Doppler ultrasound method and apparatus for monitoring blood flow and detecting emboli

• US 20020091319A1
• Filed: 12/06/2000
• Published: 07/11/2002
• Est. Priority Date: 11/11/1998
• Status: Active Grant

• Current Assignee: Spentech Incorporated
• Original Assignee: Spentech Incorporated
• Inventors: Myers, Timothy R., Moehring, Mark A.
• Granted Patent: US 6,524,249 B2
• Time in Patent Office: Days
• US Class Current: 600/454
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/0816 using echo-encephalography
• CPC Class Codes: A61B 8/463 characterised by displaying multiple images or images and diagnostic data on one display composite display in devices for short-range imaging with acoustic waves G01S7/52074
• CPC Class Codes: G01S 15/8984 Measuring the velocity vector
• CPC Class Codes: G01S 15/8988 Colour Doppler imaging
• CPC Class Codes: G01S 7/52036 using analysis of echo signal for target characterisation
• CPC Class Codes: G01S 7/52046 Techniques for image enhancement involving transmitter or receiver image enhancement by image data processing G06T5/00
• CPC Class Codes: G01S 7/52071 Multicolour displays; using colour coding; Optimising colour or information content in displays, e.g. parametric imaging
• CPC Class Codes: G01S 7/52073 Production of cursor lines, markers or indicia by electronic means

Abstract

A pulse Doppler ultrasound system and associated methods are described for monitoring blood flow and detecting emboli. A graphical information display includes simultaneously displayed depth-mode and spectrogram displays. The depth-mode display indicates the various positions along the ultrasound beam axis at which blood flow is detected. These positions are indicated as one or more colored regions, with the color indicating direction of blood flow and varying in intensity as a function of detected Doppler ultrasound signal amplitude or detected blood flow velocity. The depth-mode display also includes a pointer whose position may be selected by a user. The spectrogram displayed corresponds to the location identified by the pointer. Embolus detection is also provided.

Claims

1. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the method comprising:

compiling movement information for a plurality of locations along the ultrasound beam, the movement information including detected Doppler shift signal power and associated velocity for a length of time having a plurality of time periods; and

determining the occurrence of an embolic event from the compiled movement information for each of the time periods.

2. The method of claim 1 wherein determining the occurrence of an embolic event comprises:

subtracting a respective background power level from the compiled movement information for each of the plurality of locations; and

performing a plurality of binary characterization tests to determine whether the resultant compiled movement information is indicative of an embolic event.

3. The method of claim 2 wherein the plurality of binary characterization tests comprises identifying from the resultant compiled movement information the position of the embolic event.

4. The method of claim 3, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

5. The method of claim 3 wherein identifying the position of the embolic event comprises locating the depth of maximum detected power along the ultrasound beam.

6. The method of claim 2 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having a velocity not exceeding a high-end blood flow velocity.

7. The method of claim 6 wherein the high-end blood flow velocity is approximately 2 meters per second.

8. The method of claim 2 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having uniform motion away from or towards the source of the ultrasound beam for a minimum number of time intervals.

9. The method of claim 2 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

10. The method of claim 1, further comprising displaying the compiled movement information for observation by a user.

11. The method of claim 10 wherein determining the occurrence of an embolic event is made visually by the user.

13. The method of claim 12 wherein displaying the resultant compiled movement information comprises displaying the resultant compiled movement information along time, position and power axes.

14. The method of claim 13 wherein visually determining the occurrence of an embolic event comprises identifying the position of the embolic event.

15. The method of claim 14, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

16. The method of claim 14 wherein identifying the position of the embolic event comprises locating the depth of maximum detected power along the ultrasound beam for at least one time period.

17. The method of claim 13 wherein visually determining the occurrence of an embolic event comprises determining whether the velocity of the embolic event does not exceed a high-end blood flow velocity.

18. The method of claim 17 wherein the high-end blood flow velocity is approximately 2 meters per second.

19. The method of claim 13 wherein visually determining the occurrence of an embolic event comprises determining whether the embolic event has uniform motion away from or towards the source of the ultrasound beam for a time interval.

20. The method of claim 13 wherein visually determining the occurrence of an embolic event comprises determining whether the embolic event has sufficient power fluctuation from the background power level.

12. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the method comprising:

compiling for a plurality of time periods movement information for a plurality of locations along the ultrasound beam, the movement information including detected Doppler shift signal power and associated velocity;

subtracting a respective background power level from the compiled movement information for each time period and each of the plurality of locations;

displaying the resultant compiled movement information on a display device; and

visually determining from the displayed compiled movement information the occurrence of an embolic event.

21. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the method comprising:

compiling for a plurality of time periods movement information for a plurality of locations along the ultrasound beam, the movement information including detected Doppler shift signal power and associated velocity;

for each time period, removing movement information having a detected velocity less than a velocity threshold from the compiled movement information; and

displaying on a display device the resultant compiled movement information along time and position axes; and

visually determining from the displayed resultant compiled movement information the occurrence of an embolic event.

22. The method of claim 21 wherein visually determining the occurrence of an embolic event comprises identifying the position of the embolic event.

23. The method of claim 22, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

24. The method of claim 21 wherein visually determining the occurrence of an embolic event comprises determining whether the velocity of the embolic event does not exceed a high-end blood flow velocity.

25. The method of claim 24 wherein the high-end blood flow velocity is approximately 2 meters per second.

26. The method of claim 21 wherein visually determining the occurrence of an embolic event comprises determining whether the embolic event has uniform motion away from or towards the source of the ultrasound beam for a time interval.

28. The method of claim 27 wherein the velocity threshold is approximately equal to 7 cm/s.

29. The method of claim 27 wherein the plurality of binary characterization tests comprises identifying from the resultant compiled movement information the position of the embolic event.

30. The method of claim 29, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

31. The method of claim 29 wherein identifying the position of the embolic event comprises locating the maximum detected ultrasound power along the ultrasound beam.

32. The method of claim 27 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having a velocity not exceeding a high-end blood flow velocity.

33. The method of claim 32 wherein the high-end blood flow velocity is approximately 2 meters per second.

34. The method of claim 27 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having uniform motion away from or towards the source of the ultrasound beam for a minimum number of time intervals.

35. The method of claim 27 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

36. The method of claim 27, further comprising displaying the compiled movement information for observation by a user.

37. The method of claim 27, further comprising reviewing the results of the binary characterization tests and rejecting false positive identification of an embolic event.

38. The method of claim 37, further comprising automatically incrementing a counter when it is determined that the resultant compiled movement information is consistent with the characteristics of an embolic event.

40. The method of claim 39 wherein the velocity threshold is approximately equal to 7 cm/s.

41. The method of claim 39 wherein the plurality of binary characterization tests comprises identifying from the resultant compiled movement information the position of the embolic event.

42. The method of claim 41, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

43. The method of claim 41 wherein identifying the position of the embolic event comprises locating the maximum detected ultrasound power along the ultrasound beam.

44. The method of claim 39 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having a velocity not exceeding a high-end blood flow velocity.

45. The method of claim 44 wherein the high-end blood flow velocity is approximately 2 meters per second.

46. The method of claim 39 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having uniform motion away from or towards the source of the ultrasound beam for a minimum number of time intervals.

47. The method of claim 39 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

48. The method of claim 39, further comprising displaying the compiled movement information for observation by a user.

49. The method of claim 39, further comprising reviewing the results of the binary characterization tests and rejecting false positive identification of an embolic event.

50. The method of claim 39, further comprising automatically incrementing a counter when it is determined that the resultant compiled movement information is consistent with the characteristics of an embolic event.

27. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the Doppler ultrasound system compiling for a plurality of time periods movement information including detected Doppler shift signal power and associated velocity for a plurality of locations along the ultrasound beam, the method comprising:

removing from the compiled movement information for each time period movement information having a detected velocity less than a velocity threshold; and

performing for each time period a plurality of binary characterization tests to determine whether the resultant compiled movement information is indicative of an embolic event.

39. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the Doppler ultrasound system compiling for a plurality of time periods movement information including detected Doppler shift signal power and associated velocity for a plurality of locations along the ultrasound beam, the method comprising:

subtracting a respective background power level from the compiled movement information for each time period and each of the plurality of locations;

for each time period, removing movement information having a detected velocity less than a velocity threshold from the subtracted compiled movement information; and

performing a plurality of binary characterization tests for each time period to determine whether the resultant compiled movement information is consistent with the occurrence of an embolic event.

51. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the Doppler ultrasound system compiling for a plurality of time periods movement information including detected Doppler shift signal power and associated velocity for a plurality of locations along the ultrasound beam, the method comprising:

performing for each time period a plurality of binary characterization tests indicative of embolic events on the compiled movement information to identify the occurrence of an embolic event; and

rejecting false positive embolic events.

52. The method of claim 51 wherein performing the plurality of binary characterization tests comprises identifying from the compiled movement information the position of the embolic event.

53. The method of claim 52, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

54. The method of claim 52 wherein identifying the position of the embolic event comprises locating the maximum detected ultrasound power along the ultrasound beam.

55. The method of claim 51 wherein the plurality of binary characterization tests includes determining whether the compiled movement information is indicative of an embolic event having a velocity not exceeding a high-end blood flow velocity.

56. The method of claim 55 wherein the high-end blood flow velocity is approximately 2 meters per second.

57. The method of claim 51 wherein the plurality of binary characterization tests includes determining whether the compiled movement information is indicative of an embolic event having uniform motion away from or towards the source of the ultrasound beam for a minimum number of time intervals.

58. The method of claim 51 wherein the plurality of binary characterization tests includes determining whether the compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

59. The method of claim 51, further comprising displaying the compiled movement information for observation by a user.

60. The method of claim 51, further comprising automatically incrementing a counter when it is determined that the compiled remaining movement information is consistent with the characteristics of an embolic event.

61. A method for detecting embolic events in a Doppler ultrasound system sensing motion along an ultrasound beam, the Doppler ultrasound system compiling for a plurality of time periods movement information including detected Doppler shift signal power and associated velocity for a plurality of locations along the ultrasound beam, the method comprising:

subtracting a respective background power level from the compiled movement information for each time period and each of the plurality of locations;

performing for each time period a plurality of binary characterization tests indicative of embolic events on the resultant compiled movement information to identify the occurrence of an embolic event; and

rejecting false positive embolic events.

62. The method of claim 61 wherein performing the plurality of binary characterization tests comprises identifying from the resultant compiled movement information the position of the embolic event.

63. The method of claim 62, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

64. The method of claim 62 wherein identifying the position of the embolic event comprises locating the maximum detected ultrasound power along the ultrasound beam.

65. The method of claim 61 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having a velocity not exceeding a high-end blood flow velocity.

66. The method of claim 65 wherein the high-end blood flow velocity is approximately 2 meters per second.

67. The method of claim 61 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is indicative of an embolic event having uniform motion away from or towards the source of the ultrasound beam for a minimum number of time intervals.

68. The method of claim 61 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

69. The method of claim 61, further comprising displaying the resultant compiled movement information for observation by a user.

70. The method of claim 61, further comprising automatically incrementing a counter when it is determined that the resultant compiled movement information is consistent with the characteristics of an embolic event.

71. A Doppler ultrasound system for sensing motion along an ultrasound beam and detecting embolic events, the system comprising:

an ultrasound transducer operable to detect ultrasound signals and responsively produce corresponding electrical signals;

signal processing circuitry coupled with the transducer to receive the electrical signals and compile for a plurality of time periods movement information including detected Doppler shift signal power and associated velocity for a plurality of locations along the ultrasound beam; and

detection circuitry coupled to receive the compiled movement information from the signal processing circuitry and operable to perform a plurality of binary characterization tests for each time period to determine whether the compiled movement information is consistent with the occurrence of an embolic event.

72. The Doppler ultrasound system of claim 71 wherein the detection circuitry is further operable to subtract a respective background power level from the compiled detected Doppler ultrasound power for each of the plurality of locations and time period.

