CN111067567B - Elastic imaging method and device for measuring anisotropic elastic properties of nerves - Google Patents
Elastic imaging method and device for measuring anisotropic elastic properties of nerves Download PDFInfo
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Abstract
The invention discloses an elastic imaging method and a device for measuring anisotropic elastic properties of nerves, wherein the method comprises the following steps: the subject adopts a certain fixed position and remains stable; placing the ultrasonic probes along the nerve fiber direction and the direction vertical to the nerve fiber direction respectively; in both cases, the nerve is separately stimulated in some way; the ultrasonic probe images the nerve fiber/nerve cross section at a certain pulse repetition frequency, and a particle velocity field is obtained by a signal processing method; and further obtaining the nerve wave propagation in the two sections, and analyzing wave propagation signals to obtain a result representing the anisotropy of the nerve to be measured. The method can perform nondestructive, noninvasive and rapid characterization on the anisotropic elasticity property of the superficial peripheral nerve with larger diameter, and the measured parameters can quantitatively describe the neural anisotropy and perform early diagnosis on the neural related diseases.
Description
Technical Field
The invention relates to the technical field of medical imaging, in particular to an elastic imaging method and device for measuring anisotropic elastic properties of nerves.
Background
The nerve consists of a plurality of nerve fiber bundles and a nerve adventitia wrapped outside the nerve fiber bundles, connects a nerve center, a sensory organ and an effector together, and is a transmission path of human body information. The fiber-envelope structure of the nerve causes its elasticity to exhibit typical anisotropy, with large differences in properties in the fiber plane and perpendicular to the fiber plane. The neural structure and the corresponding anisotropic mechanical model are shown in fig. 1. Understanding the anisotropy of nerves and measuring the anisotropy of nerves in vivo help to describe the physiological and pathological states of the nervous system more clearly. Wherein, FIG. 1(a) shows the structure of a nerve, the perineurium, and the endoneurium enveloping a plurality of nerve bundles; FIG. 1(b) is a model of an anisotropic material with fibers in the 1 direction uniformly distributed within the material, resulting in a large difference in the properties of the planes along the fiber direction (e.g., the 1-2 plane, the 1-3 plane) and the planes perpendicular to the fiber direction (the 2-3 plane).
Many common diseases of the human body are related to the nervous system, such as epilepsy, carpal tunnel syndrome, Parkinson's disease, and the like. At present, some studies have confirmed that some nervous system diseases cause nervous organic changes, which in turn cause changes in the mechanical properties of nerves. For example: the nerves of carpal tunnel syndrome patients are often muscle-invaded and therefore hardened to some extent. If the neuromechanical property can be measured by a mechanical means, some diseases of the nervous system can be expected to be diagnosed or screened at an early stage.
In the related technology, no technology is available for in-vivo, noninvasive and nondestructive characterization of the anisotropic mechanical properties of nerves. The existing in-vivo neuro-elastography technology has the characteristics that the characterization is mostly limited to the condition that the nerve is along the fiber direction, the analysis method is not fine enough, and the influence of the peripheral tissues on the nerve is not considered when data analysis is carried out.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
To this end, it is an object of the present invention to provide an elastography method for measuring anisotropic elastic properties of nerves, which can perform non-destructive, non-invasive, and rapid characterization of anisotropic elastic properties of superficial peripheral nerves with large diameter.
It is another object of the present invention to provide an elastography device for measuring anisotropic elastic properties of nerves.
In order to achieve the above object, an embodiment of an aspect of the present invention provides an elastography method for measuring anisotropic elastic properties of nerves, comprising:
s1, placing an ultrasonic probe at the part to be measured, and adjusting the ultrasonic probe to enable the nerve to be measured to be in the imaging plane of the ultrasonic probe and to be parallel to the nerve to be measured;
s2, applying mechanical excitation to the nerve to be tested to enable the interface of the nerve to be tested and surrounding tissues to vibrate, and the vibration is transmitted along the interface;
s3, exciting longitudinal waves into the tissue of the part to be detected through the ultrasonic probe while applying the mechanical excitation, wherein the longitudinal waves generate reflection echoes after reaching the tissue;
s4, performing signal processing on the reflected echoes to obtain the particle motion speed and displacement of the full-field particles under the ultrasonic view;
s5, extracting the particle motion speed of the particles on the nerve fiber bundle to be detected from the particle motion speed and displacement of the particles in the full field to generate a fiber speed space-time diagram;
s6, adjusting the ultrasonic probe to be perpendicular to the nerve to be tested, executing S2-S4, extracting the particle motion speed of particles on the nerve adventitia of the nerve to be tested from the particle motion speed/displacement of the particles in the full field, and generating an envelope speed space-time diagram;
and S7, processing the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain the neural anisotropy parameters representing the nerve to be detected.
