Method and apparatus for automatic vessel tracking in ultrasound imaging

• US 6,464,641 B1
• Filed: 02/25/2000
• Issued: 10/15/2002
• Est. Priority Date: 12/01/1998
• Status: Expired due to Term

• Current Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Original Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Inventors: Mo, Larry Y. L., Pan, Lihong, Washburn, Michael J.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Imam, Ali M.
• Application Number:
  US09/514,068
• Time in Patent Office: 963 Days
• Field of Search: 600/437, 600/440-447, 600/450, 600/453, 600/454, 600/455-457, 600/407-436, 342/95, 342/120, 736/25, 736/26, 382/124, 382/128, 310/317, 310/334, 310/335
• US Class Current: 600/453
• CPC Class Codes: A61B 5/489 Blood vessels
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• 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 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/0858 involving measuring tissue layers, e.g. skin, interfaces
• CPC Class Codes: A61B 8/13 Tomography A61B8/10, A61B8/12 take precedence; tomography for radiation diagnosis A61B6/02
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: G01S 15/58 Velocity or trajectory determination systems; Sense-of-movement determination systems velocity measurement in imaging systems G01S15/8979

Abstract

Method and apparatus for automatically maintaining the range gate inside a moving blood vessel during ultrasound imaging. The range gate can be maintained at the vessel center, or at a certain distance from one of the vessel boundaries, or at a certain ratio of the respective distances from the two boundaries. The user first places the range gate on the blood flow being examined. An algorithm processes each successive image frame and automatically updates the information about vessel boundary positions and the vessel orientation angle in the vicinity of the range gate. If the range gate position relative to the vessel boundaries is different than that in the previous frame by more than a predetermined amount, the position of the range gate graphic and the orientation of the vessel slope cursor (and the Doppler angle) are automatically adjusted to the new values.

Claims

1. A method comprising the steps of:

(a) displaying an image of a blood vessel;

(b) storing a frame of image parameter values from which said image was derived, said image parameter values corresponding to respective pixels in said image;

(c) placing a graphic representing a range gate overlying said blood vessel in said image;

(d) determining a vessel slope of the blood vessel at or near said range gate based on said frame of image parameter values;

(e) placing a graphic representing said vessel slope overlying said blood vessel in said image;

(f) determining the position of a boundary of the blood vessel; and

(g) adjusting the position of said range gate if the change in the position of the boundary relative to said range gate is equal to or greater than a predetermined threshold.

2. The method as recited in claim 1, wherein said step (f) comprises the step of determining the address of a pixel on said boundary.

3. The method as recited in claim 2, wherein said pixel on said boundary is located along a line generally perpendicular to said vessel slope graphic.

4. The method as recited in claim 3, wherein said step (f) further comprises the step of searching for an edge point along said line generally perpendicular to said vessel slope graphic in accordance with a search algorithm.

5. The method as recited in claim 2, wherein said step (f) further comprises the step of searching for an edge point along a line in accordance with a search algorithm.

6. The method as recited in claim 5, wherein said search algorithm comprises the steps of:

applying a smoothing filter to reduce statistical variations;

storing the peak and minimum image parameter values and the largest difference between image parameter values corresponding to adjacent pixels;

if a difference between said peak and minimum image parameter values exceeds a predetermined threshold, searching for a point along said line having an image parameter value which satisfies at least one of a difference criterion and a value criterion; and

identifying said point as said edge point.

7. The method as recited in claim 5, wherein said image parameter values comprise B-mode intensity values for some of said pixels and color flow estimates for others of said pixels in said frame, and said step of searching for an edge point comprises the steps of:

searching for a point which is the first of X points having B-mode intensity values instead of color flow estimates; and

identifying said point as said edge point.

8. The method as recited in claim 1, wherein said step (g) comprises the step of displaying said range gate graphic at a predetermined position relative to said boundary.

9. The method as recited in claim 1, wherein said image parameter values comprise B-mode intensity values for at least some of said pixels.

10. A system comprising:

a display device comprising a multiplicity of pixels;

a memory for storing a frame of image parameter values from which said ultrasound image was derived, said image parameter values corresponding to respective pixels in said image;

a computer programmed to perform the steps of;

(a) controlling said display device to display an ultrasound image of a blood vessel with a graphic representing a range gate overlying said blood vessel;

(b) determining a vessel slope of the blood vessel at or near said range gate based on said frame of image parameter values;

(c) controlling said display device to place a graphic representing said vessel slope overlying said blood vessel in said image;

(d) determining the position of a boundary of the blood vessel; and

(e) controlling said display device to adjust the position of said range gate if the change in the position of the boundary relative to said range gate is equal to or greater than a predetermined threshold.

11. The system as recited in claim 10, wherein said step (d) comprises the step of determining the address of a pixel on said boundary.

12. The system as recited in claim 11, wherein said pixel on said boundary is located along a line generally perpendicular to said vessel slope graphic.

13. The system as recited in claim 11, wherein said step (d) further comprises the step of searching for an edge point along a line in accordance with a search algorithm.

14. The system as recited in claim 12, wherein said step (d) further comprises the step of searching for an edge point along said line generally perpendicular to said vessel slope graphic in accordance with a search algorithm.

