Medical Doppler ultrasound system for locating and tracking blood flow

• US 20070016050A1
• Filed: 06/13/2005
• Published: 01/18/2007
• Est. Priority Date: 06/13/2005
• Status: Active Grant

• Current Assignee: Spentech Incorporated
• Original Assignee: Spentech Incorporated
• Inventors: Moehring, Mark, Curry, Mark
• Granted Patent: US 8,162,837 B2
• Time in Patent Office: Days
• US Class Current: 600/454
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• 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 8/4483 characterised by features of the ultrasound transducer
• CPC Class Codes: A61B 8/4488 the transducer being a phased array
• CPC Class Codes: A61B 8/4494 characterised by the arrangement of the transducer elements devices for short-range imaging using particular transducer elements arrangements under G01S15/8909; arrangements of transducers in generation of mechanical vibrations of infrasonic, sonic or ultrasonic frequency B06B1/0607
• CPC Class Codes: A61B 8/461 Displaying means of special interest
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: A61B 8/5223 for extracting a diagnostic or physiological parameter from medical diagnostic data for algorithms to analyse biomedical images G06T7/0012
• CPC Class Codes: A61B 8/54 Control of the diagnostic device
• CPC Class Codes: G01S 15/8925 the array being a two-dimensional transducer configuration, i.e. matrix or orthogonal linear arrays
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: G01S 15/8988 Colour Doppler imaging
• CPC Class Codes: G01S 7/5202 for pulse systems
• CPC Class Codes: G01S 7/52028 using digital techniques
• CPC Class Codes: G01S 7/52047 for elimination of side lobes or of grating lobes; for increasing resolving power
• CPC Class Codes: G01S 7/52066 Time-position or time-motion displays
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

Systems and methods for processing echo signals in a Doppler ultrasound system from a region of interest. An ultrasound beam is electronically steered to deliver ultrasound to and receive echo signals from a plurality of sample locations in the region of interest. The echo signals for each sample location are processed to extract Doppler shift signals and Doppler shift data representing the Doppler shift signals are generated. The Doppler shift data accumulated for the sample locations can be used to detect the presence of blood flow in the region of interest, and identify the location in the region of interest at which the presence of blood flow is detected. The blood flow can be tracked by updating the location of the detected blood flow in the region of interest. The blood flow can be further monitored by combining the locating and tracking functionality with an m-mode ultrasound image.

Claims

1. A method for locating blood flow in a region of interest using a Doppler ultrasound system having a multi-element transducer, the method comprising:

steering an ultrasound beam to deliver ultrasound to and receive echo signals from a plurality of sample locations spatially arranged across the region of interest in two lateral dimensions relative to a reference beam axis extending from the multi-element transducer;

for each sample location, processing the echo signals to extract Doppler shift signals and generate Doppler shift data therefrom and accumulating the Doppler shift data for the plurality of sample locations;

determining from the Doppler shift data accumulated for the plurality of sample locations the presence of blood flow in the region of interest; and

identifying the location in the region of interest at which the presence of blood flow is detected.

2. The method of claim 1, further comprising:

calculating data from the Doppler shift data that represents a vector defining a location of the blood flow in the region of interest;

steering the ultrasound beam to deliver ultrasound to and receive echo signals from the direction of the blood flow based on the vector; and

processing the echo signals from the direction of the blood flow to extract Doppler shift signals and calculate Doppler shift data therefrom for the detected blood flow of interest.

3. The method of claim 2 wherein calculating data from the Doppler shift data that represents a vector defining the location of the blood flow comprises:

identifying the location of blood flow in the region of interest;

electronically steering the ultrasound beam to interrogate a region proximate the location of the blood flow;

calculating a power spectrum for the interrogated region;

determining a location in the interrogated region corresponding to a maximum calculated power from the power spectrum;

defining the vector to identify the location corresponding to the maximum calculated power in the interrogated region; and

calculating data representing the vector.

