CN108577806B - Viscoelastic detection system and method based on low frame rate laser speckle contrast imaging - Google Patents
Viscoelastic detection system and method based on low frame rate laser speckle contrast imaging Download PDFInfo
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
- A61B5/0082—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/02007—Evaluating blood vessel condition, e.g. elasticity, compliance
Abstract
The invention discloses a viscoelastic detection system and method based on low frame rate laser speckle contrast imaging, wherein the detection method comprises the following steps: carrying out orthogonal oscillation excitation on the surface of a measured sample and forming a surface wave; emitting a laser beam irradiating the surface of the measured sample, collecting multi-frame laser speckle images at a lower frame rate and exposure time, performing operation processing to obtain the propagation speed of the aliasing wave, calculating the propagation speed of the surface wave by using the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and obtaining the elasticity and viscosity of the measured sample; the detection system comprises an excitation subsystem and a laser speckle imaging subsystem. The method comprises the steps of detecting the surface wave of a detected sample in orthogonal oscillation excitation, and calculating the propagation speed of the surface wave by using the aliasing wave speed acquired by a low frame rate, so that the viscoelastic modulus of the detected sample is quantitatively solved, and the complexity and the cost of detection are reduced; and the reflective laser speckle imaging is adopted, which is beneficial to the convenience of actual detection.
Description
Technical Field
The invention relates to the technical field of viscoelastic detection, in particular to a viscoelastic detection system and method based on low frame rate laser speckle contrast imaging.
Background
The occurrence and progression of diseases (e.g., atherosclerosis, skin tumors, etc.) can alter the mechanical properties (e.g., elasticity and viscosity) of biological tissues. The measurement of the viscoelasticity of biological tissues can be used for monitoring the pathological process and achieving the purpose of early diagnosis of diseases.
The viscoelasticity measurement of biological tissue reflects the mechanical performance of biological tissue by measuring the strain of biological tissue under the action of stress, wherein the stress is applied to a sample to be measured by an external excitation device, and a strain related parameter can be measured by a laser speckle contrast imaging method. Laser speckle contrast imaging, which detects the movement of a measured object by the change of speckle patterns under disturbance, has been widely used for blood flow detection.
In optical imaging, the imaging field of view is small, generally from a few millimeters to tens of millimeters, but the propagation velocity of surface waves of biological soft tissue is generally 1m/s to 10 m/s. A fast sampling rate is required to track the propagation of the surface wave. The sampling frame rate of laser speckle contrast imaging is related to the speed of a camera, and the sampling frame rate of the camera is generally less than the speed of hundreds of frames per second, so that the tracking surface wave with high spatial resolution cannot be met. At this stage, the sampling frame rate of the system is generally increased by expensive high-speed cameras, or different parts of the signal are acquired time-divisionally by precise synchronization between acquisition and excitation, but either high-speed cameras or synchronization methods increase the complexity and cost of the system.
Disclosure of Invention
The invention aims to overcome the technical defects and provides a viscoelastic detection system and method based on low frame rate laser speckle contrast imaging, which can acquire the viscoelasticity of a sample to be detected through the low frame rate laser speckle contrast imaging.
In order to achieve the technical purpose, the technical scheme of the invention comprises a viscoelastic detection method based on low frame rate laser speckle contrast imaging, which comprises the following steps:
s1, carrying out orthogonal oscillation excitation with a certain frequency on the surface of the measured sample, and forming a surface wave on the surface of the measured sample;
s2, emitting laser beams irradiating the surface of the measured sample, collecting multi-frame laser speckle images of the measured sample in the surface wave propagation process at a low frame rate and exposure time, performing operation processing on the multi-frame laser speckle images to obtain the propagation speed of the aliasing wave, calculating the propagation speed of the surface wave by using the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and obtaining the elasticity and viscosity of the measured sample according to the propagation speed of the surface wave.
Meanwhile, the invention also provides a viscoelastic detection system based on low frame rate laser speckle contrast imaging, which comprises:
the excitation subsystem is used for carrying out orthogonal oscillation excitation of a certain frequency on the surface of the measured sample and forming a surface wave on the surface of the measured sample;
the laser speckle imaging subsystem comprises a laser used for emitting laser beams irradiated on the surface of a measured sample, a camera used for collecting multi-frame laser speckle images of the measured sample in the surface wave propagation process at a lower frame rate and exposure time, and a computer used for carrying out operation processing on the multi-frame laser speckle images, wherein the computer obtains the propagation speed of aliasing waves, calculates the propagation speed of the surface waves by using the relation between the propagation speed of the aliasing waves and the propagation speed of the surface waves, and obtains the elasticity and viscosity of the measured sample according to the propagation speed of the surface waves.
