Tissue motion analysis medical diagnostic ultrasound system and method

• US 20030158483A1
• Filed: 02/13/2003
• Published: 08/21/2003
• Est. Priority Date: 03/10/2000
• Status: Active Grant

• Current Assignee: Acuson Corporation (Siemens AG)
• Original Assignee: Acuson Corporation (Siemens AG)
• Inventors: Jackson, John I., Allison, John W., Schlesinger, Randall L.
• Granted Patent: US 6,976,961 B2
• Time in Patent Office: Days
• US Class Current: 600/449
• CPC Class Codes: A61B 8/0883 for diagnosis of the heart
• CPC Class Codes: A61B 8/485 involving measuring strain or elastic properties
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: A61B 8/5276 due to motion
• CPC Class Codes: A61B 8/543 involving acquisition triggered by a physiological signal
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: Y10S 128/916 Ultrasound 3-D imaging

Abstract

Accurate tissue motion systems and methods are provided. Motion of the ultrasound transducer is accounted for in estimates at tissue motion. Correcting for transducer motion better isolates localized tissue contractions or expansions, such as motion of the myocardial muscle or fibers. Accurate motion estimation is also provided by determining an angle of motion from the ultrasound data. The angle of motion is used to adjust velocity estimates, providing two-dimensional velocity vectors (i.e. motion estimates comprising motion in at least two dimensions). Movement of tissue is determined by correlating speckle or a feature represented by two different sets of ultrasound data obtained at different times. Additional aspects include tracking the location of a tissue of interest. A characteristic of strain, such as the strain rate or strain, is calculated for the tracked tissue of interest. Ultrasound data associated with different positions relative to the transducer are selected as a function of the tracking and used to determine the characteristic of strain. Motion estimates corrected for transducer motion may also be used to determine a strain or strain rate. In yet another aspect, motion estimates are generated with data from an intra-cardiac transducer array. The characteristic of strain is determined from the motion estimates. Other aspects discussed above may be used with an intra-cardiac transducer array, providing accurate motion analysis based on imaging from within the heart.

Claims

1. A method for providing motion estimates with an ultrasound system, the method comprising the acts of:

(a) measuring a motion of a transducer array;

(b) acquiring ultrasound information with the transducer array; and

(c) estimating a first motion of a target as a function of the ultrasound information and the measured motion of the transducer array.

2. The method of claim 1 wherein (a) comprises measuring motion with an electromagnetic position sensor.

3. The method of claim 1 wherein (a) comprises measuring motion as a function of a correlation of the ultrasound information.

4. The method of claim 1 wherein (c) comprises:

(c1) estimating a second motion of the target from the ultrasound data; and

(c2) subtracting the measured motion of the transducer from the estimated second motion.

5. The method of claim 1 further comprising:

(d) tracking a second motion as a function of the ultrasound information;

wherein (a) comprises measuring the motion of the transducer in at least two-dimensions and (c) comprises estimating the first motion of the target in at least two-dimensions as a function of the second motion.

6. The method of claim 5 wherein (d) comprises tracking one of:

a feature represented by the ultrasound information and speckle.

7. The method of claim 1 wherein (c) comprises estimating the first motion as a two-dimensional motion.

8. The method of claim 1 further comprising:

(d) determining a strain rate as a function of the first motion of the target.

9. The method of claim 1 further comprising:

(d) determining a strain as a function of the first motion of the target.

10. A medical diagnostic ultrasound system for providing motion estimates, the system comprising:

a transducer array;

a position sensor operatively connected with the transducer array;

a motion processor for estimating a first motion of a target as a function of ultrasound information from the transducer array and position data from the position sensor.

11. The system of claim 10 wherein the position sensor comprises an electromagnetic position sensor.

12. The system of claim 10 wherein the position sensor comprises a processor for measuring motion as a function of a correlation of ultrasound information.