73. The Doppler ultrasound system of claim 72 wherein for each time period the detection circuitry is further operable to remove movement information having a detected velocity less than a velocity threshold from the subtracted compiled movement information.

74. The Doppler ultrasound system of claim 73 wherein the velocity threshold approximately equal to 7 cm/s.

75. The Doppler ultrasound system of claim 71 wherein the detection circuitry is further operable to review the results of the plurality of binary characterization tests and reject false positive identification of embolic events.

76. The Doppler ultrasound system of claim 71, further comprising a display device coupled to the signal processing circuitry and the detection circuitry to display the compiled movement information for a user.

77. The Doppler ultrasound system of claim 71 wherein the detection circuitry is further operable to count the number of events determined to be embolic.

78. The Doppler ultrasound system of claim 71 wherein the plurality of binary characterization tests comprises identifying the position of the embolic event by locating the maximum power for each of the plurality of locations along the ultrasound beam.

79. The system of claim 78 wherein the plurality of binary characterizations tests further comprises determining whether the position of the embolic event occurs between a first depth and a second depth.

80. The Doppler ultrasound system of claim 71 wherein the plurality of binary characterization tests comprises determining whether the compiled movement information is consistent with an embolic event having a velocity not exceeding a high-end blood flow velocity.

81. The Doppler ultrasound system of claim 80 wherein the high-end blood flow velocity is approximately 2 meters per second.

82. The Doppler ultrasound system of claim 71 wherein the plurality of binary characterization tests comprises determining whether the compiled movement information is indicative of an embolic event having uniform motion away from or towards the ultrasound transducer for a minimum number of time intervals.

83. The Doppler ultrasound system of claim 71 wherein the plurality of binary characterization tests comprises determining whether the compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

84. A computer-readable medium having a computer executable program for detecting embolic events, the computer program comprising instructions, which when executed by a Doppler ultrasound system sensing motion along an ultrasound beam perform the steps of:

compiling for a plurality of time periods movement information for a plurality of locations along the ultrasound beam, the movement information including detected Doppler shift signal power and associated velocity; and

performing a plurality of binary characterization tests for each time period to determine whether the compiled movement information is indicative of the occurrence of an embolic event.

85. The computer readable medium of claim 84, further comprising subtracting a respective background power level from the compiled detected Doppler ultrasound power for each of the plurality of locations and time periods.

86. The computer readable medium of claim 85, further comprising removing movement information having a detected velocity less than a velocity threshold from the subtracted compiled movement information for each time period.

87. The computer readable medium of claim 86 wherein the velocity threshold approximately equal to 7 cm/s.

88. The computer readable medium of claim 84, further comprising reviewing the results of the binary characterization tests and rejecting false positive identification of embolic events.

89. The computer readable medium of claim 84 wherein the plurality of binary characterization tests comprises identifying from the compiled movement information the position of the embolic event.

90. The computer readable medium of claim 89 wherein the plurality of binary characterization tests further comprises determining whether the position of the embolic event occurs between a first depth and a second depth.

91. The computer readable medium of claim 89 wherein identifying the position of the embolic event comprises locating the depth of maximum detected power along the ultrasound beam for a plurality of time segments.

92. The computer readable medium of claim 84 wherein the plurality of binary characterization tests includes determining whether the compiled movement information is consistent with an embolic event having a velocity not exceeding a high-end blood flow velocity.

93. The computer readable medium of claim 92 wherein the high-end blood flow velocity comprises approximately 2 meters per second.

94. The computer readable medium of claim 84 wherein the plurality of binary characterization tests includes determining whether the compiled movement information is indicative of an embolic event having uniform motion away from or towards the source of the ultrasound beam for a minimum number of time intervals.

95. The computer readable medium of claim 84 wherein the plurality of binary characterization tests includes determining whether the compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

96. The computer readable medium of claim 84, further comprising displaying the compiled movement information for observation by a user.

97. The computer readable medium of claim 84, further comprising automatically incrementing a counter when it is determined that the compiled movement information is indicative of the occurrence of an embolic event.