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

• US 6,547,736 B1
• Filed: 05/18/2000
• Issued: 04/15/2003
• Est. Priority Date: 11/11/1998
• Status: Expired due to Term

• Current Assignee: Spentech Incorporated
• Original Assignee: Spentech Incorporated
• Inventors: Myers, Timothy R., Moehring, Mark A.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Imam, Ali M.
• Application Number:
  US09/574,755
• Time in Patent Office: 1,062 Days
• Field of Search: 600/437, 600/440, 600/441, 600/443, 600/447, 600/453, 600/454, 600/410, 600/455, 600/469, 736/25, 736/26, 333/138, 342/357, 324/201
• 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: A61B 8/467 characterised by special input means
• 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
• CPC Class Codes: H04B 2001/6908 using time hopping

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 and characterization are also provided.

Claims

1. A method for detecting embolic events using 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 of the plurality of locations and time periods;

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

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; and

reviewing the results of the binary characterization tests to reject any false positive identifications of an embolic event.

2. The method of claim 1 wherein the velocity threshold is approximately equal to 7 cm/s.

3. The method of claim 1 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 maximum power for each of the plurality of locations along the ultrasound beam.

6. The method of claim 1 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 comprises approximately 2 meters per second.

8. The method of claim 1 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 1 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 resultant compiled movement information for observation by a user.

11. The method of claim 1, further comprising automatically incrementing a counter when it is determined that the resultant compiled movement information is indicative of an embolic event.

12. 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 for a plurality of time periods compile 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 subtract a respective background power level from the compiled detected Doppler ultrasound power for each of the plurality of locations and time periods, remove movement information having a detected velocity less than a velocity threshold from the subtracted compiled movement information for each time period, perform for each time period a plurality of binary embolus characterization tests on the resultant compiled movement information, review the results therefrom, and reject any false positive identifications of an embolic event.

13. The Doppler ultrasound system of claim 12, further comprising a display device coupled to the signal processing circuitry and the detection circuitry to display the resultant compiled movement information for a user.

14. The Doppler ultrasound system of claim 12 wherein the detection circuitry is further operable to count the number of events determined to be embolic.

15. The Doppler ultrasound system of claim 12 wherein the velocity threshold approximately equal to 7 cm/s.

16. The Doppler ultrasound system of claim 12 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 and time periods.

17. The Doppler ultrasound system of claim 16, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

18. The Doppler ultrasound system of claim 12 wherein the plurality of binary characterization tests comprises determining whether the resultant compiled movement information is consistent with an embolic event having a velocity not exceeding a high-end blood flow velocity.

19. The Doppler ultrasound system of claim 18 wherein the high-end blood flow velocity is approximately 2 meters per second.

20. The Doppler ultrasound system of claim 12 wherein the plurality of binary characterization tests comprises determining whether the resultant compiled movement information is indicative of an embolic event having uniform motion away from or towards the ultrasound transducer for minimum time intervals.

21. The Doppler ultrasound system of claim 12 wherein the plurality of binary characterization tests comprises determining whether the resultant compiled movement information of a potential embolic event has sufficient power fluctuation from the background power level.

22. 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 and 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, perform the steps of:

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

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

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

reviewing the results of the binary characterization tests to reject any false positive identifications of an embolic event.

23. The computer readable medium of claim 22 wherein the velocity threshold approximately equal to 7 cm/s.

24. The computer readable medium of claim 22 wherein the plurality of binary characterization tests comprises identifying from the resultant compiled movement information the position of the embolic event.

25. The computer readable medium of claim 24, further comprising determining whether the position of the embolic event occurs between a first depth and a second depth.

26. The computer readable medium of claim 24 wherein identifying the position of the embolic event comprises locating the maximum power for each of the plurality of locations along the ultrasound beam.

27. The computer readable medium of claim 24 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.

28. The computer readable medium of claim 24 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.

29. The computer readable medium of claim 22 wherein the plurality of binary characterization tests includes determining whether the resultant compiled movement information is consistent with an embolic event having a velocity not exceeding a high-end blood flow velocity.

30. The computer readable medium of claim 29 wherein the high-end blood flow velocity comprises approximately 2 meters per second.

31. The computer readable medium of claim 22, further comprising displaying the resultant compiled movement information for observation by a user.

32. The computer readable medium of claim 31 wherein determining whether the resultant compiled movement information is consistent with characteristics of an embolic event is made visually by the user.

33. The computer readable medium of claim 22, 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.