Methods and displays for indicating body tissue stiffness

Abstract

This invention provides a high-precision shear wave video playback device that achieves both improved resolution and stable playback images in shear wave video systems. [Solution] For each of the multiple small regions defined within the image area, the shear wave is assumed to be a plane wave, and the wavenumber in the X and Z directions is estimated using the least squares error method.

Description

[Technical Field]

[0001] This invention relates to a method and display device for displaying the hardness of body tissues (including muscles, tendons, and organs such as the liver, mammary glands, and thyroid gland) of living organisms (human or animal) using ultrasound. In particular, it relates to a method and display device for displaying the hardness of body tissues (muscles and organs, liver glands, mammary glands, thyroid gland, etc.) for imaging or evaluating the elastic function of thin-layer structures such as ligaments and fascia within the musculoskeletal system. [Background technology]

[0002] In orthopedics, rehabilitation, sports medicine, and massage, there is a need to quantitatively measure the stiffness of biological tissues from an external perspective. Various devices and methods have been disclosed to date for measuring the stiffness of biological tissues from an external perspective.

[0003] For example, WO2015 / 151972 (see Patent Document 1) is a conventional ultrasound imaging method for imaging the tissues of living organisms (humans or animals) using ultrasound. In this disclosure, a puncture needle is pressed against the body surface near the measurement site to vibrate the living cells at the puncture site, and the propagation speed of mechanical vibration waves (transverse waves) traveling through the tissue is imaged using an ultrasound echo device.

[0004] Furthermore, Patent Document 1 (Canon Medical Systems Corporation, Patent Registration No. 05513976) discloses a conventional ultrasound diagnostic device. This device comprises an ultrasound probe, an ultrasound transmitting and receiving unit that repeatedly transmits and receives ultrasound N times to each of a plurality of ultrasound rasters via the ultrasound probe to generate an echo signal, an echo processing unit that generates complex data from the echo signal via quadrature detection processing, a phase correction unit that, for each set of N sets of complex data relating to the same depth and the same ultrasound raster, identifies a phase difference with respect to the reference phase of any of the N complex data for each set, and shifts the phase of the N complex data for each set by the identified phase difference, an interpolation processing unit that generates an interpolation set of complex data relating to interpolation rasters between adjacent ultrasound rasters by interpolation processing from the set of N complex data whose phases have been shifted, and an image data generation unit that generates image data relating to blood flow or movement information of other moving objects via autocorrelation processing from the set of N complex data whose phases have been corrected and the interpolation set generated by the interpolation processing. Furthermore, when N is an even number, the average of the phase difference for the N / 2th complex data point and the phase difference for the (N / 2)+1th complex data point in the set of complex data points is determined.

[0005] In addition, Patent Document 2 (Canon Medical Systems Corporation, Patent Registration No. 06058295) discloses a conventional ultrasound diagnostic device, medical image processing device, medical image processing method, and medical image processing program. In this ultrasound diagnostic device, the autocorrelation calculator calculates autocorrelation values ​​for the blood flow Doppler component and the tissue Doppler component. Based on the calculated autocorrelation values, the autocorrelation calculator calculates the average velocity value, variance value, and Doppler signal reflection intensity (power) of the blood flow and tissue. The velocity / variance / power calculation device generates color Doppler data at each position in a predetermined region based on the average velocity value, variance value, and Doppler signal reflection intensity of the blood flow and tissue based on multiple Doppler signals.

[0006] The displacement calculation unit 19 approximates the tissue displacement amount related to the subject's body movement (body movement displacement amount) for each depth in the second region, based on the tissue displacement amount obtained by the autocorrelation analyzer before the transmission of the push pulse (hereinafter referred to as the first displacement data) and the tissue displacement amount obtained by the autocorrelation calculator after the transmission of the push pulse (hereinafter referred to as the second displacement data), specifically the tissue displacement amount just before the end of the nth ultrasonic transmission / reception (nth time, (n-1)th time, etc.). The displacement calculation unit 19 calculates the tissue displacement amount associated with shear wave propagation (hereinafter referred to as shear wave propagation data) by subtracting the approximated body movement displacement amount from the first and second displacement data.

[0007] Furthermore, another method for measuring the stiffness of body tissues from the outside is disclosed: "Image method for bio-stiffness using shear waves" (WO 2015 / 151972, Patent Document 3). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special registration number 5513976 publication [Patent Document 2] Special registration number 6058295 publication [Patent Document 3] WO2015 / 151972A1 publication [Overview of the project] [Problems that the invention aims to solve]

[0009] However, with tablet ultrasound devices as described in the above-mentioned literature, there was a problem in that the stability of the reconstructed images or the spatial resolution were insufficient when trying to measure the elasticity of thin-layered structures such as ligaments and fascia in the musculoskeletal system, making it impossible to evaluate only the thin-layered structures.

[0010] In other words, when attempting to improve spatial resolution in an imaging system that obtains images of the stiffness of biological tissue, the quality of the reconstructed image deteriorates due to noise components contained in the measurement data. In ultrasound diagnostic devices that control each frame of elastic ultrasound images of thin-layer structures such as ligaments and fascia in the musculoskeletal system from a tablet or PC, the frame rate fluctuates over time due to the limitations of the processing power of the tablet or PC, resulting in display lag, image noise due to variations in the time interval for acquiring ultrasound signals, and a decrease in image accuracy. That is, what can be reconstructed from a single ultrasound transmission and reception signal is an image called a B-mode image, which represents the reflection intensity of ultrasound as a grayscale image. However, in the case of the shear wave image that is the target here, one image is reconstructed from 8 to 16 consecutive ultrasound reception signals. In this reconstruction, it is assumed that the ultrasound reception interval is always constant, so if the reception interval fluctuates, noise is added to the reconstructed image, or the stability of the obtained reconstructed image decreases.

[0011] Furthermore, as a conventional technique, a method has been disclosed in which the image is first converted to the spatial frequency plane and a Wiener filter and a high-pass filter are used on this plane to improve the stability of the reproduced shear wave image. However, although these filters contribute to improving the stability of the reproduced image, they have the problem of reducing the spatial resolution. In addition, when attempting to measure the elasticity of thin-layer structures such as ligaments and fascia in the musculoskeletal system using the conventional method, the spatial resolution is insufficient, making it impossible to evaluate only the thin-layer structures.

[0012] Therefore, the present invention aims to provide a shear wave image reproduction method that can achieve both stability of reproduced images and excellent spatial resolution, thereby improving the operability of an image system for obtaining images of the stiffness of body tissues, and that can evaluate the elasticity of thin-layer structures such as ligaments and fascia in the musculoskeletal system. [Means for solving the problem]

[0013] To solve the above problems, the present invention employs the following measures. However, the numbers or letters following the names of the components below are merely symbols added for convenience in understanding the drawings and are not intended to limit the concept, shape, or structure of the components.

