Filter apparatus and method for reducing signal noise using a plurality of signals obtained from a signal source

• US 5,490,515 A
• Filed: 08/29/1994
• Issued: 02/13/1996
• 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:
  US08/297,496
• Time in Patent Office: 533 Days
• Field of Search: 128/696
• 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 providing an output signal corresponding to a signal produced by a signal source, the signal produced by the signal source having a series of repetitious, generally similar features, said method reducing the presence of noise in the provided output signal and comprising the steps of:

sequentially sensing a plurality of said repetitious signal features to obtain a plurality of received signals in which noise may be present, each of said plurality of received signals corresponding to one of said repetitious signal features;

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

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

selecting a given one of the received signal as that 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, said output signal in which the presence of noise is reduced.

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 determination points in the plurality of received signals is further defined as forming a plurality of sets of 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 for 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 said output signal is further defined as altering the magnitude of the given received signal in accordance with the compliance signal.

7. The method according to claim 6 wherein the step of generating said output signal 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 said output signal is further defined as generating said output 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 said output signal 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 the plurality of received signals include feature 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 feature segments of distinguishable magnitudinal variation.

11. A method for producing an EKG output signal indicative of electrical phenomena exhibited by a patient'"'"'s heart, the phenomena including a series of repetitious, generally similar, electrical signal features associated with the functioning of the 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:

sequentially sensing a plurality of said repetitious signal features;

obtaining, from the sensing, a plurality of received EKG signals in which noise may be present, each of said plurality of received EKG signals corresponding to one of said repetitious signal features;

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 one of the received EKG signal as that 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, said EKG output signal having reduced noise.

12. The method according to claim 11 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.

13. The method according to claim 12 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.

14. The method according to claim 11 wherein the step of forming at least one set of determination points in the plurality of received EKG signals is further defined as forming a plurality of sets of 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 for a selected plurality of determination points in the given received EKG signal.

15. The method according to claim 11 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.

16. The method according to claim 11 wherein the step of generating said EKG output signal is further defined as altering the magnitude of the given received EKG signal in accordance with the compliance signal.

17. The method according to claim 16 wherein the step of generating said EKG output signal is further defined as attenuating the given received signal in accordance with the;

compliance signal.

18. A method according to claim 11 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 said EKG output signal is further defined as generating said EKG output signal from the given received EKG signal at the given determination point and the so-generated compliance signal.

19. The method according to claim 18 further defined as generating said EKG output signal from the given received EKG signal at a determination point in the center of said range of determination points.

20. The method according to claim 11 wherein the plurality of received EKG signals include feature 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 feature segments of distinguishable magnitudinal variation.

21. The method according to claim 20 wherein the plurality of received EKG signals include QRS feature segments and wherein the estimated EKG signal is generated from signal magnitudes in the QRS feature segments.

22. Signal processing apparatus for providing an output signal corresponding to a signal produced by a signal source, the signal produced by the signal source having a series of repetitious, generally similar features, said apparatus reducing the presence of noise in the provided output signal, said apparatus being suitable for use with sensor means for obtaining the signal produced by the signal source, in which signal noise may be present, said apparatus comprising:

an input receiving the signal obtained by the sensor means and forming a plurality of input signals each of which corresponds to one of the repetitious signal features;

means forming at least one set of determination points in said plurality of input signals;

a measurement circuit measuring the actual magnitude of said plurality of input signals at the determination points in the plurality of input signals;

a selector selecting a given one of said input signal as that 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 input signals other than the selected input signal, an estimated signal representing an estimated magnitude of the selected input signal for at least one determination point in the selected input signal;

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

a signal generator generating, from the selected input signal and the compliance, said output signal in which noise is reduced.

23. The signal processing apparatus according to claim 22 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 magnitudes of the input signals other than the selected input signal.

24. The signal processing apparatus according to claim 23 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 input signals other than the selected input signal.

25. The signal processing apparatus according to claim 23 wherein said forming means is further defined as forming a plurality of sets of determination points in said plurality of input signals and wherein the estimated magnitude signal generator is further defined as generating an estimated signal for a selected plurality of determination points.

26. The signal processing apparatus according to claim 22 wherein said comparator is further defined as comparing the selected input signal and the estimated signal at determination points in the selected input signal.

27. The signal processing apparatus according to claim 22 wherein the signal generator is further defined as altering the selected input signal in accordance with the compliance to generate said output signal.

28. The signal processing apparatus according to claim 27 wherein said signal generator is further defined as attenuating the selected input signal in accordance with the compliance to generate said output signal.

29. The signal processing apparatus according to claim 22 wherein said estimated magnitude signal generator is further defined as generating an estimated signal for a plurality of determination points in said selected input 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 said output signal at a determination point in said range of determination points in accordance with the so-determined compliance.

30. The signal processing apparatus according to claim 29 wherein said signal generator is further defined as generating said output signal at a determination point in the center of said range of determination points.

31. Signal processing apparatus for producing an EKG output signal indicative of electrical phenomena exhibited by a patient'"'"'s heart, the phenomena including a series of repetitious, generally similar, electrical signal features associated with the functioning of the 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 sensor means for obtaining an EKG signal in which noise may be present, said apparatus comprising:

an input receiving the EKG signal obtained by the sensor means and forming a plurality of input signals, each of which corresponds to one of the repetitious signal features;

means forming at least one set of determination points in said plurality of input signals;

a measurement circuit measuring the actual magnitude of said plurality of input signals at the determination points in the plurality of input signals;

a selector selecting a given one of said input signal as that 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 input signals other than the selected input signal, an estimated signal representing an estimated magnitude of the selected input signal for at least one determination point in the selected input signal;

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

a signal generator generating, from the selected input signal and the compliance, said EKG output signal in which noise is reduced.

32. The signal processing apparatus according to claim 31 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 magnitudes of the obtained input signals other than the selected input signal.

33. The signal processing apparatus according to claim 32 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 input signals other than the selected input signal.

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

35. The signal processing apparatus according to claim 31 wherein said comparator is further defined as comparing the selected input signal and the estimated signal at determination points in the selected input signal.

36. The signal processing apparatus according to claim 31 wherein the signal generator is further defined as altering the selected input signal in accordance with the compliance to generate said output signal.

37. The signal processing apparatus according to claim 36 wherein said signal generator is further defined as attenuating the selected input signal in accordance with the compliance to generate said output signal.

38. The signal processing apparatus according to claim 31 wherein said estimated magnitude signal generator is further defined as generating an estimated signal for a plurality of determination points in said selected input 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 said output signal at a determination point in said range of determination points in accordance with the so determined compliance.

39. The signal processing apparatus according to claim 38 wherein said signal generator is further defined as generating said output signal at a determination point in the center of said range of determination points.