Compared with the prior art, the method has the advantages that the propagation speed of the surface wave is calculated by detecting the surface wave excited by orthogonal oscillation of the measured sample and utilizing the aliasing wave speed acquired by low frame rate acquisition, so that the viscoelastic modulus of the measured sample is quantitatively solved, and the complexity and the cost of detection are favorably reduced; and the reflective laser speckle imaging is adopted, which is beneficial to the convenience of actual detection.
Drawings
FIG. 1 is a schematic diagram of a connection structure of a viscoelastic detection system based on low frame rate laser speckle contrast imaging according to the present invention;
FIG. 2 is a connection block diagram of the computer of the present invention;
FIG. 3 is a flow chart of the viscoelastic detection method based on low frame rate laser speckle contrast imaging of the present invention;
FIG. 4 is a flow chart of the laser speckle image calculation process of the present invention;
FIG. 5 is a flow chart of the calculation of the spatial distribution of the laser speckle contrast image of the present invention;
FIG. 6 is a flow chart of viscoelastic calculations of the present invention;
FIG. 7 is a spatial distribution plot of the laser speckle contrast ratio of 0.8% and 1.2% concentration agarose samples acquired under 400.5Hz continuous orthogonal excitation at low frame rate speckle contrast imaging of 10 frames/sec and the spatiotemporal distribution plot of selected regions thereof;
FIG. 8 is a two-dimensional elasticity map of a heterogeneous phantom calculated by a quantitative detection system for viscoelasticity imaged under continuous orthogonal excitation at 400.2Hz and a low frame rate speckle contrast of 10 frames/sec.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, an embodiment of the present invention provides a viscoelastic detection system 10 based on low frame rate laser speckle contrast imaging, which includes an excitation subsystem 11 and a laser speckle imaging subsystem 12.
The excitation subsystem 11 is configured to perform orthogonal oscillation excitation with a certain frequency on the surface of the measured sample 20, and form a surface wave on the surface of the measured sample 20.
Specifically, the excitation subsystem 11 includes a speaker 111 and a speaker driving device 112, a vibration diaphragm of the speaker 111 contacts the surface of the sample 20, and the speaker driving device 112 is configured to output an orthogonal oscillation signal to drive the speaker 111, when the speaker driving device is specifically configured, the speaker 111 may be placed on the upper surface of the sample 20 through the bracket, and the vibration diaphragm of the speaker 111 lightly contacts the upper surface of the sample 20, and the speaker driving device 112 may generate the orthogonal oscillation signal to drive the speaker 111, which may vibrate the sample 20 to form a surface wave on the surface of the sample 20. The present embodiment is not limited to the above-described method of forming a surface wave on the surface of the sample 20 to be measured.
The laser speckle imaging subsystem 12 comprises a laser 121 for emitting a laser beam to irradiate the surface of the sample to be measured, a camera 122 for acquiring a plurality of frames of laser speckle images of the sample to be measured in the surface wave propagation process at a low frame rate and exposure time, and a computer 123 for performing operation processing on the plurality of frames of laser speckle images, wherein the computer 123 obtains the propagation speed of the aliasing wave, calculates the propagation speed of the surface wave according to the relationship between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and obtains the elasticity and viscosity of the sample to be measured 20 according to the propagation speed of the surface wave. In the embodiment, the propagation velocity of the surface wave is calculated by detecting the surface wave excited by the orthogonal oscillation of the sample 20 to be detected and using the aliasing wave acquired by the low frame rate acquisition, so as to quantitatively solve the viscoelastic modulus of the sample 20 to be detected, which is beneficial to reducing the complexity and cost of the detection.