According to the elastic imaging method for measuring the anisotropic elastic property of the nerve, disclosed by the embodiment of the invention, the ultrasonic probe is respectively arranged along the nerve fiber direction and the direction vertical to the nerve fiber, the nerve is emitted and excited under the two conditions, the cross sections of the nerve fiber and the nerve fiber are imaged by using the ultrasonic probe, a particle velocity field is obtained by a signal processing method, the particle velocity in the particle velocity field is extracted to further obtain the nerve fluctuation propagation in the two cross sections, and the fluctuation propagation is analyzed to obtain a result for representing the anisotropy of the nerve to be measured. The method can perform in-vivo and non-invasive in-vivo characterization on the anisotropic elasticity of thicker nerves of a human body, the obtained indexes can perform objective quantitative evaluation on the neural anisotropy, the measured parameters (the wave velocity ratio/modulus ratio of a longitudinal plane and a transverse plane of the nerves) can quantitatively describe the neural anisotropy, and early diagnosis on neural related diseases (such as carpal tunnel syndrome and the like) is expected.
In addition, the elasticity imaging method for measuring the anisotropic elasticity property of the nerve according to the above embodiment of the present invention may further have the following additional technical features:
further, in an embodiment of the present invention, the S7 further includes:
calculating the skewness of the fiber speed space-time diagram and the envelope speed space-time diagramObtaining the group velocity V fluctuating in the direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
A is to be1＝V///V⊥Or with A1As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the present invention, the S7 further includes:
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
According to the formula
And
acquiring a shear modulus in a parallel nerve fiber surface and a shear modulus in a vertical nerve fiber surface, wherein rho is the density of the nerve to be measured;
a is to be2＝μL/μTOr with A2As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the present invention, the S7 further includes:
respectively transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a frequency dispersion curve of a fluctuation signal;
for a given fluctuation frequency f, the phase velocities V of the fluctuations in the parallel-fiber direction and in the perpendicular-fiber direction at the frequency f are obtained on the dispersion curve//(f) And V⊥(f)；
A is to be3(f)＝V//(f)/V⊥(f) Or with A3(f) Is a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the present invention, the S7 further includes:
respectively transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a frequency dispersion curve of a fluctuation signal;
fitting the dispersion curve by analytic solution and numerical solution to obtain muTAnd muL；
A is to be4＝μTC or A4The function of (A) is used as a parameter for representing the anisotropy of the nerve to be detected, and C is an anisotropic elastic parameter.
Further, in an embodiment of the invention, the mechanical excitation comprises electric forces, magnetic forces, acoustic radiation forces, mechanical vibrations.
Further, in an embodiment of the present invention, the transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram respectively includes: two-dimensional fourier transform and wavelet transform.
In order to achieve the above object, according to another aspect of the present invention, there is provided an elastic imaging apparatus for measuring anisotropic elastic properties of nerves, comprising:
the adjusting module is used for placing the ultrasonic probe at a part to be detected and adjusting the ultrasonic probe to enable the nerve to be detected to be in an imaging plane of the ultrasonic probe and to be parallel to the nerve to be detected;
the excitation module is used for applying mechanical excitation to the nerve to be tested so that the interface between the nerve to be tested and surrounding tissues generates vibration, and the vibration is transmitted along the interface;
the excitation module is used for exciting longitudinal waves into the tissue of the part to be detected through the ultrasonic probe while applying the mechanical excitation, and the longitudinal waves generate reflected echoes after reaching the tissue;
the processing module is used for carrying out signal processing on the reflected echo to obtain the particle motion speed and displacement of the full-field particles under the ultrasonic visual field;
the first generation module is used for extracting the particle motion speed of the particles on the nerve fiber bundle to be detected from the particle motion speed and displacement of the particles in the full field to generate a fiber speed space-time diagram;
a second generation module, configured to adjust the ultrasonic probe to be perpendicular to the nerve to be tested, execute S2-S4, extract a particle motion speed of a particle on an epineurium of the nerve to be tested from the particle motion speed/displacement of the particle in the full field, and generate an envelope speed space-time diagram;
and the characterization module is used for processing the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a neural anisotropy parameter for characterizing the nerve to be detected.
