electrode pairs as measured signals; changing the feeding electrode pair successively to pass through the plurality of electrodes and receive measured signals (U1, . . . , UM) in a number of M measuring channels (K1, . . . , KM); processing the received measured signals (U1, . . . , UM) in the number of M measuring channels (K1, . . . , KM) including reconstructing therefrom an impedance distribution of the body in an electrode plane, of the plurality of electrodes, with a reconstruction algorithm with the control unit; continuously determining, with the control unit, at least one property (e1, . . . , eM) of a set (α
) of properties comprising signal-to-noise ratio of the measured signals, freak value of of the measured signals mean value of the measured signals, phase or real and imaginary part of the measured signals, crosstalk of the measured signals common mode of the measured signals reciprocity of the measured signals, measured signal drifts, current feed fluctuations, and value and phase of the electrode-skin contact impedances, of all measured signals of all measuring channels;determining, with the control unit, channel-specific quality parameters (q1, . . . , qM) by a comparison of said at least one property of each channel with predetermined desired values; and correcting measured signals of said measuring channels based on said at least one property by adapting the reconstruction algorithm based on the at least one property by including the channel-specific quality parameters (q1, . . . , qM) among channel-specific properties in the reconstruction algorithm in a matrix that comprises a weighting matrix W(q1, . . . , qM) that comprises the channel-specific quality parameters (q1, . . . , qM), wherein the control unit determines at least another property so as to determine N properties emα
(UM) (α
=1, . . . , N) in all measuring channels for each measured signal (U1, . . . UM), and compares the determined N properties with desired values or desired ranges esollm α
determined in advance or both desired values and desired ranges determined in advance to provide results of a comparison, and corrects the measured signals of the measuring channels based on the results of the comparison based on the properties or to adapt the reconstruction algorithm based on the properties;said control unit determines channel-specific quality parameters and property-specific quality parameters qmα
(emα
, esollm α
) from the comparison of the determined properties emα
of each channel m=1, . . . , M with desired values or desired value ranges esollm α
determined in advance, wherein the channel-specific quality parameters are included in the reconstruction algorithm in such a manner that measuring channels with quality parameters that are indicative of signals of a lower quality relative to other signals are weighted less strongly than measuring channels with quality parameters that are indicative of signals with a higher quality relative to other signals; andsaid control unit forms each of the channel-specific quality parameters from the property-specific quality parameters qmα
(emα
, esollm α
), to provide the channel-specific quality parameters qm(q11, . . . , qmα
, . . . , qMN), by arithmetic or geometric averaging of the property-specific quality parameters qmα
(emα
, esollm α
) for each measuring channel, wherein the channel-specific quality parameters are standardized for an interval, wherein the lowest quality is assigned to the value 0 and the highest quality is assigned to the value 1, and wherein the measuring channels are weighted according to this standardized quality parameter in the reconstruction algorithm. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification