CN116649943A - Blood flow quantitative detection system and detection method based on diffusion speckle - Google Patents
Blood flow quantitative detection system and detection method based on diffusion speckle Download PDFInfo
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Abstract
There is provided a diffuse speckle-based quantitative blood flow detection system comprising: the laser is used for emitting measurement laser; the optical fiber probe is used for integrating the multimode light source optical fiber and the plurality of detection optical fibers, and the light source optical fiber is connected to the laser and used for vertically projecting the measuring laser to the surface of the object to be measured; the plurality of detection optical fibers can form different source-detection distances with the light source optical fibers so as to be used for collecting diffusion speckle signals with different depths, which are obtained after measuring laser is vertically projected to a body to be measured; a camera unit for receiving the diffuse speckle signals collected by the detection optical fiber under different exposure time; the analog signal output module is used for outputting an analog signal to the laser to adjust the intensity of the measured laser, so that the camera unit is prevented from saturation when the exposure time is changed; and the computer is used for controlling the analog signal output module to output an analog signal and controlling the exposure time of the camera unit and processing the received diffuse speckle signal to obtain blood flow quantitative information.
Description
Technical Field
The disclosure relates to the technical field of precise instruments, in particular to a blood flow quantitative detection system and a detection method based on diffusion speckle.
Background
Various types of blood vessels are distributed throughout tissues of a living body and are channels for blood circulation, and the blood flow conveys oxygen inhaled by the living body and various absorbed nutrient substances to various parts of the whole body, so that the blood vessels are closely related to metabolism of the human body, but the technology for detecting blood flow in blood vessels with different depths is still required to be improved since the blood vessels with different types are distributed at different depths of the tissues of the living body.
Disclosure of Invention
Technical scheme (one)
In one aspect of the present disclosure, there is provided a blood flow quantitative detection system based on diffuse speckle, comprising: the laser is used for emitting measurement laser; the optical fiber probe is used for integrating the multimode light source optical fiber and a plurality of detection optical fibers, and the light source optical fiber is connected to the laser and used for vertically projecting the measuring laser to the surface of the body to be measured; the plurality of detection optical fibers can form different source-detection distances with the light source optical fibers so as to be used for collecting diffuse speckle signals with different depths, which are obtained after measuring laser is vertically projected to a body to be measured; the camera unit is coupled to the detection optical fiber in the optical fiber probe and is used for receiving the diffuse speckle signals collected by the detection optical fiber under different exposure time; the analog signal output module is connected with the laser and used for outputting an analog signal to the laser so as to adjust and measure the laser intensity and prevent the camera unit from generating a saturation phenomenon when the exposure time is changed; and the computer is respectively connected with the analog signal output module and the camera unit and is used for controlling the analog signal output module to output an analog signal and controlling the exposure time of the camera unit and processing the received diffusion speckle signals to obtain blood flow quantitative information.
According to the embodiment of the disclosure, the laser is a semiconductor laser, the center wavelength of the emitted measurement laser is 785nm, the coherence length exceeds 30m, and the maximum output power is 50mW. .
According to the embodiment of the disclosure, the optical fiber probe is integrated with 1 light source optical fiber and at least three detection optical fibers, the light source optical fibers and the detection optical fibers in the optical fiber probe are arranged in parallel and are positioned on the same plane, and the at least three detection optical fibers and the light source optical fibers respectively keep different set distances so as to form different source-detection distances.
According to the embodiment of the disclosure, the camera unit comprises a CCD camera with a resolution of 1920 x 1200, a bit depth of 12 bits and a frame rate of 300fps, and the exposure time, the photosensitive area, the bit depth and the frame rate of the CCD camera are all adjustable.
According to the embodiment of the disclosure, a 50×50 pixel area in the horizontal direction of the projection center of the detection fiber is selected as the region of interest, and when the exposure time of the camera unit and the source-detection distance are changed, the average value of the pixels in the region of interest is kept between 75 and 95, and the maximum value is not more than 255, so as to keep the speckle signal intensity.
According to the embodiment of the disclosure, the exposure time setting range of the CCD camera is set to be 0.02-30ms, a plurality of exposure time setting values are included, the corrected space speckle contrast K (T) under each exposure time setting value is calculated and stored,
K(T)＝σ s (T)/<I>；
wherein sigma s (T) is the standard deviation of pixels within the region of interest at an exposure time T,<I>is the average value of the pixels in the region of interest.
According to the embodiment of the disclosure, denoising is performed on the space speckle contrast by a computer, motion artifacts are eliminated, then multi-exposure data curve fitting is performed according to a multi-exposure speckle model and a curve fitting model, and blood flow quantitative information is extracted.
According to an embodiment of the present disclosure, the multi-exposure speckle model is expressed as:
where K is the spatial speckle contrast, T is the camera exposure time, x is the scaling factor, x=t/τ c ，τ c Is the decorrelation time, beta is the speckle averaging effectIs a normalization factor of (a); ρ is the dynamic scattering fraction, ρ=i f /(I s +I f ) Wherein I f For dynamic scattering part, I s Is a static scattering portion; v (V) noise Is irrelevant noise
According to an embodiment of the present disclosure, the curve fitting model is based on a least squares Levenberg-Marquardt implementation.