According to the elastic imaging device for measuring the neural anisotropic elastic property, disclosed by the embodiment of the invention, the ultrasonic probe is respectively arranged along the nerve fiber direction and the direction vertical to the nerve fiber, under the two conditions, nerve emission excitation is carried out, the cross sections of the nerve fiber and the nerve fiber are imaged by using the ultrasonic probe, a particle velocity field is obtained by a signal processing method, the particle velocity in the particle velocity field is extracted to further obtain the neural fluctuation propagation in the two cross sections, and the fluctuation propagation is analyzed to obtain a result for representing the neural anisotropy to be measured. The device can perform in-vivo and non-invasive in-vivo characterization on the anisotropic elasticity of thicker nerves of a human body, the obtained indexes can perform objective quantitative evaluation on the neural anisotropy, the measured parameters (the wave velocity ratio/modulus ratio of a longitudinal section and a transverse section of the nerve) can quantitatively describe the neural anisotropy, and early diagnosis on nerve-related diseases (such as carpal tunnel syndrome and the like) is expected.
In addition, the elastic imaging device for measuring the anisotropic elastic properties of the nerves according to the above embodiment of the present invention may further have the following additional technical features:
further, in an embodiment of the invention, the characterization module is specifically configured to,
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
A is to be1＝V///V⊥Or with A1As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the invention, the characterization module is specifically configured to,
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
According to the formula
And
acquiring a shear modulus in a parallel nerve fiber surface and a shear modulus in a vertical nerve fiber surface, wherein rho is the density of the nerve to be measured;
a is to be2＝μL/μTOr with A2As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic representation of neural structure and anisotropic properties;
FIG. 2 is a flow chart of an elastography method of measuring anisotropic elastic properties of nerves according to an embodiment of the present invention;
FIG. 3 is a schematic representation of wave propagation in the median nerve using an ultrasound probe according to one embodiment of the present invention;
FIG. 4 is a typical B-Mode plot and corresponding velocity-space-time plot for the median nerve according to one embodiment of the present invention;
FIG. 5 is a schematic illustration of interfacial waves between two-phase solid materials according to one embodiment of the present invention;
FIG. 6 is a schematic diagram of an elastography device for measuring anisotropic elastic properties of nerves according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
An elastography method and apparatus for measuring anisotropic elastic properties of nerves according to an embodiment of the present invention will be described below with reference to the accompanying drawings.
An elastography method for measuring anisotropic elastic properties of nerves proposed according to an embodiment of the present invention will be described first with reference to the accompanying drawings.
FIG. 2 is a flow chart of an elastography method of measuring anisotropic elastic properties of nerves according to an embodiment of the present invention.
As shown in fig. 2, the elastography method for measuring anisotropic elastic properties of nerves comprises the following steps:
in step S1, the ultrasonic probe is placed at the site to be measured, and the ultrasonic probe is adjusted so that the nerve to be measured is in the imaging plane of the ultrasonic probe and parallel to the nerve to be measured.
In the embodiment of the invention, the method mainly comprises two parts of data acquisition and signal processing, wherein data acquisition is firstly carried out, and the acquired data is subjected to signal processing to obtain the anisotropic property of the nerve.
In the embodiment of the present invention, the median nerve is taken as an example to describe the anisotropy, and first, the subject places the part to be measured in a specific posture and a fixed specific posture. For example, the subject takes a standard sitting posture, puts the forearm flat on the table, and keeps the palm relaxed with the included angle of the big arm and the forearm at 120 degrees without exerting force actively.