13. The system of claim 10 wherein the motion processor estimates the first motion as a two-dimensional motion.

14. A method for providing motion estimates of a target with an ultrasound system, the method comprising the acts of:

(a) determining a first motion angle from ultrasound data as a function of speckle or a feature;

(b) estimating a first velocity magnitude with a motion processor as a function of ultrasound data; and

(c) determining a second velocity magnitude responsive to the motion angle and the first velocity magnitude.

15. The method of claim 14 wherein (a) comprises determining the first motion angle as a function of speckle represented by the ultrasound data.

16. The method of claim 14 wherein (a) comprises determining the first motion angle as a function of the feature of the target represented by the ultrasound data.

17. The method of claim 14 wherein the target comprises tissue and (a) comprises determining the first motion angle of the tissue.

18. The method of claim 14 further comprising:

(d) determining a second motion angle corresponding to motion along an elevation axis;

wherein (c) comprises determining the second velocity magnitude as a function of the second motion angle, the first motion angle and the first velocity magnitude.

19. The method of claim 14 further comprising:

(d) estimating a third velocity magnitude as a function of the speckle or feature; and

(e) comparing the first motion angle to an about orthogonal threshold;

wherein (c) comprises determining the second velocity magnitude as a function of the third velocity magnitude in response to (e).

20. The method of claim 14 wherein (c) comprises dividing the first velocity magnitude by a cosine of the first motion angle.

21. The method of claim 14 wherein (a) comprises determining the first motion angle as a function of the speckle or feature represented by coherent ultrasound data.

22. The method of claim 14 further comprising:

(d) calculating a characteristic of strain as a function of the second velocity magnitude.

23. The method of claim 14 further comprising:

(d) performing (a), (b) and (c) for each of a plurality of local regions within a scanned region of the target.

24. A method for providing motion estimates of a target tissue with an ultrasound system, the method comprising the acts of:

(a) determining at least first and second motion angles for at least first and second local regions, respectively, as a function of ultrasound data, the first local region a different region than the second local region; and

(b) adjusting at least first and second tissue motion estimates for the at least first and second local regions, respectively, as a function of the at least first and second motion angles, respectively.

25. The method of claim 24 further comprising:

(c) determining a characteristic of tissue strain as a function of the at least first and second tissue motion estimates.

26. A method for providing motion estimates of a target with an ultrasound system, the method comprising the acts of:

(a) measuring a velocity vector representing at least two-dimensions as a function of ultrasound data; and

(b) calculating a characteristic of strain as a function of the velocity vector.

27. The method of claim 26 wherein (a) comprises determining the velocity vector as a function of speckle or a feature of the target represented by the ultrasound data.

28. The method of claim 26 wherein (a) comprises measuring a velocity vector representing three-dimensions.

29. The method of claim 26 wherein (b) comprises calculating a maximum velocity strain.

30. The method of claim 26 further comprising:

(c) performing (a) for a plurality of locations;

wherein (b) comprises calculating the characteristic of strain as a function of the velocity vector for at least two of the plurality of locations.

31. The method of claim 30 further comprising:

(d) adjusting a Doppler velocity estimate as a function of a tracking velocity estimate.

32. The method of claim 30 further comprising:

(d) tracking the at least two of the plurality of locations as a function of time;

wherein (b) comprises calculating strain as a function of the velocity vector for the at least two of the plurality of locations as a function of time with ultrasound data selected as a function of (d).

33. The method of claim 30 further comprising:

(c) determining a time in the heart cycle; and

(d) calculating strain as a function of (c) and (b) where the characteristic of strain comprises a strain rate.

34. A medical diagnostic ultrasound system for providing motion estimates of a target, the system comprising:

a motion processor for measuring a velocity vector representing at least two-dimensions as a function of ultrasound data; and

a strain processor for calculating a characteristic of strain as a function of the velocity vector.

35. A method for providing tissue motion characterization of a target with an ultrasound system, the method comprising the acts of:

(a) tracking movement of a tissue region;

(b) calculating a characteristic of strain for the tissue region; and

(c) selecting information for (b) as a function of (a).