In another aspect of the present disclosure, there is provided a method for quantitative detection of blood flow based on diffuse speckle, detecting blood flow by the quantitative detection system of blood flow based on diffuse speckle described in any one of the above, the method for quantitative detection of blood flow based on diffuse speckle comprising: operation S10: emitting measuring laser by a laser; operation S20: integrating a multimode light source optical fiber and a plurality of detection optical fibers through an optical fiber probe, wherein the light source optical fiber is used for vertically projecting measurement laser to the surface of a body to be measured; the plurality of detection optical fibers can form different source-detection distances with the light source optical fibers, and are used for collecting diffusion speckle signals with different depths obtained after measuring laser is vertically projected to a body to be measured; operation S30: receiving, by a camera unit, diffuse speckle signals collected by a detection fiber at different exposure times; operation S40: outputting an analog signal to the laser through an analog signal output module to adjust the measured laser intensity, so as to prevent the camera unit from generating a saturation phenomenon when the exposure time is changed; operation S50: the computer controls the analog signal output module to output analog signals and control the exposure time of the camera unit, and processes the received diffuse speckle signals to obtain blood flow quantitative information.
(II) advantageous effects
As can be seen from the above technical solutions, the blood flow quantitative detection system and detection method based on diffuse speckle of the present disclosure has at least one or a part of the following advantages:
(1) By combining laser speckle contrast analysis with a multi-exposure speckle model, the influence of static scatterers and noise can be eliminated, and more accurate blood flow quantitative information can be obtained through curve fitting.
(2) The optical fiber is used for conducting light, so that the mode that the traditional LSCI uses wide-field illumination is changed, laser energy is concentrated at one point, an obtained optical signal is a diffuse speckle signal, and the detection depth is improved;
(3) The optical fiber probe integrates three groups of source-probe pairs with different distances, is slightly attached to the plane of a body to be measured during measurement, enables the optical fiber to be perpendicular to the plane to be measured, and according to the diffusion light propagation theory, photons are emitted by the light source optical fiber and reach the detection optical fiber through the banana type transmission path, monte Carlo simulation provides reference for the penetration depth of the detection optical fiber, and can be used for measuring blood flow information with different depths;
(4) The multimode fiber can obtain a plurality of speckles in each frame of image of the camera, and the system sampling rate is kept consistent with the frame rate of the camera on the premise of ensuring the laser coherence by calculating the space speckle contrast ratio to make up for the defect of low time resolution of a single-mode fiber system.
Drawings
FIG. 1 is a schematic diagram of a diffuse speckle-based quantitative blood flow detection system in accordance with an embodiment of the present disclosure;
FIG. 2 is a schematic cross-sectional view of a fiber optic probe according to an embodiment of the present disclosure;
FIG. 3 is a schematic flow diagram of a curve fitting model of an embodiment of the present disclosure;
FIG. 4 is a flow diagram of Monte Carlo simulation of an embodiment of the present disclosure;
FIG. 5 is a probe depth calculation flow chart of an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of a blood flow simulator model composition according to an embodiment of the disclosure;
FIG. 7 is a graph of results of a blood flow simulator model ICT linear fit in accordance with an embodiment of the present disclosure;
FIG. 8 is a graph comparing ρ values of blood flow simulator models according to embodiments of the present disclosure;
FIG. 9 is a graph of in vivo blood flow ICT change according to an embodiment of the present disclosure;
FIG. 10 is a graph comparing in vivo blood flow ρ values according to an embodiment of the present disclosure;
fig. 11 is a flow chart of a method for quantitative detection of blood flow based on diffuse speckle according to an embodiment of the present disclosure.
[ in the drawings, the main reference numerals of the embodiments of the present disclosure ]
The device comprises a 1-laser, a 2-fiber probe, a 3-light source fiber, a 4-detection fiber, a 5-camera unit, a 6-analog signal output module, a 7-computer and an 8-object to be detected.
Detailed Description
The present disclosure provides a blood flow quantitative detection system and a detection method based on diffuse speckle, which can rapidly measure blood flows of different depths and obtain accurate blood flow quantitative information.
Laser speckle contrast imaging (Laser Speckle Contrast Imaging, LSCI) is a non-invasive optical imaging technique that uses the speckle phenomenon created by the high coherence of laser light to reflect the hemodynamic information of biological tissue. LSCI detects spatial standard deviation sigma of pixels in a selected window of a camera by computing s (T) average Strength<I>I.e. the speckle contrast K, to represent the blood flow. In practicing the present disclosure, the inventors have appreciated that when the exposure time T is much greater than the decorrelation time τ of the electric field autocorrelation function c In this case, the square l/K of the inverse speckle contrast can be obtained from a single long-exposure image 2 To represent blood flow. However, when static scatterers are present, this approach can deviate, i/K 2 The quantitative measurement cannot be accurately performed because the quantitative measurement does not have a linear relation with the blood flow. In addition, the conventional LSCI uses wide field illumination, mainly focusing on photons that are scattered once in human tissue, limiting the penetration depth of photons in the medium, and focusing the detection depth to within 1mm, so that it is difficult to obtain blood flow information of deep tissues. The diffusion correlation spectrum (Diffuse Correlation Spectroscopy, DCS) focuses on photons scattered multiple times in human tissue to detect blood flow information reaching 15mm in depth, but it is necessary to use a single-mode fiber and a high-sensitivity single photon counting avalanche photodiode to detect photons, only one speckle signal is obtained in each frame of image of a detection camera, and then the blood flow information is obtained by calculating the intensity autocorrelation function of multiple frames of images, so that the device and calculation are complex, and the time resolution is low.
For the following purposes: (1) Single long exposure laser speckle contrast cannot obtain accurate blood flow quantitative information in the presence of static scatterers; (2) insufficient detection depth of the traditional laser speckle technology; (3) The disclosure provides a blood flow quantitative detection system and a detection method based on diffusion speckle.
For the purposes of promoting an understanding of the principles and advantages of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same.
In an embodiment of the present disclosure, there is provided a diffusion speckle-based blood flow quantitative detection system, as shown in fig. 1 and 2, including:
a laser 1 for emitting measurement laser light;
the optical fiber probe 2 is used for integrating a multimode light source optical fiber 3 and a plurality of detection optical fibers 4, wherein the light source optical fiber 3 is connected to the laser 1 and is used for perpendicularly projecting measurement laser light to the surface of a to-be-measured body; the plurality of detection optical fibers 4 can form different source-detection distances with the light source optical fibers 3 so as to be used for collecting diffusion speckle signals with different depths, which are obtained after measuring laser is vertically projected to a body to be measured;
a camera unit 5 coupled to the detection fiber 4 in the optical fiber probe 2 for receiving the diffuse speckle signals collected by the detection fiber 4 at different exposure times;
an analog signal output module 6 connected to the laser 1 for outputting an analog signal to the laser 1 to adjust the measured laser intensity, preventing the camera unit 5 from saturation when the exposure time is changed; and
and the computer 7 is respectively connected with the analog signal output module 6 and the camera unit 5 and is used for controlling the analog signal output module 6 to output an analog signal and controlling the exposure time of the camera unit 5 and processing the received diffuse speckle signals to obtain blood flow quantitative information.
According to the embodiment of the disclosure, the laser 1 is a semiconductor laser, and the central wavelength of the emitted measurement laser is 785nm; the coherence length exceeds 30m and the maximum output power is 50mW.
According to the embodiment of the disclosure, as shown in fig. 1 and 2, the optical fiber probe 2 integrates 1 light source optical fiber 3 and at least three detection optical fibers 4, the light source optical fiber 3 and the detection optical fiber 4 in the optical fiber probe 2 are arranged in parallel and are in the same plane, and the at least three detection optical fibers 4 and the light source optical fiber 3 respectively keep different set distances to form different source-detection distances. For example, the source-probe distances of the three detection fibers and the light source fiber are 5mm, 8mm and 12mm respectively, and the received optical signals are diffuse speckle signals.
According to the embodiment of the disclosure, the camera unit 5 includes a CCD camera with a resolution of 1920×1200, a bit depth of 12 bits, and a frame rate of 300fps, and the exposure time, the photosensitive area, the bit depth, and the frame rate of the CCD camera are all adjustable.
According to the embodiment of the disclosure, a 50×50 pixel area in the horizontal direction of the projection center of the detection fiber is selected as the region of interest, and when the exposure time of the camera unit 5 and the source-detection distance are changed, the average value of the pixels in the region of interest is kept between 75 and 95, and the maximum value is not more than 255, so as to maintain the speckle signal intensity.
According to the embodiment of the disclosure, the exposure time setting range of the CCD camera is set to be 0.02-30ms, a plurality of exposure time setting values are included, the corrected space speckle contrast K (T) under each exposure time setting value is calculated and stored,
K(T)＝σ s (T)/<I>；
wherein sigma s (T) is the standard deviation of pixels within the region of interest at an exposure time T,<I>is the average value of the pixels in the region of interest.
According to the embodiment of the disclosure, the computer 7 is used for denoising the space speckle contrast and eliminating motion artifacts, and then the multi-exposure data curve fitting is performed according to the multi-exposure speckle model and the curve fitting model, so that the blood flow quantitative information is extracted.
According to an embodiment of the present disclosure, the multi-exposure speckle model is expressed as:
wherein K is nullInter-speckle contrast, T is camera exposure time, x is scaling factor, x=t/τ c ，τ c Is the decorrelation time, β is the normalization factor of the speckle averaging effect; ρ is the dynamic scattering fraction, ρ=i f /( I s+I f ) Wherein I f For dynamic scattering part, I s Is a static scattering portion; v (V) noise Is irrelevant noise
According to an embodiment of the present disclosure, the curve fitting model is based on a least squares Levenberg-Marquardt implementation.
More specifically, the present disclosure provides a diffuse speckle-based quantitative blood flow detection system comprising: the laser is used for emitting measurement laser; the optical fiber probe is used for integrating a multimode light source optical fiber and a detection optical fiber, wherein the light source optical fiber vertically projects measurement laser to the surface of the to-be-measured body, and the detection optical fiber collects diffusion speckle signals with different depths; the camera unit is used for coupling the detection optical fiber and connecting with the computer, receiving speckle signals collected by the detection optical fiber under different exposure time and processing the speckle signals by the computer; the analog signal output module is used for connecting the laser with the computer, outputting an analog signal to adjust the laser intensity, and preventing the camera unit from saturation when the exposure time is changed; and a computer for connecting the analog signal output module with the camera unit, controlling the laser intensity and the camera exposure time, processing the received speckle signals, calculating the space speckle contrast K under a plurality of exposure times, and obtaining the blood flow inverse decorrelation time (Inverse Correlation Time, ICT) and the dynamic scattering fraction ρ according to the multi-exposure speckle contrast model.
