An elastography method and system

Abstract

The application belongs to the technical field of ultrasonic imaging, and relates to an elastic imaging method and system, which comprises the following steps: obtaining a characteristic direction of tissue from an ultrasonic image; respectively exciting shear waves propagating along a direction extending along a to-be-detected tissue and a direction forming a preset angle with the to-be-detected tissue according to the characteristic direction; exciting a longitudinal wave into the to-be-detected tissue through an ultrasonic probe, and generating a reflection echo after the longitudinal wave reaches the tissue; obtaining a shear wave velocity and a shear wave dispersion curve according to the reflection echo; fitting a shear wave velocity and a tissue elasticity equation, and calculating a tissue elasticity characteristic according to the shear wave velocity and the shear wave dispersion curve. The shear wave elastic imaging under the conditions of non-uniformity, anisotropy, complex structure and viscoelasticity can be realized, and more objective tissue mechanical parameters can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to an elastic imaging method and system, belonging to the technical field of ultrasonic imaging. BACKGROUND

[0002] Medical ultrasonic imaging has the advantages of low cost, non-invasive, painless, high time resolution, real-time, etc., and is an important means in modern medical imaging. With the development of electronic technology, great technological innovation has emerged in the field of ultrasound. Ultrasonic elastography based on shear wave imaging plays a huge role in the measurement of tissue elasticity, such as vascular shear wave elastography, which plays a crucial role in the quantification of the elasticity of the vessel wall. However, it is generally applicable to homogeneous, isotropic, and infinite pure elastic bodies. At this time, the method of tissue elasticity and shear wave velocity is proportional, so it can be characterized by shear wave velocity.

[0003] However, in actual situations, most tissues do not meet the above requirements, such as blood vessels, muscles, and many organs, which are not isotropic, the vessel wall is not a homogeneous tissue, and small cysts and corneas cannot be considered as infinite due to their small size. It cannot be directly related to the simple shear wave velocity and tissue elasticity, and more complex elastic excitation and elastic reconstruction methods are needed. SUMMARY

[0004] To solve the above problems, the purpose of the present application is to provide an elastic imaging method and system which can realize shear wave elastography in non-uniform, anisotropic, complex structure, and viscoelastic cases, and obtain more objective tissue mechanical parameters.

[0005] To achieve the above purpose, the present application proposes the following technical solution: an elastic imaging method, comprising: obtaining the characteristic direction of the tissue from the ultrasonic image; according to the characteristic direction, respectively exciting shear waves propagating along the extension direction of the tissue to be measured and the direction at a preset angle with the extension direction; exciting a longitudinal wave into the tissue to be measured by an ultrasonic probe, and generating a reflected echo after the longitudinal wave reaches the tissue; obtaining the shear wave velocity and the shear wave dispersion curve according to the reflected echo; fitting the shear wave velocity and the tissue elasticity equation, and calculating the tissue elasticity characteristics according to the shear wave velocity and the shear wave dispersion curve.

[0006] Further, the ultrasonic probe is a cross-shaped probe or a two-dimensional surface array probe.

[0007] Further, when using the cross-shaped probe, the two imaging surfaces are orthogonal, and two orthogonal imaging surfaces of interest are first manually selected, and then adjusted according to the characteristic direction; when using the two-dimensional surface array probe, the imaging surface is automatically selected by the characteristic direction.

[0008] Further, the shear wave velocity and the tissue elasticity equation are monomial quadratic equations, and the tissue elasticity is characterized by anisotropy parameters and viscoelasticity.

[0009] The application further discloses an elastography method, comprising: obtaining a characteristic direction of tissue from an ultrasound image; respectively exciting shear waves propagating along a direction extending along the tissue to be measured and a direction at a preset angle with the direction according to the characteristic direction; exciting a longitudinal wave into the tissue to be measured through a two-dimensional surface array probe, and generating a reflected echo after the longitudinal wave reaches the tissue; and obtaining a three-dimensional elastography result of the shear wave according to the reflected echo.

[0010] Further, for blood vessels, in addition to the three-dimensional elastography result of the shear wave, a pulse wave imaging result in the long axis direction of the blood vessel is also needed, and a blood vessel wall strain information in the short axis direction of the blood vessel is also needed, so as to comprehensively evaluate the elasticity of the blood vessel.

[0011] Further, when high frame frequency imaging is performed, motion correction is needed when multiple ultrasound emission composite imaging is performed, and the motion correction is performed through inter-frame displacement estimation and correction or through an artificial intelligence algorithm.

