Method and apparatus for determining an ultrasound fluid flow centerline

• US 7,066,888 B2
• Filed: 10/29/2004
• Issued: 06/27/2006
• Est. Priority Date: 10/29/2003
• Status: Expired due to Fees

• Current Assignee: PhysioSonics, Inc.
• Original Assignee: Allez Physionix Ltd.
• Inventors: Stein, Alan, Abend, Kenneth
• Primary Examiner(s): IMAM, ALI M
• Application Number:
  US10/976,729
• Publication Number:
  US 20050124885A1
• Time in Patent Office: 606 Days
• Field of Search: 600437-472, 736/25, 736/26, 128/916, 367/7, 367/11, 367/130, 367/138
• 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 8/085 for locating body or organic structures, e.g. tumours, calculi, blood vessels, nodules
• CPC Class Codes: G01S 15/8981 Discriminating between fixed and moving objects or between objects moving at different speeds, e.g. wall clutter filter
• CPC Class Codes: G01S 15/8984 Measuring the velocity vector
• CPC Class Codes: G01S 15/8988 Colour Doppler imaging
• CPC Class Codes: G01S 15/8993 Three dimensional imaging systems

Abstract

A method and associated apparatus are disclosed for determining the location of an effective center of fluid flow in a vessel using an ultrasound apparatus. Ultrasound energy is propagated along an axis of propagation and projects upon the vessel. A Doppler-shifted signal reflected from the fluid in the vessel is received and a set of quantities expressed as a density is derived from the Doppler shifted signal for each of a set of coordinates, the density being a function of the Doppler shift in frequency associated with each of the coordinates. One of a mean, mode or median is calculated for each of the dimensions of the set of coordinates in conjunction with the density associated therewith. This calculation is repeated throughout the field of view of the vessel to define a centerline.

Claims

1. A method for determining the location of an effective center of a fluid flow in a vessel, comprising the steps of:

(A) propagating ultrasound energy along an axis of propagation Z in a spacial coordinate system (x, y, z) in which the dimension z is in the same direction as the axis of propagation Z;

(B) projecting the ultrasound energy upon the vessel defining a set of coordinates in the spacial coordinate system where the ultrasound energy impinges upon fluid in the vessel at a given value of the dimension y;

(C) receiving a Doppler-shifted signal reflected from the fluid in the vessel at a plurality of said set of coordinates,

(D) deriving a set of quantities expressed as a density from the Doppler-shifted signal for each of said set of coordinates, the density being a function of the Doppler shift in frequency associated with each of said set of coordinates, the density being indicative of the movement of the fluid; and

(E) calculating one of the mean, mode or median of each of the dimensions of said set of coordinates in conjunction with the density associated therewith.

2. The method of claim 1, wherein said set of coordinates approximates at least a portion of a conic section.

3. The method of claim 1, further comprising the steps of repeating said steps (A)–

(E) after changing the set of coordinates to a second set of coordinates to determine another center in the fluid flow at a different point along the length of the vessel and then determining a vector v which connects the two centers and indicates the approximate direction of flow and the approximate centerline.

4. The method of claim 3, further comprising the step of repeating said steps (A)–

(E) for a plurality of center points and vectors to ascertain a centerline of the vessel over an entire field of view.

5. The method of claim 4, wherein said density is derived from at least one of Power Doppler measurements, Color Doppler measurements, and threshold flow data.

6. The method of claim 5, wherein said Power Doppler measurements occur after a Wall filter.

7. The method of claim 5, wherein said Color Doppler measurements are derived from the radial component of true velocity flow in the direction of the dimension z.

8. The method of claim 5, wherein said at least one of Power Doppler measurements, Color Doppler measurements, and threshold flow data is based on at least one of 2-D, 3-D and 4-D ultrasound techniques.

9. The method of claim 3, further comprising the step of dividing said set of coordinates into a plurality of voxels before said step (E).

10. The method of claim 9, wherein the mean is calculated as a sum of the value of the density in a voxel multiplied by the value of one of the dimensions other than z of said voxel divided by the sum of the value of densities associated with the plurality of voxels.

11. The method of claim 3, wherein the step of determining the vector v includes finding the difference between the corresponding dimensions of the effective center and the another center.