According to the embodiment of the disclosure, the analog signal output module comprises a data acquisition card and a differential amplifier, and the output voltage ranges from-15V to +15V.
According to the embodiment of the disclosure, the photosensitive area of the camera unit is adjusted to 600×400 pixels, the bit depth is adjusted to 8 bits, and the camera frame rate is stabilized at 300fps, i.e. the system sampling rate is 300Hz. Selecting a detection optical fiber projection center horizontal direction 50 x 50 pixel area as an interested area ROI (region of interest), changing the exposure time range of a camera to be 0.02-30ms, specifically 0.02ms, 0.05ms, 0.1ms, 0.2ms, 0.3ms, 0.5ms, 1ms, 2ms, 4ms, 6ms, 8ms, 12ms, 20ms and 30ms, and calculating and storing the space speckle contrast K (T) under each exposure time:
K(T)＝σ s (T)/<I> (1)；
wherein sigma s (T) is the standard deviation of pixels within the ROI at exposure time T,<I>is the average of the pixels within the ROI.
According to an embodiment of the present disclosure, the saved speckle contrast K is input into MATLAB curve fitting procedure, according to the multi-exposure speckle model, namely:
and performing multi-exposure data curve fitting through the multi-exposure speckle model, and extracting blood flow quantitative information. Where K is the spatial speckle contrast, T is the camera exposure time, x is the scaling factor, x=t/τ c ，τ c Is the decorrelation time, β is the normalization factor of the speckle averaging effect; ρ is the dynamic scattering fraction, ρ=i f /(I s +I f ) Wherein I f For dynamic scattering part, I s Is a static scattering portion; v (V) noise Is irrelevant noise
According to an embodiment of the present disclosure, the curve fitting process includes: firstly, when only a static scatterer exists, acquiring multi-exposure speckle contrast K, and calculating a beta value of a system through a formula (2), wherein the beta= 0.2478 of the detection system is provided by the disclosure; then setting the upper and lower limits of the fitting parameters, wherein x is [0, inf]ρ is [0,1 ]]，V noise Is [0,1]The method comprises the steps of carrying out a first treatment on the surface of the And finally, inputting K and T into a fitting program to obtain fitting parameter values ICT and ρ.
According to the embodiment of the disclosure, the curve fitting model is realized by a least square-based Levenberg-Marquardt algorithm, and a flow chart thereof is shown in FIG. 3, and the steps comprise:
s1: defining the multi-exposure speckle model as a function f, then k=f (T i ，a j ) The independent variable is the exposure time T and the dependent variable is the speckle contrast K. Input function f, exposure time T, speckle contrastThe degree K, the damping factor lambda, the initial value a of the fitting parameter and the residual least squares sum MIN;
s2: calculating residual errorsWhere k=f (T i ，a j ) I is the exposure time T and the index number of the corresponding speckle contrast K, j is the index number of the fitting parameter a;
s3: determining step size from lambdaWhere J is a Jacobian matrix containing all first order partial derivatives of the function f, J T The matrix is a transpose of a jacobian matrix, and I is an identity matrix;
s4: according to h LM Updating parametersWherein->And->Parameters before and after updating, respectively.
S5: according to new parametersCalculating a new residual->
S6: comparing residual S 1 And the size of the least squares sum MIN;
s7: if S 1 < MIN, output fitting parameter a and residual S 1 ；
S8: if S 1 > MIN, compare S 1 And S, adjusting the damping factor lambda, and continuing iteration from the step S2 until the fitting parameter a meeting the condition is output.
Furthermore, the above definitions of the elements and methods are not limited to the specific structures, shapes or modes mentioned in the embodiments, and may be modified or replaced simply by one skilled in the art, for example:
(1) The laser may select other wavelengths that meet penetration depth and coherence.
(2) The source-probe distance can be other fixed sizes according to the requirements of the probe depth, and a device capable of adjusting the source-probe distance can also be used;
(3) The camera unit can use CCD camera or CMOS camera with other resolution and bit depth;
(4) Laser power control may be used in any suitable manner depending on the type of laser.
In another aspect of the present disclosure, there is further provided a method for quantitative detection of blood flow based on diffuse speckle, wherein the method for quantitative detection of blood flow based on diffuse speckle includes:
operation S10: emitting measuring laser by a laser;
operation S20: the multimode light source optical fiber 3 and the plurality of detection optical fibers 4 are integrated through the optical fiber probe, wherein the light source optical fiber 3 is used for vertically projecting measurement laser to the surface of a body to be measured; the plurality of detection optical fibers 4 can form different source-detection distances with the light source optical fibers 3, and are used for collecting diffuse speckle signals with different depths obtained after measuring laser is vertically projected to a body to be measured;
operation S30: receiving, by the camera unit 5, diffuse speckle signals collected by the detection fiber 4 at different exposure times;
operation S40: outputting an analog signal to the laser 1 through an analog signal output module 6 to adjust the intensity of the measured laser, preventing the camera unit 5 from saturation when the exposure time is changed; and
operation S50: the analog signal output module 6 is controlled by the computer 7 to output an analog signal and control the exposure time of the camera unit 5, and the received diffuse speckle signal is processed to obtain blood flow quantitative information.