A typical effect graph is shown in fig. 3. This gesture is only one embodiment and is not the only gesture. Wherein, fig. 3(a) shows that the imaging plane of the ultrasonic probe is parallel to the median nerve; fig. 3(b) the ultrasound probe imaging plane is perpendicular to the median nerve. As shown in fig. 3(a), the ultrasound probe is placed on the arm, and the probe is adjusted so that the median nerve is in the imaging plane of the ultrasound probe. Fig. 4(a) shows a typical B-mode ultrasound image, and fig. 4(a) is a cross-sectional B-mode ultrasound image of the median nerve along the fiber direction.
In step S2, mechanical excitation is applied to the nerve to be measured, so that the interface between the nerve to be measured and the surrounding tissue vibrates, and the vibration propagates along the interface.
Wherein, the mechanical excitation includes but is not limited to electric field force, magnetic field force, acoustic radiation force, mechanical vibration.
Certain excitation (such as acoustic radiation force, mechanical excitation and the like) is adopted to mechanically excite the median nerve or peripheral tissues at the position of the median nerve, so that the interface of the median nerve and the peripheral tissues vibrates. The vibration propagates along the interface. At the same time as the excitation starts, the excitation system sends a synchronization signal to the acquisition system.
It should be noted that, when the two-phase medium is subjected to a mechanical excitation (e.g., an electric field force, etc.), there may be a wave propagating along the interface at the interface. The nature of the interfacial wave propagation (e.g., phase velocity, dispersion properties, etc.) is determined by the physical properties and geometry of the materials of the phases. Fig. 5(a) and (b) illustrate the propagation of interfacial waves in the case where the interface is a plane or a curved surface. In which fig. 5(a) has a planar interface between the two-phase materials, and fig. 5(b) has a curvilinear interface between the two-phase materials.
For a relatively thick nerve (e.g., median nerve) in a human body, if the peripheral tissue is regarded as a homogeneous body and the nerve is described by using the anisotropic model of fig. 1(b), the system of the nerve and the peripheral tissue viewed along both the nerve axial direction and the perpendicular nerve axial direction corresponds to the descriptions of fig. 5(a) and 5(b), respectively. Therefore, by exciting and detecting interfacial waves in tissue by a suitable method, and analyzing the signals of the interfacial waves by the interfacial wave theory, the anisotropy of the nerve can be quantitatively described.
In step S3, while applying the mechanical excitation, a longitudinal wave is excited into the tissue of the site to be measured by the ultrasonic probe, and a reflected echo is generated after the longitudinal wave reaches the tissue.
After the ultrasonic probe receives the synchronous signal sent by the excitation system, longitudinal waves are excited into the tissue. After the longitudinal wave reaches the tissue, a reflected echo is generated and received by the ultrasonic probe. In order to facilitate the collection of interface wave signals, the Pulse repetition Rate (Pulse repetition Rate) of the ultrasonic probe should reach more than 1000 frames, and the total number of sampling frames is not less than 10 frames.
In step S4, the reflected echoes are processed to obtain the particle motion velocity and displacement of the full-field particles in the ultrasonic field of view.
And processing the acquired reflected echo signals by using a specific image processing method to acquire the particle motion speed/displacement of the full-field particles under the ultrasonic field of view.
In step S5, the particle motion velocity of the particles on the nerve fiber bundle to be measured is extracted from the particle motion velocity and the displacement of the particles in the full field, and a fiber velocity space-time diagram is generated.
Referring to the B-mode ultrasound image shown in fig. 4(a), the particle motion velocities of the particles on the median nerve fiber bundle or its adventitia are extracted to obtain a velocity space-time diagram of the fiber bundle or its adventitia at each point. This velocity space-time diagram is referred to as the fiber velocity space-time diagram. A typical fiber velocity space-time diagram is shown in fig. 4(c), where fig. 4(c) is the velocity space-time diagram of the median nerve along the fiber direction, and the diagonal lines represent the velocity of wave propagation along the fiber.
In step S6, the ultrasound probe is adjusted to be perpendicular to the nerve to be measured, S2-S4 are performed, the particle motion velocity of the particles on the epineurium of the nerve to be measured is extracted from the particle motion velocity/displacement of the particles in the full field, and an envelope velocity space-time diagram is generated.
