Systems and methods for filtering artifacts from composite signals

• US 5,601,088 A
• Filed: 02/17/1995
• Issued: 02/11/1997
• Est. Priority Date: 02/17/1995
• Status: Expired due to Fees

• Current Assignee: EP Technology (Boston Scientific Corporation)
• Original Assignee: EP Technology (Boston Scientific Corporation)
• Inventors: Panescu, Dorin, Swanson, David K., Whayne, James G.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/390,104
• Time in Patent Office: 725 Days
• Field of Search: 128/696, 128/697, 128/901, 128/698, 128/716, 128/731, 128/733, 607/9, 364/724.01, 364/724.19, 364/413.05, 364/413.06
• US Class Current: 600/510
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/6855 with a distal curved tip
• CPC Class Codes: A61B 5/6858 with a distal basket, e.g. expandable basket
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: H03H 17/0263 Rank order filters
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

Analog or digital systems and methods filter an artifact from a composite signal, which comprises sample values arranged with respect to time. The systems and methods select sets of WL sample values in time-sequence along the composite signal and arrange the WL sample values of each set into ordered positions following a predetermined permutation. The systems and methods select one of the ordered positions, z, within each permutation. The systems and methods generate a filter output comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the composite signal. The systems and methods remove artifacts from signals derived from a biological event; for example, electrograms, electrocardiograms, electroencephalograms, electrogastrograms, electromyograms, and respiratory signals.

Claims

1. An element for filtering an artifact from a composite signal comprising sample values arranged with respect to time, the element comprising

means for selecting sets of WL sample values in time-sequence along the composite signal,

means for arranging the WL sample values of each set into ordered positions following a predetermined permutation,

means for determining the duration, AL, of the artifact in terms of the number of sample values that the artifact contains,

means for selecting one of the ordered positions, z, within each permutation taking into account the artifact duration, AL, and

means for generating a filter output comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the composite signal.

2. An element according to claim 1

wherein the means for arranging orders the WL sample values in magnitude from smallest to largest.

3. An element according to claim 2

wherein the means for selecting one of the ordered positions increases z as AL decreases.

4. An element according to claim 1

wherein the means for selecting sets of WL samples selects WL taking into account AL.

5. An element according to claim 4 wherein the means for selecting sets of WL sample values sets

6. An element according to claim 5 wherein the means for selecting sets of WL sample values sets

7. An element for filtering an artifact from a composite signal comprising sample values arranged with respect to time, the element comprising

means for selecting a filter window encompassing a set of WL sample values within the composite signal,

means for determining the duration, AL, of the artifact in terms of the number of sample values that the artifact contains, means for advancing the filter window in time sequence along the composite signal while, upon each advance, (I) arranging the WL sample values of the encompassed set into ordered positions following a predetermined permutation, (ii) selecting one of the ordered positions, z, within the permutation taking into account the artifact duration AL, and (iii) generating an output comprising the sample value occupying the ordered position, z, and

means for generating a filtered signal comprising the outputs arranged with respect to time in sequence with the composite signal, the filtered signal being essentially free of the artifact.

8. An element according to claim 7

wherein the means for arranging orders the WL sample values in magnitude from smallest to largest.

9. An element according to claim 7

wherein the means for selecting sets of WL samples selects WL taking into account AL.

10. An element according to claim 7 wherein the means for selecting sets of WL sample values sets

11. An element according to claim 7 wherein the means for selecting sets of WL sample values sets

12. A system according to claim 7 further including means for increasing z as AL decreases.

13. A nonlinear filter for processing a signal derived from a biological event comprising sample values arranged with respect to time, the derived biological signal having an artifact signal portion and a useful signal portion, the filter comprising

a derived biological signal input,

means for establishing a sample window that encompasses a predetermined number of sample values X(k), where k=1 to WL, and WL varies according to the number of sample values that the artifact signal portion contains,

means for advancing the sample window sequentially along the biological signal in increments of one sample value, while, upon each advance:

sorting the sample values X(k) within the sample window into a permutation from the smallest to the largest sample values X(p[k]), where p[k] comprises a sort position of the permutation,

selecting a sort position p[f] expressed as ##EQU14## where z is the sort position of WL positions and generating an interim output comprising the value of X(p[f]), and

means for generating a filter output comprising the interim outputs arranged with respect to time in sequence with the composite signal.

14. A filter according to claim 13

wherein the means for establishing sets WL to at least twice the number of sample values that the artifact signal portion contains.

