Method and system for acquiring biosignals in the presence of HF interference

• US 8,108,039 B2
• Filed: 07/13/2007
• Issued: 01/31/2012
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: NeuroWave Systems Inc.
• Original Assignee: NeuroWave Systems Inc.
• Inventors: Saliga, Thomas V., Bibian, Stephane, Zikov, Tatjana
• Primary Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US11/827,906
• Publication Number:
  US 20090018429A1
• Time in Patent Office: 1,663 Days
• Field of Search: 600544-547, 600/509
• US Class Current: 600/544
• CPC Class Codes: A61B 18/1402 Probes for open surgery
• CPC Class Codes: A61B 2018/00601 Cutting
• CPC Class Codes: A61B 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• CPC Class Codes: A61B 2018/1412 Blade
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/398 Electrooculography [EOG], e.g. detecting nystagmus; Electroretinography [ERG]
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: G01R 29/26 Measuring noise figure; Measuring signal-to-noise ratio

Abstract

The present invention, herein is a method and apparatus that significantly limits the effect of high frequency (“HF”) interferences on acquired electro-physiological signals, such as the EEG and EMG. Preferably, this method comprises of two separate electronic circuitries and steps or electronics for processing the signals. One circuit is used to block the transmission of HF interferences to the instrumentation amplifiers. It is comprised of a front-end active filter, a low frequency electromagnetic interference (“EMI”) shield, and an isolation barrier interface which isolates the patient from earth ground. The second circuit is used to measure the difference in potential between the two isolated sides of the isolation barrier. This so-called “cross-barrier” voltage is directly representative of the interference level that the instrumentation amplifier is subjected to. This circuit is used to confirm that the acquired signals are not corrupted by the interference.

Claims

1. A method of acquiring biopotential signals from a subject in the presence of electrical interference comprising the steps of:

attaching at least 2 electrodes to a subject,

acquiring and filtering biopotential signals from the subject using amplification circuitry, with said circuitry comprising;

at least one input filter for high frequency (HF) electrical interference rejection, and

an isolation barrier;

obtaining a quantitative measure of the level of HF electrical interference, and transmitting the biopotential signals and measured HF electrical interference level to a processor, wherein electrical interference consisting of frequencies 20 kHz or above is removed.

2. The method of claim 1 wherein said method includes the step of delivery of an anesthesia or sedation drug during surgery to reach and maintain a predetermined desired level of sedation or anesthesia using a closed-loop controller.

3. The method of claim 1 wherein said at least one input filter passes low frequency signals, but filters out portions of signals with frequencies above 56 kHz.

4. The method of claim 1 wherein said quantitative measurement of the level of HF electrical interference in the form of a voltage is measured across the isolation barrier.

5. The method of claim 1 wherein said processor uses the said measure of HF electrical interference to modify at least one behavior of the at least one input filter.

6. The method of claim 1 wherein said signals acquired from said subject are EEG signals.

7. A method of acquiring biopotential signals from a subject in the presence of electrical interference comprising the steps of:

attaching at least 2 electrodes to a subject,

acquiring and filtering biopotential signals from the subject using circuitry, with said amplification circuitry comprising;

at least one active input filter for high frequency (HF) electrical interference rejection, and

an isolation barrier where data is transmitted via magnetic coupling; and

transmitting the biopotential signals to a processor,

wherein a quantitative measurement of the magnitude of HF electrical interference in the form of a voltage is measured across said isolation barrier.

8. The method of claim 7 wherein said method includes the step of delivery of an anesthesia or sedation drug during surgery to reach and maintain a predetermined desired level of sedation or anesthesia using a closed-loop controller.

9. The method of claim 7 wherein said at least one active input filter passes low frequency signals, but filters out portions of signals with frequencies above 56 kHz.

10. The method of claim 7 further comprising a step of obtaining a quantitative measure of the level of HF electrical interference, and transmitting the biopotential signals and measured HF electrical interference level to a processor, wherein said processor uses said measure of the level of HF electrical interference to modify at least one behavior of the at least one active input filter.

11. The method of claim 7 wherein said at least one active input filter is a modified Sallen-Key filter.

12. The method of claim 7 wherein said signals acquired from said subject are EEG signals.

13. An apparatus for acquiring and filtering biopotential signals from a subject in the presence of high frequency (HF) electrical interference comprising:

at least 2 electrodes, adapted to be attached to a subject,

an amplification circuitry for high frequency (HF) electrical interference rejection connected to said at least 2 electrodes, with said circuitry comprising;

at least one active input filter,

a multistage amplification circuitry,

a signal optimized low frequency shield,

an isolation barrier where power is transmitted via an optimized transformer and data is transmitted via at least one data coil;

wherein said amplification circuitry for HF electrical interference rejection measures the level of HF electrical interference across said isolation barrier, and transmits the biopotential signals and measured HF electrical interference level to a processor.

14. The apparatus of claim 13 wherein said at least one active input filter is a modified Sallen-Key filter.

15. The apparatus of claim 13 wherein said at least one active input filter passes low frequency signals, but filters out those portions of signals with frequencies above 56 kHz.

16. The apparatus of claim 13 wherein said processor uses said measured HF electrical interference level to modify at least one behavior of the at least one active input filter.

17. The apparatus of claim 13 wherein said apparatus is used for closed-loop control anesthesia or sedation drug delivery.

18. The apparatus of claim 13 wherein said measure of the level of HF electrical interference is done through capacitive coupling between the two isolated circuits.

19. The apparatus of claim 13 wherein said biopotential signals acquired from said subject are EEG signals.