4. The method of claim 3 wherein steering the ultrasound beam to interrogate a region proximate the location of the blood flow comprises:

delivering ultrasound to a plurality of interrogation locations proximate to the location of the blood flow;

for each interrogation location proximate to the location of the blood flow, processing the echo signals to extract Doppler shift signals and generate Doppler shift data therefrom and accumulating the Doppler shift data for the plurality of interrogation locations.

5. The method of claim 4 wherein spacing of the interrogation locations is denser than the sample locations spatially arranged across the region of interest.

6. The method of claim 2 wherein steering the ultrasound beam to deliver ultrasound to and receive echo signals from the direction of the blood flow based on the vector comprises:

calculating respective apodization weights and delays for each transducer element of the multi-element transducer in accordance with the vector;

driving each transducer element in accordance with the respective apodization weights and delays; and

receiving echo signals in accordance with the respective apodization weights and delays.

7. The method of claim 1 wherein processing the echo signals to extract Doppler shift signals and generate Doppler shift data comprises:

bandpass filtering the echo signals at a first frequency;

digitizing the filtered echo signals into digital data representing the filtered echo signals;

processing the digital data to provide data representing demodulated filtered echo signals;

digitally low-pass filtering the data representing of the demodulated filtered echo signals; and

decimating the digitally low-pass filtered data over a depth of interest to provide Doppler shift data.

8. The method of claim 1 wherein determining from the Doppler shift data accumulated for the plurality of sample locations the presence of blood flow in the region of interest comprises:

calculating Doppler signal strength for the echo signals for the sample locations from the Doppler shift data; and

identifying a maximum calculated Doppler signal strength associated with one of the sample locations as the location of blood flow in the region of interest.

9. The method of claim 8 wherein calculating Doppler signal strength for the echo signals for the sample locations from the Doppler shift data comprises:

constructing a covariance matrix for each of the sample locations;

calculating a respective ray defining a direction for each of the sample locations;

calculating a minimum variance power spectrum from the covariance matrix and the respective rays of each sample location.

10. The method of claim 1, further comprises processing the echo signals of detected blood flow to extract Doppler shift signals and calculate Doppler shift data therefrom, and processing the Doppler shift data to determine blood flow velocity.

11. The method of claim 1, further comprising locating an acoustic window through which ultrasound is delivered and echo signals are received to locate blood flow in the region of interest.

12. The method of claim 11 wherein locating an acoustic window comprises:

delivering ultrasound from the multi-element transducer;

receiving echo signals;

processing the echo signals to determine an average power of the echo signals;

comparing the average power to a first power threshold;

in response to the average power being less than the first power threshold, repositioning the multi-element transducer;

comparing the average power to a second power threshold; and

in response to the average power being greater than the second power threshold, steering the ultrasound beam to deliver ultrasound to and receive echo signals from the plurality of sample locations over the region of interest.

13. A method of monitoring blood flow in a region of interest using a Doppler ultrasound system having a multi-element transducer, the method comprising:

locating blood flow in the region of interest;

defining a vector identifying the location of blood flow in the region of interest;

delivering ultrasound to the location of the blood flow in accordance with the vector;

receiving first echo signals from the location of the blood flow in accordance with the vector;

processing the first echo signals from the location of the blood flow to determine Doppler signal strength and a blood flow velocity toward the probe in the region of interest;

updating the vector identifying the location of the blood flow in the region of interest;

delivering an ultrasound beam to the location of the blood flow in accordance with the updated vector;

receiving second echo signals from the location of the blood flow in accordance with the updated vector; and

processing the second echo signals from the location of the blood flow to determine Doppler signal strength and a blood flow velocity toward the probe.

14. The method of claim 13 wherein locating blood flow in the region of interest comprises identifying a location corresponding to a maximum calculated Doppler signal strength in the region of interest.

15. The method of claim 13 wherein defining a vector identifying the location of the blood flow in the region of interest comprises:

delivering ultrasound to a region proximate to the location of the blood flow;

processing echo signals from the region proximate to the location of the blood flow to extract Doppler shift signals and calculate Doppler shift data therefrom;

constructing a minimum variance power spectrum from the Doppler shift data;

identifying a location corresponding to a maximum calculated Doppler signal strength in the region proximate to the location of the blood flow from the minimum variance power spectrum;

defining the vector as the one identifying the location.