The laser speckle imaging subsystem 12 of the present embodiment is a reflective imaging subsystem, that is, the laser 121 generates a laser beam irradiated on the surface of the sample 20 to be measured, and the camera 122 collects a laser speckle image in the surface wave propagation process, the camera 122 of the present embodiment may be a CCD (Charge Coupled Device) camera or a CMOS (Complementary Metal Oxide Semiconductor) camera, and the camera 122 of the present embodiment does not need an extremely high collection frame rate, generally, tens of frames/second can meet the requirements, for example, 10 frames/second and 20 frames/second, i.e., an expensive high-speed camera is not needed to increase the collection frame rate to thousands or even tens of thousands. It should be noted that the low frame rate mentioned above is in the order of tens of frames/second, for example, 10 frames/second and 20 frames/second, which is in contrast to the prior art that requires hundreds, thousands or tens of thousands of acquisition frame rates.
In this embodiment, the acquisition frame rate of the laser speckle image is smaller than the frequency of the quadrature oscillation excitation, for example, the frequency of the quadrature oscillation excitation is 400HZ, and the acquisition frame rate is 20 frames/second, which is much lower than the frequency of the quadrature oscillation excitation.
As shown in fig. 2, the computer 123 includes a laser speckle contrast calculation module 123a, a data preprocessing module 123b, and a viscoelasticity calculation module 123c, wherein: the laser speckle contrast calculation module 123a is configured to obtain a frame of laser speckle images collected by the camera, construct a two-dimensional spatial speckle contrast image according to a contrast value corresponding to each pixel of the frame of laser speckle images, obtain a two-dimensional spatial speckle contrast image of each frame of laser speckle images, and construct a three-dimensional spatial speckle contrast image to obtain a spatial-temporal distribution of the laser speckle contrast images; the data preprocessing module 123b is used for performing filtering processing on the space-time distribution of the laser speckle contrast image; the viscoelasticity calculation module 123c is configured to calculate a propagation velocity of the alias wave according to the filtered time-space distribution of the laser speckle contrast image, obtain a propagation velocity of the surface wave from the propagation velocity of the alias wave, change the frequency of the orthogonal oscillation excitation, obtain the frequency dispersion characteristic of the surface wave, and solve the viscosity and elasticity of the measured sample according to the frequency dispersion characteristic fitting of the surface wave.
Specifically, the laser speckle contrast calculation module 123a in this embodiment includes a spatial speckle contrast calculation module, a two-dimensional image construction module, and a three-dimensional image construction module, where the spatial speckle contrast calculation module is configured to obtain a frame of laser speckle image collected by the camera, and select a spatial window with a size of W × W on the frame of laser speckle image, and then W × W pixels in the spatial window form a spatial window with a size of W × W2Calculating the spatial speckle contrast C in the spatial window; the two-dimensional image construction module is used for sliding the space window, traversing the whole frame of laser speckle image, acquiring contrast values C (x, y) corresponding to all pixels, and constructing a two-dimensional space speckle contrast image by taking the contrast value C (x, y) corresponding to each pixel as gray; the three-dimensional image construction module is used for acquiring a two-dimensional space speckle contrast image of a space window of each frame of laser speckle image, and constructing a three-dimensional space speckle contrast image to acquire the space-time distribution C (x, y, t) of the laser speckle contrast image, wherein x and y represent two-dimensional space, and t represents time.
The viscoelasticity calculation module 123c comprises a surface wave velocity calculation module, an elastic distribution calculation module, a frequency dispersion characteristic acquisition module and a viscoelasticity calculation module, wherein the surface wave velocity calculation module is used for selecting a calculation window with a set size in the time-space distribution of the laser speckle contrast image, calculating the propagation velocity of the aliasing wave through the transit time of the aliasing wave propagation in the calculation window, sliding the calculation window, traversing all pixels of the image to obtain the two-dimensional space distribution of the aliasing wave propagation, collecting the relationship between the aliasing wave propagation velocity and the surface wave propagation velocity, and calculating the propagation velocity of the surface wave; the elasticity distribution calculation module is used for calculating the space distribution of the elasticity of the measured sample according to the propagation speed of the surface wave; the frequency dispersion characteristic acquisition module is used for changing the frequency of orthogonal oscillation excitation and acquiring the propagation speed of surface waves under different frequencies, namely the frequency dispersion characteristic of the surface waves; the viscoelasticity calculation module is used for substituting the frequency dispersion characteristic of the surface wave into a frequency dispersion equation, and then the viscosity and the elasticity of the measured sample can be obtained through fitting and solving.