36. The method of claim 35 wherein (a) comprises tracking speckle represented by ultrasound data.

37. The method of claim 35 wherein (a) comprises tracking a tissue feature represented by ultrasound data.

38. The method of claim 35 further comprising:

(d) estimating a velocity magnitude responsive to a motion angle.

39. The method of claim 35 further comprising:

(d) measuring movement of a transducer array; and

(e) estimating a velocity value as a function of the movement of the transducer array.

40. The method of claim 35 further comprising:

(d) performing (a), (b) and (c) for a plurality of local tissue regions.

41. The method of claim 35 wherein (c) comprises selecting ultrasound data associated with the tissue region where the ultrasound data is associated with different positions relative to a transducer as a function of time.

49. The method of claim 35 wherein (a) comprises tracking movement of a tissue region within a two-dimensional area.

42. A medical diagnostic ultrasound system for providing tissue motion characterization of a target, the system comprising:

a motion processor for tracking movement of a tissue region; and

a strain processor for calculating a characteristic of strain for the tissue region;

wherein ultrasound information for calculating the characteristic of strain is selected in response to the tracked movement of the tissue region.

43. A method for providing a characteristic of strain with an ultrasound system, the method comprising the acts of:

(a) generating motion estimates with an intra-cardiac transducer array; and

(b) calculating the characteristic of strain for tissue in response to the motion estimates.

44. The method of claim 43 further comprising:

(c) tracking movement of a tissue region; and

(d) selecting ultrasound information for (b) as a function of (c);

wherein (b) comprises calculating the characteristic of strain for the tissue region as a function of the selected ultrasound information.

45. The method of claim 43 wherein (a) comprises measuring a velocity vector representing at least two-dimensions as a function of ultrasound data, and (b) comprises calculating the characteristic of strain as a function of the velocity vector.

46. The method of claim 43 further comprising:

(c) determining a first motion angle as a function of speckle or a feature; and

(d) estimating a first velocity magnitude with a motion processor as a function of ultrasound data;

wherein (b) comprises calculating the motion estimate responsive to the motion angle and the first velocity magnitude.

47. The method of claim 43 further comprising:

(c) measuring a motion of a transducer array;

wherein (a) comprises estimating a motion of a target as a function of ultrasound information and the measured motion of the transducer array.

48. A medical diagnostic ultrasound system for providing a characteristic of strain, the system comprising:

an intra-cardiac transducer array;

a motion processor for generating motion estimates from information from the intra-cardiac transducer array; and

a strain processor for calculating the characteristic of strain for tissue in response to the motion estimates.

50. A method for accurately estimating velocity with a medical diagnostic ultrasound system, the method comprising the acts of:

(a) estimating a Doppler velocity of a tissue region along a line in a target;

(b) estimating a two-dimensional velocity vector for the tissue region;

(c) comparing the Doppler velocity to a magnitude of the two-dimensional velocity vector along the line; and

(d) determining the existence of aliasing as a function of (c).

51. The method of claim 51 wherein (b) comprises tracking the tissue region as a function of speckle or a feature represented by ultrasound data.

52. The method of claim 51 wherein (d) comprises determining the existence of aliasing where the Doppler velocity and the magnitude of the two-dimensional velocity vector along the line are substantially different.

53. The method of claim 52 wherein (d) comprises determining the existence of aliasing where the Doppler velocity and the magnitude of the two-dimensional velocity vector along the line are signed differently.

54. The method of claim 51 further comprising:

(e) indicating the existence of aliasing to a user.

55. The method of claim 51 further comprising:

(e) adjusting a velocity range in response to the existence of aliasing.

56. The method of claim 51 further comprising:

(e) calculating a corrected velocity as a function of the Doppler velocity and the magnitude of the two-dimensional velocity vector along the line.

57. The method of claim 56 wherein (e) comprises:

(e1) summing the Doppler velocity with n multiplied by the Nyquist velocity range where n is selected such that a difference between the corrected velocity and a two-dimensional magnitude of the two-dimensional velocity vector is minimized; and

(e2) dividing the sum of (e1) by the cosine of the angle of the two-dimensional velocity vector relative to the line.