[0012] Further, the shear waves propagating along the direction extending along the tissue to be measured and perpendicular to the direction extending along the tissue to be measured are respectively excited.

[0013] The application further discloses an elastography system, comprising: a characteristic direction determination module, configured to obtain a characteristic direction of tissue from an ultrasound image; a shear wave excitation module, configured to respectively excite shear waves propagating along a direction extending along the tissue to be measured and a direction at a preset angle with the direction according to the characteristic direction; an ultrasound module, configured to excite a longitudinal wave into the tissue to be measured through an ultrasound probe, and generate a reflected echo after the longitudinal wave reaches the tissue; a shear wave feedback module, configured to obtain a shear wave velocity and a shear wave dispersion curve according to the reflected echo; and a tissue elasticity module, configured to fit a shear wave velocity and tissue elasticity equation, and calculate a tissue elasticity characteristic according to the shear wave velocity and the shear wave dispersion curve.

[0014] The application further discloses an elastography system, comprising: a characteristic direction determination module, configured to obtain a characteristic direction of tissue from an ultrasound image; a shear wave excitation module, configured to respectively excite shear waves propagating along a direction extending along the tissue to be measured and a direction at a preset angle with the direction according to the characteristic direction; an ultrasound module, configured to excite a longitudinal wave into the tissue to be measured through a two-dimensional surface array probe, and generate a reflected echo after the longitudinal wave reaches the tissue; and an imaging module, configured to obtain a three-dimensional elastography result of the shear wave according to the reflected echo.

[0015] The application has the following advantages due to the above technical scheme: the shear wave elastography can be realized under complex tissue conditions such as non-uniformity, anisotropy, complex structure and viscoelasticity, and more objective tissue mechanical parameters can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a schematic diagram of an elastography method in an embodiment of the present application;

[0017] Figure 2 is a schematic diagram of an elastography method in another embodiment of the present application. DETAILED DESCRIPTION

[0018] In order for those skilled in the art to better understand the technical solutions of the present application, the present application is described in detail through specific embodiments. However, it should be understood that the specific embodiments are provided only for better understanding of the present application, and they should not be understood as limiting the present application. In the description of the present application, it should be understood that the terms used are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0019] For the problem that the tissue to be measured is not a homogeneous, isotropic, and infinite pure elastic body, the present application proposes an elastography method and system, which excites a shear wave propagating along a direction extending along the tissue to be measured and a direction at a preset angle with the tissue to be measured, and fits the relationship between the shear wave velocity and the elasticity of the tissue, so as to obtain the elasticity performance of the tissue or the three-dimensional elastography result of the shear wave. Compared with the prior art, the scheme in the present application can realize shear wave elastography under the conditions of non-homogeneity, anisotropy, complex structure, and viscoelasticity, and obtain more objective mechanical parameters of the tissue. The embodiments are described below with reference to the accompanying drawings.

[0020] Embodiment one

[0021] The present embodiment discloses an elastography method, as shown in Figure 1 , which comprises:

[0022] S1 first performs ultrasonic imaging on the target tissue to obtain an ultrasonic image.

[0023] In this step, the acoustic radiation force can be used to excite the region of interest of the object to be detected, and high-speed ultrasonic imaging is performed on the region of interest to obtain ultrasonic image data of the region of interest of the object to be detected. Exemplarily, the ultrasonic image data can include at least one of RF (Radio Frequency, radio frequency) data, envelope data, and B-mode data.

[0024] S2 obtains the characteristic direction of the tissue from the ultrasonic image, and obtains the characteristic direction through tissue segmentation and gray level co-occurrence matrix processing. The characteristic direction can be the extension direction of muscle fibers or the extension direction of the long axis of blood vessels. For example, for blood vessel imaging, according to the strong reflection of the blood vessel wall, a threshold segmentation method is used to obtain a binary image of the blood vessel wall region, and according to the gray level co-occurrence matrix parameters of the image, the extension direction of the long axis is obtained.

[0025] S3 according to the characteristic direction, when the angle between the extension direction of interest and the sound beam direction is 15°-75°, respectively excite out the shear wave propagating along the extension direction of the tissue to be measured and the direction at a preset angle with it; preferably, respectively excite out the shear wave propagating along the extension direction of the tissue to be measured and perpendicular to the extension direction of the tissue to be measured.

[0026] The depth of the shear wave excitation position is proportional to the pulse length, for example, 1cm depth uses A us pulse length, 2cm uses A+10us pulse length, etc.