The subject kept the same posture, and the ultrasound probe was rotated 90 degrees so that the probe plane was placed perpendicular to the median nerve, and a typical B-mode ultrasound image is shown in fig. 4(B), which is a B-mode ultrasound image of a section of the median nerve perpendicular to the direction of the fibers.
The same procedure as in steps S2-S4 is performed to obtain the particle motion velocity/displacement of the full-field particles in the ultrasound visual field when the ultrasound probe plane is perpendicular to the median nerve, and with reference to the B-mode ultrasound diagram shown in fig. 4(B), the particle motion velocity/displacement of the particles on the median nerve adventitia is interpolated to extract the particle motion velocity of the particles on the median nerve adventitia, thereby obtaining the velocity-space-time diagram of each point on the nerve adventitia. This velocity space-time diagram is referred to as the envelope velocity space-time diagram. A typical envelope velocity-space-time diagram is shown in fig. 4(d), where fig. 4(d) is the propagation velocity of the wave along the nerve-surrounding tissue interface in the median nerve cross-section, where the box lines in fig. 4(c) and 4(d) represent the paths of the velocity field for spatial interpolation and spatial sampling.
And carrying out spatial sampling and spatial interpolation on the particle motion speed/displacement of the full-field particles, obtaining a speed space-time field of the nerve fiber or nerve capsule fluctuation in a section along the fiber direction, and obtaining a speed space-time field of the nerve capsule fluctuation in a section perpendicular to the fiber direction.
It will be appreciated that when the probe is placed along the nerve fibre, the point of action of the stimulus is located on the nerve fibre or on the nerve's envelope, or the line of action of the stimulus passes through the nerve fibre; when the probe is placed in a direction vertical to the nerve fibers, the action point (or action line) can be positioned inside the nerve to be tested, on the envelope of the nerve to be tested or outside the nerve to be tested, and the shortest distance between the excited action point (or action line) and the envelope of the cross section of the nerve is not more than 2 cm.
In step S7, the fiber velocity space-time diagram and the envelope velocity space-time diagram are processed to obtain a neural anisotropy parameter representing the nerve to be measured.
The embodiment of the invention comprises a plurality of modes for processing the fiber speed space-time diagram and the envelope speed space-time diagram, and specifically comprises the following steps:
(1) calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain the group speed V which fluctuates in the direction parallel to the nerve fiber to be measured (along the fiber direction)//And group velocity V fluctuating vertically in the direction of the nerve fiber to be measured⊥；
A is to be1＝V///V⊥Or with A1As a function of the independent variable as a characterisationAnd measuring parameters of the neural anisotropy.
(2) Calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain the group speed V fluctuating in the direction parallel to the nerve fiber to be measured//And group velocity V fluctuating vertically in the direction of the nerve fiber to be measured⊥；
According to the formula
And
acquiring a shear modulus in a parallel nerve fiber surface and a shear modulus in a vertical nerve fiber surface, wherein rho is the density of a nerve to be measured and can be determined through an in vitro experiment;
a is to be2＝μL/μTOr with A2As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
(3) Respectively transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a dispersion curve of the fluctuation signal, wherein the transformation comprises but is not limited to two-dimensional Fourier transform (2D-FFT) and wavelet transform;
for a given fluctuation frequency f, the phase velocities V of the fluctuations in the parallel-to-fiber direction and in the perpendicular-to-fiber direction at the frequency f are obtained on the dispersion curve//(f) And V⊥(f)；
A is to be3(f)＝V//(f)/V⊥(f) Or with A3(f) Is a function of the independent variable as a parameter for characterizing the anisotropy of the nerve to be measured.