More specifically, in the implementation process, references are provided for the detection depths of different source-probe pairs according to Monte Carlo simulation; according to the detection depth, a blood flow imitation model is manufactured, blood flows with different depths are measured, ICT and rho are obtained, and the measurement accuracy of a detection system is verified; and moderately heating local tissues, measuring ICT and rho values before and after moderately heating by using different source-probe pairs, and evaluating the change of blood flow and recovery condition.
According to an embodiment of the present disclosure, a Monte Carlo simulation is performed according to a flowchart as shown in FIG. 4. The input parameters include: typical optical properties of human tissue at 785nm wavelength, the absorption coefficient μ is set a ＝0.025cm -1 About the scattering coefficient mu s ’＝8.5cm -1 An anisotropy factor of 0.9; the number of photons used for simulation was 108; the position of the photons after each scattering is recorded during the simulation. The flow chart for calculating the detection depth of the source-probe pair according to the position of each photon scattering is shown in fig. 5, and the steps are as follows:
recording the depth h of photons after each scattering event;
calculating the average value of the depth h after each scattering as the penetration depth h1 of the photon;
calculating the average value of all photon penetration depths h1 as the average detection depth hmean of the source-probe pair;
recording the maximum depth hm of all scattering events of photons;
the average of all photon maximum depths hm is calculated as the maximum detection depth hmax for the source-probe pair.
Wherein, the average detection depth corresponding to the source-detection pairs of 5mm, 8mm and 12mm is about 1.8mm, 3.1mm and 4.6mm, and the maximum detection depth is about 3.5mm, 5.2mm and 6.7mm.
According to an embodiment of the present disclosure, a blood flow simulator model is fabricated based on the average detection depth. Simulating a static scatterer in human tissue using a polytetrafluoroethylene block; two round tubes made of the same polytetrafluoroethylene material are buried at positions with different distances from the surface of the polytetrafluoroethylene block and are parallel to the surface of the round tubes to simulate blood vessels with different depths of a human body; injecting fat emulsion solution into the circular tube at different flow rates by using a syringe pump for simulating blood flow of a human body; the on-off of the superficial and deep blood flows are controlled respectively, three groups of source-probe pairs are used for measuring respectively, ICT and rho values are obtained and compared, and the accuracy of the detection system is verified.
According to embodiments of the present disclosure, the above-described detection system is used for in vivo blood flow detection before and after moderate warming. Firstly, three groups of source-probe pairs are used for measuring blood flow information under the normal state of the same part; and then moderately heating the part to be measured to cause blood flow change, and measuring ICT and rho values after moderately heating by using three groups of source-probe pairs to evaluate blood flow change and recovery condition.
In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure.
According to an embodiment of the present disclosure, as shown in fig. 1, a diffuse speckle-based blood flow quantitative detection system includes: a laser 1 for emitting measurement laser light; the optical fiber probe 2 is used for integrating the multimode light source optical fiber 3 and the detection optical fiber 4; the light source optical fiber 3 vertically projects measuring laser to the surface of a body to be measured, and the detection optical fiber 4 collects diffuse speckle signals with different depths; the camera unit 5 is used for coupling the detection optical fiber 4 and connecting with the computer 7, receiving the speckle signals collected by the detection optical fiber 4 under different exposure time and processing the speckle signals by the computer 7; the analog signal output module 6 is used for connecting the laser 1 and the computer 7, outputting an analog signal to adjust the laser intensity, and preventing the camera unit 5 from generating a saturation phenomenon when the exposure time is changed; and a computer 7 for connecting the analog signal output module 6 with the camera unit 5, controlling the laser intensity and the camera exposure time, processing the received speckle signals, and obtaining blood flow quantitative information according to the multi-exposure speckle contrast model of formula (2).
According to the embodiment of the disclosure, the laser 1 is a semiconductor laser, and an output end is connected to one end of a light source optical fiber through an SFC connector. The emitted laser has a central wavelength of 785nm, has a large penetration depth in human tissues, and can provide deep tissue blood flow information. The coherence length exceeds 30m, and high coherence can be maintained when using multimode optical fibers. The maximum output power is 50mW, and the temperature regulation controller is equipped, so that the time required for stabilization in the process of intensity regulation is less than 2s, and the time resolution of multi-exposure quantitative measurement is effectively improved. The input control end of the laser 1 is connected with an analog signal output module 6 for adjusting the laser intensity.
According to the embodiment of the present disclosure, the fiber optic probe 2 integrates one light source fiber 3 and three detection fibers 4. One end of the light source optical fiber 3 is connected with the laser through an SFC optical fiber connector and used for transmitting light, and the other end is integrated on the optical fiber probe 2, is parallel to the detection optical fiber 4 and is positioned on the same plane, and meanwhile, the fixed source-detection distances are respectively 5mm, 8mm and 12mm. As shown in fig. 2, a schematic cross-sectional view of a fiber optic probe is provided. Three detection optical fibers 4 are integrated on the optical fiber probe 2 at one end, and are coupled to the camera unit 5 at the other end, and slightly contact with the photosensitive area of the camera unit, so as to vertically project the collected scattered speckle signals to the photosensitive area. During measurement, the optical fiber probe 2 is attached to the measurement plane of the to-be-measured body 8, and is kept relatively static especially in body measurement, so that the influence of motion artifact on measurement accuracy is reduced. Optionally, a mask is used in the measurement to cover the fiber optic probe 2 and the body under test 8 to reduce noise.
