CN111449629B - Optical coherence elastography method and device - Google Patents

Abstract

The application discloses an optical coherence elastography method and device, wherein the optical coherence elastography method utilizes ultrasonic beams to induce a sample to be measured to generate a first elastic wave and a second elastic wave with vertical propagation directions, so that when the first elastic wave and the second elastic wave are imaged by utilizing the optical coherence elastography method, imaging results containing elastic information in the first direction and the second direction can be obtained, and therefore the elastic information of the sample to be measured in the first direction and the elastic information of the sample to be measured in the second direction can be obtained according to the imaging results, the purpose of measuring the axial direction and the lateral direction elastic information of the sample to be measured is achieved, and the purpose of comprehensively and accurately evaluating the anisotropic elastic characteristics of the sample to be measured is achieved.

Description

Optical coherence elastography method and device

technical field

The present application relates to the field of imaging technology, and more specifically, to an optical coherent elastography method and device.

Background technique

The difference in the elastic mechanical properties of biological tissues comes from the differences in the composition, structure and interaction of biomolecules, cells and samples. The measurement of the elasticity of biological tissues is of great significance for evaluating the physiological functions of samples, and can be used for eyeball, cardiovascular, breast, etc. , liver and other parts of the disease diagnosis. Age-related macular degeneration (AMD), a degenerative disease of the pigment epithelium in the macular area of the retina, is one of the main causes of irreversible blindness in people over 60 years old. Retinal elasticity measurement can be used for risk assessment and early diagnosis of wet AMD, so as to achieve early intervention and treatment, so as to delay disease progression and improve treatment effect, which has very important clinical application value.

Optical Coherence Elastography (OCE) is the mainstream method for measuring the elasticity of biological tissue. Imaging modes for elastic mechanical parameters such as shear modulus and Young's modulus. Optical coherence tomography (Optical coherence tomography, OCT) is a non-invasive high-resolution three-dimensional medical imaging technology, with a spatial resolution of about 10 μm, a biological tissue imaging depth of 2-3 mm, and an imaging field of view of about 1 cm. Different calculation methods and measurement principles can be used for structural imaging of biological tissues, angiographic imaging and elastography.

However, in the prior art, when the ultrasonic beam-induced optical coherent elastography method is used to image biological tissue, only the lateral elastic information of the measured biological tissue perpendicular to the external force direction can be obtained, but the measured biological tissue cannot obtain the The axial elastic information in the direction of the external force makes it impossible to comprehensively and accurately evaluate the anisotropic elastic characteristics of biological tissues.

Contents of the invention

In order to solve the above technical problems, this application provides an optical coherent elastography method and device to achieve the purpose of measuring the axial and lateral elastic information of the tested sample, and to achieve a comprehensive and accurate evaluation of the measured sample's anisotropic The purpose of the elastic characteristics of the opposite sex.

In order to achieve the above technical purpose, the embodiment of the present application provides the following technical solutions:

A method of optical coherence elastography comprising:

Ultrasonic sound beams are used to induce the sample to be tested to generate a first elastic wave and a second elastic wave, the propagation direction of the first elastic wave is the first direction, the propagation direction of the second elastic wave is the second direction, and the first elastic wave is propagated in the second direction. a direction is perpendicular to the second direction;

Using an optical coherence tomography method, image the first elastic wave and the second elastic wave, and obtain the elastic information of the sample to be measured in the first direction and the sample to be measured according to the imaging result. Elasticity information in the second direction.

Optionally, the use of ultrasonic beams to induce the sample to be tested to generate the first elastic wave and the second elastic wave includes:

Multiple ultrasonic beams are used to form a multi-point vibration source in the sample to be tested, and the multi-point vibration source induces the surface and/or inside of the sample to be tested to generate the first elastic wave and the Describe the second elastic wave.

Optionally, when the first elastic wave and the second elastic wave are located on the surface of the sample to be tested, the first elastic wave and the second elastic wave are surface Rayleigh waves and longitudinal shear waves respectively. Wave.

Optionally, when the first elastic wave and the second elastic wave are located inside the sample to be tested, the first elastic wave and the second elastic wave are longitudinal shear waves and transverse shear waves respectively Wave.

Optionally, the optical coherence tomography method is used to image the first elastic wave and the second elastic wave, and obtain elastic information and The elastic information of the sample to be tested in the second direction includes:

Using an optical coherence tomography method, imaging the first elastic wave and the second elastic wave on the surface of the sample to be tested, and obtaining the elasticity of the surface of the sample to be tested in a first direction according to the imaging result information and elastic information of the surface of the sample to be tested in the second direction;

Imaging the first elastic wave and the second elastic wave inside the sample to be tested by using an optical coherence tomography method, and acquiring the elasticity of the surface of the sample to be tested in a first direction according to the imaging result information and the elasticity information of the surface of the sample to be measured in the second direction.