For convenience of explaining a specific detection process of the viscoelastic detection system 10 based on low frame rate laser speckle contrast imaging according to the present embodiment, as shown in fig. 3 to 6, the present embodiment provides a viscoelastic detection method based on low frame rate laser speckle contrast imaging, which includes the following steps:
s1, carrying out orthogonal oscillation excitation with a certain frequency on the surface of the measured sample, and forming a surface wave on the surface of the measured sample;
in this embodiment, a surface wave may be formed on the surface of the sample to be measured by the excitation subsystem, or may be formed on the surface of the sample to be measured by other methods.
S2, emitting laser beams irradiating the surface of the measured sample, collecting multi-frame laser speckle images of the measured sample in the surface wave propagation process at a low frame rate and exposure time, performing operation processing on the multi-frame laser speckle images to obtain the propagation speed of the aliasing wave, calculating the propagation speed of the surface wave by using the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and obtaining the elasticity and viscosity of the measured sample according to the propagation speed of the surface wave.
In this embodiment, a computer performs arithmetic processing on a plurality of frames of laser speckle images, where the arithmetic processing includes:
s21, acquiring a certain frame of laser speckle image collected by a camera, constructing a two-dimensional space speckle contrast image according to a contrast value corresponding to each pixel of the frame of laser speckle image, acquiring the two-dimensional space speckle contrast image of each frame of laser speckle image, and constructing a three-dimensional space speckle contrast image to acquire the space-time distribution of the laser speckle contrast image;
the step S21 is obtained by the laser speckle contrast calculation module 123a of the computer through calculation, and the calculation flow is as follows:
s211, acquiring a certain frame of laser speckle image collected by a camera, selecting a space window with the size of W multiplied by W on the frame of laser speckle image, and forming W multiplied by W pixels in the space window into a space window with the size of W2Calculating the spatial speckle contrast C in the spatial window;
the calculation formula of the spatial speckle contrast C is as follows:
wherein W is the size of the spatial window, IiRepresenting the gray value of the ith pixel in the W x W spatial window,
to this W2An average value of the individual pixel grays;
the embodiment calculates the spatial speckle contrast C of the spatial window of a certain frame of laser speckle image, and assigns a pixel at the central position of the spatial window. It should be noted that the spatial window with the size W × W should be smaller than the frame of laser speckle image.
S212, sliding the space window, traversing the whole frame of laser speckle image, acquiring contrast values C (x, y) corresponding to all pixels, and constructing a two-dimensional space speckle contrast image by taking the contrast value C (x, y) corresponding to each pixel as gray;
the contrast value C (x, y) in this embodiment represents a contrast value corresponding to a horizontal coordinate of x pixels and a vertical coordinate of y pixels in the frame of laser speckle image.
S213, acquiring a two-dimensional space speckle contrast image of a space window of each frame of laser speckle image, and constructing a three-dimensional space speckle contrast image to acquire a space-time distribution C (x, y, t) of the laser speckle contrast image, wherein x and y represent two-dimensional space, and t represents time.
The spatial-temporal distribution C (x, y, t) of the laser speckle contrast image in this embodiment represents a contrast value corresponding to a horizontal coordinate of x pixels and a vertical coordinate of y pixels in the frame of laser speckle image at time t, that is, a contrast value of any pixel in each frame of laser speckle contrast image can be obtained through the spatial-temporal distribution C (x, y, t) of the laser speckle contrast image, and the spatial-temporal distribution C (x, y, t) of the laser speckle contrast image can describe the distribution of the laser speckle contrast values.
S22, filtering the space-time distribution of the laser speckle contrast image;
in the step S22, the data preprocessing module 123b of the computer performs arithmetic processing, specifically, the processing includes performing bandpass filtering, directional filtering, and the like on the temporal-spatial distribution of the laser speckle contrast image; specifically, the speckle contrast imaging can be filtered by spatial averaging, namely, a spatial smoothing filtering method is adopted in a spatial domain, and then, band-pass filtering is carried out on each pixel in the space in a time domain according to the frequency of an aliasing wave and in the vicinity of the frequency of the aliasing wave; which can improve the signal-to-noise ratio by the above-mentioned filtering processing to facilitate calculation of the propagation velocity of the aliasing wave.
