Systems and methods for filtering signals derived from biological events

• US 5,605,157 A
• Filed: 02/17/1995
• Issued: 02/25/1997
• 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, Whayne, James G.
• Primary Examiner(s): Manuel, George
• Assistant Examiner(s): SCHAETZLE, KENNEDY
• Application Number:
  US08/390,587
• Time in Patent Office: 739 Days
• Field of Search: 128/901, 128/696, 128/721, 128/723, 128/731, 128/733, 382/262, 364/413.02, 364/413.03, 364/413.06
• US Class Current: 600/508
• 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

Abstract

Systems and methods provide non-linear, non-median filters for signals derived from biological events. The systems and methods select a set of n sample values arranged with respect to time from the derived biological signal input. The systems and methods arrange the n sample values of the set into ordered positions following a predetermined permutation. The systems and methods select one of the ordered positions, z, within the permutation, where z is an odd positive integer greater or equal to one but less than or equal to n. The systems and methods generate a processed output comprising the sample value occupying the ordered position, z, in the permutation.

Claims

1. An analog or digital processing element for analyzing a derived biological signal comprising sample values arranged with respect to time, the element comprising

means for selecting a set of n sample values from the derived biological signal,

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

means for selecting one of the ordered positions, z, within the permutation, where z is a positive integer and:

##EQU14## and where;

<

z<

n, and

the expression;

##EQU15## represents the integer part of;

##EQU16## and, means for generating a processed output comprising the sample value occupying the ordered position, z, in the permutation.

3. An element according to claim 1 or 2

wherein the derived biological signal has a determinable characteristic, and

wherein the positive integer z is selected taking into account the characteristic of the derived biological signal.

4. An element according to claim 1 or 2

wherein the predetermined permutation orders the n sample values in magnitude from smallest to largest.

5. An element according to claim 4

wherein the derived biological signal has a determinable duration and period, and

wherein the value of the positive integer z increases as the duration of the derived biological signal decreases.

6. An element according to claim 1 or 2

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 filter output 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.

7. An element according to claim 6

where

2. An analog or digital element for filtering a derived biological signal comprising sample values arranged with respect to time, the element comprising

means for selecting sets of n sample values in time-sequence along the derived biological signal input,

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

means for selecting one of the ordered positions, z, within each permutation, where z comprises a positive integer and:

##EQU17## and where;

<

z<

n, and

the expression;

##EQU18## represents the integer part of;

##EQU19## and, means for generating a filter output comprising the sample values occupying the ordered position, z, of each permutation arranged in time-sequence with the derived biological signal.

8. A system for filtering a derived biological signal comprising

a source element for transmitting the derived biological signal as sample values arranged with respect to time, and

a filter element comprising

an input for the derived biological signal,

a signal processor coupled to the input that filters the derived biological signal by steps comprising

selecting a filter window encompassing a set of n sample values within the derived biological signal, and

advancing the filter window in time sequence along the derived biological signal while, upon each advance, (i) arranging the n sample values of the encompassed set into ordered positions following a predetermined permutation, (ii) selecting one of the ordered positions, z, within the permutation, where z comprises a positive integer and:

##EQU20## and where;

<

z<

n, and

the expression;

##EQU21## represents the integer part of;

##EQU22## and, (iii) generating an output comprising the sample value occupying the ordered position, z, and

an output coupled to the signal processor that generates a filtered signal comprising the outputs arranged with respect to time in sequence with the derived biological signal.

9. A system according to claim 8

wherein the derived biological signal has a determinable characteristic, and

wherein the positive integer z is selected taking into account the characteristic of the derived biological signal.

10. A system according to claim 8

wherein the predetermined permutation orders the n sample values in magnitude from smallest to largest.

11. A system according to claim 10

wherein the derived biological signal has a determinable duration and period, and

wherein the value of the positive integer z increases as the duration of the biological signal decreases.

12. An element according to claim 8

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 filter output 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.