[0014] [1] A method for displaying tissue stiffness, comprising: applying pressure to a vibrator in contact with the surface of a living organism to cause sinusoidal vibration of the tissue; transmitting and receiving ultrasonic signals to a predetermined image area of ​​the sinusoidal-vibrated tissue (a detection area consisting of a predetermined plane defined by the specifications of the ultrasonic probe or arbitrarily set) from near the surface of the tissue; and continuously acquiring a plurality of shear wave images (consisting of the 1st to Nth frame images) to display the state of the muscle of the tissue in a video; The process involves a "detection step" in which sinusoidal vibration is applied to body tissue by a vibrator to generate periodic displacement fluctuations in a predetermined range of biological tissue, and ultrasonic Doppler signal components due to displacement fluctuations in the image region included in the biological tissue where the displacement fluctuations have occurred are detected by ultrasonic transmission and reception using an ultrasonic probe. A "micro-region setting step" is performed in which a micro-region R consisting of a predetermined size plane that can divide the image area of ​​the ultrasound probe is set across the entire image area in an overlapping state where at least adjacent parts overlap each other, and the position and identifier of each set micro-region within the image area are defined. Assuming that the shear wave propagating in a specific direction in each minute region is a plane wave (with XZ dimensions) on orthogonal two-dimensional coordinate axes, A "one-direction (vertical) minute calculation step" is repeatedly performed, in which the wavenumber and velocity of the shear wave in a minute region (Δx) of a specific minute region are calculated in the one-dimensional direction (Z-axis direction) of the other coordinate axis (the other coordinate axis i.e., the Z-axis) based on the phase distribution of the plane wave shear wave at each point of one coordinate (X-coordinate) of the specified minute region. Also, The "other-direction (lateral) minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave in the minute region (Δz) of the other coordinate (Z coordinate) are calculated in the one-dimensional direction (X-axis direction) of the other coordinate axis (the first coordinate axis i.e., the X-axis) based on the phase distribution of the plane wave shear wave at each point of the other coordinate (Z coordinate) among the orthogonal two-dimensional coordinates (X-coordinate, Z-coordinate) of the first minute region, Based on the wavenumber and velocity of each shear wave in the two-dimensional direction (X, Z direction) of the minute region, obtained by repeating the "one-direction (vertical direction) minute calculation step" and the "other-direction (horizontal direction) minute calculation step" within these minute regions, minute region information of the shear wave propagation velocity and propagation direction (slope in the XZ plane) of the minute region is acquired. The aforementioned specific minute region is varied in an overlapping state where parts of the minute regions with different identifiers, which were set by the minute region setting step, overlap each other. The "one-way (vertical) minute calculation step" and the "other-way (horizontal) minute calculation step" within the minute region of the variable identifier are repeated while shifting the center of each minute region by pixel units (using a set number of pixels between 1 and 5 pixels as the unit), This method is characterized by acquiring shear wave propagation images at each coordinate in the two-dimensional direction of the entire image region.

[0015] Furthermore, before the detection step or the micro-region setting step, the system may include an "arbitrary setting step" in which a specific region, i.e., a Doppler image region, consisting of any size and any angle with respect to the biological surface, is set within the image region (detection region).

[0016] [2] In the aforementioned one-direction (vertical) infinitesimal calculation step and the other-direction (horizontal) infinitesimal calculation step, Within each minute area, taking the midpoint (center point) in one direction (X direction, Z direction) of the two-dimensional direction as the phase reference point, integrating the complex amplitude of the shear wave velocity at each coordinate in the plus and minus directions of the other direction in the two-dimensional direction within each minute area, obtaining the complex amplitude distribution of the shear wave in the one-dimensional direction which is this one direction, and applying the one-dimensional least squares error method to the complex amplitude distribution of the shear wave in this one-dimensional direction to obtain the wave number and velocity of the shear wave in this one-dimensional direction may also be acceptable.

[0017] [3] Based on the wave number and velocity of each shear wave in the two-dimensional direction (X, Z direction) of the minute area obtained by repeating the "one-direction (vertical direction) minute calculation step" and "other-direction (horizontal direction) minute calculation step" within the specific one minute area, further including an image generation step of acquiring the minute area information of the shear wave propagation velocity and propagation direction (inclination within the X-Z plane) of the minute area and generating an image element corresponding to the minute area information, and further It may also be acceptable to have a video display step of displaying the image element generated within the specific one minute area as a shear wave video on the display device at the coordinate position of the minute area within the display screen.

[0018] [4] The repetition of the "one-direction (vertical direction) minute calculation step" and "other-direction (horizontal direction) minute calculation step" within the specific one minute area may be processed simultaneously or sequentially continuously in each minute area included in the set image area.

[0019] [5] It may further include a "complex amplitude map derivation step" of performing Fourier analysis on the Doppler displacement signal detected by the ultrasonic probe based on the excitation frequency component and deriving a complex amplitude map. The complex amplitude map derivation step can confirm the phase wall treatment (jump) locations by creating a phase map and obtain an image with higher-precision resolution. Also, in this step, the process of calculating the Poisson's ratio may be included.

[0020] [6] A shear strain calculation step that calculates the shear strain in each direction included in the image region based on the difference in displacement fluctuations between two adjacent or nearby minute regions, The process further includes a shear strain image generation step, which generates shear strain image elements by converting the shear strain values ​​of each minute region obtained in the shear strain calculation step into corresponding color maps or grayscale maps in a stepwise manner. In the video display step, shear strain image elements may be displayed by superimposing them or by switching between them.

[0021] [7] Furthermore, the biological hardness display device of the present invention is A vibrator that applies pressure to the surface of a living organism to cause sinusoidal vibrations in the fascial tissue of the body, An ultrasonic probe that transmits and receives ultrasonic signals by contacting the body surface near the body surface, A processing device that acquires shear wave images based on received ultrasound signals and processes the state of loose connective tissue in body tissue, A display device for the mobility of body tissue, comprising: a processing device that processes a shear wave image including the state of loosely connected tissue in the body tissue and displays it on a display unit; The aforementioned ultrasonic probe uses a predetermined depth range of loosely connected tissue within a predetermined excitation range of body tissue that has been contact-excited by a vibrator as its detection area, and receives the ultrasonic Doppler signal component that has been affected by the Doppler effect in the detection area by quadrature detection. Furthermore, the processing apparatus is The "arbitrary setting step" involves arbitrarily setting a specific image area within the image area (detection area) that has an arbitrary size and an arbitrary angle relative to the biological surface, The process involves a "detection step" in which sinusoidal vibration is applied to body tissue by a vibrator to generate periodic displacement fluctuations in a predetermined range of biological tissue, and ultrasonic Doppler signal components due to displacement fluctuations in the image region contained in the biological tissue are detected by ultrasonic transmission and reception of an ultrasonic probe. A "micro-region setting step" is performed to define a micro-region R consisting of a predetermined size plane that can divide the set image region, and to define the position and identifier of each set micro-region within the image region. Assuming that the shear wave propagating in a specific direction within each minute region is a two-dimensional plane wave, The "one-directional minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave of a plane wave in a specific minute region are calculated in the one-dimensional direction of another coordinate axis based on the phase distribution of the plane wave shear wave at each point in one coordinate of that minute region. Also, The "multi-direction minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave of the other coordinates in the other coordinate region are calculated in the one-dimensional direction of the other coordinate axis based on the phase distribution of the plane wave shear wave at each point in the other coordinates of the one minute region. The aforementioned specific minute region is varied in an overlapping state where parts of the minute regions with different identifiers, which were set by the minute region setting step, overlap each other. The "one-way minute calculation step" and the "other-way minute calculation step" within the minute region of the variable identifier are repeated while shifting the center of each minute region by pixels, This method acquires shear wave propagation images at each coordinate in the two-dimensional direction across the entire image region. The display device is characterized by continuously displaying shear wave propagation images acquired by scanning with an ultrasonic probe, according to the scanning range of the ultrasonic probe.