15. The system as recited in claim 10, wherein said image parameter values comprise B-mode intensity values for at least some of said pixels.

16. The system as recited in claim 13, wherein said search algorithm comprises the steps of:

applying a smoothing filter to reduce statistical variations;

storing the peak and minimum image parameter values and the largest difference between image parameter values corresponding to adjacent pixels;

if a difference between said peak and minimum image parameter values exceeds a predetermined threshold, searching for a point along said line having an image parameter value which satisfies at least one of a difference criterion and a value criterion; and

identifying said point as said edge point.

17. The system as recited in claim 13, wherein said image parameter values comprise B-mode intensity values for some of said pixels and color flow estimates for others of said pixels in said frame, and said step of searching for an edge point comprises the steps of:

searching for a point which is the first of X points having B-mode intensity values instead of color flow estimates; and

identifying said point as said edge point.

18. The system as recited in claim 10, further comprising:

an ultrasound transducer array comprising a multiplicity of transducer elements;

a transmit beamformer for pulsing selected transducer elements to transmit a series of ultrasound transmit beams in a scan plane;

a receive beamformer coupled to selected transducer elements of said transducer array for acquiring respective receive signals subsequent to respective beam transmits;

a signal processor for forming vectors of image parameter values from said receive signals;

a scan converter for converting said vectors into a frame of image parameter values and storing said frame of image parameter values in said memory; and

a video processor comprising a grayscale mapping for mapping said frame of image parameter values retrieved from said memory into grayscale pixel values.

19. A system comprising:

means for displaying an image of a blood vessel;

means for storing a frame of image parameter values from which said ultrasound image was derived, said image parameter values corresponding to respective pixels in said image;

means for placing a graphic representing a range gate overlying said blood vessel in said image;

means for determining a vessel slope of the blood vessel at or near said range gate based on said frame of image parameter values;

means for placing a graphic representing said vessel slope overlying said blood vessel in said image;

means for determining the position of a boundary of the blood vessel; and

means for adjusting the position of said range gate if the change in the position of the boundary relative to said range gate is equal to or greater than a predetermined threshold.

20. A system comprising:

a display device comprising a multiplicity of pixels displaying an ultrasound image of a blood vessel with a graphic representing a range gate and a graphic representing a vessel slope overlying said blood vessel; and

a computer programmed to perform the steps of;

determining the position of a first boundary of said blood vessel; and

controlling said display device to adjust the position of said range gate if the change in the position of the boundary relative to said range gate is equal to or greater than a predetermined threshold.

21. The system as recited in claim 20, wherein said position determining step comprises the step of determining the address of a pixel on said first boundary.

22. The system as recited in claim 21, wherein said pixel on said first boundary is located along a line generally perpendicular to said vessel slope graphic.

23. The system as recited in claim 20, wherein said computer is further programmed to perform the step of determining the position of a second boundary of said blood vessel, said controlling step comprising the step of adjusting the position of said range gate relative to said first and second boundaries.

24. The system as recited in claim 23, wherein said pixels on said first and second boundaries are located along a line generally perpendicular to said vessel slope graphic.

25. A method of operating a computerized ultrasound imaging system, comprising the steps of:

searching along a line for a point on a boundary of a moving blood vessel in accordance with a search algorithm;

determining a location of said point on said boundary; and

automatically adjusting the position of a range gate to track said moving blood vessel, said adjustment being a function of at least said location of said point on said boundary.

26. The method as recited in claim 25, wherein said searching step comprises the steps of searching from a center point and storing a point as an edge point if it is the first of a plurality of points displaying B-mode intensity data instead of color flow velocity data.

27. The method as recited in claim 25, wherein said searching step comprises the steps of searching from a center point and storing a point as an edge point if it is the first of a plurality of points displaying B-mode intensity data instead of color flow power data.

28. The method as recited in claim 25, wherein said searching step comprises the steps of searching from a center point along a line by replacing each B-mode intensity value by an average of itself and its two neighbors, and storing a point as an edge point if a difference between a peak B-mode intensity value and a minimum B-mode intensity value along the averaged line exceeds a threshold.

29. A computerized ultrasound imaging system programmed to search along a line for a point on a boundary of a moving blood vessel in accordance with a search algorithm, determine a location of said point on said boundary, and automatically adjust the position of a range gate to track said moving blood vessel, said adjustment being a function of at least said location of said point on said boundary.

30. The system as recited in claim 29, wherein said searching step comprises the steps of searching from a center point and storing a point as an edge point if it is the first of a plurality of points displaying B-mode intensity data instead of color flow velocity data.

31. The system as recited in claim 29, wherein said searching step comprises the steps of searching from a center point and storing a point as an edge point if it is the first of a plurality of points displaying B-mode intensity data instead of color flow power data.

32. The system as recited in claim 29, wherein said searching step comprises the steps of searching from a center point along a line by replacing each B-mode intensity value by an average of itself and its two neighbors, and storing a point as an edge point if a difference between a peak B-mode intensity value and a minimum B-mode intensity value along the averaged line exceeds a threshold.