According to the embodiment of the disclosure, the camera unit 5 is a CCD camera with a resolution of 1920×1200, a bit depth of 12 bits, a frame rate of 300fps, and an exposure time of adjustable. The camera unit 5 is connected to the computer 7 via USB3.0, ensuring the image transmission rate.
According to an embodiment of the present disclosure, the analog signal output module 6 includes a data acquisition card and a differential amplifier. The output voltage range of the data acquisition card is 0-3.3V, the data acquisition card is connected with a computer 7, and is controlled by a LabVIEW upper computer program DAQ module, two paths of analog signals are output to the input end of the differential amplifier, one path of signals are kept unchanged, and the other path of signals are changed to enable the output signals of the module to be changed so as to adjust the intensity of the laser; the differential amplifier has amplification factor of 10, and the output end is directly connected with the control port of the laser 1 to control the laser intensity. The analog signal output module 6 outputs a voltage range of-15V to +15v, controls the power of the laser to be between 0 and 50mW, and keeps the average value of pixels in the ROI to be 75-95 and the maximum value to be not more than 255, namely the maximum value of 8bit depth of the camera, when the exposure time and the source-detection distance of the camera unit 5 are changed, so as to keep the speckle signal intensity and avoid the phenomenon of overlow or saturation.
According to the embodiment of the disclosure, the photosensitive area of the camera unit 5 is adjusted to 600×400 pixels, the bit depth is adjusted to 8 bits, so that the camera frame rate is stabilized at 300fps, i.e. the system sampling rate is 300Hz. The size, bit depth and frame rate of the photosensitive area of the camera can be adjusted according to the specific imaging range and sampling rate requirements; then selecting a 50 x 50 pixel region in the horizontal direction of the projection center of the detection optical fiber as an ROI (region of interest), and because the detection optical fiber is a single-point quantitative measurement, calculating by using a space speckle contrast without considering a space resolution problem, selecting the 50 x 50 pixel region as the ROI, and increasing the ROI region by a common technician to improve the signal to noise ratio; finally, the camera exposure time range is changed to be 0.02-30ms, specifically 0.02ms, 0.05ms, 0.1ms, 0.2ms, 0.3ms, 0.5ms, 1ms, 2ms, 4ms, 6ms, 8ms, 12ms, 20ms and 30ms, and the corrected spatial speckle contrast K (T) at each exposure time is calculated and stored:
K(T)＝σ s (T)/<I> (1)；
wherein sigma s (T) is the standard deviation of pixels within the ROI at exposure time T,<I>is the average of the pixels within the ROI. The selection of the exposure time ranges and amounts can be adjusted accordingly: the exposure time range is increased, and the linear range of flow measurement is increased; the number of exposures increases, the measurement accuracy improves, but the time resolution decreases.
According to an embodiment of the present disclosure, the computer 7 inputs the acquired multi-exposure speckle contrast data into a MATLAB curve fitting procedure. Firstly, denoising the K: firstly, N frames of space speckle contrast K are acquired for each exposure time, N=300, the acquisition time is 1 second, the acquisition time required for a large exposure time is increased, and N can be adjusted according to the time resolution requirement. These K values fluctuate up and down around the baseline value due to artifacts caused by movements such as human respiration. The method comprises the steps of sorting 300 frames K from large to small, removing data of the over-high frames of the front 100 frames and the over-low frames of the rear 100 frames, eliminating the influence of motion artifact, and calculating the average value of the rest 100 frames K to be used as a calculation frame of each exposure time; then according to the multi-exposure speckle model, namely:
multiple exposure data curve fitting was performed using the curve fitting model shown in fig. 3, and blood flow quantitative information was extracted.
According to an embodiment of the present disclosure, a method for quantitatively detecting blood flow based on diffuse speckle is based on the detection system described above, and includes:
determining detection depths of different source-probe pairs according to Monte Carlo simulation; according to the detection depth, a blood flow imitation model is manufactured, blood flows with different depths are measured, ICT and rho are obtained, and the measurement accuracy of a detection system is verified; and moderately heating local tissues, measuring ICT and rho values before and after moderately heating by using different source-probe pairs, and evaluating the change of blood flow and recovery condition.
According to the embodiment of the disclosure, the flow quantitative measurement is performed on the blood flow simulation model shown in fig. 6 by using the average detection depth provided by the monte carlo simulation, and the accuracy of the detection system is verified. The imitation model comprises: the polytetrafluoroethylene block is used for simulating a static scattering body in human tissues, and two round holes with diameters of 2mm are parallel to the surface of the static scattering body and used for penetrating into a round tube; two round tubes made of polytetrafluoroethylene are 2mm in outer diameter and 1mm in inner diameter, the lower surface of one round tube is 2mm away from the surface of the imitation body and used for simulating shallow blood vessels, and the lower surface of the other round tube is 5mm away from the surface of the imitation body and used for simulating deep blood vessels; preparing a fat emulsion solution with the concentration of 1% by using a fat emulsion solution with the concentration of 20% and distilled water, wherein the fat emulsion solution is used for simulating human blood; and a syringe pump for injecting the fat emulsion solution into the circular tube, wherein the injection flow is in the range of 47.1-471 mu L/min, and the maximum flow velocity in the circular tube is 10mm/s. The flow is measured by using a source-probe pair of 5mm and 12mm, the on-off of the shallow and deep blood flows are respectively controlled, quantitative measurement values ICT and rho are obtained, and then linear fitting is carried out on the measurement values. Fig. 7 and 8 are graphs showing the results of ICT linear fitting of the blood flow simulator model and a graph showing the comparison of ρ values of the blood flow simulator model. The different source-probe pair measurement values are in good linear relation, so that the influence of a static scattering body is eliminated, and accurate measurement can be performed in a larger flow range; the source-detection distance of 12mm is increased, double-layer blood flow can be covered, and ICT and rho are increased; ICT and ρ were reduced for the 12mm measurement when only deep blood flow was present; whereas the 5mm source-probe pair only detects superficial blood vessels, the ICT and ρ of the superficial and double-layer blood flows do not change much.
