Filter apparatus and method for reducing signal noise using multiple signals obtained from a single source

• US 5,421,342 A
• Filed: 06/02/1993
• Issued: 06/06/1995
• Est. Priority Date: 01/18/1991
• Status: Expired due to Term

• Current Assignee: Mortara Instrument, Inc. (Baxter International Inc.)
• Original Assignee: Mortara Instrument, Inc. (Baxter International Inc.)
• Inventors: Mortara, David W.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/071,337
• Time in Patent Office: 734 Days
• Field of Search: 128/696, 364/413.06
• US Class Current: 600/508
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: H03H 21/0043 Adaptive algorithms

Abstract

An apparatus and method directed to an adaptive noise filtering arrangement. The arrangement has the ability to estimate a first set of data for a first time-dependent variable based upon at least two sets of data for two time-dependent variables related to the first time-dependent variable. Additionally, the arrangement has the ability to filter an actual set of data for the first time-dependent variable based upon the first set of data and the actual set of data. The estimated first set of data and filtered actual set of data can be printed or displayed in a graphical format for analysis.

Claims

1. A method for producing an output signal indicative of phenomena exhibited by a signal source, said method reducing the presence of noise in the produced output signal so that the output signal is an accurate indication of the signal source phenomena, said method comprising the steps of:

positioning a plurality of sensors with respect to the signal source such that each of said sensors is subjected to a unique representation of the phenomena exhibited by the signal source which is different than the representation for each of the other sensors of said plurality;

obtaining, from the sensors, a plurality of received signals in which noise may be present;

forming at least one set of common determination points in the plurality of received signals;

measuring the actual magnitude of said received signals at the determination points;

selecting a given received signal as one for which a corresponding output signal having reduced noise will be produced;

generating, from the actual magnitudes of the received signals other than the given received signal, an estimated signal representing an estimated magnitude of the given received signal for at least one determination point in the given received signal;

comparing the given received signal and the estimated signal on the basis of their magnitudinal properties;

generating a compliance signal from said comparison of the given received signal and estimated signal indicative of the compliance between the signals, differences in the given received signal and estimated signal being attributable to noise in the given received signal; and

generating, from the given received signal and the compliance signal, a signal indicative of the phenomena exhibited by the signal source in which noise is reduced so that the accuracy of the indication provided by the signal is improved, said signal so generated comprising said output signal.

2. The method according to claim 1 wherein the step of generating an estimated signal is further defined as generating an estimated signal having a magnitude that minimizes the difference between the magnitude of the estimated signal and the actual signal magnitudes of the received signals other than the given received signal.

3. The method according to claim 2 wherein the step of generating an estimated signal is further defined as generating an estimated signal, the magnitude of which produces the least squared error with respect to the actual magnitudes of the received signals other than the given received signal.

4. The method according to claim 1 wherein the step of forming at least one set of common determination points in the plurality of received signals is further defined as forming a plurality of sets of common determination points in the plurality of received signals and wherein the step of generating an estimated signal is further defined as generating an estimated signal representing the estimated magnitude of the given received signal over a selected plurality of determination points in the given received signal.

5. The method according to claim 1 wherein the comparing step is further defined as comparing the given received signal and the estimated signal at at least one determination point in the given received signal.

6. The method according to claim 1 wherein the step of generating the signal indicative of the phenomena exhibited by the signal source is further defined as altering the magnitude of the given received signal in accordance with the compliance signal.

7. The method according to claim 1 wherein the step of generating a signal indicative of the phenomena exhibited by the signal source is further defined as attenuating the given received signal in accordance with the compliance signal.

8. A method according to claim 1 wherein the step of generating the estimated signal is further defined as generating an estimated signal for a plurality of determination points in the given received signal;

the step of generating a compliance signal is further defined as providing the compliance for each determination point in a range of said determination points and generating a compliance signal for a given determination point in said range from the compliance for each determination point in the range; and

the step of generating a signal indicative of the signal source phenomena is further defined as generating such a signal from the given received signal at the given determination point and the so-generated compliance signal.