13. An element according to claim 12

where

14. A method for processing a derived biological signal comprising the steps of

receiving the derived biological signal comprising sample values arranged with respect to time,

selecting a set of n sample values from the derived biological signal,

arranging the n sample values of the set into ordered positions following a predetermined permutation, and

selecting one of the ordered positions, z, within the permutation, where z is a positive integer and:

##EQU23## where;

<

z<

n, and

the expression;

##EQU24## represents the integer part of;

##EQU25## generating an output comprising the sample value occupying the ordered position, z, and

using the generated output.

16. A method according to claim 14 or 15

wherein the derived biological signal has a determinable characteristic, and

wherein the step of selecting the positive integer z takes into account the characteristic of the derived biological signal.

17. A method according to claim 14 or 15

wherein the permutation that the step of arranging follows comprises ordering the n sample values in magnitude from smallest to largest.

18. A method according to claim 17

wherein the derived biological signal has a determinable duration and period, and

wherein the value of the positive integer z is increased as the duration of the biological signal decreases.

19. A method according to claim 14 or 15

wherein the step of using the biological signal includes the analysis of a depolarization wave front in myocardial tissue.

20. A method according to claim 14 or 15

wherein the step of using the derived biological signal includes the analysis of body tissue biopotential morphologies.

21. A method according to claim 14 or 15

wherein the step of using the derived biological signal includes the analysis of electroencephalograms.

22. A method according to claim 14 or 15

wherein the step of using the derived biological signal includes the analysis of respiratory signals.

23. A method according to claim 14 or 15

wherein the step of using the derived biological signal includes the analysis of electrogastrograms.

24. A method according to claim 14 or 15

wherein the step of using the derived biological signal includes the analysis of electromyograms.

15. A method for filtering a derived biological signal comprising the steps of

receiving the derived biological signal comprising sample values arranged with respect to time,

selecting sets of n sample values in time-sequence along the derived biological signal,

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

selecting one of the ordered positions, z, within each permutation, where z comprises a positive integer and:

##EQU26## where;

<

z<

n, and

the expression;

##EQU27## represents the integer part of;

##EQU28## and, generating a filter output comprising the sample values occupying the ordered position, z, of each permutation arranged in time-sequence with the derived biological signal, and

using the generated filter output.

25. A method for filtering a derived biological signal comprising the steps of

receiving the derived biological signal comprising sample values arranged with respect to time,

selecting a filter window encompassing a set of n sample values within the derived biological signal,

advancing the filter window sequentially along the derived biological signal while, upon each advance, (i) arranging the n sample values of the encompassed set into ordered positions following a predetermined permutation, (ii) selecting one of the ordered positions, z, within the permutation, where z comprises a positive integer and:

where;

1<

z<

n, and

the expression;

##EQU29## represents the integer part of;

##EQU30## and, (iii) generating an output comprising the sample value occupying the ordered position, z, and

generating a filtered signal comprising the outputs arranged with respect to time in sequence with the biological signal.

26. A method according to claim 25

wherein the derived biological signal has a determinable characteristic, and

wherein the step of selecting of the positive integer z takes into account the characteristic of the biological signal.

27. A method according to claim 25

wherein the step of arranging follows a permutation that orders the n sample values in magnitude from smallest to largest.

28. A method according to claim 27

wherein the derived biological signal has a determinable duration and period, and

wherein the value of the positive integer z increases as the duration of the derived biological signal decreases.

29. A method according to claim 25

and further including the step of using the filtered signal to analyze a depolarization wave front in myocardial tissue.

30. A method according to claim 25

and further including the step of using the filtered signal to analyze body tissue biopotential morphologies.

31. A method according to claim 25

and further including the step of using the derived biological signal to analyze electroencephalograms.

32. A method according to claim 25

and further including the step of using the derived biological signal to analyze respiratory signals.

33. A method according to claim 25

and further including the step of using the derived biological signal to analyze electrogastrograms.

34. A method according to claim 25

and further including the step of using the derived biological signal to analyze electromyograms.