According to the embodiment of the disclosure, an infrared physiotherapy lamp is used for moderately heating a to-be-detected area during body measurement, so that blood flow change is caused. The region to be measured of the skin of the human body is the inner side of the forearm, and optionally, the positions of the wrist, the fingertip and the like are used. The distance between the infrared physiotherapy lamp and the small arm is kept at a constant distance of 30cm, the uniform moderate heating time is 10min, and the recovery time is 34min, so that the measurement consistency is kept, and the infrared physiotherapy lamp can be adjusted according to actual conditions. And after three groups of data are measured by each group of source-detection distance, an average value is obtained, and random errors generated in the measurement process are reduced. The exposure time ranges and amounts selected according to the present disclosure, the measurements were taken every 2 minutes. As shown in fig. 9, which shows the change of ICT before and after moderate heating of the physiotherapy lamp, the ρ value is divided into a baseline value before moderate heating, 0-16min after moderate heating, 18-34min after moderate heating, and average value is obtained for each interval ρ after recovery in fig. 10. As the source-probe distance increases, the probe depth increases, the covered blood vessels increase, and the blood flow increases, so that the ICT and ρ measured increase. After the physical therapy lamp is moderately heated, the vasodilating blood flow is increased, and ICT and rho are obviously higher than those before moderate heating and after recovery; over time, the tissue gradually returns to normal, the measured ICT gradually decreases from the peak to normal, and ρ is also comparable to the baseline value before moderate warming.
Based on the results, the three groups of source-probe pairs have obvious differences in measurement results and change conditions, and the detection system and the detection method provided by the disclosure can accurately and quantitatively measure single-point blood flow of blood flows with different depths.
Thus, embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that, in the drawings or the text of the specification, implementations not shown or described are all forms known to those of ordinary skill in the art, and not described in detail. Furthermore, the above definitions of the elements and methods are not limited to the specific structures, shapes or modes mentioned in the embodiments, and may be simply modified or replaced by those of ordinary skill in the art.
From the foregoing description, those skilled in the art will clearly recognize the present disclosure of a diffuse speckle-based quantitative blood flow detection system and method.
In summary, the present disclosure provides a blood flow quantitative detection system and a detection method based on diffusion speckle, which combine a multi-exposure speckle contrast model, and can eliminate the influence of static scatterers and noise, and obtain accurate blood flow information, including inverse decorrelation time and dynamic scattering fraction ρ. Based on the detection system, the invention also provides a blood flow quantitative detection method based on the diffusion speckle, which comprises the following steps: providing references for the detection depths of different source-probe pairs according to Monte Carlo simulation; according to the detection depth, a blood flow imitation model is manufactured, ICT and rho of blood flows with different depths are measured, and the measurement accuracy of a detection system is verified; and moderately heating local tissues, measuring ICT and rho values before and after moderately heating by using different source-probe pairs, and evaluating the change of blood flow and recovery condition.
It should also be noted that the foregoing describes various embodiments of the present disclosure. These examples are provided to illustrate the technical content of the present disclosure, and are not intended to limit the scope of the claims of the present disclosure. A feature of one embodiment may be applied to other embodiments by suitable modifications, substitutions, combinations, and separations.
It should be noted that in this document, having "an" element is not limited to having a single element, but may have one or more elements unless specifically indicated.
In addition, unless specifically stated otherwise, herein, "first," "second," etc. are used for distinguishing between multiple elements having the same name and not for indicating a level, a hierarchy, an order of execution, or a sequence of processing. A "first" element may occur together with a "second" element in the same component, or may occur in different components. The presence of an element with a larger ordinal number does not necessarily indicate the presence of another element with a smaller ordinal number.
In this context, the so-called feature A "or" (or) or "and/or" (and/or) feature B, unless specifically indicated, refers to the presence of B alone, or both A and B; the feature A "and" (and) or "AND" (and) or "and" (and) feature B, means that the nail and the B coexist; the terms "comprising," "including," "having," "containing," and "containing" are intended to be inclusive and not limited to.
Further, in this document, terms such as "upper," "lower," "left," "right," "front," "back," or "between" are used merely to describe relative positions between elements and are expressly intended to encompass situations of translation, rotation, or mirroring. In addition, in this document, unless specifically indicated otherwise, "an element is on another element" or similar recitation does not necessarily mean that the element contacts the other element.
Furthermore, unless specifically described or steps must occur in sequence, the order of the above steps is not limited to the list above and may be changed or rearranged according to the desired design. In addition, the above embodiments may be mixed with each other or other embodiments based on design and reliability, i.e. the technical features of the different embodiments may be freely combined to form more embodiments.
While the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be understood that the foregoing embodiments are merely illustrative of the invention and are not intended to limit the invention, and that any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the present disclosure are intended to be included within the scope of the present disclosure.