(4) Respectively transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a dispersion curve of the fluctuation signal, wherein the transformation comprises but is not limited to two-dimensional Fourier transform (2D-FFT) and wavelet transform;
fitting the dispersion curve through analytic solution and numerical solution to obtain muTAnd muL；
Wherein the analytical solution is obtained by analyzing fig. 5(a) or (b) based on a mechanical theory; numerical solution is obtained by comparing FIG. 5(a)Or (b) performing finite element modeling analysis. The main required parameters of the analytical solution and numerical solution model are as follows: young's modulus, poisson's ratio, density of the tissue surrounding the nerve; nerve diameter, anisotropic elastic parameter μTAnd C; among these parameters, the young's modulus of the surrounding tissue needs to be measured using the prior art; dividing each of the other parameters by muTAnd C, the existing data can be consulted or read out from the ultrasonic image; by varying μTAnd C, seeking the optimal approximation of the dispersion curve of the theoretical/analytical solution and the actually measured dispersion curve;
a is to be4＝μTC or A4The function of (A) is used as a parameter for representing the anisotropy of the nerve to be measured, and C is an anisotropic elastic parameter.
According to the elastic imaging method for measuring the anisotropic elastic property of the nerve, provided by the embodiment of the invention, a subject adopts a certain fixed body position and keeps stable, the ultrasonic probes are respectively placed along the nerve fiber direction and the direction vertical to the nerve fiber, in the two conditions, the nerve is respectively emitted and excited in a certain mode, the ultrasonic probes image the cross section of the nerve fiber/nerve at a certain pulse repetition frequency, a particle velocity field is obtained through a signal processing method, nerve fluctuation propagation in the two cross sections is further obtained, and a fluctuation propagation signal is analyzed to obtain a result representing the anisotropy of the nerve to be measured. The method can perform in-vivo and non-invasive in-vivo characterization on the anisotropic elasticity of thicker nerves of a human body, the obtained indexes can perform objective quantitative evaluation on the neural anisotropy, the measured parameters (the wave velocity ratio/modulus ratio of a longitudinal plane and a transverse plane of the nerves) can quantitatively describe the neural anisotropy, and early diagnosis on neural related diseases (such as carpal tunnel syndrome and the like) is expected.
Next, an elastography apparatus for measuring anisotropic elastic properties of nerves according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 6 is a schematic diagram of an elastography device for measuring anisotropic elastic properties of nerves according to an embodiment of the present invention.
As shown in fig. 6, the elastic imaging apparatus for measuring anisotropic elastic properties of nerves includes: an adjustment module 100, an excitation module 200, an excitation module 300, a processing module 400, a first generation module 500, a second generation module 600, and a characterization module 700.
The adjusting module is used for placing the ultrasonic probe at the part to be measured and adjusting the ultrasonic probe to enable the nerve to be measured to be in an imaging plane of the ultrasonic probe and to be parallel to the nerve to be measured;
the excitation module is used for applying mechanical excitation to the nerve to be tested so that the interface of the nerve to be tested and surrounding tissues generates vibration, and the vibration is transmitted along the interface;
the excitation module is used for exciting longitudinal waves into the tissue of the part to be detected through the ultrasonic probe while applying mechanical excitation, and the longitudinal waves generate reflected echoes after reaching the tissue;
the processing module is used for carrying out signal processing on the reflected echo to obtain the particle motion speed and displacement of the full-field particles under the ultrasonic visual field;
the first generation module is used for extracting the particle motion speed of particles on the nerve fiber bundle to be detected from the particle motion speed and displacement of particles in the full field to generate a fiber speed space-time diagram;
the second generation module is used for adjusting the ultrasonic probe to be perpendicular to the nerve to be detected, executing S2-S4, extracting the particle motion speed of particles on the nerve adventitia of the nerve to be detected from the particle motion speed/displacement of particles in the full field, and generating an envelope speed space-time diagram;
and the characterization module is used for processing the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain the neural anisotropy parameters for characterizing the nerve to be measured.
The device can perform in-vivo and non-destructive and non-invasive in-vivo characterization on the anisotropic elasticity property of the thicker nerve of the human body, and the obtained indexes can perform objective quantitative evaluation on the anisotropy of the nerve.