[0022] This invention estimates the in-vivo displacement amplitude from a Doppler signal, derives a complex amplitude map by performing Fourier analysis at the excitation frequency, then derives the wavenumber of the shear wave in the X and Z directions for each set minute region, and estimates the propagation velocity and propagation direction from these derived wavenumbers.

[0023] To address the challenge of degraded image stability during resolution improvement in shear wave video systems, this method is characterized by estimating the wavenumber in the X and Z directions using the least squares error method, assuming the shear wave is a plane wave for each of the multiple minute regions set within the image area, thereby contributing to improved spatial resolution of shear wave video. [Effects of the Invention]

[0024] The tissue stiffness display device and display method provided by the present invention improve the operability of the video system for obtaining tissue stiffness images by achieving both stability of the reproduced image and excellent spatial resolution. [Brief explanation of the drawing]

[0025] [Figure 1] Diagram illustrating the configuration of the biological stiffness display device in Example 1. [Figure 2] Diagram illustrating the image region and micro-region examples in Example 1. [Figure 3] Extraction diagram of a minute region in Example 1 (top) and estimation calculation diagrams in the X-axis direction (left) and Z-axis direction (right). [Figure 4] Flowchart of the shear wave calculation method for the comparative example using the two-dimensional least squares error method. [Figure 5] A conceptual diagram illustrating the procedure for a unidirectional (vertical) infinitesimal calculation step (calculation of the phase of each X coordinate). [Figure 6] A conceptual diagram illustrating the procedure for the infinitesimal calculation step in the other direction (lateral direction) (calculation of the phase of each Z coordinate). [Figure 7] A flowchart of the shear wave calculation method of the present invention, which repeats a one-dimensional minute calculation step for each X and Z coordinate. [Figure 8] A conceptual diagram illustrating the propagation of shear waves into the mobile layer of a fascial model. [Figure 9] Conceptual diagrams of fascial models under large shear strain (top) and small shear strain (bottom). [Figure 10] This diagram illustrates shear strain due to phase difference (left) and shear strain due to amplitude difference (right). [Figure 11] Correlation diagram showing the relationship between shear strain due to phase difference and phase difference (left), and shear strain due to amplitude difference and amplitude difference (right). [Figure 12] An example of displaying a partially high-resolution velocity image obtained by processing a portion of a shear wave image with high resolution. [Figure 13] The image on the left shows a video display of the relaxed and extended state of the Achilles tendon according to the present invention, and the image on the right shows a video display of a comparative example. [Figure 14]Examples of phase display images (left) and high-resolution velocity images (right) of a portion of a shear wave image. [Figure 15] Latissimus dorsi muscle measurement status (left), ultrasound shear velocity image (center), and shear wave phase display image (right) - example display. [Figure 16] The formula for introducing the adhesion coefficient k according to the present invention (upper right), the phase representation image of the adhesion coefficient (middle), and the velocity image (lower) of its change. [Figure 17] Examples of switching between phase image (left) and velocity image (right) of shear wave propagation in an extended state, and one-dimensional analysis of each image. [Figure 18] Examples of calculating shear wave propagation velocity (top) and shear wave phase at each Z coordinate. [Figure 19] Figure 18 shows the correlation between shear wave propagation velocity (vertical axis) and shear wave phase (horizontal axis). [Figure 20] The shear wave propagation velocity distribution diagram according to the present invention (top), and the shear wave propagation velocity distribution diagram for a comparative example (bottom). [Modes for carrying out the invention]

[0026] This invention relates to a method and display device for displaying the hardness of body tissues (including muscles, tendons, and organs such as the liver, mammary glands, and thyroid gland) of living organisms (human or animal) using ultrasound. In particular, it relates to a method and display device for displaying the hardness of body tissues (muscles and organs, liver glands, mammary glands, thyroid gland, etc.) for imaging or evaluating the elastic function of thin-layer structures such as ligaments and fascia within the musculoskeletal system.

[0027] Here, loose connective tissue refers to tissue containing collagen fibers that connects the boundaries between soft tissues, and is a concept that includes fascia in muscles, surrounding bursae and adipose tissue in tendons, surrounding fat, bursa, or synovial membrane in ligaments, and epineurium in peripheral nerves. When these loose connective tissues become abnormal, problems such as adhesion, density changes, inflammation associated with adhesion, and problems with bodily movement occur. The hardness indication method of the present invention makes it possible to evaluate these problems.

[0028] Furthermore, abnormalities in body tissues other than muscles include tumors (e.g., cancer), tissue necrosis and inflammation, adhesion and fibrosis between tissues, and changes in macroscopic elastic structure. The hardness indication method of the present invention enables evaluation related to these problems.

[0029] The present invention provides a method for displaying the stiffness of a living organism by applying pressure to the surface of the organism to cause the tissue to vibrate sinusoidally, and by transmitting and receiving ultrasonic signals from near the surface of the organism to a predetermined image area (detection area) of the sinusoidally vibrated tissue using an ultrasonic probe, and by continuously acquiring a plurality of shear wave images (consisting of the 1st to Nth frames) to display the state of the muscle of the tissue in motion, and comprises the following steps.

[0030] In other words, The process involves a "detection step" in which sinusoidal vibration is applied to body tissue by a vibrator to generate periodic displacement fluctuations in a predetermined range of biological tissue, and ultrasonic Doppler signal components due to displacement fluctuations in the image region contained in the biological tissue are detected by ultrasonic transmission and reception of an ultrasonic probe. The system includes a "micro-region setting step" which sets a micro-region R consisting of a predetermined-size plane that can divide the set image region, and automatically sets the range of each divided micro-region and an identifier for individually identifying each micro-region. Then, the following two micro-calculation steps are repeated for each micro-region. In other words, Assuming that the shear wave propagating in a specific direction in each minute region is a plane wave (with XZ dimensions) on orthogonal two-dimensional coordinate axes, The "one-directional minute calculation step" is repeated (Figure 5) to calculate the wavenumber and velocity of the shear wave in a minute region (Δx) of a specific minute region based on the phase distribution of the plane wave shear wave at each point of one coordinate (X coordinate) of that coordinate (X coordinate), in the one-dimensional direction (vertical direction). Also, The "other-direction (lateral) minute calculation step" is repeated (Figure 6), in which the wavenumber and velocity of the shear wave in the minute region (Δz) of the other coordinate (Z coordinate) are calculated in the one-dimensional direction of the other coordinate axis, based on the phase distribution of the plane wave shear wave at each point of the other coordinate (Z coordinate) among the orthogonal two-dimensional coordinates (X coordinate, Z coordinate) of the aforementioned minute region, Based on the wavenumber and velocity of each shear wave in the two-dimensional direction (X, Z direction) of the micro-region obtained by repeatedly performing a "one-direction (vertical direction) micro-calculation step" and a "other-direction (horizontal direction) micro-calculation step" within a single micro-region, micro-region information (Figure 3) of the shear wave propagation velocity and propagation direction (slope in the XZ plane) at the phase reference point A of the single micro-region is acquired.