An optical coherent elastography system, comprising: an imaging unit and an acoustic radiation force excitation unit; wherein,

The acoustic radiation force excitation unit is configured to form multiple ultrasonic beams and transmit them to the sample to be tested, so that the multiple beams of ultrasonic beams induce the sample to be tested to generate a first elastic wave and a second elastic wave, and the first The propagation direction of the elastic wave is a first direction, the propagation direction of the second elastic wave is a second direction, and the first direction is perpendicular to the second direction;

The imaging unit is configured to transmit a detection beam to the sample to be measured, and receive the detection beam reflected and scattered by the sample to be measured, and to use an optical coherence tomography method to detect The light beam images the first elastic wave and the second elastic wave, and obtains the elastic information of the sample to be measured in the first direction and the elastic information of the sample to be measured in the second direction according to the imaging results .

Optionally, it also includes: a coupling unit;

The coupling unit includes an acoustic reflection surface and a light incident surface, and the acoustic reflection surface has optical transparency and acoustic reflection characteristics;

The probe beam is incident through the light incident surface and transmits through the acoustic reflection surface to the sample to be tested. After the ultrasonic sound beam is reflected by the acoustic reflection surface, it travels in the same direction or a similar direction as the probe beam. Transfer to the sample to be tested.

Optionally, the coupling unit includes: a first dielectric structure, an intermediate dielectric structure, and a second dielectric structure; wherein,

The intermediate dielectric structure is disposed between the first dielectric structure and the second dielectric structure, and the first dielectric structure includes the light incident surface;

The second dielectric structure includes an acoustic incident surface, and the contact surface between the intermediate dielectric structure and the second dielectric structure is the acoustic reflection surface.

Optionally, the difference between the optical refractive index of the first dielectric structure, the optical refractive index of the second dielectric structure, and the optical refractive index of the intermediate dielectric structure is smaller than a first preset difference;

The difference between the acoustic impedance of the second medium structure and the acoustic impedance of the intermediate medium structure is greater than a second preset difference.

Optionally, both the first dielectric structure and the second dielectric structure are prisms, and the intermediate dielectric structure is a silicone oil layer or a water layer;

or

The first medium structure and the second medium structure are both silicone oil layers or water layers or phosphate buffered saline solution layers or physiological saline layers, and the intermediate medium structure is a glass layer.

It can be seen from the above technical solutions that the embodiments of the present application provide an optical coherent elastography method and device, wherein the optical coherent elastography method uses ultrasonic sound beams to induce the sample to be tested to generate a first elastic wave whose propagation direction is vertical and the second elastic wave, so that when the optical coherence tomography method is used to image the first elastic wave and the second elastic wave, an imaging result containing elastic information in both directions of the first direction and the second direction can be obtained, thereby The elastic information of the sample to be tested in the first direction and the elastic information of the sample to be tested in the second direction can be obtained according to the imaging result, so as to realize the measurement of the axial and lateral elastic information of the sample to be tested The purpose is to achieve the purpose of comprehensively and accurately evaluating the anisotropic elastic characteristics of the tested sample.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present application, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is a schematic diagram of the measurement principle of optical coherence elastography in the prior art;

Fig. 2 is a schematic flow chart of an optical coherent elastography method provided by an embodiment of the present application;

Fig. 3 is a schematic diagram of array arrangement of an array type ultrasonic transducer;

Figure 4 is a schematic diagram of the induced compression wave and shear wave when two point vibration sources act on the inside of the sample to be tested;

Figure 5 is a schematic diagram of the induced compression wave and shear wave when two point vibration sources act on the surface of the sample to be tested;

Fig. 6 is the schematic diagram of the principle of M-B scanning;

FIG. 7 is a schematic structural diagram of an optical coherent elastography system provided by an embodiment of the present application;

FIG. 8 is a schematic structural diagram of an imaging unit provided by an embodiment of the present application;

FIG. 9 is a schematic structural diagram of an imaging unit provided by another embodiment of the present application;

FIG. 10 is a schematic structural diagram of an imaging unit provided by another embodiment of the present application;

Fig. 11 is a schematic structural diagram of an acoustic radiation force excitation unit provided by an embodiment of the present application;

Fig. 12 is a schematic structural diagram of a coupling unit provided by an embodiment of the present application;

Fig. 13 is a schematic structural diagram of a coupling unit provided by another embodiment of the present application;

Fig. 14 is a schematic structural diagram of a coupling unit provided by another embodiment of the present application.

Detailed ways

As mentioned in the background technology, when the ultrasonic acoustic beam-induced optical coherence elastography method in the prior art is used to image biological tissues, it can only obtain the lateral elasticity information of the measured biological tissue in the direction of vertical external force, but cannot obtain the measured biological tissue. The axial elastic information of biological tissue parallel to the direction of external force, the specific reason will be explained below.

When measuring the elasticity of biological tissue, first use external force to induce elastic waves in the tissue, then detect the propagation of elastic waves through the imaging platform, and finally calculate the elastic modulus in the direction of elastic wave propagation according to the propagation speed of elastic waves. Therefore, in the elastic measurement of anisotropic biological tissue, the construction of the elastic wave imaging platform is the basis of the measurement, and the elastic wave that simultaneously induces the axial propagation of the external force and the lateral propagation perpendicular to the external force is the key to the measurement .