Claims (10)
1. A diffuse speckle-based quantitative blood flow detection system, comprising:
a laser (1) for emitting a measuring laser;
the optical fiber probe (2) is used for integrating a multimode light source optical fiber (3) and a plurality of detection optical fibers (4), wherein the light source optical fiber (3) is connected to the laser (1) and is used for perpendicularly projecting measurement laser to the surface of a body to be measured; the plurality of detection optical fibers (4) can form different source-detection distances with the light source optical fibers (3) so as to be used for collecting diffuse speckle signals with different depths, which are obtained after measuring laser is vertically projected to a body to be measured;
a camera unit (5) coupled to the detection fiber (4) in the fiber optic probe (2) for receiving the diffuse speckle signals collected by the detection fiber (4) at different exposure times;
the analog signal output module (6) is connected with the laser (1) and is used for outputting an analog signal to the laser (1) to adjust the measured laser intensity and prevent the camera unit (5) from generating a saturation phenomenon when the exposure time is changed; and
and the computer (7) is respectively connected with the analog signal output module (6) and the camera unit (5) and is used for controlling the analog signal output module (6) to output an analog signal and controlling the exposure time of the camera unit (5) and processing the received diffuse speckle signals to obtain blood flow quantitative information.
2. The quantitative detection system for blood flow based on diffuse speckle according to claim 1, wherein the laser (1) is a semiconductor laser, the central wavelength of the emitted measuring laser light is 785nm, the coherence length is more than 30m, and the maximum output power is 50mW.
3. The quantitative detection system for blood flow based on diffuse speckle according to claim 1, wherein the optical fiber probe (2) integrates 1 light source optical fiber (3) and at least three detection optical fibers (4), the light source optical fiber (3) and the detection optical fiber (4) in the optical fiber probe (2) are arranged in parallel and are in the same plane, and the at least three detection optical fibers (4) and the light source optical fiber (3) respectively keep different set distances to form different source-detection distances.
4. The diffuse speckle-based quantitative blood flow detection system of claim 1, the camera unit (5) comprising a CCD camera with a resolution of 1920 x 1200, a bit depth of up to 12 bits, a frame rate of up to 300fps, the CCD camera exposure time, photosensitive area, bit depth, frame rate being all adjustable.
5. The diffuse speckle-based quantitative blood flow detection system of claim 4, wherein a 50 x 50 pixel area in the horizontal direction of the projection center of the detection fiber is selected as the region of interest, and the average value of pixels in the region of interest is kept at 75-95, and the maximum value is not more than 255 when the exposure time of the camera unit (5) and the source-detection distance are changed, so as to maintain the speckle signal intensity.
6. The quantitative detection system for blood flow based on diffuse speckle as claimed in claim 4, wherein the exposure time setting range of the CCD camera is set to 0.02-30ms, comprising a plurality of exposure time setting values, the corrected spatial speckle contrast K (T) at each exposure time setting value is calculated and stored,
K(T)＝σ s (T)/<I>；
wherein sigma s (T) is the standard deviation of pixels within the region of interest at an exposure time T,<I>is the average value of the pixels in the region of interest.
7. The quantitative blood flow detection system based on diffuse speckle according to claim 6, wherein the computer (7) is used for denoising the contrast of the space speckle and eliminating motion artifacts, and then the curve fitting of the multi-exposure data is carried out according to the multi-exposure speckle model and the curve fitting model, so that quantitative blood flow information is extracted.
8. The diffuse speckle-based quantitative blood flow detection system of claim 6, the multi-exposure speckle model being represented as:
where K is the spatial speckle contrast, T is the camera exposure time, x is the scaling factor, x=t/τ c ，τ c It is the time of the de-correlation,beta is a normalization factor of the speckle average effect; ρ is the dynamic scattering fraction, ρ=i f /(I s +I f ) Wherein I f For dynamic scattering part, I s Is a static scattering portion; v (V) noise Is extraneous noise.
9. The diffuse speckle-based quantitative blood flow detection system of claim 6, wherein the curve fitting model is based on least squares Levenberg-Marquardt implementation.
10. A method for quantitative detection of blood flow based on diffuse speckle, the method for quantitative detection of blood flow based on diffuse speckle being performed by the quantitative detection system of blood flow based on diffuse speckle according to any one of claims 1 to 9, the method comprising:
operation S10: emitting measuring laser light by a laser (1);
operation S20: the multimode light source optical fiber (3) and the plurality of detection optical fibers (4) are integrated through the optical fiber probe (2), wherein the light source optical fiber (3) is used for vertically projecting measuring laser to the surface of a body to be measured; the detection optical fibers (4) can form different source-detection distances with the light source optical fibers (3) and are used for collecting diffuse speckle signals with different depths obtained after measuring laser is vertically projected to a body to be measured;
operation S30: receiving, by a camera unit (5), diffuse speckle signals collected by a detection fiber (4) at different exposure times;
operation S40: outputting an analog signal to the laser (1) through an analog signal output module (6) to adjust the measured laser intensity, so as to prevent the camera unit (5) from generating a saturation phenomenon when the exposure time is changed; and
operation S50: the computer (7) controls the analog signal output module (6) to output analog signals and controls the exposure time of the camera unit (5), and processes the received diffuse speckle signals to obtain blood flow quantitative information.
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