S23, calculating the propagation speed of the aliasing wave according to the space-time distribution of the laser speckle contrast image after filtering processing, acquiring the propagation speed of the surface wave according to the propagation speed of the aliasing wave, changing the frequency of orthogonal oscillation excitation, acquiring the frequency dispersion characteristic of the surface wave, and solving the viscosity and elasticity of the measured sample according to the frequency dispersion characteristic fitting of the surface wave.
In the step S23, the calculation process is performed by the viscoelasticity calculation module 123c of the computer, and the specific process flow is as follows:
s231, selecting a calculation window with a set size in the time-space distribution of the laser speckle contrast image, calculating the propagation speed of the aliasing wave in the calculation window through the transit time of the aliasing wave propagation, sliding the calculation window, traversing all pixels of the image to obtain the two-dimensional space distribution of the aliasing wave propagation, collecting the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and calculating the propagation speed of the surface wave;
for example, the size of the calculation window is a × b, all pixels of the calculation window can be fully averaged in the x direction to obtain the distribution of the speckle contrast value in the calculation window in the y-t direction, and the propagation velocity of the aliasing wave is calculated according to the transit time of the aliasing wave propagating in the y direction; and sliding the calculation window, traversing the whole image to obtain the two-dimensional distribution of the aliasing wave propagation speed, thereby realizing the calculation of the propagation speed of the surface wave through the propagation speed of the aliasing wave, wherein the calculation formula of the propagation speed of the surface wave is as follows:
wherein, VrealIs the propagation velocity of the surface wave, VcalFor calculating the propagation velocity, omega, of the resulting aliased wave0Frequency, ω, excited for quadrature oscillationsFor the sampling frame rate of the laser speckle image, round () represents rounding, and N is the rounded integer.
S232, calculating the elastic spatial distribution of the measured sample according to the propagation velocity of the surface wave;
in this embodiment, the spatial distribution of the elasticity of the measured sample is the shear modulus or young's modulus of the measured sample, and for convenience of description, this embodiment is described by calculating the shear modulus of the measured sample; the calculation formula of the shear elastic modulus of the tested sample is as follows:
G'≈ρ(1.05Vreal)2
wherein G' is the shear elastic modulus of the sample to be measured, rho is the density of the sample to be measured, and VrealIs the propagation velocity of the surface wave on the measured sample.
S233, changing the frequency of the orthogonal oscillation excitation, and obtaining the propagation speed of the surface wave under different frequencies, namely the frequency dispersion characteristic of the surface wave;
specifically, by changing the frequency of the orthogonal oscillation excitation, the propagation velocity of the surface wave at different frequencies can be measured, and the frequency dispersion relation of the surface wave can be obtained.
And S234, substituting the frequency dispersion characteristic of the surface wave into a frequency dispersion equation, and fitting to solve the viscosity and elasticity of the measured sample.
Since the mechanical properties of biological tissues under low-frequency oscillation can be generally described by a Voigt model, the Voigt model is formed by connecting a spring and a clay pot in parallel, and the spring and the clay pot are ideal elastic bodies and sticky bodies for model construction. For viscoelastic solids with air on the top surface, the velocity of the shear wave Vs and the velocity of the surface wave VrealThe relation can be approximated as Vs/Vreal1.05, the dispersion equation for viscoelastic solid surface waves can be described by the following equation: .
Wherein, ω is the angular frequency of the surface wave, and the relationship with the frequency f is ω 2 × pi f; ρ is the density of the sample measured, μ1The modulus of elasticity, μ, of the sample to be measured2The viscous modulus of the sample to be measured.
For biological soft tissues like skin, mucosa etc., it is generally assumed that the density is close to that of water and is 1000kg/m3The dispersion equation is formed by the parameter mu1、μ2The description and rho describe the relationship between the propagation speed and the frequency of the surface wave, so that the elastic modulus mu can be obtained by a curve fitting method1And viscous modulus μ2。
To further illustrate the advantages of the viscoelastic detection system and method based on low frame rate laser speckle contrast imaging of the present embodiment, a phantom test is now described.