9. The method according to claim 8 further defined as generating a signal indicative of the signal source phenomena from the given received signal at a determination point in the center of said range of determination points.

10. The method according to claim 1 wherein said plurality of received signals are obtained simultaneously.

11. The method according to claim 1 wherein the plurality of received signals are obtained sequentially.

12. The method according to claim 1 wherein the plurality of received signals include segments of distinguishable magnitudinal variation and wherein the step of generating the estimated signal is further defined as generating an estimated signal from the actual magnitudes of the received signals other than the given received signal in the segments of distinguishable magnitudinal variation.

13. The method according to claim 1 wherein the steps of the method are carried out with respect to each of the plurality of received signals.

14. A method for producing an EKG output signal indicative of phenomena exhibited by a patient'"'"'s heart, said method reducing the presence of noise in the produced EKG output signal so that the EKG output signal is an accurate indication of the heart phenomena, said method comprising the steps of:

positioning a plurality of electrodes with respect to the heart in accordance with an electrode positioning protocol such that each of said electrodes is subjected to a unique representation of the phenomena exhibited by the heart which is different than the representation for each of the other electrodes of said plurality;

obtaining, from the electrodes, a plurality of received EKG signals in which noise may be present;

forming at least one set of common determination points in the plurality of received EKG signals;

measuring the actual magnitude of said received EKG signals at the determination points;

selecting a given received EKG signal as one for which a corresponding EKG output signal having reduced noise will be produced;

generating, from the actual magnitudes of the received EKG signals other than the given received EKG signal, an estimated EKG signal representing an estimated magnitude of the given received EKG signal for at least one determination point in the given received EKG signal;

comparing the given received EKG signal and the estimated EKG signal on the basis of their magnitudinal properties;

generating a compliance signal from said comparison of the given received EKG signal and estimated EKG signal indicative of the compliance between the signals, differences in the given received EKG signal and estimated EKG signal being attributable to noise in the given received EKG signal; and

generating, from the given received EKG signal and the compliance signal, a signal indicative of the phenomena exhibited by the heart in which noise is reduced so that the accuracy of the indication provided by the signal is improved, said signal so generated comprising said EKG output signal.

15. The method according to claim 14 wherein the step of generating an estimated EKG signal is further defined as generating an estimated EKG signal having a magnitude that minimizes the difference between the magnitude of the estimated EKG signal and the actual signal magnitudes of the received EKG signals other than the given received EKG signal.

16. The method according to claim 15 wherein the step of generating an estimated EKG signal is further defined as generating an estimated EKG signal, the magnitude of which produces the least squared error with respect to the actual magnitudes of the received EKG signals other than the given received EKG signal.

17. The method according to claim 14 wherein the step of forming at least one set of common determination points in the plurality of received EKG signals is further defined as forming a plurality of sets of common determination points in the plurality of received EKG signals and wherein the step of generating an estimated EKG signal is further defined as generating an estimated EKG signal representing the estimated magnitude of the given received EKG signal over a selected plurality of determination points in the given received EKG signal.

18. The method according to claim 14 wherein the comparing step is further defined as comparing the given received EKG signal and the estimated EKG signal at at least one determination point in the given received EKG signal.

19. The method according to claim 14 wherein the step of generating the signal indicative of the phenomena exhibited by the heart is further defined as altering the magnitude of the given received EKG signal in accordance with the compliance signal.

20. The method according to claim 19 wherein the step of generating a signal indicative of the phenomena exhibited by the heart is further defined as attenuating the given received signal in accordance with the compliance signal.

21. A method according to claim 14 wherein the step of generating the estimated EKG signal is further defined as generating an estimated EKG signal for a plurality of determination points in the given received signal;

the step of generating a compliance signal is further defined as providing the compliance for each determination point in a range of said determination points and generating a compliance signal for a given determination point in said range from the compliance for each determination point in the range; and

the step of generating a signal indicative of the heart phenomena is further defined as generating such a signal from the given received EKG signal at the given determination point and the so-generated compliance signal.

