Apparatus and method for efficient representation of periodic and nearly periodic signals for analysis

• US 7,239,988 B2
• Filed: 03/19/2002
• Issued: 07/03/2007
• Est. Priority Date: 03/19/2001
• Status: Active Grant

• Current Assignee: BSP Medical Limited
• Original Assignee: Bsp Biological Signal Processing Ltd.
• Inventors: Ben-David, Tamir, Beker, Amir, Hasson, Assaf
• Primary Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US10/469,994
• Publication Number:
  US 20040093192A1
• Time in Patent Office: 1,932 Days
• Field of Search: 703/21, 703/22, 703/2, 600/509, 600/517, 600/521, 600/523
• US Class Current: 703/2
• CPC Class Codes: A61B 5/339 Displays specially adapted therefor
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/4884 inducing physiological or psychological stress, e.g. applications for stress testing
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: G06F 17/14 Fourier, Walsh or analogous domain transformations , e.g. Laplace, Hilbert, Karhunen-Loeve, transforms for correlation function computation G06F17/156; spectrum analysers G01R23/16

Abstract

Apparatus for graphically representing a substantially periodic signal having substantially periodic segments, comprising a graphic transformer for converting the periodic segments into encodings respectively for arrangement in a first dimension and successively indexing the encodings to form a two-dimensional coded image, thereby to represent, within the image, dynamic changes of the periodic segments over the signal.

Claims

1. Apparatus for graphically representing a substantially periodic signal having substantially periodic segments, the apparatus comprising:

a graphic encoder for converting said periodic segments into encodings respectively of properties thereof for arrangement in a single first dimension, and

an indexer, associated with said graphic encoder, for successively indexing said encodings to show a succession of said segments over a second dimension, thereby to represent, within said two dimensions, dynamic changes of said properties of said periodic segments over said signal.

2. Apparatus according to claim 1, further comprising a period identifier, associated with said graphic transformer, for identifying a period of said signal, thereby to enable segmentation of said signal into said periodic segments.

3. Apparatus according to claim 2, wherein said period identifier comprises a time-oriented aligner and a morphology-oriented aligner to allow substantial alignment of said periodic segments.

4. Apparatus according to claim 3, wherein said time oriented aligner is operable to effect said alignment by defining a reference point in each of a plurality of said periodic segments.

5. Apparatus according to claim 3, wherein said morphology oriented aligner is operable to effect said alignment against a segment template.

6. Apparatus according to claim 5, wherein said segment template is at least one chosen from a list comprising:

a set of local maxima and minima of said periodic segment, a characteristic overall shape of said periodic segment, and a characteristic portion of said periodic segment.

7. Apparatus according to claim 3, wherein said time-orientated aligner and said morphology-oriented aligner are operable together to effect alignment of said periodic segments.

8. Apparatus according to claim 3, wherein said time-orientated aligner is operable to effect alignment of said periodic segments.

9. Apparatus according to claim 3, wherein said morphology-orientated aligner is operable to effect alignment of said periodic segments.

10. Apparatus according to claim 1, wherein said periodic segment comprises a complex of features and wherein said graphic transformer is associated with a feature encoder for encoding a feature of said periodic segment into said encoding.

11. Apparatus according to claim 10, wherein said encoding comprises a color scale used against a relative position within said period, thereby to form said encoding as a continuous colored line representing said feature at respective positions of said periodic segment.

12. Apparatus according to claim 10, wherein said encoding comprises a gray scale used against a relative position within said period, thereby to form said encoding as a continuous gray scale line representing said at least one feature at respective positions of said period.

13. Apparatus according to claim 10, wherein said encoding comprises a gray scale used against a relative position within said period, thereby to form said encoding as a continuous gray scale contour map.

14. Apparatus according to claim 10, wherein said graphic transformer further comprises a segment smoother operable in association with said feature encoder to effect smoothing of data within said periodic segment.

15. Apparatus according to claim 10, wherein said feature is amplitude.

16. Apparatus according to claim 14, wherein said segment smoother comprises an interpolation filter and a signal data reducer.

17. Apparatus according to claim 16, wherein said interpolation filter is operable to selectively interpolate data of regions of respective periodic segments to enable a smooth representation of said data.

18. Apparatus according to claim 16, wherein said signal data reducer is operable to selectively reduce data of regions of respective periodic segments to enable a smooth representation of said data.

19. Apparatus according to claim 1, wherein said signal is a biological signal.

20. The apparatus of claim 19, wherein said signal is an ECG signal.

21. The apparatus of claim 20, wherein said ECG signal is at least one of a group comprising an exercise ECG test signal and a rest ECG signal.

22. The apparatus of claim 20, wherein said ECG signal is a Holter recording signal.

23. The apparatus of claim 3, wherein said period identifier is operable to use selected frequency band components to carry out said alignment.

24. The apparatus of claim 23, wherein said period identifier is further operable to use said selected frequency band components to improve said alignment.

25. The apparatus of claim 24, wherein said period identifier further comprises:

a noise reducer operable to reduce noise in said aligned periodic segments,

a filter for selected frequency components, said filter operable upon said aligned periodic segments following noise reduction, and

a matrix orderer operable to order said aligned periodic segments in chronological order, following said frequency filtering.

26. The apparatus of claim 23, wherein said signal is an ECG signal.

27. The apparatus of claim 24, wherein said period identifier further comprises:

a period averager, usable in association with said time-oriented aligner and said morphology-oriented aligner to provide averaging over said period segments,

a template filter for filtering over said period segments, and

an array filter for filtering over an array of segments, to further improve said alignment.

