Determining material stiffness using multiple aperture ultrasound

• US 10,675,000 B2
• Filed: 05/16/2016
• Issued: 06/09/2020
• Est. Priority Date: 10/01/2007
• Status: Active Grant

• Current Assignee: Maui Imaging, Inc.
• Original Assignee: Maui Imaging, Inc.
• Inventors: Specht, Donald F., Brewer, Kenneth D.
• Primary Examiner(s): Park, Patricia J
• Application Number:
  US15/155,908
• Publication Number:
  US 20160256134A1
• Time in Patent Office: 1,485 Days
• Field of Search: None
• CPC Class Codes: A61B 8/145 characterised by scanning multiple planes
• CPC Class Codes: A61B 8/4444 related to the probe
• CPC Class Codes: A61B 8/4477 using several separate ultrasound transducers or probes
• 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 8/485 involving measuring strain or elastic properties
• CPC Class Codes: A61B 8/488 involving Doppler signals
• 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: G01S 15/8915 using a transducer array
• CPC Class Codes: G01S 15/8922 the array being concentric or annular
• CPC Class Codes: G01S 15/8929 using a three-dimensional transducer configuration
• CPC Class Codes: G01S 15/8959 using coded signals for correlation purposes
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: G01S 15/8993 Three dimensional imaging systems
• CPC Class Codes: G01S 15/8997 using synthetic aperture techniques
• CPC Class Codes: G01S 7/52022 using a sequence of pulses, at least one pulse manipulating the transmissivity or reflexivity of the medium
• CPC Class Codes: G01S 7/52042 determining elastic properties of the propagation medium or of the reflective target diagnostic techniques involving the measurement of strain A61B8/485
• CPC Class Codes: G03B 42/06 using ultrasonic, sonic or infrasonic waves

Abstract

Changes in tissue stiffness have long been associated with disease. Systems and methods for determining the stiffness of tissues using ultrasonography may include a device for inducing a propagating shear wave in tissue and tracking the speed of propagation, which is directly related to tissue stiffness and density. The speed of a propagating shear wave may be detected by imaging a tissue at a high frame rate and detecting the propagating wave as a perturbance in successive image frames relative to a baseline image of the tissue in an undisturbed state. In some embodiments, sufficiently high frame rates may be achieved by using a ping-based ultrasound imaging technique in which unfocused omni-directional pings are transmitted (in an imaging plane or in a hemisphere) into a region of interest. Receiving echoes of the omnidirectional pings with multiple receive apertures allows for substantially improved lateral resolution.

Claims

1. An ultrasound imaging system, comprising:

a first ultrasound transducer array configured to transmit an init wavefront that induces a propagating shear wave in a region of interest;

a second ultrasound transducer array configured to transmit circular waveforms into the region of interest and receive echoes of the circular waveforms; and

a processor configured to form a plurality of B-mode images of the region of interest from the circular waveforms to detect the propagating shear wave in the region of interest;

wherein the processor is configured to form a first frame of the plurality of B-mode images by combining sub-images formed by echoes received by multiple elements of the second ultrasound transducer array;

wherein the processor is configured to form a second frame of the plurality of B-mode images by;

transmitting a first unfocused ultrasound ping from a first transmitter transducer element of the second ultrasound transducer array;

forming a first image layer using echoes of only the first ultrasound ping received by elements of a first receive aperture of the second ultrasound transducer array;

forming a second image layer using echoes of only the first ultrasound ping received by elements of a second receive aperture of the second ultrasound transducer array; and

combining the first image layer and the second image layer with the electronic controller to form the first frame;

wherein the processor is further configured to calculate a speed of the propagating shear wave by identifying a first position of the shear wave in the first frame of the plurality of B-mode images, identifying a second position of the shear wave in the second frame of the plurality of B-mode images, determining a distance traveled by the shear wave between the first frame and the second frame, determining a time elapsed between the first frame and the second frame, and dividing the distance traveled by the time elapsed.

2. The system of claim 1, wherein the first ultrasound transducer array comprises an array of phased-array elements.

3. The system of claim 1, wherein the first ultrasound transducer array comprises an annular array of piezoelectric rings, and the processor is further configured to focus the init wavefront at various depths by adjusting phasing delays.

4. The system of claim 3, wherein the first ultrasound transducer array comprises a switched ring transducer.

5. The system of claim 1 wherein the first ultrasound transducer array comprises a single piezoelectric transducer.

6. The system of claim 1, wherein the plurality of B-mode images of the region of interest are formed at a frame rate between 500 fps and 4,000 fps.

7. The system of claim 1, wherein the processor is configured to identify the propagating shear wave as a speckle pattern moving through the region of interest.

8. The system of claim 1, wherein the processor is configured to define an image window identifying a section of the region of interest with a combination of zooming, panning, and depth selection.

9. The system of claim 8, wherein the system is configured to display a contemporaneous B-mode image of a selected image window while calculating and displaying a modulus of elasticity of an object in the region of interest.