22. The method according to claim 21 further defined as generating a signal indicative of the heart phenomena from the given received EKG signal at a determination point in the center of said range of determination points.

23. The method according to claim 14 wherein said plurality of received EKG signals are obtained simultaneously.

24. The method according to claim 14 wherein the plurality of received EKG signals are obtained sequentially.

25. The method according to claim 14 wherein the plurality of received EKG signals include segments of distinguishable magnitudinal variation and wherein the step of generating the estimated EKG signal is further defined as generating an estimated EKG signal from the actual magnitudes of the received EKG signals other than the given received EKG signal in the segments of distinguishable magnitudinal variation.

26. The method according to claim 25 wherein the plurality of received EKG signals include QRS segments and wherein the estimated EKG signal is generated from signal magnitudes in the QRS segments.

27. The method according to claim 14 wherein the steps of the method are carried out with respect to each of the plurality of received EKG signals.

28. Signal processing apparatus for producing an output signal indicative of phenomena exhibited by a signal source, said apparatus reducing the presence of noise in the produced output signal so that the output signal is an accurate indication of the signal source phenomena, said apparatus being suitable for use with a plurality of sensors positioned with respect to the signal source so as to obtain a plurality of signals in which noise may be present, each of the obtained signals containing a unique representation of the phenomena exhibited by the signal source which is different than the representation found in each of the other obtained signals of said plurality, said apparatus comprising:

an input receiving the signals obtained by said sensors and forming at least one set of common determination points in said plurality of signals;

a measurement circuit measuring the actual magnitude of said signals obtained by the sensors at the determination points in the signals;

a selector selecting a given obtained signal as one for which a corresponding output signal having reduced noise will be produced;

an estimated magnitude signal generator for generating, from the actual magnitudes of the obtained signals other than the selected signal, an estimated signal representing an estimated magnitude of the selected signal for at least one determination point in the selected signal;

a comparator comparing the selected signal and the estimated signal on the basis of their magnitudinal properties and determining the compliance between the selected signal and the estimated signal, differences in the selected and estimated signal being attributable to noise in the selected signal; and

a signal generator generating, from the selected signal and the compliance, a signal indicative of the phenomena exhibited by the signal source in which the noise is reduced so that the accuracy of the indication provided by the signal is improved, said signal generator providing said signal so generated as said output signal.

29. The signal processing apparatus according to claim 28 wherein said estimated magnitude signal generator is further defined as generating an estimated signal having a magnitude that minimizes the difference between the magnitude of the estimated signal and the actual magnitude of the obtained signals other than the selected signal.

30. The signal processing apparatus according to claim 28 wherein said estimated magnitude signal generator is further defined as generating an estimated signal, the magnitude of which produces the least squared error with respect to the actual magnitudes of the obtained signals other than the selected signal.

31. The signal processing apparatus according to claim 28 wherein the input is further defined as forming a plurality of sets of common determination points in said plurality of signals and wherein the estimated magnitude signal generator is further defined as generating an estimated signal over a selected plurality of determination points.

32. The signal processing apparatus according to claim 28 wherein said comparator is further defined as comparing the selected signal and the estimated signal at determination points in the selected signal.

33. The signal processing apparatus according to claim 28 wherein the signal generator is further defined as altering the selected signal in accordance with the compliance to generate the signal indicative of the phenomena exhibited by the signal source.

34. The signal processing apparatus according to claim 28 wherein said signal generator is further defined as attenuating the selected signal in accordance with the compliance to generate the signal indicative of the phenomena exhibited by the signal source.

35. The signal processing apparatus according to claim 28 wherein said estimated magnitude signal generator is further defined as generating an estimated signal for a plurality of determination points in said selected signal;

wherein said comparator is further defined as determining the compliance for each determination point in a range of said determination points and for providing a compliance for a given determination point in said range from the compliance for each determination point in the range; and

wherein said signal generator is further defined as generating a signal indicative of the signal source phenomena at a determination point in said range of determination points in accordance with the so-determined compliance.

