SYSTEMS AND METHODS FOR IMPROVING ULTRASOUND IMAGE QUALITY BY APPLYING WEIGHTING FACTORS

• US 20130253325A1
• Filed: 03/26/2013
• Published: 09/26/2013
• Est. Priority Date: 04/14/2010
• Status: Active Grant

• Current Assignee: Maui Imaging, Inc.
• Original Assignee: Donald F. Specht, Josef R. Call, Kenneth D Brewer
• Inventors: CALL, Josef R., SPECHT, Donald F., BREWER, Kenneth D.
• Granted Patent: US 9,668,714 B2
• Time in Patent Office: Days
• US Class Current: 600/447
• CPC Class Codes: A61B 8/145 characterised by scanning multiple planes
• CPC Class Codes: A61B 8/4245 involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
• CPC Class Codes: A61B 8/4427 Device being portable or laptop-like
• CPC Class Codes: A61B 8/4477 using several separate ultrasound transducers or probes
• 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 8/461 Displaying means of special interest
• CPC Class Codes: A61B 8/5207 involving processing of raw data to produce diagnostic data, e.g. for generating an image reconstruction G06T11/00
• CPC Class Codes: A61B 8/5246 combining images from the same or different imaging techniques, e.g. color Doppler and B-mode
• CPC Class Codes: A61B 8/5253 combining overlapping images, e.g. spatial compounding
• CPC Class Codes: A61B 8/54 Control of the diagnostic device
• CPC Class Codes: G01S 15/8913 using separate transducers for transmission and reception
• CPC Class Codes: G01S 15/8927 using simultaneously or sequentially two or more subarrays or subapertures
• CPC Class Codes: G01S 15/8952 using discrete, multiple frequencies
• 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 7/52063 Sector scan display
• CPC Class Codes: G06N 3/084 Backpropagation, e.g. using gradient descent

Abstract

Systems and methods for improving the quality of ultrasound images made up of a combination of multiple sub-images include giving more weight to sub-image information that is more likely to improve a combined image quality. Weighting factor information may be determined from the geometry (e.g., angle or path length) of a location of one or more specific transducer elements relative to a specific point within a region of interest or a region of an image. In some embodiments, any given pixel (or other discrete region of an image) may be formed by combining received echo data in a manner that gives more weight to data that is likely to improve image quality, and/or discounting or ignoring data that is likely to detract from image quality (e.g., by introducing noise or by increasing point spread).

Claims

1. A method of forming an ultrasound image, the method comprising:

transmitting an unfocused first circular wave front ultrasound signal into a region of interest from a first transmit aperture and receiving echoes of the first circular wave front ultrasound signal at a first receive aperture to form a first image layer;

transmitting an unfocused second circular wave front ultrasound signal into a region of interest from a second transmit aperture and receiving echoes of the second circular wave front ultrasound signal at the first receive aperture to form a second image layer;

applying a weighting factor to at least one pixel of the first image layer to obtain a modified first image layer; and

combining the modified first image layer with the second image layer to form a combined image.

2. The method of claim 1, further comprising applying a weighting factor to a least one pixel of the second image layer to obtain a modified second image layer.

3. The method of claim 1, further comprising, prior to applying the weighting factor, determining a value of the weighting factor by determining an angle between a point represented by the at least one pixel and the first transmit aperture, and determining the value of weighting factor as a mathematical function of the determined angle.

4. The method of claim 1, further comprising, prior to applying the weighting factor, determining a value of the weighting factor by determining an angle between a point represented by the at least one pixel and the first receive aperture, and determining the weighting factor as a mathematical function of the determined angle.

5. The method of claim 3, wherein determining the value of the weighting factor comprises determining whether the angle exceeds a threshold value, selecting a first value for the weighting factor if the angle exceeds the threshold value, and selecting a second value for the weighting factor if the angle does not exceed the threshold value.

6. The method of claim 4, wherein determining the value of the weighting factor comprises determining whether the angle exceeds a threshold value, selecting a first value for the weighting factor if the angle exceeds the threshold value, and selecting a second value for the weighting factor if the angle does not exceed the threshold value.

7. The method of claim 1 further comprising, prior to applying the weighting factor, determining a value of the weighting factor by:

determining a first distance from one of the first or second transmit apertures to a point represented by the at least one pixel;

determining a second distance from the point to the first receive aperture;

summing the first distance and the second distance to obtain a total path length; and

determining the weighting factor as a mathematical function of the total path length.

8. The method of claim 1, wherein applying the weighting factor comprises multiplying the weighting factor by a pixel intensity value of the at least one pixel.

9. The method of claim 1, wherein applying the weighting factor decreases the value of pixels that are identified as likely to contain more than a threshold level of noise.

10. The method of claim 1, further comprising transmitting the first circular wave front at a first frequency, and transmitting the second circular wavefront at a second frequency, the first frequency being greater than the second frequency, and applying a weighting factor to at least one pixel in the second image based on the difference between the first frequency and the second frequency.

11. The method of claim 4, wherein the mathematical function is selected from the group consisting of a monotonic function, a linear function, a normal distribution, a parabolic function, a geometric function, an exponential function, a Gaussian distribution, and a Kaiser-Bessel distribution.

12. The method of claim 1 further comprising, prior to applying the weighting factor, determining a value of the weighting factor by evaluating a quality of a point-spread-function of the first transmit aperture and the first receive aperture, determining that a pixel image obtained using the first transmit aperture and the first receive aperture will improve image quality, and assigning a non-zero positive value to the weighting factor.

