Doppler ultrasound method and apparatus for monitoring blood flow

• US 7,537,568 B2
• Filed: 07/01/2003
• Issued: 05/26/2009
• Est. Priority Date: 11/11/1998
• Status: Expired due to Fees

• Current Assignee: Spentech Incorporated
• Original Assignee: Spentech Incorporated
• Inventors: Moehring, Mark A.
• Primary Examiner(s): Winakur; Eric F
• Assistant Examiner(s): BOR, HELENE CATHERINE
• Application Number:
  US10/612,822
• Publication Number:
  US 20050075568A1
• Time in Patent Office: 2,156 Days
• Field of Search: 600437-472, 736/26, 333/138, 342/457
• 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 8/488 involving Doppler signals
• 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. 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 Doppler ultrasound system, comprising:

an ultrasound transducer operable to emit ultrasound signals into the subject along an ultrasound beam axis;

an ultrasound receiver for detecting echo signals resulting from the ultrasound signals emitted into the subject;

an analog-to-digital converter (ADC) circuit coupled to the ultrasound receiver to quantize the echo signals received by the ultrasound receiver into digital sample values; and

a processor coupled to the ADC circuit and operable to process the digital sample values and to calculate Doppler shift signals as a function of time for a plurality of locations along the ultrasound beam axis and to further calculate detected Doppler signal power data as a function of time and associate the detected Doppler signal power data to the Doppler shift signals for the plurality of locations along the ultrasound beam axis, the Doppler shift signals representative of blood flow detected along the ultrasound beam axis as a function of time.

2. The system of claim 1 wherein the processor comprises:

first processing circuitry for processing the digital sample values to calculate data representative of quadrature vectors, each quadrature vector having a first vector component and a second vector component;

digital filter circuitry coupled to the first processing circuitry for processing the data representative of the quadrature vectors to provide filtered quadrature vector data, the filtered quadrature vector data representative of the quadrature vectors having noise from outside a bandwidth of interest removed;

clutter removal circuitry coupled to the digital filter circuitry for processing the filtered quadrature vector data to provide clutter cancelled vector data, the clutter cancelled vector data representative of the filtered quadrature vector data having contribution from stationary reflectors removed; and

second processing circuitry coupled to the clutter removal circuitry for processing the clutter cancelled vector data to provide the blood flow velocity data as a function of time for the plurality of locations along the ultrasound beam axis.

3. The system of claim 2 wherein the second processing circuitry coupled to the clutter removal circuitry further processes the clutter cancelled vector data to provide detected Doppler signal power data as a function of time for the plurality of locations along the ultrasound beam axis.

4. The system of claim 2 wherein the first and second vector components comprises a real vector component and an imaginary vector component, respectively.

5. The system of claim 1 wherein the blood flow data representative of blood flow detected along the ultrasound beam axis comprises first blood flow velocity data representative of blood flow in a first direction, and second blood flow velocity data representative of blood flow in a second direction.

6. The system of claim 1 wherein the processor coupled to the ADC is further operable to generate data indicating blood flow velocities as a function of time for a selected location along the ultrasound beam axis.

7. A data processing engine for a Doppler ultrasound system having an ultrasound transducer from which ultrasound signals are emitted into the subject along an ultrasound beam axis and an ultrasound receiver detecting echo signals resulting from the ultrasound signals emitted into the subject, the data processing engine comprising:

an analog-to-digital converter (ADC) circuit coupled to the ultrasound receiver to quantize the echo signals received by the ultrasound receiver into digital sample values, the digital sample values stored as sample vectors;

a memory for storing data; and

a processor coupled to the ADC circuit and the memory, the processor operable to process the digital sample vectors to calculate blood flow velocity data for a plurality of locations along the ultrasound beam axis and operable to process the sample vectors to calculate detected Doppler signal power data and relate the Doppler signal power data to the blood flow velocity data for the plurality of locations along the ultrasound beam axis, the processor further operable to store the blood flow velocity data and related detected Doppler signal power data for a plurality of time intervals in the memory.

8. The data processing engine of claim 7 wherein the processor operable to process the digital sample vectors to calculate blood flow velocity data comprises a processor operable to process the digital sample vectors to calculate mean blood flow velocity data for the plurality of locations along the ultrasound beam axis.

9. The data processing engine of claim 7 wherein the processor operable to process the digital sample vectors to calculate blood flow velocity data comprises a processor operable to process the digital sample vectors to calculate median blood flow velocity data for the plurality of locations along the ultrasound beam axis.

10. The data processing engine of claim 7 wherein the processor operable to process the digital sample vectors to calculate blood flow velocity data comprises a processor operable to process the digital sample vectors to calculate peak blood flow velocity data for the plurality of locations along the ultrasound beam axis.

11. The data processing engine of claim 10 wherein the first processing circuitry comprises processing circuitry for calculating data representative of quadrature vectors, each quadrature vector having a first vector component and a second vector component.