[0027] The depth of the shear wave excitation position is proportional to the pulse intensity, for example, 1cm depth uses B intensity, 2cm uses 2B intensity, etc.

[0028] The depth of the shear wave excitation position is inversely proportional to the pulse frequency, for example, 1cm depth uses C frequency, 2cm uses C / 2 frequency, etc.

[0029] Wherein, the excitation of the shear wave includes but is not limited to electric field force, magnetic field force, acoustic radiation force, mechanical vibration. Take a certain excitation (such as acoustic radiation force, mechanical excitation, etc.), the mechanical excitation is carried out on the position of the tissue, so that the interface of the tissue and the surrounding tissue produces vibration. The vibration propagates along the interface. At the same time of starting the excitation, the excitation system sends a synchronization signal to the acquisition system.

[0030] S5 fit the shear wave velocity and the tissue elasticity equation, and calculate the tissue elasticity characteristics according to the shear wave velocity and the shear wave dispersion curve. The shear wave velocity and the tissue elasticity equation may be a quadratic equation, or may be fitted according to the existing formula, that is, the parameters are unknown before fitting, and the corresponding parameter value is obtained according to the shear wave velocity. The tissue elasticity is characterized by anisotropy parameters and viscoelasticity.

[0031] Embodiment two

[0032] Based on the same inventive concept, the embodiment discloses an elastic imaging method, as shown in Figure 2 , comprising:

[0033] S1 first performs ultrasonic imaging on the target tissue to obtain an ultrasonic image.

[0034] In this step, the interested region of the object to be detected can be excited by acoustic radiation force, and high-speed ultrasonic imaging is performed on the interested region to obtain ultrasonic image data of the interested region of the object to be detected. Exemplarily, the ultrasonic image data can include at least one of RF (Radio Frequency, radio frequency) data, envelope data, and B-mode data.

[0035] S2 obtains the characteristic direction of the tissue from the ultrasound image, and the characteristic direction is obtained through tissue segmentation and a gray level co-occurrence matrix processing. The characteristic direction can be the extension direction of muscle fibers or the extension direction of the long axis of blood vessels. The result is an angle in the imaging plane.

[0036] S3, according to the characteristic direction, when the included angle between the extension direction of interest and the sound beam direction is 15°-75°, respectively excites shear waves propagating along the extension direction of the tissue to be measured and in a direction at a preset angle with the extension direction of the tissue to be measured; preferably, respectively excites shear waves propagating along the extension direction of the tissue to be measured and perpendicular to the extension direction of the tissue to be measured.

[0037] S4 excites a longitudinal wave into the tissue to be measured by using a two-dimensional surface array probe. After the longitudinal wave reaches the tissue, a reflected echo is generated. When the two-dimensional surface array probe is used, the imaging plane is automatically selected through the characteristic direction.

[0038] The three-dimensional elastic imaging result of the shear wave is obtained according to the reflected echo, and only one shear wave excitation is needed.

[0039] When a blood vessel related application is performed, a coordinate transformation can be performed when the shear wave propagates in the short axis direction. For example, the short axis direction of the blood vessel is annular, the shear wave propagates along the circular ring, and the position of the blood vessel wall is expressed in polar coordinates with the center of gravity of the blood vessel as the coordinate origin. In this coordinate, the propagation of the shear wave is along the angular direction. Similarly, in three-dimensional imaging, the shear wave propagates along the blood vessel wall in an ellipsoidal shape. Through a suitable coordinate transformation, the propagation direction of the shear wave of interest is one-dimensional after the coordinate transformation, which is beneficial to fast calculation and subsequent processing.

[0040] For a blood vessel, in addition to the three-dimensional elastic imaging result of the shear wave, the pulse wave imaging result in the long axis direction of the blood vessel also needs to be considered, and the blood vessel wall strain information in the short axis direction of the blood vessel also needs to be considered, so as to perform comprehensive evaluation of the elasticity of the blood vessel. For example, the comprehensive elasticity information of the blood vessel wall Q=a* shear wave elastic imaging result+ pulse imaging result / b+c / blood vessel wall strain.

[0041] When high frame rate imaging is performed, motion correction is needed when multiple ultrasound transmissions are combined for imaging. The motion correction is performed through inter-frame displacement estimation and correction or through an artificial intelligence algorithm.

[0042] Embodiment three

[0043] Based on the same inventive concept, the embodiment discloses an elastic imaging system, which comprises:

[0044] A characteristic direction determination module is configured to obtain the characteristic direction of the tissue from the ultrasound image.