[0031] Furthermore, the repetition process of the two minute calculation steps performed in the aforementioned specific minute region is also executed in the minute regions of different identifiers (each minute region in the direction of the arrows in Figure 2) set by the minute region setting step. That is, in the minute regions of other identifiers that are adjacent or distant, shifted by pixels vertically and / or horizontally from the minute regions in which the repetition process of the minute calculation steps has been executed so far, the "one-direction (vertical) minute calculation step" is repeated (Figure 5), and the "other-direction (horizontal) minute calculation step" is repeated (Figure 6) within each identifier's minute region. When the centroid of each minute region is taken as the position reference point A, different minute regions are defined by moving the phase reference point A in pixel units within a range of 1 to 5 pixels. Each minute region is then moved pixel by pixel so that at least adjacent minute regions overlap each other. By performing estimation in the X-axis direction and estimation of the phase slope in the Z-axis direction at each defined position reference point A, the minute region information (Figure 3) within each minute region included in the image region is acquired as a corresponding video element (for example, a single corresponding level of chromaticity or density selected from multiple chromaticity gauges or density gauges set in steps according to velocity and wavenumber).

[0032] Then, as a video display step, the shear wave propagation image and the video elements of the minute region information corresponding to each coordinate in the two-dimensional direction of the entire image area are superimposed and displayed. The video display step is a step in which, as a shear wave image to be displayed on the display device, the image area of ​​the ultrasonic probe is displayed on the display screen of the display device, and the video elements of the corresponding minute region information are superimposed and displayed at the coordinate positions of the minute regions corresponding to each coordinate on the two-dimensional coordinate axis.

[0033] Also, as a step prior to the detection step, The system may also include a "complex amplitude map derivation step" in which a Fourier analysis is performed on the excitation frequency component based on the Doppler displacement signal detected by an ultrasonic probe to derive a complex amplitude map.

[0034] Also, as a step prior to the detection step, The system may also include an "arbitrary setting step" for arbitrarily setting a specific image area (a two-dimensional image area consisting of a plane or curved surface) that is included in the image area (detection area) and has an arbitrary size (XZ dimensions) and an arbitrary angle (including depth and inclination) relative to the biological surface. In this arbitrary setting step, the user of the device inputs and sets the type of body tissue to be measured (e.g., muscle, tendon, organ, liver gland, mammary gland, thyroid gland), the items to be measured, and the size of the search area into the device. The device then references pre-set measurement parameters as set values ​​according to the settings, and applies these set values ​​in the fine detection step and the micro-area setting step.

[0035] (Detection step) When vibrations of approximately 1 kHz or less are applied to a medium such as biological tissue (hereinafter referred to as the target object) using a small vibrator, the vibrations propagate within the target object as shear waves (Figure 1). When ultrasonic pulses are transmitted and received from an ultrasonic probe, the ultrasonic waves reflected from scatterers inside the target object undergo the Doppler effect due to periodic displacement fluctuations caused by the shear waves. The ultrasonic Doppler signal component is obtained from this received ultrasonic wave by quadrature detection, as shown in Figure 1. This is the detection step.

[0036] (Steps to set a micro-region, and steps to calculate micro-regions in one and two directions) In the detection step, a minute region R is set within the image area. Within this minute region, displacement estimation, derivation of the shear wave phase distribution, and phase slope estimation are performed to estimate the shear wave velocity and propagation direction, and the obtained estimated values ​​are taken as the values ​​of the center position of the minute region. This series of processes is repeated while scanning the minute region in one direction (X) and the other direction (Z), thereby estimating the shear wave propagation parameters across the entire image area. Here, the one direction (X) and the other direction (Z) are mutually orthogonal axis directions.

[0037] In the aforementioned one-direction (vertical) infinitesimal calculation step and the other-direction (horizontal) infinitesimal calculation step, Within each minute region, the midpoint (center point) in one of the two-dimensional directions (X direction, Z direction) is used as the phase reference point. The complex amplitude of the shear wave velocity at each coordinate is integrated into the positive and negative directions of the other two-dimensional direction within each minute region to obtain the complex amplitude distribution of the shear wave in that one-dimensional direction. The one-dimensional least squares error method is then applied to this one-dimensional complex amplitude distribution of the shear wave to determine the wavenumber and velocity of the shear wave in that direction.

[0038] The image generation step further includes obtaining micro-region information of the shear wave propagation velocity and propagation direction (slope in the XZ plane) of the micro-region based on the wavenumber and velocity of each shear wave in the two-dimensional direction (X direction, Z direction) of the micro-region obtained by repeating the "one-direction (vertical direction) micro-calculation step" and the "other-direction (horizontal direction) micro-calculation step" within the specified one micro-region, and generating image elements corresponding to said micro-region information, and further, The method includes a video display step in which image elements generated within a specific minute region are displayed as shear wave images on a display device, at the coordinate positions of the minute region within the display screen.

[0039] The method for displaying biological stiffness according to claim 1, wherein the "one-direction (vertical direction) minute calculation step" and the "other-direction (horizontal direction) minute calculation step" within a specific minute region are repeated simultaneously or sequentially in each minute region included in a set image region.

[0040] The tissue stiffness display device of Embodiment 1 of the present invention basically consists of the following configuration as shown in Figure 1.

[0041] • Miniature vibrator (1): It incorporates a vibrator and an eccentric weight, and has a partially spherical bio-contact portion. It applies vibrations of approximately 50Hz to 200Hz to excite mechanical vibration waves (shear waves) within the body tissue. • Measurement unit for shear wave propagation speed: Shear waves excited in a living organism propagate within the organism (2). At this time, the propagation speed of the shear wave changes depending on the stiffness of the tissue, so by measuring the propagation speed of the shear wave, the elasticity of the element can be measured and visualized. • Ultrasonic probe (3): Transmits and receives ultrasound. Ultrasonic transmitting / receiving unit (4): Amplifies the received ultrasonic waves. • Quadrature detection unit (5): A device for obtaining Doppler signals from ultrasound. • Excitation frequency estimation unit (6): Estimates the frequency of shear waves from ultrasonic Doppler signals using the short-time autocorrelation method. • IQ signal adaptive filter (7): Reduces noise in the obtained ultrasonic Doppler signal. • Shear wave complex amplitude equalization unit (8): This unit obtains an image of the shear wave from the signal after passing through the adaptive filter, but first obtains information about the same shear wave using a continuous frame of ultrasound. • Shear wave video playback unit (9)(10): A device that plays back shear wave video and displays the played back shear wave video. • Pressure estimation unit (11): A device that estimates the pressure on a living organism from changes in the excitation frequency. • Pressure display unit (12): A device that displays the estimated pressure.

