US-20260123917-A1 - DETERMINING MATERIAL STIFFNESS USING MULTIPLE APERTURE ULTRASOUND

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.

Inventors

• Donald F. Specht
• Kenneth D. Brewer

Assignees

• MAUI IMAGING, INC.

Dates

Publication Date

20260507

Application Date

20250610

Claims (6)

1. 1 . (canceled)
2. 2 . A method of determining a stiffness of a tissue with ultrasound, the method comprising the steps of: forming a baseline image of a region of interest with a ping-based ultrasound imaging system; transmitting an ultrasonic pulse with a shear-wave-initiating transducer, the ultrasonic pulse being configured to induce a propagating shear wave in the region of interest; transmitting a series of transmit pulses at known time intervals with the ping-based ultrasound imaging system as the propagating shear wave travels through the region of interest; generating a series of image frames from echoes of the series of transmit pulses; subtracting the baseline image from the series of image frames to produce a series of difference images that include a speckle pattern with pixel values representing substantially only the propagating shear wave as it moves through the region of interest; and calculating a propagation speed of the propagating shear wave in the region of interest by determining the position of the speckle pattern in the series of difference frames at the known time intervals.
3. 3 . The method of claim 2 , further comprising calculating a tissue stiffness of the region of interest from the propagation speed.
4. 4 . The method of claim 2 , wherein transmitting a series of transmit pulses comprises transmitting the series of transmit pulses with a first ultrasound transducer array, and further comprising receiving echoes from the series of transmit pulses with a second ultrasound transducer array.
5. 5 . The method of claim 2 , wherein the series of transmit pulses are transmitted at a frame rate between 1,000 and 75,000 fps.
6. 6 . The method of claim 2 , further comprising determining that a first segment of the shear wave is propagating faster than adjacent segments of the shear wave, and calculating a first segment propagation speed of the first segment.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 18/588,967, filed on Feb. 27, 2024, titled “DETERMINING MATERIAL STIFFNESS USING MULTIPLE APERTURE ULTRASOUND,” now U.S. Patent Application Publication No. US20250032093-A1, which is a continuation of U.S. application Ser. No. 16/897,116, filed on Jun. 9, 2020, titled “DETERMINING MATERIAL STIFFNESS USING MULTIPLE APERTURE ULTRASOUND,” now U.S. Pat. No. 11,944,500, which is a continuation of U.S. application Ser. No. 15/155,908, filed May 16, 2016, titled “DETERMINING MATERIAL STIFFNESS USING MULTIPLE APERTURE ULTRASOUND,” now U.S. Pat. No. 10,675,000, which is a division of U.S. application Ser. No. 13/773,340, filed Feb. 21, 2013, titled “Determining Material Stiffness Using Multiple Aperture Ultrasound,” now U.S. Pat. No. 9,339,256, which application claims the benefit of U.S. Provisional Application No. 61/601,482, filed Feb. 21, 2012, titled “Determining Material Stiffness Using Multiple Aperture Ultrasound,” all of which are incorporated by reference herein. This application is also related to the following U.S. patent applications: Ser. No. 11/865,501, filed Oct. 1, 2007, now U.S. Pat. No. 8,007,439, and titled “Method And Apparatus To Produce Ultrasonic Images Using Multiple Apertures”; Ser. No. 12/760,375, filed Apr. 14, 2010, published as 2010/0262013 and titled “Universal Multiple Aperture Medical Ultrasound Probe”; Ser. No. 12/760,327, filed Apr. 14, 2010, now U.S. Pat. No. 8,473,239, and titled “Multiple Aperture Ultrasound Array Alignment Fixture”; Ser. No. 13/279,110, filed Oct. 21, 2011, now U.S. Pat. No. 9,282,945, and titled “Calibration of Ultrasound Probes”; Ser. No. 13/272,098, filed Oct. 12, 2011 and titled “Multiple Aperture Probe Internal Apparatus and Cable Assemblies”; Ser. No. 13/272,105, filed Oct. 12, 2011, now U.S. Pat. No. 9,247,926, and titled “Concave Ultrasound Transducers and 3D Arrays”; Ser. No. 13/029,907, filed Feb. 17, 2011, now U.S. Pat. No. 9,146,313, and titled “Point Source Transmission And Speed-Of-Sound Correction Using Multi-Aperture Ultrasound Imaging”; and Ser. No. 13/690,989, filed Nov. 30, 2012 and titled “Motion Detection Using Ping-Based and Multiple Aperture Doppler Ultrasound.” INCORPORATION BY REFERENCE All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. FIELD This disclosure generally relates to imaging methods and devices for determining a material stiffness using a multiple aperture ultrasound probe to produce and track ultrasonic shear waves. BACKGROUND Changes in tissue stiffness have long been associated with disease. Traditionally, palpation is one of the primary methods of detecting and characterizing tissue pathologies. It is well known that a hard mass within an organ is often a sign of an abnormality. Several diagnostic imaging techniques have recently been developed to provide for non-invasive characterization of tissue stiffness. One measure of tissue stiffness is a physical quantity called Young's modulus, which is typically expressed in units of Pascals, or more commonly kilo Pascals (kPa). If an external uniform compression (or stress, S) is applied to a solid tissue and this induces a deformation (or strain, e) of the tissue, Young's modulus is defined simply as the ratio between applied stress and the induced strain: E=S/e. Hard tissues have a higher Young's modulus than soft tissues. Being able to measure the Young's modulus of a tissue helps a physician in differentiating between benign and malignant tumors, detecting liver fibrosis and cirrhosis, detecting prostate cancer lesions, etc. A collection of diagnostic and imaging modalities and processing techniques have been developed to allow clinicians to evaluate tissue stiffness using ultrasonography. These techniques are collectively referred to herein as Elastography. In addition to providing information about tissue stiffness, some elastography techniques may also be used to reveal other stiffness properties of tissue, such as axial strain, lateral strain, Poisson's Ratio, and other common strain and strain-related parameters. Any of these or other strain-related parameters may be displayed in shaded grayscale or color displays to provide visual representations of such strain-related parameters. Such information may be displayed in relation to two or three dimensional data. Elastography techniques may be broadly divided into two categories, “quasi-static elastography” techniques and “dynamic elastography” techniques. In quasi-static elastography, tissue strain is induced by mechanical compression of a tissue region of interest, such as by pressing against a tissue with a probe a hand or other device. In other cases, strain may be induced by compression caused by muscular a