[0045] The shear wave excitation module is configured to excite shear waves propagating along the extension direction of the tissue to be measured and the direction at a preset angle with the extension direction of the tissue to be measured according to the characteristic direction.

[0046] The ultrasound module is configured to excite a longitudinal wave into the tissue to be measured by the ultrasound probe, and the longitudinal wave generates a reflected echo after reaching the tissue.

[0047] The shear wave feedback module is configured to obtain a shear wave velocity and a shear wave dispersion curve according to the reflected echo.

[0048] Embodiment four

[0049] Based on the same inventive concept, the embodiment discloses an elastic imaging system, comprising:

[0050] The characteristic direction determination module is configured to obtain a characteristic direction of the tissue from an ultrasound image.

[0051] The shear wave excitation module is configured to excite shear waves propagating along the extension direction of the tissue to be measured and the direction at a preset angle with the extension direction of the tissue to be measured according to the characteristic direction.

[0052] The ultrasound module is configured to excite a longitudinal wave into the tissue to be measured by the two-dimensional surface array probe, and the longitudinal wave generates a reflected echo after reaching the tissue.

[0053] The imaging module is configured to obtain a three-dimensional elastic imaging result of the shear wave according to the reflected echo.

[0054] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0055] The present application is described with reference to flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device that implements the functions described in the flowcharts and / or block diagrams. Figure 1 one flow or multiple flows and / or blocksFigure 1 means for performing the function specified by the block or blocks.

[0056] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a Figure 1 one or more flowcharts and / or blocks Figure 1 means for performing the function specified by the block or blocks.

[0057] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the flowcharts and / or blocks Figure 1 one or more flowcharts and / or blocks Figure 1 means for performing the function specified by the block or blocks.

[0058] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, rather than limit the technical solutions of the present application. Although the present application has been described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalent replaced without departing from the spirit and scope of the present application, and any modification or equivalent replacement should be covered in the protection scope of the claims of the present application. The above-mentioned content is merely a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, and all changes or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An elastographic method, characterized by, The method comprises the following steps: obtaining a characteristic direction of the tissue from an ultrasound image; stimulating shear waves propagating along a direction extending along the tissue to be measured and a direction at a preset angle with respect to the direction according to the characteristic direction; exciting a longitudinal wave into the tissue to be measured by an ultrasound probe, and generating a reflected echo after the longitudinal wave reaches the tissue; obtaining a shear wave velocity and a shear wave dispersion curve according to the reflected echo; fitting a shear wave velocity and a tissue elasticity equation, and calculating a tissue elasticity characteristic according to the shear wave velocity and the shear wave dispersion curve; the shear wave velocity and the tissue elasticity equation are a monomial quadratic equation, and the tissue elasticity characteristic is represented by an anisotropic parameter and a viscoelastic parameter.

2. The elastomeric imaging method of claim 1, wherein, The ultrasound probe is a cross-shaped probe or a two-dimensional surface array probe.

3. The elastography method of claim 2, wherein, When the cross-shaped probe is used, two imaging surfaces are orthogonal, two orthogonal imaging surfaces of interest are manually selected first, and then adjusted according to the characteristic direction; when the two-dimensional surface array probe is used, the imaging surface is automatically selected through the characteristic direction.

4. The elastography method of any one of claims 1-3, wherein, Shear waves propagating along a direction extending along the tissue to be measured and a direction perpendicular to the direction extending along the tissue to be measured are respectively stimulated.

5. An elastography system characterized by, The method comprises the following steps: a characteristic direction determination module is configured to obtain a characteristic direction of the tissue from an ultrasound image; a shear wave stimulation module is configured to stimulate shear waves propagating along a direction extending along the tissue to be measured and a direction at a preset angle with respect to the direction according to the characteristic direction; an ultrasound module is configured to excite a longitudinal wave into the tissue to be measured by an ultrasound probe, and generate a reflected echo after the longitudinal wave reaches the tissue; a shear wave feedback module is configured to obtain a shear wave velocity and a shear wave dispersion curve according to the reflected echo; a tissue elasticity module is configured to fit a shear wave velocity and a tissue elasticity equation, and calculate a tissue elasticity characteristic according to the shear wave velocity and the shear wave dispersion curve; the shear wave velocity and the tissue elasticity equation are a monomial quadratic equation, and the tissue elasticity characteristic is represented by an anisotropic parameter and a viscoelastic parameter.

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