[0042] When vibrations with a frequency of approximately 1 kHz or less are applied using a small vibrator, the vibrations propagate through the object as shear waves. At the same time, if an ultrasonic pulse is transmitted from an ultrasonic probe to the object, the ultrasonic waves reflected from scatterers within the object and received by the ultrasonic probe undergo phase modulation due to the Doppler effect.

[0043] At this time, the ultrasonic signal reflected from the position (x, z) within the object is expressed as shown in equation (1).

[0044]

number

[0045] However, Δφ(x,z) is the Doppler signal component,

[0046]

number

[0047] The received ultrasonic signal is quadrature-detected using the reference signal of equation (3).

[0048]

number

[0049] At this time, the quadrature detection output is,

[0050]

number

[0051] However, *wave complex conjugate.

[0052] Therefore, the Doppler signal component can be calculated using equation (5).

[0053]

number

[0054] Here, Re and Im are operators that take the real and imaginary parts of a complex number.

[0055] Next, we consider performing a Fourier analysis on the obtained Doppler signal component using the angular frequency of the shear wave to obtain the complex amplitude.

[0056]

number

[0057] Here, ΔT is the period of the shear wave,

[0058]

number

[0059] Furthermore, N is the period during which the Fourier analysis is performed.

[0060] Substituting equation (2) into equation (6), the complex amplitude F is expressed by the following equation.

[0061]

number

[0062]

number

[0063] That is the case.

[0064] (Estimation of shear wave propagation parameters using the 2D least squares error method) Now, as shown in Figure 2, consider a two-dimensional micro-region R within the image area. This micro-region has a width of Δx in the X direction and Δz in the Z direction, as shown in Figure 3. A phase reference point A is established near the center of the infinitesimal region (x0, z0). First, the complex amplitude within the infinitesimal region is multiplied by the phase conjugate of the complex amplitude at this phase reference point, and the phase reference is calculated. point andWe find a complex number whose phase term is the phase difference. This process is performed to ensure that the phase wrap round does not affect the calculation of the phase slope using the least squares error method later.

[0065]

number

[0066] Phase θ of ΔF(x,z) e (x,z) is

[0067]

number

[0068] θ e For (x,z), apply the two-dimensional least squares error method within a small region R, and the first-order coefficient a with respect to x and z. x and a z We find the coefficient of the first order, which is equal to the phase gradient, and the wave number k in the x direction. x and the wave number k in the z direction z teeth,

[0069]

number

[0070] This can be determined as follows: From this, the wave number k, propagation velocity v, and propagation direction φ of the shear wave are,

[0071]

number

[0072] It can be obtained from this.

[0073] By using the above estimated value as the central value of the micro-region and repeatedly performing the same process while scanning the micro-region in the x and z directions, a high-resolution image covering the entire image region can be obtained.

[0074] (Estimation of shear wave propagation parameters using the one-dimensional least squares error method twice) In the two-dimensional least-squares method for estimating shear wave propagation parameters, it is necessary to calculate the inverse of a 3x3 square matrix in order to perform the least-squares method. If the Gauss-Jordan method, which is considered to have a relatively low computational cost, is used to calculate this inverse matrix, the required computational cost is n³, where n is the number of rows and columns. In other words, if n=3, the computational cost becomes 27.

[0075] On the other hand, to find the slope 'a' of a linear function using the one-dimensional least squares error method, the inverse matrix is ​​not required and can be calculated using the following formula.

[0076]

number

[0077] Here y i is the data for which the slope is calculated using the least squares error method, and N is the number of data points. Some terms in equation (14) do not depend on the data and can be calculated in advance. For this reason, the amount of computation required for each data point is very small, and assuming this amount of computation is 1, the amount of computation required for shear wave video is 1 + 1 = 2, because the slope calculation is required twice in the x and z directions using the one-dimensional least squares error method. In other words, using the one-dimensional least squares error method (Figure 7) compared to the two-dimensional least squares error method (Figure 4) reduces the amount of computation required to 2 / 27 = 7.4%, enabling faster video playback (Figure 20).

[0078] In shear wave image reproduction using the one-dimensional least-squares error method, the wavenumber kx in the x-direction is first determined. Specifically, as shown in Figure 5, the complex amplitude F is first integrated in the Z-direction.

[0079]

number

[0080] A reference point B is provided near the center of the one-dimensional array, and the difference from the complex amplitude of this reference point is obtained. This processing is to prevent the influence of phase wrap-around when applying the least squares error method.

[0081] [Number]

[0082] Here, x0 is the coordinate of the reference point B. ΔG x When the phase of is obtained,

[0083] [Number]

[0084] θ e,x For θ(x), when the phase slope ax is obtained by the least squares error method, since the phase slope is equal to the wave number, the following equation is obtained.

[0085] [Number]

[0086] Next, the wave number in the Z direction is obtained by a similar method (Fig. 6).

[0087] From these results, the shear wave propagation parameters are estimated using equation (13). By repeating the same process while scanning the micro-region R in the X and Z directions, a high-resolution image of the shear wave propagation parameters is obtained. However, while each micro-region R has predetermined vertical and horizontal dimensions Δx and Δz (Figure 3), adjacent micro-regions R are set to be shifted by 1 to several pixels, which is smaller than the vertical and horizontal dimensions Δx and Δz. As a result, adjacent micro-regions R are defined in a state where they overlap each other, as shown in Figure 2. Note that the direction of adjacent micro-regions R is not limited to directly sideways and directly downwards as shown in Figure 2, but may also be diagonally upwards and diagonally downwards, rotational and radial directions, or combinations thereof. Depending on the shape of the tissue in the detection area, not only the size of the micro-regions but also the direction of shift, the distance or angle of shift can be set.

[0088] (Features of the present invention) The following 1 to 3 are features of the present invention. Feature 1: Independent estimation of shear wave propagation parameters for each minute region. By dividing the image area into numerous minute plane regions that overlap each other at least among adjacent regions, and estimating shear wave image parameters such as shear wave velocity and shear wave propagation direction for each defined minute region, a high-resolution shear wave image with a spatial resolution uniquely determined by the size of the minute region can be obtained.

[0089] Feature 2: Setting the size of the micro-region according to the organ being observed. By varying the size of the micro-region according to the biological organ being imaged, the system aims to stabilize the reconstructed image and achieve high resolution that corresponds to the elastic structure of the organ.