16. The method of claim 15 wherein delivering ultrasound to a region proximate the location of the blood flow comprises delivering ultrasound to a plurality of interrogation locations proximate to the location of the blood flow and processing echo signals from the region proximate the location of the blood flow comprises, for each interrogation location proximate to the location of the blood flow, processing the echo signals to extract Doppler shift signals and generate Doppler shift data therefrom and accumulating the Doppler shift data for the plurality of interrogation locations.

17. The method of claim 13 wherein updating the vector identifying the location of the blood flow in the region of interest comprises:

delivering ultrasound to a region proximate to the location identified by the defined vector;

processing echo signals from the region proximate to the location identified by the defined vector to extract Doppler shift signals and calculate Doppler shift data therefrom;

constructing a minimum variance power spectrum from the Doppler shift data;

identifying a location corresponding to a maximum calculated Doppler signal strength in the region proximate to the location identified by the defined vector from the minimum variance power spectrum; and

defining an updated vector as the vector identifying the location corresponding to the maximum calculated Doppler signal strength.

18. The method of claim 17, further comprising:

comparing the maximum calculated Doppler signal strength in the region proximate to the location identified by the defined vector to a first power threshold;

in response to the maximum calculated Doppler signal strength less than the first power threshold, locating blood flow in the region of interest;

defining a new vector identifying the location of the blood flow in the region of interest;

delivering an ultrasound beam to the location of blood flow in accordance with the new vector;

receiving echo signals from the location of blood flow in accordance with the new vector; and

processing the echo signals from the location of blood flow to determine Doppler signal strength and a blood flow velocity.

19. The method of claim 13 wherein locating blood flow in the region of interest comprises:

steering an ultrasound beam to deliver ultrasound to and receive echo signals from a plurality of sample locations across the region of interest;

for each sample location, processing the echo signals to extract Doppler shift signals and calculate Doppler shift data therefrom; and

determining from the Doppler shift data accumulated for the sample locations the presence of blood flow in the region of interest.

20. The method of claim 19, further comprising:

calculating data from the Doppler shift data that represents a vector defining a location of blood flow in the region of interest;

steering the ultrasound beam to deliver ultrasound to and receive echo signals from the direction of the location of the blood flow based on the calculated vector; and

processing the echo signals from the direction of the location of the blood flow to extract Doppler shift signals and calculate Doppler shift data therefrom for the blood flow in the region of interest.

21. The method of claim 13 wherein processing the first echo signals from the location of the blood flow to determine Doppler signal strength and a blood flow velocity comprises:

bandpass filtering the echo signals at a carrier frequency;

digitizing the filtered echo signals into digital data representing the filtered echo signals;

processing the digital data to provide data representing demodulated filtered echo signals;

digitally low-pass filtering the data representing the demodulated filtered echo signals;

decimating the digitally low-pass filtered data over a depth of interest to provide Doppler shift data for the blood flow in the region of interest;

calculating power data representing Doppler signal strength from the Doppler shift data; and

calculating velocity data representing of a blood flow velocity from the Doppler shift data.

22. The method of claim 21, further comprising:

processing the power data and the velocity data to generate display data for displaying the power data and velocity data in a power m-mode image.

23. The method of claim 13 wherein delivering an ultrasound beam to the location of the blood flow in accordance with the vector comprises:

calculating respective apodization weights and delays for each transducer element of the multi-element transducer from the vector;

delivering ultrasound from each transducer element in accordance with the respective apodization weights and delays; and

receiving echo signals in accordance with the respective apodization weights and delays.

24. The method of claim 13, further comprising locating an acoustic window through which ultrasound is delivered and echo signals are received to locate blood flow in the region of interest.

25. The method of claim 24 wherein locating an acoustic window comprises:

delivering ultrasound from the multi-element transducer;

receiving echo signals;

processing the echo signals to determine an average power of the echo signals;

comparing the average power to a first power threshold;

in response to the average power being less than the first power threshold, repositioning the multi-element transducer;

comparing the average power to a second power threshold; and

in response to the average power being greater than the second power threshold, steering the ultrasound beam to deliver ultrasound to and receive echo signals from the plurality of sample locations over the region of interest.

