ELECTROIMPEDANCE TOMOGRAPH WITH COMMON-MODE SIGNAL SUPPRESSION
First Claim
1. An electroimpedance tomography comprising:
- a plurality of electrodes for placement on a body of a patient;
a control and evaluating unit;
a selector switch;
a measuring amplifier;
an AD converter;
a symmetrical AC power source used to reduce common-mode signals, said electrodes being connected to said control and evaluating unit via said selector switch, wherein said control and evaluating unit cooperates with said selector switch such that two of said electrodes as an electrode pair are each supplied with an alternating current from said AC power source and the detected analog voltage signals of the other said electrodes are processed in order to reconstruct therefrom the impedance distribution of the body in the plane of the electrodes; and
a common-mode signal measuring electrode, said control and evaluating unit detuning the common-mode signal of the alternating current on the body against the ground by means of said common-mode signal measuring electrode and, based on this, the symmetry of said AC power source such that the common-mode signal on the body is minimized, and the corresponding detuning parameters are stored for each electrode pair.
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Accused Products
Abstract
An electroimpedance tomograph with a plurality of electrodes (1) is provided, which can be placed on the body of a patient and are connected via a selector switch (60) with a control and evaluating unit (20). The control and evaluating unit (20) cooperates with the selector switch (60) such that two electrodes each are supplied with an alternating current from an AC power source (22) and the detected analog voltage signals of the other electrodes are processed in order to reconstruct therefrom the impedance distribution of the body in the plane of the electrodes, wherein a symmetrical AC power source is used to reduce common-mode signals. To further suppress interferences due to common-mode signals, provisions are made for the control and evaluating unit (20) to be set up, furthermore, for detuning the common-mode signal of the alternating current on the body against the ground by means of a common-mode signal measuring electrode (4) and, based on this, the symmetry of the symmetrical AC power source such that the common-mode signal on the body is minimized, and the corresponding detuning parameters are stored for each electrode pair.
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Citations
13 Claims
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1. An electroimpedance tomography comprising:
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a plurality of electrodes for placement on a body of a patient;
a control and evaluating unit;
a selector switch;
a measuring amplifier;
an AD converter;
a symmetrical AC power source used to reduce common-mode signals, said electrodes being connected to said control and evaluating unit via said selector switch, wherein said control and evaluating unit cooperates with said selector switch such that two of said electrodes as an electrode pair are each supplied with an alternating current from said AC power source and the detected analog voltage signals of the other said electrodes are processed in order to reconstruct therefrom the impedance distribution of the body in the plane of the electrodes; and
a common-mode signal measuring electrode, said control and evaluating unit detuning the common-mode signal of the alternating current on the body against the ground by means of said common-mode signal measuring electrode and, based on this, the symmetry of said AC power source such that the common-mode signal on the body is minimized, and the corresponding detuning parameters are stored for each electrode pair. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An electroimpedance tomograph comprising:
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a plurality of electrodes, which can be placed on the body;
a patient and are connected to a control and evaluating unit connected to said plurality of electrodes;
a symmetrical AC power source used to reduce common-mode signals;
a selector switch, said control and evaluating unit cooperating with said selector switch such that each of two electrodes forming an electrode pair are supplied with an alternating current from said AC power source and the detected analog voltage signals of the other electrodes are processed in order to reconstruct therefrom the impedance distribution of the body in the plane of the electrodes;
a common-mode signal measuring electrode;
an analog control loop circuit with a differential amplifier, where one input of said differential amplifier is connected to ground and the other input thereof is connected to an output of said common-mode signal measuring electrode, said analog control loop circuit supplying a common-mode signal of the alternating current on the body, and that the output of said differential amplifier is connected to a center tap of said symmetrical AC power source in order to detune said AC power source such that the common-mode signal on the body is minimized. - View Dependent Claims (11, 12, 13)
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Specification