In the prior art, referring to Fig. 1, during imaging, the ultrasonic sound beam is used to induce micro-vibration of the sample to be tested. After measuring the vibration amplitude of the sample through OCT imaging technology, the propagation of the elastic wave is reconstructed, and the propagation velocity of the elastic wave is calculated. Analyze the elastic mechanical properties of the sample to be tested in the direction of elastic wave propagation. In Fig. 1, a transverse shear wave is induced using the acoustic radiation force, and the direction of propagation of the transverse shear wave is perpendicular to the vibration direction. Because, through the wave velocity measurement of the transverse shear wave, the lateral elastic information analysis of the vertical external force in the sample can be realized. In Fig. 1, the OCT converging lens is a component of the optical coherence tomography unit, and the OCT incident beam is the detection beam emitted by the optical coherence tomography unit.

Conventional OCE technology relies on the detection of transverse shear waves and surface Rayleigh waves, whose propagation direction is perpendicular to the direction of external force, and can only measure the elastic modulus in the lateral direction (perpendicular to the external force). Although the compressional wave is a longitudinal wave, its propagation direction is parallel to the direction of the external force, but the compressional wave propagates too fast in biological tissue (about 1500m/s), and the current OCT technology cannot capture the propagation process of the compressional wave due to the limitation of the imaging frame rate. Calculate its propagation speed. Therefore, in most studies, biological tissue is assumed to be an isotropic material, and only the lateral elastic modulus is measured to characterize the elastic properties of biological tissue in all directions. The axial elastic modulus cannot be measured, resulting in inability to comprehensively and accurately evaluate the anisotropic elastic properties of the sample.

In view of this, an embodiment of the present application provides an optical coherent elastography method, including:

Ultrasonic sound beams are used to induce the sample to be tested to generate a first elastic wave and a second elastic wave, the propagation direction of the first elastic wave is the first direction, the propagation direction of the second elastic wave is the second direction, and the first elastic wave is propagated in the second direction. a direction is perpendicular to the second direction;

Using an optical coherence tomography method, image the first elastic wave and the second elastic wave, and obtain the elastic information of the sample to be measured in the first direction and the sample to be measured according to the imaging result. Elasticity information in the second direction.

The optical coherence elastography method uses ultrasonic sound beams to induce the sample to be tested to generate a first elastic wave and a second elastic wave whose propagation direction is vertical, so that the optical coherence tomography method is used to analyze the first elastic wave and the second elastic wave During imaging, an imaging result including elastic information in the first direction and the second direction can be obtained, so that the elastic information of the sample to be measured in the first direction and the elastic information of the sample to be measured in the first direction can be obtained according to the imaging result. The elastic information in the second direction realizes the purpose of measuring the axial and lateral elastic information of the tested sample, and realizes the purpose of comprehensively and accurately evaluating the anisotropic elastic characteristics of the tested sample.

The following will clearly and completely describe the technical solutions in the embodiments of the application with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only some of the embodiments of the application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

The embodiment of the present application provides an optical coherent elastography method, as shown in Figure 2, including:

S101: Using an ultrasonic sound beam to induce the sample to be tested to generate a first elastic wave and a second elastic wave, the propagation direction of the first elastic wave is the first direction, and the propagation direction of the second elastic wave is the second direction, so The first direction is perpendicular to the second direction;

S102: Using an optical coherence tomography method, image the first elastic wave and the second elastic wave, and acquire the elastic information of the sample to be tested in the first direction and the to-be-measured sample according to the imaging result Elasticity information of the sample in the second direction.

In step S101 of this embodiment, the first direction and the second direction are two directions perpendicular to each other. Generally, the first direction and the second direction may be an axial direction and a lateral direction, respectively, And further, the axial direction refers to the direction parallel to the external force, and the lateral direction refers to the direction perpendicular to the external force.

In step S101 , the purpose of inducing elastic waves in the first direction and elastic waves in the second direction of the sample to be tested can be achieved by forming multi-point vibration sources in the sample to be tested.

Specifically, a feasible execution process of step S101 includes:

S1011: Using multiple ultrasonic beams to form a multi-point vibration source in the sample to be tested, the multi-point vibration source induces the surface and/or inside of the sample to be tested to generate the first elastic wave and the second elastic wave.

When a device such as an acoustic radiation force excitation unit is used to generate multiple ultrasonic beams incident on the sample to be tested, the multiple ultrasonic beams will generate multi-point mechanical drives in the sample to form a multi-point vibration source.