26. A method for processing echo signals from a region of interest in a Doppler ultrasound system, the method comprising:

electronically steering an ultrasound beam to deliver ultrasound to and receive echo signals from the region of interest, the region including a plurality of sample locations, each location having a beam axis associated therewith, at least two different planes are defined in which two or more of the beam axes lie;

for each sample location, processing the echo signals to extract Doppler shift signals; and

generating Doppler shift data representing the Doppler shift signals.

27. A method for processing echo signals from a region of interest in a Doppler ultrasound system, the method comprising:

electronically steering an ultrasound beam to deliver ultrasound to and receive echo signals from the region of interest, the region including a plurality of sample locations arranged across the region of interest in two lateral dimensions relative to an ultrasound beam axis from which the ultrasound beam is delivered;

for each sample location, processing the echo signals to extract Doppler shift signals; and

generating Doppler shift data representing the Doppler shift signals.

28. The method of claim 27 wherein processing the echo signals to extract Doppler shift signals and generating the Doppler shift data comprises:

bandpass filtering the echo signals at a first frequency;

digitizing the filtered echo signals into digital data representing the filtered echo signals;

processing the digital data to provide data representing demodulated filtered echo signals;

digitally low-pass filtering the data representing the demodulated filtered echo signals; and

decimating the digitally low-pass filtered data over a depth of interest to provide Doppler shift data.

29. The method of claim 27, further comprising processing the Doppler shift data to calculate Doppler signal strength for the echo signals for the sample locations.

30. The method of claim 27, further comprising processing the Doppler shift data to determine a direction of motion for detected motion at the sample locations.

31. The method of claim 27, further comprising processing the Doppler shift data to calculate Doppler signal strength for the echo signals for the sample locations and determine a direction of motion for detected motion at the sample locations.

32. The method of claim 31, further comprising generating data for displaying the calculated Doppler signal strength for the echo signals for the sample locations and determine a direction of motion for detected motion at the sample locations

33. A Doppler ultrasound system, comprising:

a probe having a multi-element transducer including a plurality of transducer elements;

a transmitter circuit operably coupled to the transducer elements of the transducer and configured to generate respective drive signals for driving the transducer elements to deliver an ultrasound beam;

a receiver circuit operably coupled to the transducer elements of the transducer and configured to receive echo signals detected by the respective transducer elements and generate in response thereto echo data representing the echo signals; and

a processor operably coupled to the transmitter and receiver circuits and configured to control the transmit circuit in generating drive signals for the transducer elements and configured to process the echo data from the receiver circuit and extract therefrom Doppler shift signals represented by Doppler shift data, the processor further configured to process the Doppler shift data to locate blood flow in a region of interest and automatically calculate data representing a vector identifying the location of the blood flow in the region of interest.

34. The Doppler ultrasound system of claim 33 wherein the processor comprises a processor further configured to control the transmitter circuit to deliver ultrasound to the location of the blood flow in the region of interest in accordance with the vector, to receive echo signals from the location of the blood flow in the region of interest in accordance with the vector, and process the data from the receiver circuit to extract Doppler shift signals and generate Doppler shift data therefrom for the blood flow in the region of interest.

35. The Doppler ultrasound system of claim 33 wherein the processor comprises a processor further configured to control the transmitter circuit to deliver ultrasound to a plurality of sample locations over a region of interest, each location having a beam axis associated therewith, at least two different planes are defined in which two or more of the beam axes lie, the processor further configured to process the data from the receiver circuit to extract Doppler shift signals, generate Doppler shift data therefrom for each of the sample locations, and determine from the Doppler shift data for the sample locations the presence of blood flow in the region of interest.

36. The Doppler ultrasound system of claim 33 wherein the receiver circuit comprises a plurality of receive circuits, each receive circuit operably coupled to a respective one of the transducer elements and configured to receive the echo signals detected by the respective transducer element and generate in response thereto echo data representing the respective echo signal.