The experimental object is a biological tissue imitation body, the biological imitation body of the type is prepared from agarose powder, fat milk and deionized water, and the imitation body or the similar imitation body is widely used for detecting the viscoelasticity of the biological tissue. The biological tissue imitation body made of agarose has rich elasticity, and the fat emulsion can change the scattering property of the biological tissue imitation body, so that the reduced scattering coefficient of the biological tissue imitation body conforms to the actual tissue. The method comprises the steps of taking a semiconductor laser with the wavelength of 785nm as a light source, irradiating the semiconductor laser on a biological imitation, collecting reflected light through an imaging light path, carrying out speckle imaging on the surface of the biological imitation by using a CCD camera at a low frame rate, obtaining an original laser speckle image through the viscoelastic detection system based on low frame rate laser speckle contrast imaging, calculating the value of laser speckle contrast, calculating the propagation speed of aliasing waves, and solving the propagation speed of surface waves. Calculating the shear elastic modulus of the measured sample according to the propagation speed of the surface wave; further changing the excitation frequency, calculating the dispersion curve of surface wave propagation, substituting the dispersion curve into a dispersion equation, and fitting to obtain the elastic modulus mu of the measured sample1And viscous modulus μ2。
In the specific embodiment, agarose imitation bodies with 3 concentrations are adopted in the imitation body experiment, and the mass proportion of the agarose powder is 0.6%, 0.8% and 1.2% respectively; a 1.6% fat emulsion solution was added to each sample. According to the nature of the agarose mimetibody, the shear elastic modulus of the sample increases after the agarose mass specific gravity increases.
As shown in FIG. 7(a), the propagation process of the surface wave can be clearly seen by the spatial distribution of the laser speckle contrast at a certain time under the excitation of the 400.5Hz orthogonal continuous wave of the agarose sample with the concentration of 0.8%. In the spatial direction, the amplitude of vibration of the surface wave becomes small due to attenuation, resulting in an increase in the laser speckle contrast ratio.
FIG. 7(b) is the distribution of speckle contrast values in the y-direction over time after the pixel values in the black box area of FIG. 7(a) are averaged together along the x-direction; as shown in fig. 7(b), it can be seen that the aliasing wave oscillates at a frequency of 1Hz, because the laser speckle contrast ratio is modulated by a surface wave excited by 400.5Hz continuous orthogonal excitation, and vibrates at a frequency of 801Hz, and because the sampling frame rate is 10 frames/sec, the frequency of the aliasing wave is 1 Hz; the farther the surface wave propagates with increasing time, and the nearly linear relationship; the slope represents the propagation velocity of the surface wave excited at a frequency of 400.5 Hz.
FIG. 7(c) is a graph of the spatial distribution of laser speckle contrast values for a 1.2% concentration agarose sample under 400.5Hz continuous wave excitation; comparing fig. 7(c) to fig. 7(a), it can be seen that the wavelength of the surface wave on the 0.8% concentration sample is less than that of the 1.2% concentration sample, which indicates that the propagation velocity of the surface wave on the 0.8% concentration sample is lower than that of the 1.2% concentration sample.
FIG. 7(d) is a time variation of the distribution of speckle contrast values in the y-direction after the pixel values of the black box area in FIG. 7(c) are averaged together in the x-direction; comparing fig. 7(d) with fig. 7(b), it can be seen that the slope of the straight line representing the position where the peak or trough is located in fig. 7(b) is smaller than that in fig. 7(d), which indicates that the propagation velocity of the aliasing wave on the 0.8% concentration sample is smaller than that on the 1.2% concentration sample.
Calculating the propagation velocity of aliasing waves of a calculation window by selecting the calculation window with 40 pixels in the x direction and 60 pixels in the y direction in space, sliding the calculation window, and traversing the whole image to obtain the distribution of the propagation velocity of the aliasing waves in two-dimensional distribution in space; the two-dimensional distribution of the propagation velocity of the aliasing wave can be converted into the propagation velocity of the surface wave by the relationship between the propagation velocity of the aliasing wave and the propagation velocity of the surface wave, and can be converted into a two-dimensional elastic diagram by the relationship between the shear modulus and the propagation velocity of the surface wave.
As shown in fig. 8, the system samples at a speed of 10 frames/second under 400.2Hz continuous orthogonal excitation, and the obtained two-dimensional distribution of the shear elastic modulus of the non-uniform sample is obtained, in the figure, the upper half part of the non-uniform sample is 0.8% concentration agarose sample, and the lower half part is 0.6% concentration agarose sample, and it can be seen that the boundary between the two concentration samples in the elasticity diagram is very clear.