The acoustic radiation force excitation unit includes structures such as a waveform generator, an amplifier, and an array ultrasonic transducer. The waveform generator generates a high-frequency sine wave, square wave, or triangle wave synchronized with the OCT. After being amplified by the amplifier, the array type transducer is excited. Ultrasonic transducers generate multiple points of acoustic radiation force. The array form of the arrayed ultrasonic transducer is shown in Figure 3. For example, the arrayed ultrasonic transducer includes 8×8 array elements, and each array element is an ultrasonic transducer. The spacing is 1.5mm, and the effective area array size of the ultrasonic transducer is 10.5×10.5mm. Subsequent design of parameters such as the number of array elements and spacing will be optimized based on the theoretical analysis of elastic waves and the control method of array elements. The acoustic radiation force is the interaction between a sound wave and obstacles on its transmission path, and the amplitude |F| of the acoustic radiation force at a given location in space can be evaluated by the following formula:

Among them, α represents the attenuation coefficient of ultrasound in tissue, which is related to the frequency of ultrasound, I represents the average intensity of the sound beam at the position to be measured, which is related to the sound field of the ultrasonic transducer, and c represents the propagation speed of ultrasound in tissue. Therefore, the ultrasonic radiation force increases with the increase of tissue attenuation coefficient and ultrasonic intensity. By controlling the distance between the ultrasonic transducer and the tissue and changing the focus position of the acoustic radiation force on the sample, the acoustic radiation force can be focused on the tissue surface or inside the tissue.

When two point vibration sources act on the tissue simultaneously, each point vibration source independently induces compression waves and shear waves inside the tissue. Classical compression waves are longitudinal waves that propagate parallel to the direction of vibration, while shear waves are transverse waves that propagate perpendicular to the direction of vibration. In Fig. 4, the thin dotted arrow indicates the propagation direction of the transverse shear wave induced by the point vibration source, the thin solid arrow indicates the vibration direction, the dotted circle indicates the position of the wave front at this moment, and the line segments on the left and right indicate that it comes from two different point vibration source. Where two transverse shear waves meet, due to the superposition of waves, a shear wave whose vibration direction is parallel to the propagation direction is generated, so it is called longitudinal shear wave.

When the point vibration source is located inside the sample to be tested, each point vibration source induces compression waves and shear waves inside the tissue, as shown in 4. At the place where the transverse shear waves induced by two point vibration sources converge, due to the superposition of waves, longitudinal shear waves whose vibration direction is parallel to the propagation direction are generated, which propagate up and down to the vibration source respectively. At the same time, a transverse shear wave perpendicular to the vibration direction of the vibration source is generated and propagates to both sides of the vibration source. That is, when the first elastic wave and the second elastic wave are located inside the sample to be tested, the first elastic wave and the second elastic wave are longitudinal shear waves and transverse shear waves, respectively.

When the point vibration source is located on the surface of the sample to be tested, the surface Rayleigh wave induced by the point vibration source propagates to both sides of the vibration source, the propagation direction is perpendicular to the direction of the external force, and the propagation depth is within about 1 wavelength from the tissue surface, as shown in the figure 5. At the same time, the point vibration source induces longitudinal shear waves and compression waves on the surface of the tissue, and propagates along the axial direction of the external force. That is, when the first elastic wave and the second elastic wave are located on the surface of the sample to be tested, the first elastic wave and the second elastic wave are surface Rayleigh waves and longitudinal shear waves respectively. The tissues in Fig. 4 and Fig. 5 are the samples to be tested.

Correspondingly, step S102 specifically includes:

S1021: Using an optical coherence tomography method, image the first elastic wave and the second elastic wave on the surface of the sample to be measured, and acquire the surface of the sample to be measured in a first direction according to the imaging result The elasticity information of the surface of the sample to be tested and the elasticity information of the surface of the sample to be measured in the second direction;

S1022: Using an optical coherence tomography method, image the first elastic wave and the second elastic wave inside the sample to be measured, and acquire the surface of the sample to be measured in a first direction according to the imaging result and the elasticity information of the surface of the sample to be tested in the second direction.

The elastic wave reconstruction process in the optical coherence tomography process is described below.

In order to capture fast-propagating elastic waves at the maximum frame rate, an OCT (optical coherence tomography) data acquisition method based on M-B scanning can be used, the principle of which is shown in Figure 6. B-scan refers to the combination of multiple processed signal lines along the depth direction that are spaced side by side into a two-dimensional "anatomical image" (that is, OCT B-mode image) that reflects the internal tomographic section of the measured object. M-scan refers to sampling multiple times at the same lateral position of the sample, and unfolding the sampled signal lines in chronological order to form a one-dimensional timing diagram (that is, an OCT M mode image). In the process of repeated ultrasonic induction of elastic waves, the OCT unit collects one M-mode timing image at each lateral position, and then reconstructs the M-mode timing images at different lateral positions into a B-mode two-dimensional planar image that changes with time . For example, in a system using a 100 kHz swept light source, the frame rate of elastic wave imaging by the M-B scan method can be maximized, about 100,000 frames per second.