37. The Doppler ultrasound system of claim 36 wherein each receive circuit comprises:

an amplifier configured to bandpass filter and amplify the respective echo signal in generating an output signal; and

an analog-to-digital converter circuit coupled to the amplifier and configured to digitize the output signal from the amplifier and generate digital echo data representing the output signal.

38. The Doppler ultrasound system of claim 33 wherein the transmitter circuit comprises a plurality of transmit circuits, each transmit circuit operably coupled to a respective one of the transducer elements and configured to generate a drive signal for driving the respective transducer element.

39. The Doppler ultrasound system of claim 33 wherein the processor configured to locate blood flow in the region of interest comprises a processor configured to control the transmitter circuit to deliver ultrasound to a plurality of sample locations over the region of interest, the sample locations arranged spatially across a surface having a lateral extent in two-dimensions relative to a normal axis extending from the multi-element transducer, the processor further configured to process the data from the receiver circuit to extract Doppler shift signals and generate Doppler shift data therefrom for each of the sample locations, and configured to determine from the Doppler shift data accumulated for the sample locations the presence of blood flow in the region of interest.

40. The Doppler ultrasound system of claim 39 wherein the processor determines from the Doppler shift data accumulated for the sample locations the presence of blood flow in the region of interest by determining the power of the Doppler signals and identifying a location corresponding to a maximum calculated power in the region of interest.

41. The Doppler ultrasound system of claim 40 wherein the processor is further configured to calculate the power of the Doppler signals for the sample locations from the Doppler shift data by:

constructing a covariance matrix for each of the sample locations;

calculating a respective ray defining a direction for each of the sample locations;

calculating a minimum variance power spectrum from the covariance matrix and the respective rays of each sample location;

determine a maximum calculated power from the minimum variance power spectrum to identify the location of blood flow in the region of interest.

42. A processing system for locating blood flow using a Doppler ultrasound system having a transmit circuit configured to independently drive transducer elements of a multi-element transducer and further having a receive circuit configured to generate respective receive echo signals in response to each of the transducer elements detecting echo signals, the processing system comprising:

an analog-to-digital converter (ADC) circuit operably coupled to the receive circuit and configured to digitize the receive echo signals into data representing the respective receive echo signals; and

a processor operably coupled to the ADC and transmit circuit and configured to generate control signals that control the transmit circuit in the driving of the transducer elements and configured to process the data from the ADC and generate Doppler shift data therefrom representing Doppler shift signals, the processor further configured to process the Doppler shift data to locate blood flow in a region of interest and calculate data representing a vector identifying the location of blood flow.

43. The processing system of claim 42 wherein the processor comprises a processor further configured to generate control signals that control the transmitter circuit to drive the transducer elements to deliver ultrasound to a plurality of sample locations over a region of interest, each location having a beam axis associated therewith, at least two different planes are defined in which two or more of the beam axes lie, the processor further configured to process the data representing the respective receive echo signals generated in response to echo signals from the sample locations to generate Doppler shift data representing Doppler shift signals for the sample locations and further configured to determine from the Doppler shift data for the sample locations the presence of blood flow in the region of interest.

44. The processing system of claim 42 wherein the processor configured to locate blood flow in the region of interest comprises a processor configured to generate control signals that control the transmit circuit to deliver ultrasound to a plurality of sample locations over the region of interest, the sample locations arranged spatially across the region of interest, the region of interest having a lateral extent in two-dimensions relative to a normal axis extending from the multi-element transducer, the processor further configured to process the data representing the respective receive echo signals to extract Doppler shift signals and generate Doppler shift data therefrom for each of the sample locations, and configured to determine from the Doppler shift data accumulated for the sample locations the presence of blood flow in the region of interest.

45. The processing system of claim 44 wherein the processor determines from the Doppler shift data accumulated for the sample locations the presence of blood flow in the region of interest by calculating Doppler signal strength of the echo signals and identifying a location corresponding to a maximum calculated Doppler signal strength in the region of interest.