12. The data processing engine of claim 11 wherein the first and second vector components comprises a real vector component and an imaginary vector component.

13. The data processing engine of claim 7 wherein the processor comprises:

first processing circuitry for processing the sample vectors to calculate data representative of quadrature vectors;

digital filter circuitry coupled to the first processing circuitry for processing the data representative of the quadrature vectors to provide filtered quadrature vector data, the filtered quadrature vector data representative of the quadrature vectors having noise from outside a bandwidth of interest removed;

clutter removal circuitry coupled to the digital filter circuitry for processing the filtered quadrature vector data to provide clutter cancelled vector data, the clutter cancelled vector data representative of the filtered quadrature vector data having contribution from stationary reflectors removed; and

second processing circuitry coupled to the clutter removal circuitry for processing the clutter cancelled vector data to provide the blood flow velocity data.

14. The system of claim 13 wherein the second processing circuitry coupled to the clutter removal circuitry further processes the clutter cancelled vector data to provide detected Doppler signal power data as a function of time for the plurality of locations along the ultrasound beam axis.

15. The data processing engine of claim 7 wherein the processor further generates spectrogram data indicating blood flow velocities as a function of time for a selected location along the ultrasound beam axis.

16. In a Doppler ultrasound system emitting pulsed ultrasound signals along an ultrasound beam axis and detecting echo signals resulting therefrom, a method for generating blood flow information of a subject to which the Doppler ultrasound system is applied, the method comprising:

for each pulse of ultrasound, quantizing the detected echo signals to generate a plurality of digital sample values representative of the echo signals; and

processing digital sample values from a plurality of the detected echo signals to calculate data representative of blood flow velocity detected for a plurality of locations along the ultrasound beam axis;

generating detected Doppler signal power data from a plurality of detected echo signals and associating the detected Doppler signal power data to the blood flow velocity for the plurality of locations along the ultrasound beam axis; and

accumulating the data representative of blood flow velocity for the plurality of locations along the ultrasound beam axis and the associated detected Doppler signal power data for a plurality of time intervals.

17. The method of claim 16, further comprising calculating filter coefficients based on the rate at which the detected echo signals are quantized and wherein processing the digital sample values comprises:

generating a quadrature vector from the plurality of digital sample values of each pulse of ultrasound;

processing each quadrature vector using the filter coefficients to calculate filtered quadrature vector data representative of the quadrature vector having noise from outside a bandwidth of interest removed; and

calculating from a plurality of quadrature vectors clutter cancelled vector data representative of the filtered quadrature vectors having contribution from stationary reflectors removed from the filtered quadrature vectors; and

processing the clutter cancelled vector data to provide the data representative of blood flow information.

18. The method of claim 17 wherein quantizing comprises quantizing the detected echo signals at four times the frequency of the emitted ultrasound signals.

19. The method of claim 18 wherein generating quadrature vectors from the plurality of digital sample values of each pulse of ultrasound comprises:

dividing the sample values into sets of four values, each set having first, second, third and fourth values; and

for each set, subtracting the third from the first values to generate a real vector component of the quadrature vector and subtracting the fourth from the second values to generate an imaginary vector component of the quadrature vector.

20. The method of claim 17, further comprising calculating detected Doppler signal power for the plurality of locations along an ultrasound beam axis from the clutter cancelled vector data.

21. The method of claim 16 wherein processing the digital sample values to calculate data representative of blood flow velocity further comprises calculating mean blood flow velocity data as a function of time for locations along the ultrasound beam axis.

22. The method of claim 16 wherein processing the digital sample values to calculate data representative of blood flow velocity comprises calculating median blood flow velocity data as a function of time for locations along the ultrasound beam axis.

23. The method of claim 16 wherein processing the digital sample values to calculate data representative of blood flow velocity comprises calculating peak blood flow velocity data as a function of time for locations along the ultrasound beam axis.

24. The method of claim 16, further comprising generating data to representing spectral information indicating blood flow velocities at the selected one of the displayed locations.

25. In a Doppler ultrasound system emitting ultrasound signals along an ultrasound beam axis and detecting echo signals resulting therefrom, a method for providing blood flow information of a subject to which the Doppler ultrasound system is applied, the method comprising:

quantizing the detected echo signals to generate a plurality of digital sample values representative of the echo signals;

generating quadrature vectors from the plurality of digital sample values; and

processing the quadrature vectors to calculate blood flow velocity data as a function of time for a plurality of locations along the ultrasound beam axis and to calculate detected Doppler signal power data as a function of time and associated to the blood flow velocity data for the plurality of locations.

26. The method of claim 25, further comprising processing the quadrature vectors to calculate detected Doppler signal power data as a function of time for the plurality of locations along the ultrasound beam axis at which the blood flow data is calculated.

27. The method of claim 25 wherein quantizing comprises quantizing the detected echo signals at four times the frequency of the emitted ultrasound signals.