Further, in one embodiment of the invention, the characterization module, in particular for,
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain the group speed V fluctuating in the direction parallel to the nerve fiber to be measured//And group velocity V fluctuating vertically in the direction of the nerve fiber to be measured⊥；
A is to be1＝V///V⊥Or with A1As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the present invention, the characterization module is specifically configured to calculate slopes of the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a group velocity V fluctuating in a direction parallel to the nerve fiber to be measured//And group velocity V fluctuating vertically in the direction of the nerve fiber to be measured⊥；
According to the formula
And
acquiring a shear modulus in a parallel nerve fiber surface and a shear modulus in a vertical nerve fiber surface, wherein rho is the density of a nerve to be measured;
a is to be2＝μL/μTOr with A2As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the present invention, the characterization module is specifically configured to transform the fiber velocity space-time diagram and the envelope velocity space-time diagram respectively to obtain a dispersion curve of the fluctuation signal;
for a given fluctuation frequency f, the phase velocities V of the fluctuations in the parallel-to-fiber direction and in the perpendicular-to-fiber direction at the frequency f are obtained on the dispersion curve//(f) And V⊥(f)；
A is to be3(f)＝V//(f)/V⊥(f) Or with A3(f) Is a function of the independent variable as a parameter for characterizing the anisotropy of the nerve to be measured.
Further, in an embodiment of the present invention, the characterization module is specifically configured to transform the fiber velocity space-time diagram and the envelope velocity space-time diagram respectively to obtain a dispersion curve of the fluctuation signal;
fitting the dispersion curve through analytic solution and numerical solution to obtain muTAnd muL；
A is to be4＝μTC or A4The function of (A) is used as a parameter for representing the anisotropy of the nerve to be measured, and C is an anisotropic elastic parameter.
It should be noted that the foregoing explanation of the embodiment of the elastic imaging method for measuring anisotropic elastic properties of nerves is also applicable to the device of the embodiment, and is not repeated herein.
According to the elastic imaging device for measuring the elastic properties of the neural anisotropy, provided by the embodiment of the invention, the ultrasonic probe is respectively arranged along the direction of the nerve fiber and the direction vertical to the nerve fiber, the nerve is emitted and excited under the two conditions, the cross sections of the nerve fiber and the nerve fiber are imaged by using the ultrasonic probe, a particle velocity field is obtained by a signal processing method, the particle velocity in the particle velocity field is extracted to further obtain the neural fluctuation propagation in the two cross sections, and the fluctuation propagation is analyzed to obtain a result representing the neural anisotropy to be measured. The device can perform in-vivo and non-invasive in-vivo characterization on the anisotropic elasticity of thicker nerves of a human body, the obtained indexes can perform objective quantitative evaluation on the neural anisotropy, the measured parameters (the wave velocity ratio/modulus ratio of a longitudinal section and a transverse section of the nerve) can quantitatively describe the neural anisotropy, and early diagnosis on nerve-related diseases (such as carpal tunnel syndrome and the like) is expected.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. An elastography method of measuring anisotropic elastic properties of nerves, characterized by the steps of:
s1, placing an ultrasonic probe at the part to be measured, and adjusting the ultrasonic probe to enable the nerve to be measured to be in the imaging plane of the ultrasonic probe and to be parallel to the nerve to be measured;
s2, applying mechanical excitation to the nerve to be tested to enable the interface of the nerve to be tested and surrounding tissues to vibrate, and the vibration is transmitted along the interface;
s3, exciting longitudinal waves into the tissue of the part to be detected through the ultrasonic probe while applying the mechanical excitation, wherein the longitudinal waves generate reflection echoes after reaching the tissue;
s4, performing signal processing on the reflected echoes to obtain the particle motion speed and displacement of the full-field particles under the ultrasonic view;
s5, extracting the particle motion speed of the particles on the nerve fiber bundle to be detected from the particle motion speed and displacement of the particles in the full field to generate a fiber speed space-time diagram;
s6, adjusting the ultrasonic probe to be perpendicular to the nerve to be tested, executing S2-S4, extracting the particle motion speed of particles on the nerve adventitia of the nerve to be tested from the particle motion speed/displacement of the particles in the full field, and generating an envelope speed space-time diagram;
and S7, processing the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain the neural anisotropy parameters representing the nerve to be detected.