In order to use the OCT unit to detect the tiny vibrations in the sample to be tested with high sensitivity and realize the propagation imaging of weak-amplitude elastic waves, a vibration measurement method based on phase analysis can be used. First, through Fast Fourier Transformation (FFT), the interference signal collected by the OCT unit that changes with wavelength is transformed into a complex signal that changes with depth, and the complex signal is band-pass filtered to remove low-frequency noise. OCT complex signal Contains the magnitude A(x, y, z, t) part and the phase Part, where (x, y, z) represents the spatial position of the scan, and t represents the sampling moment. According to the Doppler principle, the phase change of the OCT signal can be used to calculate the vibration velocity and displacement of the scattering particles in the sample. Velocity V and OCT phase change of scattered particles in the sample within the time interval ΔT The average relationship is as follows:

Among them, n represents the optical refractive index of the sample, λ represents the central wavelength of light in vacuum, θ represents the angle between the moving direction of the particle and the probe beam, V×cos(θ) represents the velocity component of the particle along the direction of the probe beam, and the phase change can be calculated by OCT complex signal as follows:

Among them, F _{x, y, z, t} and F _{x, y, z, t+1} represent at different time (t and t+1 time), respectively, at the same position (lateral position x, y and depth position z ) on the OCT complex signal, the time interval between t and t+1 is ΔT.

Calculation of elastic modulus:

Having measured the propagation velocities of longitudinal shear waves, transverse shear waves, and surface Rayleigh waves, we will calculate Young's modulus in the direction of elastic wave propagation. The relationship between the propagation velocity of transverse shear wave and Young's modulus E can be expressed by the following formula:

Among them, ρ represents the sample density, V _Shear represents the propagation velocity of the transverse shear wave, and v represents the Poisson's ratio of the biological tissue. Incompressible biological soft samples have a density ρ of ~1000 kg/m ³ and a Poisson's ratio v of biological tissue of approximately 0.5.

Since the formation of longitudinal shear waves originates from the superposition of transverse shear waves, the relationship between the propagation velocity of longitudinal shear waves and Young's modulus can also be expressed by the above formula, so after measuring the propagation velocity of longitudinal shear waves, The axial Young's modulus can be calculated using the above.

The surface Rayleigh wave usually propagates in the range of about 1 wavelength from the surface. Therefore, the lateral Young's modulus near the surface of the sample can be measured by the Rayleigh wave, and its calculation method is as follows:

Among them, V _Rayleigh represents the propagation speed of Rayleigh wave.

The optical coherent elastography system provided by the embodiment of the present application is described below, and the optical coherent elastography system described below may be referred to in correspondence with the optical coherent elastography method described above.

Correspondingly, an embodiment of the present application provides an optical coherent elastography system, as shown in FIG. 7 , including: an imaging unit 100 and an acoustic radiation force excitation unit 200; wherein,

The acoustic radiation force excitation unit 200 is configured to form multiple ultrasonic beams and transmit them to the sample A10 to be tested, so that the multiple beams of ultrasonic beams induce the sample A10 to be tested to generate the first elastic wave and the second elastic wave. The propagation direction of the first elastic wave is a first direction, the propagation direction of the second elastic wave is a second direction, and the first direction is perpendicular to the second direction;

The imaging unit 100 is configured to transmit a probe beam to the sample A10 to be tested, and receive the probe beam reflected by the sample A10 to be tested, and to use an optical coherence tomography method to, according to the reflected probe beam Imaging the first elastic wave and the second elastic wave, and acquiring elastic information of the sample to be tested in a first direction and elastic information of the sample to be tested in a second direction according to imaging results.

Optionally, still referring to FIG. 7 , the optical coherent elastography system further includes: a coupling unit 300;

The coupling unit 300 includes an acoustic reflection surface and a light incident surface, and the acoustic reflection surface has optical transparency and acoustic reflection characteristics;

The probe beam is incident through the light incident surface, and transmits through the acoustic reflection surface to the sample to be tested. After being reflected and scattered by the sample, the beam passes through the acoustic reflection surface and returns to the imaging optical path; After the beam is reflected by the acoustic reflection surface, it transmits to the sample to be measured along the same direction or a similar direction as the detection beam.

Optionally, referring to FIG. 8 , the imaging unit 100 includes: a light source 110, an optical coupler 150, a reference arm 120, a sample arm 140, and an imaging device 130; wherein,

The light source 110 is used to provide light to be processed;

The optical coupler 150 is used for dividing the light to be processed into a reference beam and the detection beam, and for receiving the reference beam reflected by the reference arm 120 and reflected by the sample A10 to be measured and The scattered detection beam; the reference beam reflected by the reference arm 120 and the detection beam reflected and scattered by the sample A10 to be measured interfere in the optical coupler 150;

The imaging device 130 is configured to perform structural imaging and vibration measurement on the sample A10 to be tested according to the interference signal.

The imaging unit 100 may be an optical coherence tomography unit 100 based on a frequency-sweeping light source 111, or an optical coherence tomography unit 100 based on a continuous-spectrum light source 113, that is, optional, the light source 110 is a frequency-sweeping Light source 111 unit or continuous spectrum light source 113 unit.

9 and 10, FIG. 9 is a schematic structural diagram of an optical coherence tomography unit 100 based on a swept-frequency light source 111, and FIG.

