ELECTRO-PHYSIOLOGICAL MEASUREMENT WITH REDUCED MOTION ARTIFACTS

• US 20120116198A1
• Filed: 07/06/2010
• Published: 05/10/2012
• Est. Priority Date: 07/13/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Veen, Jeroen, Meftah, Mohammed, Lambert, Nicolaas, De Boer, Bart Michiel, Feddes, Bastiaan, Gourmelon, Lena, Rietman, Ronald, Husen, Sri Andari
• Granted Patent: US 9,603,542 B2
• Time in Patent Office: Days
• US Class Current: 600/372
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/302 for capacitive or ionised electrodes, e.g. metal-oxide-semiconductor field-effect transistors [MOSFET]
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths

Abstract

The present invention relates to an apparatus and method (4,5,6,7,2) for capacitive measurement of electrophysiological signals (1) wherein motion artifacts are suppressed or reduced by providing a feedback mechanism. An average voltage between a capacitive sensor electrode (1) and the body (3) is controlled so as to reduce or minimize motion-induced signals.

Claims

1. An apparatus configured to measure at least one electrophysiological signal of a body, comprising

at least one capacitive sensor electrode and

an arrangement configured to control an average voltage between the at least one capacitive sensor electrode and the body for reducing or minimizing motion-induced signals.

2. The apparatus according to claim 1, comprising at least one reference electrode arranged close to or in galvanic contact with the body, wherein the at least one reference electrode is connected to a voltage source, a current source or a reference potential.

3. The apparatus according to claim 1, comprising at least two sensor electrodes coupled to inputs of a differential amplifier.

4. The apparatus according to claim 1, comprising at least two sensor electrodes configured to measure essentially the same electrophysiological signal and being arranged at different distances to the body and/or supplied with different average voltages, a feedback signal being generated based on the output signals of the sensor electrodes so as to bring the average voltages to a defined value.

5. The apparatus according to claim 1, wherein at least one buffer amplifier is provided configured to convert an output signal of the sensor electrode, applied to an input of the buffer amplifier, into an output signal while keeping the average voltage on the sensor electrode at a level defined by a signal applied to a further input of the buffer amplifier.

6. The apparatus according to claim 4, comprising at least three sensor electrodes, the at least three sensor electrodes being arranged

in a triangular fashion, or

in form of concentric circles, or

in the form of small segments, the segments of all electrodes being distributed in an interspersed manner, or

in segments being arranged in form of a ring or a matrix.

7. The apparatus according to claim 1, comprising an oscillator or vibrator for oscillating or vibrating at least one of the sensor electrode, or a support or casing supporting or housing the sensor electrode, and a feedback loop coupled to the oscillator or vibrator to generate a feedback signal for reducing or minimizing the average voltage.

8. The apparatus according to claim 7, wherein the frequency of the oscillation or vibration is outside of the bioelectric frequency band of the electrophysiological signal to be measured.

9. The apparatus according to claim 1, comprising an extractor configured to extract an indicator of an average voltage between the at least one sensor electrode and the body from the sensor electrode signal, wherein the apparatus is configured to use the indicator to generate a feedback signal.

10. The apparatus according to claim 1, comprising an estimator configured to determine a power estimate or an entropy estimate of at least one output signal of the at least one sensor electrode and to generate a feedback signal based on the at least one output signal of the at least one sensor electrode so as to bring the average voltage to a defined value.

11. An apparatus, in particular according to claim 1, comprising an equalizer for equalizing a transfer function V_o/V_bio,

wherein V_o is an output signal of a buffer amplifier configured to receive an electrophysiological signal V_bio of interest, the apparatus configured to adaptively control the transfer V_o/V_bio, such that equalization is achieved.

12. The apparatus according to claim 11, comprising means configured for at least one of:

applying a reference signal (V_ref) to the body using at least one reference electrode for the purpose of equalizing the buffer input capacitance of capacitive biosignal sensing,

modulating the reference signal to a value above the maximum frequency that is expected in the signal of interest,

subtracting the applied reference signal from the measured and buffered reference signal,

demodulating and low pass filtering the resulting signal and using this signal to control the amplification,

providing an integrator in the arrangement implemented as a feedback arrangement configured to bring the gain of the buffer amplifier to unity.

13. The apparatus according to claim 1, comprising a controller for controlling the average voltage between the body and electrode to minimize the motion-induced signal, reconstructing the input signal using a measured variation of a capacitance of the sensor electrode, and generating a feedback signal by processing the reconstructed input signal.

14. A method for measuring at least one electrophysiological signal of a body, comprising controlling an average voltage between a capacitive sensor electrode and the body so as to reduce or minimize motion-induced signals.

15. A computer program, comprising program code means for causing a computer to carry out steps of controlling an average voltage between a capacitive sensor electrode and the body so as to reduce or minimize motion-induced signals.