2. The elastography method of measuring neuroanisotropic elastic properties of claim 1, wherein said S7 further comprises:
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
A is to be1＝V///V⊥Or with A1As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
3. The elastography method of measuring neuroanisotropic elastic properties of claim 1, wherein said S7 further comprises:
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
According to the formula
And
acquiring a shear modulus in a parallel nerve fiber surface and a shear modulus in a vertical nerve fiber surface, wherein rho is the density of the nerve to be measured;
a is to be2＝μL/μTOr with A2As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
4. The elastography method of measuring neuroanisotropic elastic properties of claim 1, wherein said S7 further comprises:
respectively transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a frequency dispersion curve of a fluctuation signal;
for a given fluctuation frequency f, the phase velocities V of the fluctuations in the parallel-fiber direction and in the perpendicular-fiber direction at the frequency f are obtained on the dispersion curve//(f) And V⊥(f)；
A is to be3(f)＝V//(f)/V⊥(f) Or with A3(f) Is a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
5. The elastography method of measuring neuroanisotropic elastic properties of claim 1, wherein said S7 further comprises:
respectively transforming the fiber velocity space-time diagram and the envelope velocity space-time diagram to obtain a frequency dispersion curve of a fluctuation signal;
fitting the dispersion curve by analytic solution and numerical solution to obtain muTAnd muL；
A is to be4＝μTC or A4The function of (A) is used as a parameter for representing the anisotropy of the nerve to be detected, and C is an anisotropic elastic parameter.
6. An elastography method for measuring neuroanisotropic elastic properties according to claim 1, characterized in that said mechanical excitation comprises electric, magnetic, acoustic radiation, mechanical vibrations.
7. An elastography method for measuring neuroanisotropic elastic properties according to claim 4 or 5, wherein said transforming said fiber velocity space-time diagram and said envelope velocity space-time diagram respectively comprises: two-dimensional fourier transform and wavelet transform.
8. An elastography device for measuring anisotropic elastic properties of nerves, comprising:
the adjusting module is used for placing the ultrasonic probe at a part to be detected and adjusting the ultrasonic probe to enable the nerve to be detected to be in an imaging plane of the ultrasonic probe and to be parallel to the nerve to be detected;
the excitation module is used for applying mechanical excitation to the nerve to be tested so that the interface between the nerve to be tested and surrounding tissues generates vibration, and the vibration is transmitted along the interface;
the excitation module is used for exciting longitudinal waves into the tissue of the part to be detected through the ultrasonic probe while applying the mechanical excitation, and the longitudinal waves generate reflected echoes after reaching the tissue;
the processing module is used for carrying out signal processing on the reflected echo to obtain the particle motion speed and displacement of the full-field particles under the ultrasonic visual field;
the first generation module is used for extracting the particle motion speed of the particles on the nerve fiber bundle to be detected from the particle motion speed and displacement of the particles in the full field to generate a fiber speed space-time diagram;
the second generation module is used for adjusting the ultrasonic probe to be perpendicular to the nerve to be detected, applying mechanical excitation to the nerve to be detected, enabling an interface between the nerve to be detected and surrounding tissues to generate vibration, transmitting the vibration along the interface, exciting a longitudinal wave to the inside of the tissue of the part to be detected through the ultrasonic probe while applying the mechanical excitation, generating a reflected echo after the longitudinal wave reaches the tissue, performing signal processing on the reflected echo to obtain the particle motion speed and displacement of a full-field particle under an ultrasonic field, extracting the particle motion speed of a particle on the neural adventitia of the nerve to be detected from the particle motion speed/displacement of the full-field particle, and generating an envelope speed space-time diagram;
and the characterization module is used for processing the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a neural anisotropy parameter for characterizing the nerve to be detected.
9. An elastography device for measuring neuroanisotropic elastic properties according to claim 8, characterized in that said characterization module, in particular for,
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
A is to be1＝V///V⊥Or with A1As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
10. An elastography device for measuring neuroanisotropic elastic properties according to claim 8, characterized in that said characterization module, in particular for,
calculating the slope of the fiber speed space-time diagram and the envelope speed space-time diagram to obtain a group speed V which fluctuates in a direction parallel to the nerve fiber to be detected//And group velocity V fluctuating in the direction perpendicular to the nerve fiber to be measured⊥；
According to the formula
And
acquiring a shear modulus in a parallel nerve fiber surface and a shear modulus in a vertical nerve fiber surface, wherein rho is the density of the nerve to be measured;
a is to be2＝μL/μTOr with A2As a function of the independent variable as a parameter characterizing the anisotropy of the nerve to be measured.
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