In the structure shown in Figure 9, the light to be processed (usually weakly coherent light) output by the frequency-sweeping laser light source 111 passes through the polarization controller 112 and then enters the optical coupler 150 for splitting, and a part of the light to be processed enters the reference arm as a reference beam 120 , a part of the light to be processed enters the sample arm 140 as a detection beam. The reference beam is reflected by the mirror 122 after passing through the lens 121 of the reference arm 120 . After passing through the lens 141 of the sample arm 140, the detection beam is focused on the sample A10 to be tested. The scattered light returned by the sample arm 140 and the reference arm 120 (i.e. the probe beam reflected and scattered by the sample A10 to be measured) and the reflected light (i.e. the reference beam reflected by the mirror) interfere in the optical coupler 150, resulting in After photodetector detection 131 and signal processing, structural imaging and vibration measurement of the sample A10 to be tested are realized.

In the structure shown in FIG. 10 , the light to be processed output by the continuous spectrum light source 113 passes through the optical isolator 114 and then split by the optical coupler 150. A part of the light enters the sample arm 140 as a detection beam, and the other part enters the reference beam as a reference beam. arm 120. The reference beam is reflected by the mirror 122 after passing through the polarization controller and the lens 121 . The probe beam is focused on the sample A10 to be tested after passing through the polarization controller and the lens 141 . The scattered light returned by the sample arm 140 and the reference arm 120 (i.e. the probe beam reflected and scattered by the sample A10 to be measured) and the reflected light (i.e. the reference beam reflected by the mirror) interfere in the optical coupler 150, and the interference After the signal passes through the converging lens 132, it is split by the grating 133, and the interference light of different wavelengths is separated in space. After passing through another converging lens 134, the photoelectric conversion is carried out on the camera 135. After the signal on the camera 135 is processed, Realize the structural imaging and vibration measurement of the sample A10 to be tested.

For the acoustic radiation force excitation unit 200, refer to FIG. 11, which shows a possible structure of the acoustic radiation force excitation unit 200. The acoustic radiation force excitation unit 200 includes: a waveform generator 210, an amplifier 220 and an ultrasonic converter. Energy unit;

The ultrasonic transducer unit is an ultrasonic transducer 230 or an array of ultrasonic transducers 230 .

The waveform generator 210 generates a high-frequency sine wave, square wave or triangle wave according to the control information of the host computer. After the high-frequency sine wave, square wave or triangle wave is amplified by the amplifier 220, it drives the ultrasonic transducer 230 to work, realizing the measurement of the sample A10 to be tested. Remote Mechanics Incentives. The ultrasonic sound beam output by the ultrasonic transducer 230 enters the sample A10 to be tested through the ultrasonic coupling material (water or ultrasonic glue), forms an acoustic radiation force field on the sample A10 to be tested, and induces tiny vibrations of the tissue. Acoustic radiation force has the advantages of non-invasive, non-contact and remote focusing.

Still referring to FIG. 7 , the coordinate system in FIG. 7 is an XZ coordinate system established with the propagation direction of the detection beam emitted by the imaging unit 100 as the Z axis and the direction perpendicular to the Z axis and parallel to the paper as the X axis. In the structure shown in FIG. 7 , the propagation direction of the probe beam emitted by the imaging unit 100 is parallel to the Z axis, and the propagation direction of the ultrasonic sound beam formed by the acoustic radiation force excitation unit 200 is parallel to the X axis. The incident surface can optionally be perpendicular to the Z-axis, so that the probe beam can directly enter the light incident surface vertically without changing the beam propagation direction, and the normal direction of the acoustic reflection surface can be optionally parallel to the XZ plane and parallel to the ultrasonic acoustic plane. The beam is set at a certain angle, and the angle can be selected as an equal angle of 45°, so that the ultrasonic sound beam can enter the measured sound beam in parallel with the detection beam after being reflected by the sound reflecting surface. Sample A10.

The method of parallel incidence of ultrasonic sound beam and detection beam can directly induce elastic vibration parallel to the direction of detection beam, which improves the sensitivity of the system for vibration detection compared with the excitation method of oblique incidence of ultrasonic sound beam. Moreover, compared with back-incidence or orthogonal-incidence methods, the method in which the ultrasonic sound beam and the probe beam are incident in parallel can be very conveniently applied to clinical detection (such as fundus tissue elastography, etc.).

The feasible structure of the coupling unit 300 in the optical coherent elastography device provided in the embodiment of the present application will be specifically described below.

On the basis of the above embodiments, in one embodiment of the present application, the coupling unit 300 includes: a first dielectric structure 310, an intermediate dielectric structure 330, and a second dielectric structure 320; wherein,

The intermediate dielectric structure 330 is disposed between the first dielectric structure 310 and the second dielectric structure 320, and the first dielectric structure 310 includes a light incident surface;

The second dielectric structure 320 includes an acoustic incident surface, and the contact surface between the intermediate dielectric structure 330 and the second dielectric structure 320 is the acoustic reflection surface.

The difference between the optical refractive index of the first dielectric structure 310, the optical refractive index of the second dielectric structure 320, and the optical refractive index of the intermediate dielectric structure 330 is less than a first preset difference;

The difference between the acoustic impedance of the second dielectric structure 320 and the acoustic impedance of the intermediate dielectric structure 330 is greater than a second preset difference.