13. The method of claim 1 further comprising, prior to applying the weighting factor, determining a value of the weighting factor by evaluating a quality of a point-spread-function of the first transmit aperture and the first receive aperture, determining that a pixel image obtained using the first transmit aperture and the first receive aperture will degrade image quality, and assigning a value of zero to the weighting factor.

14. The method of claim 1, further comprising changing an image window by zooming or panning to a different portion of the region of interest, determining a new weighting factor value based on the changed image window.

15. A method of identifying transmit elements not blocked by an obstacle, the method comprising:

transmitting an unfocused first circular wave front ultrasound signal from a first transmit aperture and receiving echoes of the first circular wave front ultrasound signal at a first receive aperture;

determining whether deep echo returns from within the region of interest are received by identifying if a time delay associated with the received echoes exceeds a threshold value; and

identifying the first transmit aperture as being clear of an obstacle if deep echo returns are received.

16. A method of identifying transducer elements blocked by an obstacle, the method comprising:

transmitting an unfocused first circular wave front ultrasound signal from a first transmit aperture and receiving echoes of the first circular wave front ultrasound signal at a first receive aperture;

determining whether strong shallow echo returns are received by identifying a plurality of echo returns with intensity values greater than a threshold intensity and with time delays less than a threshold time delay; and

identifying the first transmit aperture as being blocked by an obstacle if strong shallow echo returns are received.

17. An ultrasound imaging system comprising:

an ultrasound transmitter configured to transmit unfocused ultrasound signals into a region of interest;

an ultrasound receiver configured to receive ultrasound echo signals returned by reflectors in the region of interest;

a beamforming module configured to determine positions of the reflectors within the region of interest for displaying images of the reflectors on a display;

first user-adjustable controls configured to select a designated aperture from a plurality of transmit apertures and receive apertures of the ultrasound transmitter and ultrasound receiver; and

second user-adjustable controls configured to increase or decrease a speed-of-sound value used by the beamforming module to determine the positions of reflectors detected with the designated aperture.

18. The system of claim 17, wherein the designated aperture is a transmit aperture.

19. The system of claim 17, wherein the designated aperture is a receive aperture.

20. An ultrasound imaging system, comprising:

a first transmit aperture configured to transmit first and second unfocused circular wave front ultrasound signals into a region of interest;

a first receive aperture configured to receive echoes of the first and second circular wave front ultrasound signals; and

a controller configured to form a first image layer from received echoes of the first circular wave front ultrasound signal, and configured to form a second image layer from received echoes of the second circular wave front ultrasound signal, the controller being further configured to apply a weighting factor to at least one pixel of the first image layer to obtain a modified first image layer, and to combine the modified first image layer with the second image layer to form a combined image.

21. The system of claim 20, wherein the controller is configured to apply a weighting factor to a least one pixel of the second image layer to obtain a modified second image layer.

22. The system of claim 20, wherein the controller is configured to determine a value of the weighting factor by determining an angle between a point represented by the at least one pixel and the first transmit aperture, the controller being further configured to determine the value of weighting factor as a mathematical function of the determined angle.

23. The system of claim 20, wherein the controller is configured to determine a value of the weighting factor by determining an angle between a point represented by the at least one pixel and the first receive aperture, the controller being further configured to determine the weighting factor as a mathematical function of the determined angle.

24. The system of claim 23, wherein determining the value of the weighting factor comprises determining whether the angle exceeds a threshold value, selecting a first value for the weighting factor if the angle exceeds the threshold value, and selecting a second value for the weighting factor if the angle does not exceed the threshold value.

25. The system of claim 22, wherein determining the value of the weighting factor comprises determining whether the angle exceeds a threshold value, selecting a first value for the weighting factor if the angle exceeds the threshold value, and selecting a second value for the weighting factor if the angle does not exceed the threshold value.

26. The system of claim 20, wherein the controller is configured to determine a value of the weighting factor by:

determining a first distance from one of the first or second transmit apertures to a point represented by the at least one pixel;

determining a second distance from the point to the first receive aperture;

summing the first distance and the second distance to obtain a total path length; and

determining the weighting factor as a mathematical function of the total path length.

27. The system of claim 20, wherein applying the weighting factor comprises multiplying the weighting factor by a pixel intensity value of the at least one pixel.

28. The system of claim 20, wherein applying the weighting factor decreases the value of pixels that are identified as likely to contain more than a threshold level of noise.

29. The system of claim 20, wherein the first transmit aperture is configured to transmit the first circular wave front at a first frequency and the second circular wavefront at a second frequency, the first frequency being greater than the second frequency, and the controller is configured to apply a weighting factor to at least one pixel in the second image based on the difference between the first frequency and the second frequency.

30. The system of claim 23, wherein the mathematical function is selected from the group consisting of a monotonic function, a linear function, a normal distribution, a parabolic function, a geometric function, an exponential function, a Gaussian distribution, and a Kaiser-Bessel distribution.

31. The system of claim 20, wherein the controller, prior to applying the weighting factor, is configured to determine a value of the weighting factor by evaluating a quality of a point-spread-function of the first transmit aperture and the first receive aperture, the controller being configured to determine that a pixel image obtained using the first transmit aperture and the first receive aperture will improve image quality, the controller being further configured to assign a non-zero positive value to the weighting factor.

32. The system of claim 20, wherein the controller is configured to determine a value of the weighting factor by evaluating a quality of a point-spread-function of the first transmit aperture and the first receive aperture, the controller being configured to determine that a pixel image obtained using the first transmit aperture and the first receive aperture will degrade image quality, the controller being further configured to assign a value of zero to the weighting factor.

33. The system of claim 20, wherein the controller is further configured to change an image window by zooming or panning to a different portion of the region of interest, the controller further being configured to determine a new weighting factor value based on the changed image window.