46. The processing system of claim 45 wherein the processor is further configured to calculate Doppler signal strength of the echo signals for the sample locations from the Doppler shift data by:

constructing a covariance matrix for each of the sample locations;

calculating a respective ray defining a direction for each of the sample locations;

calculating a minimum variance power spectrum from the covariance matrix and the respective rays of each sample location;

determine a maximum calculated Doppler signal strength from the minimum variance power spectrum to identify the location of blood flow in the region of interest.

47. The processing system of claim 42 wherein the processor comprises a processor further configured to generate control signals that control the transmitter circuit to drive the transducer elements to deliver ultrasound to the location of blood flow in the region of interest in accordance with the vector and to further process the data representing the respective receive echo signals generated in response to echo signals from the location of blood flow in the region of interest in accordance with the vector to generate Doppler shift data for the detected blood flow.

48. The processing system of claim 47 wherein the processor is further configured to electronically steer the ultrasound beam to interrogate a region proximate the location of the blood flow, calculate an angular power spectrum for the interrogated region;

determine a location in the interrogated region corresponding to a maximum calculated Doppler signal strength from the angular power spectrum, and calculate data representing an updated vector to identify the location corresponding to the maximum calculated Doppler signal strength in the interrogated region.

49. The processing system of claim 48 wherein the processor is configured to electronically steer the ultrasound beam to interrogate a region proximate the location of the blood flow by delivering ultrasound to a plurality of interrogation locations proximate to the location of the blood flow, and the processor is further configured to, for each interrogation location proximate to the location of the blood flow, process the echo signals to extract Doppler shift signals and generate Doppler shift data therefrom and accumulate the Doppler shift data for the plurality of interrogation locations.

50. The processing system of claim 49 wherein the processor is further configured to deliver ultrasound to a plurality of interrogation locations more densely spaced than the spacing of the sample locations arranged across the region of interest.

51. The processing system of claim 42 wherein the ADC circuit comprises a plurality of ADC circuits, each ADC circuit configured to digitize a respective receive echo signal from the receive circuit.

52. A Doppler ultrasound system having a transmit circuit configured to independently drive transducer elements of a multi-element transducer and further having a receive circuit configured to generate respective receive echo signals in response to each of the transducer elements detecting echo signals, the processing system comprising:

an analog-to-digital converter (ADC) circuit operably coupled to the receive circuit and configured to digitize the receive echo signals into data representing the respective receive echo signals;

a memory for storing data; and

a processor operably coupled to the ADC and transmit circuit and configured to generate control signals that control the transmit circuit to deliver ultrasound to a plurality of sample locations arranged spatially across the region of interest, the region of interest having a lateral extent in two-dimensions relative to a normal axis extending from the multi-element transducer, the processor further configured to process the data from the receive circuit to extract Doppler shift signals and generate Doppler shift data therefrom for each of the sample locations, and configured to store the Doppler shift data for the sample locations in the memory.

53. The ultrasound system of claim 52 wherein the processor is configured to process the data from the receive circuit to extract Doppler shift signals and generate the Doppler shift data by:

bandpass filtering the echo signals at a first frequency;

digitizing the filtered echo signals into digital data representing the filtered echo signals;

processing the digital data to provide data representing demodulated filtered echo signals;

digitally low-pass filtering the data representing the demodulated filtered echo signals; and

decimating the digitally low-pass filtered data over a depth to the depth of interest to provide Doppler shift data.

54. The ultrasound system of claim 52 wherein the processor is further configured to process the Doppler shift data to calculate a power for the Doppler signals for the sample locations.

55. The ultrasound system of claim 52 wherein the processor is further configured to process the Doppler shift data to determine a direction of motion for detected motion at the sample locations.

56. The ultrasound system of claim 52 wherein the processor is further configured to process the Doppler shift data to calculate a power for the Doppler signals for the sample locations and determine a direction of motion for detected motion at the sample locations.

57. The ultrasound system of claim 56 wherein the processor is further configured to generate data for displaying the calculated a power for the Doppler signals for the sample locations and the direction of motion for the detected motion at the sample locations.

58. The ultrasound system of claim 52 wherein the ADC circuit comprises a plurality of ADC circuits, each ADC circuit configured to digitize a respective receive echo signal from the receive circuit.