In this embodiment, the coupling unit 300 is a "sandwich structure" with an intermediate dielectric structure 330 sandwiched between the first dielectric structure 310 and the second dielectric structure 320, wherein the first dielectric structure 310, the second dielectric structure 320 and the intermediate The optical refractive index difference of the dielectric structure 330 is smaller than the first preset difference, that is, the optical refractive index of the first dielectric structure 310, the second dielectric structure 320 and the intermediate dielectric structure 330 match, so that the entire coupling unit 300 Optically transparent to the detection beam, the detection beam will not be reflected too much, and the loss of the detection beam passing through the coupling unit 300 is reduced;

However, there is a large acoustic impedance mismatch between the intermediate dielectric structure 330 and the second dielectric structure 320, so that the intermediate dielectric structure 330 can cooperate with the second dielectric structure 320 to form the acoustic reflection surface, and realize the detection of the detection beam. While being transparent, it realizes the reflection of the ultrasonic sound beam.

Optionally, referring to FIG. 12, both the first dielectric structure 310 and the second dielectric structure 320 are prisms;

The intermediate dielectric structure 330 is a silicone oil layer or a water layer.

Specifically, in one embodiment of the present application, both the first dielectric structure 310 and the second dielectric structure 320 are prisms, the intermediate dielectric structure 330 is a silicone oil layer, and at this time the coupling unit 300 is a prism-silicon oil - Prism structure. The gap between the two prisms is about 0.1-1 mm, and the gap is filled with non-volatile silicone oil with matching optical refractive index, low acoustic impedance, to form the silicone oil layer. Silicone oil and glass have a good optical refractive index match (the optical refractive index of silicone oil is 1.4, and that of glass is about 1.5), but they have a large acoustic impedance mismatch (the acoustic impedance of silicone oil is 0.74×10 ⁵ g/( cm ² ·s), and the acoustic impedance of glass is 12.1×10 ⁵ g/(cm ² ·s)), therefore, the silicone oil layer is optically transparent but can act as an ultrasound reflector.

In FIG. 12 , since the frequency of the ultrasonic sound beam is generally above 1 MHz and cannot propagate in the air, in order to enable the ultrasonic sound beam to enter the coupling unit 300, there is an additional gap between the coupling unit 300 and the acoustic radiation force excitation unit 200. The transparent ultrasonic coupling agent 240 is filled, and the ultrasonic coupling agent 240 (water or ultrasonic glue) is also filled between the coupling unit 300 and the sample A10 to be tested. The purpose of filling the ultrasonic coupling agent 240 in these gaps is to provide ultrasonic sound beam the transmission medium.

Referring to FIG. 13, optionally, the first medium structure 310 and the second medium structure 320 are both silicone oil layers or water layers or phosphate buffered saline solution layers or physiological saline layers;

The intermediate dielectric structure 330 is a glass layer.

In the structure shown in FIG. 13 , the intermediate dielectric structure 330 is a glass layer, and the first dielectric structure 310 and the second dielectric structure 320 are material layers that match the optical refractive index of the glass layer and have relatively low acoustic impedance. Specifically, in one embodiment of the present application, both the first medium structure 310 and the second medium structure 320 are water placed in a water tank, and the intermediate medium structure 330 is a glass layer inserted into the water tank. The structure of the coupling unit 300 is water-glass-water, and the contact surface between the glass layer and water serves as the sound reflection surface.

On the basis of the above embodiments, another embodiment of the present application provides another feasible structure of the coupling unit 300 .

Referring to FIG. 14 , the coupling unit 300 includes: a third dielectric structure 340 and an impedance mismatch film 350;

The third dielectric structure 340 includes an acoustic incident surface and an adhering surface that forms a preset angle with the transmission direction of the ultrasonic sound beam;

The impedance mismatch film 350 is attached on the attaching surface.

Wherein, the difference between the optical refractive index of the third dielectric structure 340 and the optical refractive index of the impedance mismatch film 350 is smaller than a first preset difference;

The difference between the acoustic impedance of the third dielectric structure 340 and the acoustic impedance of the impedance mismatch film 350 is greater than a second preset difference.

That is, the optical refractive index of the third dielectric structure 340 and the impedance mismatch film 350 are matched, but the acoustic impedance is mismatched, so that the impedance mismatch film 350 can form a coupling unit with the third dielectric structure 340 300 is optically transparent, and makes the impedance mismatch film 350 and the third dielectric structure 340 form an acoustic reflection surface capable of reflecting ultrasound beams.

In this embodiment, when the probe beam is incident from the upper side of the impedance matching film 350 and the ultrasonic sound beam is incident from the left side of the third dielectric structure 340, the impedance mismatching film 350 and the first The contact surface of the three-dielectric structure 340 is the acoustic reflection surface.