[0090] For example, in parallel muscles such as the biceps brachii, where the direction of action coincides with the direction of muscle fibers, and in musculoskeletal organs such as tendons and ligaments, the fibrous tissue inside the organ is oriented parallel to the biological surface. In such organs, by selecting a micro-region that is long in the X direction parallel to the biological surface but short in the Z direction perpendicular to it, the orientation, tension, and relaxation of the fibers within the organ can be visualized with high resolution.

[0091] Conversely, in cases of organ fibrosis due to disease, the fibers generally orient themselves randomly. Therefore, by setting the size of a micro-region such that the lengths in the X and Z directions are equal, for example, it becomes possible to observe the organ with spatial resolution independent of the fiber direction.

[0092] Furthermore, since the tensile force of muscle fibers changes depending on muscle tension and relaxation, differences in fiber elasticity can serve as one indicator for evaluating whether the muscle is generating force normally.

[0093] Tendons and ligaments are pulled by external muscles. In this case, even though tendons and ligaments are passive tissues that receive force from external muscles, observing changes in their elasticity allows us to determine whether their function is normal.

[0094] Feature 3: The orientation of muscle fibers within the observed area is simultaneously observed using ultrasound imaging, and the tilt of the minute region is adaptively changed according to the observation results of the ultrasound image.

[0095] In pennate muscles, such as the gastrocnemius muscle, where the direction of the fibers does not coincide with the direction of action, the fiber orientation does not coincide with the longitudinal direction of the muscle but is oriented diagonally. When applying this method to such pennate muscles, the fiber orientation is first observed using ultrasound images (B-mode images), and by tilting a micro-region in the direction of the fiber orientation, the elastic properties of the fibers within the muscle can be observed with high resolution.

[0096] (Other features) Furthermore, as another feature, the system may include a step in which excitation processing is performed using a small vibrator (1) with an eccentric weight, and a "leveling step" is performed, which involves overlapping processing of the C-SWE method by phase equalization, thereby outputting multiple frame images acquired sequentially in time series with a common shear wave phase.

[0097] In other words, the "equalization step" involves "rotating the shear wave phase information of the Nth frame (where N is an integer of 2 or more) so that the phases of the images within a predetermined reference region A are the same," thereby matching the average value of the shear wave phase (real phase, imaginary phase) in all images with that of the first frame. In the example, the "equalization step" was performed for each of the frames from the 2nd frame to the 16th frame and below, where N ≤ 16, in order to obtain a continuous image of the correct gold state during vibration.

[0098] (Equalization step) As an "equalization step," the C-SWE method is duplicated using phase equalization, and this process ensures that the shear wave phases of multiple frames acquired sequentially in time series are shared before output.

[0099] The complex amplitude of the shear wave in a specific region A on the image of each frame (generally selected as a point close to the exciter where the amplitude of the shear wave is large) is used as the reference complex amplitude, and the specific region A of each pixel in the second to Nth (up to 16th) frames is equalized with the specific region A of the first frame (to make it the same as the reference phase).

[0100] Equalization is a process that makes the complex amplitudes of shear waves recorded in multiple consecutive frames identical by focusing on the complex amplitude in a specific region A within the image. This equalization process allows for averaging of the complex amplitudes of the shear waves in the frame direction, and therefore, the signal-to-noise ratio (S / N ratio) of the final shear wave image can be improved through equalization and subsequent averaging.

[0101] In frequency testing of body tissue stiffness using vibration, there was a problem in that the frequency (phase, frame interval Δt) of the shear wave changed each time between images at each frame rate due to the pressure applied by the examiner. There was also a problem in that frequency noise between the first harmonic region and the second harmonic region could not be eliminated. In response to this, the present invention performs overlapping processing using the phase equalization C-SWE method instead of phase difference.

[0102] Specifically, the process involved "rotating the shear wave phase information of the Nth frame so that the phases of the images within a predetermined reference region A are identical," thereby aligning the average value of the shear wave phase (real part phase, imaginary part phase) for all images with that of the first frame. This eliminates changes in the processed image due to frequency changes.

[0103] Because the C-SWE method uses phase equalization rather than phase difference for redundant processing, image changes due to frequency variations are eliminated. Furthermore, the system is robust against frame and excitation frequency fluctuations. Additionally, provided the ultrasonic device has a sufficient signal-to-noise ratio, it is possible to increase the playback rate of shear wave images.

[0104] A fluctuation in the excitation frequency (if this fluctuation is small, around 10%) corresponds to a change in the phase of the shear wave in each consecutive frame. In shear wave video, it is necessary to perform "countable averaging" between consecutive frames to improve the signal-to-noise ratio of the playback image, but if the phase changes as described above, countable averaging cannot be performed.

[0105] Phase equalization processing involves rotating the shear wave phase (phase equalization processing) so that the average phase of a reference region set within each frame matches the average phase of the first frame. This process improves the signal-to-noise ratio (S / N) of the final shear wave image through countable averaging, even if the frequency of the shear wave changes. Therefore, it is an essential technique, especially in systems where noise is expected to be high, such as tablet echo-based shear wave image systems.

[0106] (The concept of complex amplitude undergoing averaging) In the equivalent processing of this invention, the complex amplitude of the shear wave is a more generalized form of phase, referring to both phase and amplitude. In the equivalent processing step of this embodiment, the complex amplitude of the shear wave is a concept that includes both phase and amplitude, The equalization process is performed on both the "shear wave phase" and the "shear wave complex amplitude" together. In the equalization step of this invention, the shear wave is averaged, including not only the phase but also the amplitude. This is because the averaging process cannot be performed unless both the "phase" and "amplitude" are made equal.

[0107] However, as an alternative, the shear wave may be processed by extracting at least the "phase" and averaging it. This is because, as an example of other forms of transmission processing, the complex amplitude of a shear wave has a relatively large contribution from the "phase" and a relatively small contribution from the "amplitude". By simplifying the target of the complex amplitude averaging process according to the required specifications, both accuracy and imaging speed can be ensured.

[0108] (Pixel overlay step) The waveform information of the shear wave within a specific region A of every image (average phase, i.e., phase and amplitude > average value of the complex amplitude consisting of the real and imaginary parts) is compared with the waveform information within the specific region A of the initial frame (reference waveform information). The process is performed so that the waveform information (complex amplitude value) becomes identical (the time axis is rewound so that the waveforms are identical), and the pixels of each frame are superimposed. This allows the same shear wave image to be reproduced even if the frame rate fluctuates over time.

[0109] (Settings for specific area A) The following describes how to set a specific region during the averaging process of the equalization step. In setting the specific region, the width and position in the lateral and depth directions of specific region A are set to wavelength-position conditions within a predetermined magnification range relative to the wavelength of the shear wave, in order to avoid smoothing the phase of the shear wave. For example, it is set to a value between 1 / 5 and 1 / 10 of the wavelength of the shear wave. In addition, the position of region A is set to include the edge closest to the exciter in order to select the portion where the amplitude of the shear wave is large.