28. The method of claim 27 wherein generating quadrature vectors from the plurality of digital sample values comprises:

dividing the sample values into sets of four values, each set having first, second, third and fourth values; and

for each set, subtracting the third from the first values to generate a real vector component of the quadrature vector and subtracting the fourth from the second values to generate an imaginary vector component of the quadrature vector.

29. The method of claim 25, further comprising calculating filter coefficients based on the rate at which the detected echo signals are quantized, and wherein processing the quadrature vectors to calculate blood flow data comprises:

processing each quadrature vector using the filter coefficients to calculate filtered quadrature vector data representative of the quadrature vector having noise from outside a bandwidth of interest removed;

calculating from the data for a plurality of quadrature vectors clutter cancelled vector data representative of the filtered quadrature vectors having contribution from stationary reflectors removed from the filtered quadrature vectors; and

processing the clutter cancelled vector data to provide blood flow velocity data as a function of time for the plurality of locations along the ultrasound beam axis.

30. The method of claim 29, further comprising calculating detected Doppler signal power for each of the first plurality of locations along an ultrasound beam axis from the clutter cancelled vector data.

31. The method of claim 25, further comprising processing the quadrature vectors to calculate a mean velocity for each of the plurality of locations along the ultrasound beam axis.

32. The method of claim 25, further comprising processing the quadrature vectors to calculate a median velocity for each of the plurality of locations along the ultrasound beam axis.

33. The method of claim 25, further comprising processing the quadrature vectors to calculate a peak velocity for each of the plurality of locations along the ultrasound beam axis.

34. The method of claim 25, further comprising generating data representing spectral information indicating blood flow velocities at the selected one of the displayed locations.

35. A computer-readable medium having computer executable instructions for controlling digital processing circuitry in a Doppler ultrasound system to process detected ultrasound echo signals and provide blood flow information, by:

controlling an analog-to-digital converter (ADC) circuit to quantize the detected ultrasound echo signals to generate a plurality of digital sample values representative of the ultrasound echo signal;

generating quadrature vectors from the plurality of digital sample values;

processing the quadrature vectors to calculate blood flow velocity data as a function of time for a plurality of locations along the ultrasound beam axis and to calculate detected Doppler signal power data as a function of time; and

processing the blood flow velocity data and the detected Doppler signal power data to relate the Doppler signal power data to the blood flow velocity data for the plurality of locations along the ultrasound beam axis.

36. The computer readable medium of claim 35 wherein the computer executable instructions for processing the blood flow data comprises processing the quadrature vectors to calculate detected Doppler signal power data for the plurality of locations along the ultrasound beam axis at which the blood flow data is calculated.

37. The computer readable medium of claim 35 wherein the computer executable instructions for controlling the ADC circuit comprises computer executable instructions for controlling the ADC circuit to quantize the detected echo signals at four times the frequency of the emitted ultrasound signals.

38. The computer readable medium of claim 37 wherein the computer executable instructions for generating quadrature vectors from the plurality of digital sample values comprises computer executable instructions for:

dividing the sample values into sets of four values, each set having first, second, third and fourth values; and

for each set, subtracting the third from the first values to generate a real vector component of the quadrature vector and subtracting the fourth from the second values to generate an imaginary vector component of the quadrature vector.

39. The computer readable medium of claim 35, further comprising computer executable instructions for calculating filter coefficients based on the rate at which the detected echo signals are quantized, and wherein the computer executable instructions for processing the quadrature vectors to calculate blood flow data comprises computer executable instructions for:

processing the quadrature vectors using the filter coefficients to calculate filtered quadrature vector data representative of the quadrature vectors having noise from outside a bandwidth of interest removed; and

calculating clutter cancelled vector data representative of the filtered quadrature vector data having contribution from stationary reflectors removed from the filtered quadrature vector data.

40. The computer readable medium of claim 39, further comprising computer executable instructions for calculating the detected Doppler signal power as a function of time for the plurality of locations along an ultrasound beam axis from the clutter cancelled vector data.

41. The computer readable medium of claim 35, further comprising computer executable instructions for processing the quadrature vectors to calculate a mean velocity for the plurality of locations along the ultrasound beam axis.

42. The computer readable medium of claim 35, further comprising computer executable instructions for processing the quadrature vectors to calculate a median velocity for the plurality of locations along the ultrasound beam axis.

43. The computer readable medium of claim 35, further comprising computer executable instructions for processing the quadrature vectors to calculate a peak velocity for the plurality of locations along the ultrasound beam axis.

44. The computer readable medium of claim 35, further comprising computer executable instructions for processing the blood flow data to display spectral information indicating blood flow velocities at the selected one of the locations along the ultrasound beam axis.

45. The computer readable medium of claim 35 wherein the computer executable instructions for processing the blood flow data to generate data that is representative of blood flow as a function of time detected for the plurality of locations along the ultrasound beam axis comprises computer executable instructions for processing the blood flow data to generate data representative of blood flow in a first direction and generate data representative of blood flow in a second direction.