As mentioned above, the preset angle refers to the angle that can reflect the ultrasonic sound beam and be parallel or approximately parallel to the detection beam, for example, when the detection beam is parallel to the Z axis and the ultrasonic sound beam is parallel On the X-axis, the preset angle may be about 45°.

To sum up, the embodiment of the present application provides an optical coherent elastography method and device, wherein the optical coherent elastography method utilizes an ultrasonic beam to induce the sample to be tested to generate a first elastic wave and a second elastic wave whose propagation direction is vertical Elastic waves, so that when the first elastic wave and the second elastic wave are imaged by the optical coherence tomography method, the imaging result including the elastic information in the first direction and the second direction can be obtained, so that according to the The imaging result acquires the elastic information of the sample to be tested in the first direction and the elastic information of the sample to be tested in the second direction, so as to realize the purpose of measuring the axial and lateral elastic information of the sample to be tested, and realize The purpose of comprehensively and accurately evaluating the anisotropic elastic characteristics of the tested sample.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. An optical coherence elastography system, comprising: an imaging unit, an acoustic radiation force excitation unit, and a coupling unit; wherein,,

the sound radiation force excitation unit is used for forming a plurality of ultrasonic sound beams to be transmitted to a sample to be detected, so that the ultrasonic sound beams induce the sample to be detected to generate a first elastic wave and a second elastic wave, the propagation direction of the first elastic wave is a first direction, the propagation direction of the second elastic wave is a second direction, and the first direction is perpendicular to the second direction;

the imaging unit is used for transmitting a detection light beam to the sample to be detected, receiving the detection light beam reflected and scattered by the sample to be detected, imaging the first elastic wave and the second elastic wave according to the reflected and scattered detection light beam by using an optical coherence tomography method, and acquiring the elastic information of the sample to be detected in a first direction and the elastic information of the sample to be detected in a second direction according to an imaging result;

the coupling unit comprises an acoustic reflecting surface and a light incident surface, wherein the acoustic reflecting surface has optical transparency and acoustic reflection characteristics;

the detection light beam is incident through the light incidence surface and transmitted to the sample to be detected through the sound reflection surface, and the ultrasonic sound beam is transmitted to the sample to be detected along the same direction or a similar direction with the detection light beam after being reflected by the sound reflection surface.

2. The optical coherence elastography system of claim 1, wherein the coupling unit comprises: a first dielectric structure, an intermediate dielectric structure, and a second dielectric structure; wherein,,

the intermediate medium structure is arranged between the first medium structure and the second medium structure, and the first medium structure comprises the light incidence surface;

the second medium structure comprises an acoustic incidence surface, and the contact surface of the intermediate medium structure and the second medium structure is the acoustic reflection surface.

3. The optical coherence elastography system of claim 2, wherein a difference between an optical refractive index of the first medium structure, an optical refractive index of the second medium structure, and an optical refractive index of the intermediate medium structure is less than a first predetermined difference;

the difference between the acoustic impedance of the second medium structure and the acoustic impedance of the intermediate medium structure is greater than a second preset difference.

4. The optical coherence elastography system of claim 3, wherein the first and second media structures are prisms, and the intermediate media structure is a silicon oil layer or a water layer;

or (b)

The first medium structure and the second medium structure are both a silicon oil layer or a water layer or a phosphate buffer salt solution layer or a physiological saline layer, and the middle medium structure is a glass layer.

5. The optical coherence elastography system of claim 1, wherein the inducing the plurality of ultrasonic acoustic beams to induce the sample to be measured to generate a first elastic wave and a second elastic wave comprises:

and forming a plurality of vibration sources in the sample to be tested by utilizing a plurality of ultrasonic sound beams, wherein the vibration sources induce the surface and/or the inside of the sample to be tested to generate the first elastic wave and the second elastic wave.

6. The optical coherence elastography system of claim 5, wherein when the first elastic wave and the second elastic wave are located on the surface of the sample to be measured, the first elastic wave and the second elastic wave are a surface rayleigh wave and a longitudinal shear wave, respectively.

7. The optical coherence elastography system of claim 5, wherein when the first elastic wave and the second elastic wave are inside the sample to be measured, the first elastic wave and the second elastic wave are longitudinal shear wave and transverse shear wave, respectively.

8. The optical coherence elastography system of claim 5, wherein the imaging the first elastic wave and the second elastic wave according to the reflected and scattered probe beam by using the optical coherence tomography method, and obtaining the elasticity information of the sample to be measured in the first direction and the elasticity information of the sample to be measured in the second direction according to the imaging result comprises:

imaging the first elastic wave and the second elastic wave of the surface of the sample to be detected according to the reflected and scattered detection light beams by using an optical coherence tomography method, and acquiring the elastic information of the surface of the sample to be detected in a first direction and the elastic information of the surface of the sample to be detected in a second direction according to imaging results;

and imaging the first elastic wave and the second elastic wave in the sample to be detected according to the reflected and scattered detection light beams by using an optical coherence tomography method, and acquiring the elastic information of the surface of the sample to be detected in the first direction and the elastic information of the surface of the sample to be detected in the second direction according to imaging results.

Images