[0110] The reason for setting the magnitude of the shear wavelength within a pixel in a specific region A to a predetermined value less than 1 times the shear wavelength, for example, within the range of 1 / 5 to 1 / 10, is that if it is too small, the noise becomes excessive, and if it is too large than the wavelength of the shear wave, the entire image is averaged out to zero. By setting the average shear wavelength within a pixel within a predetermined range as described above, it is possible to continuously output an appropriate denoised image.

[0111] (Moving average processing) Since identical shear wave phase images are obtained in consecutive frames, noise in the shear wave playback image can be reduced by applying a moving average process to the consecutive frames.

[0112] (Estimation of excitation frequency) The excitation frequency is estimated frame by frame (automatic tracking) from the ultrasonic Doppler signal using upsampling and short-interval autocorrelation, and the shear wave image is reproduced using the estimated excitation frequency.

[0113] Since the excitation is performed using a sine wave, it is sufficient to acquire data only for the DC component, the fundamental frequency component, and the second harmonic plus the third harmonic frequency component. Everything else is treated as noise. However, the fundamental frequency component and the second harmonic plus the third harmonic frequency component must undergo estimation frequency processing, and the estimated frequencies calculated during this processing must be used.

[0114] (Display of pressure amount) A mechanism may be added to estimate the "vibrational pressure on the living body" from the temporal variation of the excitation frequency (problem: however, the frequency will fluctuate depending on the pressure) and display the "amount of pressure".

[0115] (Noise processing issues) The ultrasonic device of the present invention uses vibration to vibrate body tissue with a sinusoidal wave. Therefore, the ultrasonic transmission and reception data only needs to acquire the DC component, the fundamental wave component, and the second and third harmonic frequency components, and everything else should be treated as noise. Based on this idea, the fundamental wave component and the second harmonic plus third harmonic frequency components are subjected to estimated frequency processing, and the estimated frequency calculated by this processing is used. In a continuous frequency image group of frames 1 to N (where N is a positive integer less than or equal to 18), the pixel frequencies of a specific region A, which is part of the field of view, are unified to the predetermined estimated frequency calculated above and superimposed, and a continuous output can be obtained, thereby obtaining a continuous image with a high signal-to-noise ratio.

[0116] [Example of an embodiment] An example of an embodiment in which shear wave video playback was performed using the method described here is shown in Figures 12 and onward.

[0117] (Key point 1 of the present invention) The essence of this invention lies in dividing an image region into multiple minute regions R, assuming that the shear wave propagates in a specific direction as a plane wave within each minute region R, and then using the least squares error method to determine the wavenumbers in the X and Z directions of the assumed plane wave, thereby estimating and calculating the shear wave propagation velocity and propagation direction as shear wave propagation parameters.

[0118] Key point of the invention 1: Estimation of independent shear wave propagation parameters for each minute region. The key feature is that by dividing the image area into numerous minute regions and estimating shear wave image parameters such as shear wave velocity and shear wave propagation direction for each minute region, a high-resolution shear wave image with a spatial resolution uniquely determined by the size of the minute region can be obtained.

[0119] (Key point of the invention 2) Another key feature of the present invention is setting the size of the microregion according to the organ being observed. By changing the size of the microregion according to the biological organ being visualized, the stabilization of the reconstructed image and the high resolution corresponding to the elastic structure of the organ are achieved. For example, in musculoskeletal organs such as the biceps brachii (parallel muscles) where the direction of action and the direction of muscle fibers coincide, as well as tendons and ligaments, the fibrous material inside the organ is oriented parallel to the biological surface. In such organs, by selecting a microregion that is long in the X direction parallel to the biological surface but short in the Z direction perpendicular to it, the orientation of the fibers within the organ and the degree of tension and relaxation can be visualized with high resolution.

[0120] Conversely, in cases of organ fibrosis due to disease, the fibers generally orient themselves randomly. Therefore, by setting the size of a micro-region such that the lengths in the X and Z directions are equal, for example, it becomes possible to observe the organ with spatial resolution independent of the fiber direction.

[0121] (Key point of the invention, part 3) Furthermore, the third key feature of this invention is that the orientation of muscle fibers within the observed area is simultaneously observed using an echocardiogram, and the inclination of a minute region is adaptively changed according to the observation results of the echocardiogram.

[0122] In pennate muscles, such as the gastrocnemius muscle, where the direction of the fibers does not coincide with the direction of action, the fiber orientation does not coincide with the longitudinal direction of the muscle but is oriented diagonally. When applying this method to such pennate muscles, the system first observes the fiber orientation using echocardiography (B-mode imaging), and then, by tilting a micro-region in the direction of the fiber orientation, it is possible to observe the elastic properties of the fibers within the muscle with high resolution. The system then estimates the pressure on the living body from the temporal variation of the excitation frequency and displays it on the screen.

[0123] One of the advantages of this invention is that it can obtain high-resolution shear wave images. By arbitrarily setting the size of the micro-region, sub-millimeter resolution can be obtained. This makes it possible to visualize minute structures within the musculoskeletal system, such as fascia and intramuscular tendons. In particular, visualization of fascia is attracting attention in pain treatment, but the mechanism of fascia hydrorelease remains unclear due to the lack of appropriate imaging technology. This invention can help elucidate the mechanism of fascia hydrorelease, and in turn contribute to reducing the dosage and improving the usefulness of this pain treatment technique.

[0124] In addition to the above, the ultrasonic signals received by each transducer are spectrally analyzed, and through multilayer neural network analysis after training, foreign objects can be classified into one of several object spectral models with different sizes or hardnesses. The classified object spectral models are then displayed on a map with a color or shape that corresponds one-to-one with the detected surface. By having multiple receivers arranged in a two-dimensional array and adjacent receivers overlap in signal detection, the general shape and thickness (depth) of the foreign object can be clearly recognized.

[0125] (Device for measuring biological stiffness) Furthermore, the biological stiffness measuring device of the present invention comprises one of the above-mentioned biological stiffness measuring devices that acquires non-contact detection data, and an analytical device that analyzes the acquired detection data. The biological stiffness measuring device in this biological stiffness measuring device method is used not only for muscle stiffness testing but also for detecting tumors or hardened areas in internal organs.

[0126] It is well known that the stiffness of body tissues changes as diseases such as cancer and liver cirrhosis progress. However, this invention makes the vibrator smaller and lighter, improving operability when obtaining a biopsy, while also enabling non-invasive measurement and visualization of body tissue stiffness. In the musculoskeletal field, this will enable functional evaluation of muscles and tendons, etc. This is expected to be useful in the digestive field for assessing the stiffness of tissues such as the liver, and in the breast for early detection of cancer, etc.

[0127] The measuring device of the present invention can also be applied to internal organs, the thyroid gland, and the mammary glands. For example, in the liver, it is expected that this method will enable the measurement of changes in liver stiffness due to chronic hepatitis, cirrhosis, and non-alcoholic fatty liver, which was previously only possible in the ultrasound rooms of large hospitals, to be performed even in small clinic-level medical facilities. Regarding the mammary glands, it has been pointed out that current X-ray mammography has difficulty in detecting malignant tumors in young women with high breast density, and that there are problems with X-ray exposure. In addition, it has been pointed out that in conventional ultrasound diagnosis, malignant tumors are generally depicted as areas with low echogenicity, and interpretation can be difficult, requiring the experience of the examiner.