To verify the present invention, the phantom also measured its shear elastic modulus using a high frame rate method based on acquisition and excitation synchronization. The shear elastic modulus of 0.6%, 0.8% and 1.2% concentration samples were 1.79. + -. 0.05m/s, 2.83. + -. 0.07m/s and 4.93. + -. 0.31m/s, respectively, as measured by low frame rate speckle contrast imaging methods. The shear elastic modulus measured by the high frame rate method is 1.86 +/-0.19 m/s,2.69 +/-0.17 m/s and 5.05 +/-0.56 m/s respectively, and the propagation speeds of the surface waves measured by the two methods are not obviously different, namely, the viscoelastic detection system and method based on the low frame rate laser speckle contrast imaging can still accurately measure the viscoelasticity on the basis of the speckle contrast imaging with the low frame rate, the low frame rate speckle contrast imaging avoids the synchronization requirements of an expensive high-speed camera and a complex system, the detection system and the detection method are greatly simplified, the detection cost is reduced, and the application is convenient.
The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (9)
1. A viscoelastic detection method based on low frame rate laser speckle contrast imaging is characterized by comprising the following steps:
s1, carrying out orthogonal oscillation excitation with a certain frequency on the surface of the measured sample, and forming a surface wave on the surface of the measured sample;
s2, emitting a laser beam irradiating the surface of the measured sample, acquiring multi-frame laser speckle images of the measured sample in the surface wave propagation process at a lower frame rate and exposure time, performing operation processing on the multi-frame laser speckle images to obtain the propagation speed of an aliasing wave, calculating the propagation speed of the surface wave by using the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and obtaining the elasticity and viscosity of the measured sample according to the propagation speed of the surface wave;
obtaining the propagation velocity of the aliasing wave as:
selecting a calculation window with a set size in the time-space distribution of the laser speckle contrast image, and calculating the propagation speed of the aliasing wave through the transit time of the aliasing wave propagation in the calculation window;
calculating the propagation velocity formula of the surface wave as follows:
wherein, VrealIs the propagation velocity of the surface wave, VcalFor calculating the propagation velocity, omega, of the resulting aliased wave0Frequency, ω, excited for quadrature oscillationsFor the sampling frame rate of the laser speckle image, round () represents rounding, and N is the rounded integer.
2. The method for detecting viscoelasticity of claim 1, wherein the obtaining of the temporal and spatial distribution of the laser speckle contrast image in the arithmetic processing is specifically: s21, acquiring a certain frame of laser speckle image collected by a camera, constructing a two-dimensional space speckle contrast image according to a contrast value corresponding to each pixel of the frame of laser speckle image, acquiring the two-dimensional space speckle contrast image of each frame of laser speckle image, and constructing a three-dimensional space speckle contrast image to acquire the space-time distribution of the laser speckle contrast image;
s22, filtering the space-time distribution of the laser speckle contrast image;
the elasticity and the viscosity of the tested sample are obtained specifically as follows:
s23, calculating the space-time distribution of the laser speckle contrast image according to the propagation velocity of the aliasing wave as the space-time distribution of the laser speckle contrast image after filtering processing; and after the propagation speed of the surface wave is obtained from the propagation speed of the aliasing wave, the frequency of orthogonal oscillation excitation is changed to obtain the frequency dispersion characteristic of the surface wave, and the viscosity and elasticity of the measured sample are worked out according to the frequency dispersion characteristic of the surface wave in a fitting mode.
3. The viscoelasticity detection method according to claim 2, wherein step S21 includes:
s211, acquiring a certain frame of laser speckle image collected by a camera, selecting a space window with the size of W multiplied by W on the frame of laser speckle image, and forming W multiplied by W pixels in the space window into a space window with the size of W2Calculating the spatial speckle contrast C in the spatial window;
s212, sliding the space window, traversing the whole frame of laser speckle image, acquiring contrast values C (x, y) corresponding to all pixels, and constructing a two-dimensional space speckle contrast image by taking the contrast value C (x, y) corresponding to each pixel as gray;
s213, acquiring a two-dimensional space speckle contrast image of a space window of each frame of laser speckle image, and constructing a three-dimensional space speckle contrast image to acquire a space-time distribution C (x, y, t) of the laser speckle contrast image, wherein x and y represent two-dimensional space, and t represents time.