15. A filter according to claim 14

wherein the means for establishing sets WL so that WL exceeds twice the number of sample values that the periodic artifact signal portion contains by k, ##EQU15##

16. A filter according to claim 14 wherein the means for advancing sets f of the sort position p[f] to ##EQU16## where the expression:

##EQU17## represents the integer part of;

##EQU18##

17. A filter according to claim 14

wherein the means for generating the filter output retains a prescribed number, y₁, of beginning sample values from the derived biological signal and a number, y₂, of ending sample values from the derived biological signal and arranges the outputs between the prescribed number of beginning and ending sample values to keep the filter output arranged with respect to time in sequence with the derived biological signal.

18. A filter according to claim 17

wherein the means for advancing operates so that f of the sort position p[f] is expressed as ##EQU19## where z is the sort position of WL positions, and wherein

19. A method for processing a composite signal comprising sample values arranged with respect to time, the composite signal having an artifact signal portion and a useful signal portion, the method comprising the steps of

selecting sets of WL sample values in time-sequence along the composite signal,

arranging the WL sample values of each set into ordered positions following a predetermined permutation,

determining the duration AL of the artifact signal position in terms of the number of sample values the artifact signal position contains,

selecting one of the ordered positions, z, within each permutation taking into account AL, and

generating a filter output comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the composite signal.

20. A method according to claim 19 further comprising the step of ordering the WL sample values in magnitude from smallest to largest.

21. A method according to claim 20 further comprising the step of increasing z as AL decreases.

22. A method according to claim 21 further comprising the step of setting

23. A method according to claim 21 further comprising the step of setting

24. A method according to claim 19 wherein the composite signal comprises a depolarization wave front in myocardial tissue.

25. A method according to claim 19 wherein the composite signal comprises body tissue biopotential morphology.

26. A method according to claim 19 wherein the composite signal comprises electroencephalograms.

27. A method according to claim 19 wherein the composite signal comprises respiratory signals.

28. A method according to claim 19 wherein the composite signal comprises electrogastrograms.

29. A method according to claim 19 wherein the composite signal comprises electromyograms.

30. An element that filters a pacing artifact from an electrogram comprising

means for selecting sets of WL sample values in time-sequence along the electrogram,

means for arranging the WL sample values of each set into ordered positions following a predetermined permutation,

means for determining the duration AL of the artifact in terms of the number of sample values that the artifact contains

means for selecting one of the ordered positions, z, within each permutation taking into account AL, and

means for generating a filtered electrogram comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the electrogram, the filtered electrogram being essentially free of the pacing artifact.

32. A system according to claim 30 or 31 further including means for increasing z an AL decreases.

33. A system according to claim 30 or 31

wherein the means for arranging of WL sample values orders the WL sample values in magnitude from smallest to largest.

34. A system according to claim 30 or 31 wherein

35. A system according to claim 30 or 31 wherein the means for selecting sets of WL sample values sets

31. A system for analyzing an electrogram comprising

electrode means for sensing an electrogram in myocardial tissue,

pacing means for conditioning the electrode means to emit a pacing signal and to sense an electrogram as a result of the pacing signal, the electrogram including a pacing artifact having a duration AL expressed in terms of the number of sample values that the pacing artifact contains,

a signal processor that filters the pacing artifact from the electrogram by steps comprising (i) selecting sets of WL sample values in time-sequence along the electrogram, (ii) arranging the WL sample values of each set into ordered positions following a predetermined permutation, (iii) selecting one of the ordered positions, z, within each permutation taking into account AL, and (iv) generating a filtered electrogram comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the electrogram, the filtered electrogram being essentially free of the pacing artifact.

36. A method for analyzing an electrogram comprising the steps of

emitting a pacing signal and sensing an electrogram as a result of the pacing signal, the electrogram including a pacing artifact,

selecting sets of WL sample values in time-sequence along the electrogram,

arranging the WL sample values of each set into ordered positions following a predetermined permutation,

determining the duration AL of the pacing artifact in terms of the number of sample values that the artifact signal position contains,

selecting one of the ordered positions, z, within each permutation taking into account AL, and

generating a filtered electrogram comprising the sample values occupying the ordered position, z, of each permutation in time-sequence with the electrogram, the filtered electrogram being essentially free of the pacing artifact.

37. A method according to claim 36 further comprising the step of ordering the WL sample values in magnitude from smallest to largest.

38. A method according to claim 36 further comprising the step of increasing as AL decreases.

39. A method according to claim 36 wherein WL is selected such that

40. A method according to claim 36 wherein WL is selected such that