36. The signal processing apparatus according to claim 35 wherein said signal generator is further defined as generating a signal indicative of the signal source phenomena at a determination point in the center of said range of determination points.

37. Signal processing apparatus for producing an EKG output signal indicative of phenomena exhibited by a patient'"'"'s heart, said apparatus reducing the presence of noise in the produced EKG output signal so that the EKG output signal is an accurate indication of the heart phenomena, said apparatus being suitable for use with a plurality of electrodes positioned with respect to the heart in accordance with an electrode positioning protocol so as to obtain a plurality of EKG signals in which noise may be present, each of the obtained EKG signals containing a unique representation of the phenomena exhibited by the heart which is different than the representation found in each of the other obtained EKG signals of said plurality, said apparatus comprising:

an input receiving the EKG signals obtained by said electrodes and forming at least one set of common determination points in said plurality of EKG signals;

a measurement circuit measuring the actual magnitude of said EKG signals obtained by the electrodes at the determination points in the EKG signals;

a selector selecting a given obtained EKG signal as one for which a corresponding EKG output signal having reduced noise will be produced;

an estimated magnitude signal generator for generating, from the actual magnitudes of the obtained EKG signals other than the selected signal, an estimated EKG signal representing an estimated magnitude of the selected EKG signal for at least one determination point in the selected EKG signal;

a comparator comparing the selected EKG signal and the estimated EKG signal on the basis of their magnitudinal properties and determining the compliance between the selected EKG signal and the estimated EKG signal, differences in the selected and estimated EKG signals being attributable to noise in the selected signal; and

a signal generator generating, from the selected EKG signal and the compliance, a signal indicative of the phenomena exhibited by the heart in which the noise is reduced so that the accuracy of the indication provided by the signal is improved, said signal generator providing said signal so generated as said EKG output signal.

38. The signal processing apparatus according to claim 37 wherein said estimated magnitude signal generator is further defined as generating an estimated EKG signal having a magnitude that minimizes the difference between the magnitude of the estimated EKG signal and the actual magnitude of the obtained EKG signals other than the selected signal.

39. The signal processing apparatus according to claim 38 wherein said estimated magnitude signal generator is further defined as generating an estimated EKG signal, the magnitude of which produces the least squared error with respect to the actual magnitudes of the obtained EKG signals other than the selected signal.

40. The signal processing apparatus according to claim 37 wherein the input is further defined as forming a plurality of sets of common determination points in said plurality of EKG signals and wherein the estimated magnitude signal generator is further defined as generating an estimated EKG signal over a selected plurality of determination points.

41. The signal processing apparatus according to claim 37 wherein said comparator is further defined as comparing the selected EKG signal and the estimated EKG signal at determination points in the selected EKG signal.

42. The signal processing apparatus according to claim 37 wherein the signal generator is further defined as altering the selected EKG signal in accordance with the compliance to generate the signal indicative of the phenomena exhibited by the heart.

43. The signal processing apparatus according to claim 37 wherein said signal generator is further defined as attenuating the selected EKG signal in accordance with the compliance to generate the signal indicative of the phenomena exhibited by the heart.

44. The signal processing apparatus according to claim 37 wherein said estimated magnitude signal generator is further defined as generating an estimated signal for a plurality of determination points in said selected EKG signal;

wherein said comparator is further defined as determining the compliance for each determination point in a range of said determination points and for providing a compliance for a given determination point in said range from the compliance for each determination point in the range; and

wherein said signal generator is further defined as generating a signal indicative of the heart phenomena at a determination point in said range of determination points in accordance with the so determined compliance.

45. The signal processing apparatus according to claim 44 wherein said signal generator is further defined as generating a signal indicative of the heart phenomena at a determination point in the center of said range of determination points.