4. The method for detecting viscoelasticity of claim 3, wherein the spatial speckle contrast C in step S211 is calculated by the following formula:
wherein W is the size of the spatial window, IiRepresenting the gray value of the ith pixel in the W x W spatial window,
to this W2Average value of the individual pixel grays.
5. The viscoelasticity detection method according to claim 3, wherein step S23 includes:
s231, selecting a calculation window with a set size in the time-space distribution of the laser speckle contrast image after filtering processing, calculating the propagation speed of the aliasing wave through the transit time of the aliasing wave propagation in the calculation window, sliding the calculation window, traversing all pixels of the image to obtain the two-dimensional space distribution of the aliasing wave propagation, acquiring the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and calculating the propagation speed of the surface wave;
s232, calculating the elastic spatial distribution of the measured sample according to the propagation velocity of the surface wave;
s233, changing the frequency of the orthogonal oscillation excitation, and obtaining the propagation speed of the surface wave under different frequencies, namely the frequency dispersion characteristic of the surface wave;
and S234, substituting the frequency dispersion characteristic of the surface wave into a frequency dispersion equation, and fitting to solve the viscosity and elasticity of the measured sample.
6. The method for detecting viscoelasticity of claim 5, wherein the dispersion equation in step S234 is:
wherein, ω is the angular frequency of the surface wave, and the relationship with the frequency f is ω 2 × pi f; ρ is the density of the sample measured, μ1The modulus of elasticity, μ, of the sample to be measured2The viscous modulus of the sample to be measured.
7. A viscoelastic detection system based on low frame rate laser speckle contrast imaging, comprising:
the excitation subsystem is used for carrying out orthogonal oscillation excitation of a certain frequency on the surface of the measured sample and forming a surface wave on the surface of the measured sample;
the laser speckle imaging subsystem comprises a laser for emitting laser beams irradiated on the surface of a measured sample, a camera for acquiring a plurality of frames of laser speckle images of the measured sample in the surface wave propagation process at a lower frame rate and exposure time, and a computer for performing operation processing on the plurality of frames of laser speckle images, wherein the computer obtains the propagation speed of an aliasing wave, calculates the propagation speed of the surface wave by using the relation between the propagation speed of the aliasing wave and the propagation speed of the surface wave, and obtains the elasticity and viscosity of the measured sample according to the propagation speed of the surface wave;
obtaining the propagation velocity of the aliasing wave as:
selecting a calculation window with a set size in the time-space distribution of the laser speckle contrast image, and calculating the propagation speed of the aliasing wave through the transit time of the aliasing wave propagation in the calculation window;
calculating the propagation velocity formula of the surface wave as follows:
wherein, VrealIs the propagation velocity of the surface wave, VcalFor calculating the propagation velocity, omega, of the resulting aliased wave0Frequency, ω, excited for quadrature oscillationsFor the sampling frame rate of the laser speckle image, round () represents rounding, and N is the rounded integer.
8. The viscoelastic fluidic system of claim 7, wherein the excitation subsystem comprises a speaker having a diaphragm in contact with the surface of the sample under test and a speaker driver for outputting quadrature oscillation signals to drive the speaker.
9. The viscoelastic detecting system according to claim 8, wherein the computer comprises:
the laser speckle contrast calculation module is used for acquiring a certain frame of laser speckle image acquired by the camera, constructing a two-dimensional space speckle contrast image according to a contrast value corresponding to each pixel of the frame of laser speckle image, acquiring the two-dimensional space speckle contrast image of each frame of laser speckle image, and constructing a three-dimensional space speckle contrast image so as to acquire the space-time distribution of the laser speckle contrast image;
the data preprocessing module is used for filtering the space-time distribution of the laser speckle contrast image;
and the viscoelasticity calculation module is used for calculating the propagation speed of the aliasing wave according to the spatial-temporal distribution of the laser speckle contrast image after the filtering processing, acquiring the propagation speed of the surface wave according to the propagation speed of the aliasing wave, changing the frequency of orthogonal oscillation excitation, acquiring the frequency dispersion characteristic of the surface wave, and fitting and solving the viscosity and elasticity of the measured sample according to the frequency dispersion characteristic of the surface wave.
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| CN104622502A (en) * | 2013-11-08 | 2015-05-20 | 日立阿洛卡医疗株式会社 | Apparatus and method for ultrasonic diagnosis |
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