[0128] In addition to the above, the present invention allows for intuitive visualization of the hardness of biological tissue caused by malignant tumors, and is therefore expected to facilitate the detection of malignant tumors when used in combination with conventional methods.

Claims

1. A method for displaying body tissue stiffness, comprising applying pressure to a vibrator in contact with the surface of a living organism to cause sinusoidal vibration of the body tissue, transmitting and receiving ultrasonic signals from near the body surface to a predetermined image area of ​​the sinusoidally vibrated body tissue using an ultrasonic probe, and continuously acquiring multiple shear wave images to display the state of the muscle tissue in a video, The process involves a "detection step" in which sinusoidal vibration is applied to body tissue by a vibrator to generate periodic displacement fluctuations in a predetermined range of biological tissue, and ultrasonic Doppler signal components due to displacement fluctuations in the image region contained in the biological tissue are detected by ultrasonic transmission and reception of an ultrasonic probe. The "micro-region setting step" involves setting multiple micro-regions R within a defined image region in an overlapping state where at least adjacent portions overlap each other across the entire image region, and defining the position and identifier of each set micro-region within the image region. Assuming that the shear wave propagating in a specific direction within each minute region is a two-dimensional plane wave, The "one-directional minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave of a plane wave in a specific minute region are calculated in the one-dimensional direction of another coordinate axis based on the phase distribution of the plane wave shear wave at each point in one coordinate of that minute region. Also, The "multi-direction minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave of the other coordinates in the other coordinate region are calculated in the one-dimensional direction of the other coordinate axis based on the phase distribution of the plane wave shear wave at each point in the other coordinates of the one minute region. The aforementioned specific minute region is transformed by the minute region setting step into minute regions of different identifiers, each set in an overlapping state where at least adjacent portions overlap each other. The "one-way minute calculation step" and the "other-way minute calculation step" within the minute region of the variable identifier are repeated while shifting the center of each minute region by pixels, A method for displaying biological stiffness, characterized by acquiring shear wave propagation images at each coordinate in the two-dimensional direction of the entire image area.

2. In the aforementioned one-way infinitesimal calculation step and the other-way infinitesimal calculation step, A method for displaying biological stiffness according to claim 1, wherein the midpoint of one of the two-dimensional directions within each minute region is used as the phase reference point, the complex amplitude of the shear wave velocity at each coordinate is integrated into the positive and negative directions of the other direction orthogonal to the aforementioned one of the two-dimensional directions within each minute region to obtain the complex amplitude distribution of the shear wave in the one-dimensional direction, and the one-dimensional least squares error method is applied to this complex amplitude distribution of the shear wave in the one-dimensional direction to determine the phase slope in each direction, thereby determining the wavenumber and velocity of the shear wave in each direction.

3. The image generation step further includes obtaining micro-region information of the shear wave propagation velocity and propagation direction of the micro-region based on the wavenumber and velocity of each shear wave in the two-dimensional direction of the micro-region obtained by repeating the "one-directional micro-calculation step" and the "other-directional micro-calculation step" within the aforementioned specific micro-region, and generating image elements corresponding to said micro-region information, and further, The method for displaying biological stiffness according to claim 1, characterized by having a video display step of displaying image elements generated within a specific minute region as shear wave images to be displayed on a display device, at the coordinate positions of the minute region within the display screen.

4. The method for displaying biological stiffness according to claim 1, wherein the "one-directional microcalculation step" and the "other-directional microcalculation step" within a specific microregion are repeated simultaneously or sequentially in each microregion included in the set image region.

5. The method for displaying biological stiffness according to claim 1, further comprising a "complex amplitude map derivation step" of performing a Fourier analysis on the excitation frequency component based on a Doppler displacement signal detected by an ultrasonic probe to derive a complex amplitude map.

6. A shear strain calculation step that calculates the shear strain in each direction included in the image region based on the difference in displacement fluctuations between two adjacent or nearby minute regions, The process further includes a shear strain image generation step, which generates shear strain image elements by converting the shear strain values ​​of each minute region obtained in the shear strain calculation step into corresponding color maps or grayscale maps in a stepwise manner. The method for displaying biological stiffness according to claim 1, characterized in that, in the video display step, shear strain image elements are displayed superimposed or switched.

7. A vibrator that applies pressure to the surface of a living organism to cause sinusoidal vibrations in the fascial tissue of the body, An ultrasonic probe that transmits and receives ultrasonic signals by contacting the body surface near the body surface, A processing device that acquires shear wave images based on received ultrasound signals and processes the state of loose connective tissue in body tissue, A display device for the mobility of body tissue, comprising: a processing device that processes a shear wave image including the state of loosely connected tissue in the body tissue and displays it on a display unit; The aforementioned ultrasonic probe uses a predetermined depth range of loosely connected tissue within a predetermined excitation range of body tissue that has been contact-excited by a vibrator as its detection area, and receives the ultrasonic Doppler signal component that has been affected by the Doppler effect in the detection area by quadrature detection. Furthermore, the processing apparatus is An "arbitrary setting step" is performed to arbitrarily set a specific image region within the image area that has an arbitrary size and an arbitrary angle relative to the biological surface, The process involves a "detection step" in which sinusoidal vibration is applied to body tissue by a vibrator to generate periodic displacement fluctuations in a predetermined range of biological tissue, and ultrasonic Doppler signal components due to displacement fluctuations in the image region contained in the biological tissue are detected by ultrasonic transmission and reception of an ultrasonic probe. A "micro-region setting step" is performed to define a micro-region R consisting of a predetermined size plane that can divide the set image region, and to define the position and identifier of each set micro-region within the image region. Assuming that the shear wave propagating in a specific direction within each minute region is a two-dimensional plane wave, The "one-directional minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave of a plane wave in a specific minute region are calculated in the one-dimensional direction of another coordinate axis based on the phase distribution of the plane wave shear wave at each point in one coordinate of that minute region. Also, The "multi-direction minute calculation step" is repeated, in which the wavenumber and velocity of the shear wave of the other coordinates in the other coordinate region are calculated in the one-dimensional direction of the other coordinate axis based on the phase distribution of the plane wave shear wave at each point in the other coordinates of the one minute region. The aforementioned specific minute region is varied in an overlapping state where parts of it overlap with the minute regions of different identifiers set by the minute region setting step. The "one-way minute calculation step" and the "other-way minute calculation step" within the minute region of the variable identifier are repeated while shifting the center of each minute region by pixels, This method acquires shear wave propagation images at each coordinate in the two-dimensional direction across the entire image region. The display device is characterized by continuously displaying shear wave propagation images acquired by scanning with an ultrasonic probe on the display device according to the scanning range of the ultrasonic probe.

Images