28. The apparatus of claim 27, wherein said period averager is operable to average respective periods by averaging a predetermined number of consecutive periods in said array of periodic segments having a substantially low level of noise in a frequency band of interest to create a lower noise array of periodic segments.

29. The apparatus of claim 28, wherein said template filter is operable in association with said period averager, so that said lower noise array of periodic segments is selected frequency filterable to create a template array of periodic segments.

30. The apparatus of claim 29, wherein said array filter is operable in association with said time-oriented aligner and said morphology-oriented aligner by selected frequency filtering said array of periodic segments to create a filtered array of periodic segments.

31. The apparatus of claim 30, wherein said filtered array of period segments is realignable using said template array of periodic segments as a segment template.

32. An electronic graphic representation of a periodic or semi-periodic signal, comprising:

a. a first dimension carrying a one-dimensional encoding representing properties for a periodic segment of said signal, and

b. a second dimension representing a continuation of said properties over successive segments,

thereby to form a two-dimensional coded image representative of dynamic changes within the periodicity of said signal.

33. The representation of claim 32, wherein said properties comprise a feature of said periodic segment.

34. The representation of claim 32, comprising visual encoding of said feature.

35. The representation of claim 32, comprising visual encoding of derived properties of said feature.

36. The representation of claim 32, wherein said visual encoding comprises a gray scale.

37. The representation of claim 32, wherein said visual encoding comprises a color scale.

38. The representation of claim 32, wherein said periodic signal is a biological signal.

39. The representation of claim 38, wherein said periodic signal is an ECG signal.

40. A method of representing a substantially periodic signal having substantially periodic segments to show dynamic changes in the periodicity of a signal, the method comprising:

transforming said periodic segments into single dimensional encodings of properties thereof respectively for arrangement in a first dimension and

successively indexing said encodings to form a two-dimensional coded image, thereby to represent, within said image, dynamic changes of said periodic segments over said signal.

41. A method according to claim 40, further comprising identifying a period of said signal, thereby to enable segmentation of said signal into said periodic segments.

42. A method according to claim 40, wherein identification of said period of said signal further comprises the steps of:

a. aligning said periodic segments according to at least one chosen from a list of time orientation and morphology orientation; and

b. reducing noise in said aligned periodic segments.

43. A method according to claim 41, wherein said period identification is performed using selected frequency band components to carry out said alignment.

44. A method according to claim 43, wherein said period identification of said period further comprises the steps of:

a. filtering a selected frequency band from said noise-reduced aligned periodic segments; and

b. ordering said filtered periodic segments in a matrix in chronological order.

45. A method according to claim 41, wherein said period identification uses said selected frequency band components to improve said aligning of said periodic segments.

46. A method according to claim 45, wherein said signal is a biological signal.

47. A method according to claim 46, wherein said signal is an ECG signal.

48. A method according to claim 47, wherein said ECG signal is obtained during at least one chosen from a list comprising exercise ECG tests and rest ECG tests.

49. A method according to claim 47, wherein signal ECG is obtained during a Holter recording.

50. A method according to claim 40, wherein at least one of a list comprised of said identifying and said transforming, takes place in a personal digital assistant-like device.

51. A method according to claim 40, wherein at least one of a list comprised of said identifying and said transforming, takes place in a portable ECG device.

52. A method according to claim 40, further comprising manipulating said two-dimensional image graphically.

53. A method according to claim 52, wherein said manipulation comprises at least one chosen from a list comprising zoom in and zoom out.

54. A method according to claim 40, wherein said two-dimensional coded image is decodable to yield a representation of said segmented periodic segments.

55. A method according to claim 54, wherein said periodic segments are accessible by pointing on said two-dimensional image.

56. A method according to claim 40, wherein said substantially periodic signal comprises a set of signals collected from at least two non-continuous signal portions.

57. A method according to claim 55, wherein said set of signals comprises a plurality of records spanning a period of an order of magnitude within a range of seconds to years.

58. A method according to claim 56, wherein said period is of an order of magnitude reaching hours.

59. A method according to claim 56, wherein said period is within a range of orders of magnitude between hours and years.

60. A method according to claim 55, wherein said signal is a record of a biological signal comprising at least one chosen from a list comprising:

EEG signals and ECG signals, wherein said signal is correlated to a series of repetitive external stimuli.

62. A method according to claim 60, further comprising identifying said signal segments.

61. A method of representing a non-periodic signal containing a plurality of recurring signal segments to show dynamic changes in said signal segments, the method comprising:

transforming said signal segments into single dimensional encodings of properties of said segments respectively for arrangement in a first dimension, and

successively indexing said encodings to form a two-dimensional coded image, thereby to represent, within said image, dynamic changes of said signal segments over said signal.

63. Apparatus for analysis of a substantially periodic signal having substantially periodic segments and long-term evolution of trends appearing over a large number of said segments, the apparatus comprising:

an encoder for converting said periodic segments into encodings respectively of properties thereof, and

an aligner for aligning said encodings such that corresponding properties of successive segments are aligned, thereby enabling extraction over said aligned segment encoding of parameters indicative of said long-term evolution of trends.

64. Apparatus according to claim 63, wherein said substantially periodic signal comprises high frequency information and wherein said aligner is configured to make use of properties derived at least partially from said high frequency information.

65. Apparatus according to claim 63, wherein said alignment comprises morphology oriented alignment.

66. Apparatus according to claim 63, wherein said alignment comprises time oriented alignment.

67. Apparatus according to claim 63, wherein said alignment comprises morphology oriented alignment and time oriented alignment.