12. The method of claim 11, wherein the special coordinate system is a rectangular coordinate system and wherein said step of determining the vector v is calculated in accordance with the following mathematical statement of proportionality:

v=(v_x, v_y, v_z)∝

({overscore (x)}(y₂)−

{overscore (x)}(y₁), y₂−

y₁, {overscore (z)}(y₂)−

{overscore (z)}(y₁)).

13. The method of claim 11, wherein the speed s of the vector v is calculated by dividing the measured radial velocity by the cosine of the angle between the z direction and the direction of the approximate centerline.

14. The method of claim 13, wherein the radial component v_n of the vector v_n in a voxel n is related to the measured Doppler frequency

15. The method of claim 13, wherein the radial component v_n of the vector v_n in a voxel n is related to the measured Doppler frequency

16. The method of claim 15, wherein volume flow, {dot over (Q)}, is related to the Doppler frequency, f_n, by the formula

17. The method of claim 15, wherein volume flow, {dot over (Q)}, is related to the Doppler frequency, f_n, by the formula {dot over (Q)}=kF₁/p₀ where

18. The method of claim 9, further comprising the step of determining the lumen area by

(F) selecting a plane perpendicular to the centerline;

(G) finding the intersection of the plane with the vessel; and

(H) counting the number of pixels within the intersection.

19. The method of claim 15, further including the step of displaying a color on a display corresponding to the vector v_n of a voxel n.

20. The method of claim 15, further including the step of displaying the degree of translucency in a vessel on a display based on the vector v_n of a voxel n.

21. The method of claim 15, further including the steps of:

(F) obtaining the vector v_n in at least one voxel running through the centerline calculated at a first point in time; and

(G) adjusting a beam associated with an ultrasound probe to relocate the vector v_n found in said step (F).

22. The method of claim 15, further including the steps of:

(F) obtaining a plurality of true vector velocities for a plurality of voxels running through the centerline; and

(G) finding the peak systolic velocity from the plurality of true vector velocities.

23. The method of claim 15, further including the step of finding the peak speed of the true vector velocity from a plurality of true vector velocities on the centerline to locate the position of a stenosis in said vessel.

24. The method of claim 15, wherein the centerline has a first set of coordinates corresponding to the intersection of the centerline with one edge of the field of view, said method further comprising the steps of:

(F) repeating said steps (A)–

(E) for a plurality of center points and vectors to ascertain a first centerline of the vessel over a first field of view;

(G) repeating said steps (A)–

(E) for a plurality of center points and vectors to ascertain a second centerline of the vessel over a second field of view; and

(H) aligning the first centerline with the second centerline to form a composite image of the first and second fields of view.

25. The method of claim 15, further including the steps of:

(F) modeling the vessel on a display based on finding the true vector velocity over a plurality of voxels and the centerline;

(G) slicing the vessel into at least two sections via a plane that passes through the walls of the vessel and the centerline; and

(H) displaying one of the at least two sections of the vessel on a display.

26. An ultrasound apparatus comprising:

a transducer array for;

(A) propagating ultrasound energy along an axis of propagation Z in a spacial coordinate system (x, y, z) in which the dimension z is in the same direction as the axis of propagation Z;

(B) projecting the ultrasound energy upon the vessel defining a set of coordinates in the spacial coordinate system where the ultrasound energy impinges upon fluid in the vessel at a given value of the dimension y;

(C) receiving a Doppler-shifted signal reflected from the fluid in the vessel at a plurality of said set of coordinates; and

a processor for;

(D) deriving a set of quantities expressed as a density from the Doppler- shifted signal for each of said set of coordinates, the density being a function of the Doppler shift in frequency associated with each of said set of coordinates, the density being indicative of the movement of the fluid; and

(E) calculating one of the mean, mode or median of each of the dimensions of said set of coordinates in conjunction with the density associated therewith.

27. The apparatus of claim 26, wherein said set of coordinates approximates at least a portion of a conic section.

28. The apparatus of claim 27, wherein said processor performs said functions (A)–

(F) after changing the set of coordinates to a second set of coordinates to determine another center in the fluid flow at a different point along the length of the vessel and then determining a vector v which connects the two centers and indicates the approximate direction of flow and the approximate centerline.

29. The apparatus of claim 28, wherein said processor performs said functions (A)–

(E) for a plurality of center points and vectors to ascertain a centerline of the vessel over an entire field of view.