Near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device and detection method

Abstract

The present invention discloses a near-infrared diffuse coherent spectrum local cerebral blood flow speckle imaging device and a detection method thereof. The imaging device of the present invention comprises a light source module, an optical heterodyne detection module and an imaging acquisition module. The present invention is based on optical heterodyne detection technology and laser speckle imaging technology. The laser emitted by the laser is divided into two paths, namely, local oscillator light and excitation light, through an optical fiber beam splitter. The excitation light is transmitted to the surface of the local tissue of the brain of the biological being to be tested through a source optical fiber probe. Then, the probe optical fiber probe uses a multimode optical fiber to collect diffuse reflection signal light carrying local blood flow information. The optical fiber coupler and the local oscillator light are homodyne interfered to generate diffuse coherent light, and a laser speckle image is formed on the photosensitive surface of a CMOS camera. Finally, the near-infrared diffuse coherent spectrum speckle contrast analysis algorithm is used to extract the flow velocity characteristic value speckle contrast by computer processing, and the actual relative flow velocity of the local cerebral blood flow is reconstructed, so as to achieve the purpose of non-invasively and accurately detecting the local cerebral blood flow velocity and flow size.

Description

Technical Field

[0001] The present invention relates to the field of biomedical detection equipment, and in particular to a near-infrared diffuse coherence spectrum local cerebral blood flow speckle imaging device and a detection method thereof. Background Art

[0002] Cerebrovascular disease is a neurological disease caused by rupture of cerebral blood vessels or thrombosis, which leads to intracranial hemorrhage or ischemia, resulting in cerebral blood circulation disorders. In the medical field, cerebrovascular disease has become one of the three major diseases that seriously endanger human life and health, along with cancer and coronary heart disease, due to its high incidence, high recurrence rate, high disability rate, high mortality rate and multiple complications.

[0003] Local cerebral blood flow has important clinical value for the medical evaluation of Alzheimer's disease, cerebrovascular disease, brain tumors and ischemic stroke. In the research and application of brain tissue blood flow, the traditional blood flow detection method mainly relies on photon counters and uses the single-photon detection technology of photomultiplier tubes to achieve the exponential amplification of the single-photon photoelectric effect. However, this method has certain problems. The photoelectric conversion gain of photomultiplier tubes is large but the quantum efficiency is low, while the quantum efficiency of avalanche diodes is high but the gain is relatively low; the single-photon counting rate is limited by time, and the time domain continuous monitoring effect of cerebral blood flow changes is not good; and the blood flow information obtained by single-photon counting can only be one-dimensional time-related information, and it is impossible to obtain high-resolution two-dimensional brain tissue blood flow imaging.

[0004] In view of the shortcomings of single photon counting technology combined with optical fiber communication technology, in order to improve the temporal resolution and filter out the interference of scalp blood flow, and realize the direct extraction of deep local cerebral blood flow information, the present invention discloses a new method for non-invasively detecting local cerebral blood flow information based on diffuse coherence spectroscopy technology of optical heterodyne detection structure. Summary of the invention

[0005] 1. Problems to be solved technically

[0006] The present invention proposes a near-infrared diffuse coherent spectroscopy local cerebral blood flow speckle imaging device and a detection method thereof, which can non-invasively detect the local blood flow of deep head tissues, realize the reconstruction of its relative velocity index and two-dimensional flow velocity imaging. The purpose of the present invention is to propose an optical heterodyne detection technology to overcome the sensitivity and scalp blood flow interference problems in traditional blood flow detection methods, and based on the improved laser speckle imaging technology, use the near-infrared diffuse coherent spectroscopy speckle contrast analysis algorithm to reconstruct the actual relative flow velocity and flow size information from the laser speckle formed by the diffuse coherent light.

[0007] (II) Technical solution

[0008] In one aspect of the present disclosure, a local cerebral blood flow speckle imaging device based on near-infrared diffuse coherent spectroscopy of an optical heterodyne structure is provided, which has a flexible and variable source-detection distance, can select the optimal source-detection distance for different detection depths and cross-sections of biological tissues to be measured, and reconstruct local blood flow velocity and flow size, and has the characteristics of stability, flexibility and applicability of traditional hardware correlators and convenience and speed of software correlators.

[0009] A near-infrared diffuse coherent spectrum local cerebral blood flow speckle imaging device comprises: a light source module for emitting near-infrared laser; an optical heterodyne detection module for generating and collecting beat frequency coherent signals, with a flexible and variable source-detection distance; and an imaging acquisition module for collecting laser speckle images.

[0010] In the disclosed embodiment, the light source module includes: a laser, one end of which is connected to the first single-mode optical fiber for emitting laser; a light source driver, which is connected to the laser and is used to supply power and adjust the operating temperature and actual output power of the laser.

[0011] In the disclosed embodiment, the optical heterodyne detection module includes: a single-mode fiber splitter, one input end of which is connected to the first single-mode fiber output by the laser, and is used to split one light source into two paths, namely local oscillator light and excitation light, and two output ends of which are connected to another two single-mode fibers, namely the second single-mode fiber and the third single-mode fiber; a single-mode fiber adjustable optical attenuator, one input end of which is connected to the second single-mode fiber split by the single-mode fiber splitter, and one output end of which is connected to the fourth single-mode fiber, and is used to attenuate the local oscillator light into a reference light with a power smaller than that of the signal light; a source fiber probe, which is connected to the third single-mode fiber split by the single-mode fiber splitter; The invention relates to a multimode fiber optic coupler, wherein the first multimode fiber optic coupler has two input ends connected to the fourth single-mode fiber of the single-mode fiber adjustable optical attenuator and the first multimode fiber of the probe fiber optic probe, and the other output end is connected to the second multimode fiber optic coupler, and is used to couple the reference light and the signal light into one path to generate a beat frequency signal by interference, and output multi-mode coherent light.

[0012] In the embodiment of the present disclosure, the imaging acquisition module includes: an optical collimator, which is connected to the second multimode optical fiber output by the multimode optical fiber coupler and is used to maintain the coherent laser resonant cavity and the collimation of the focused coherent light beam; a high-speed CMOS camera, which is connected to the optical collimator and is used to collect and record the laser speckle image generated by the coherence and diffusion of the signal light and the reference light on the CMOS photosensitive surface; a computer, which is connected to the high-speed CMOS camera and analyzes the laser speckle image collected by it and realizes two-dimensional flow velocity imaging.

[0013] In the disclosed embodiment, the laser adopts a fiber Bragg grating (FBG) semiconductor laser with a central wavelength of 851.1 nm, and has a built-in TEC temperature-controlled near-infrared light source, and the adjustable maximum output optical power is 200 mW.

[0014] In the disclosed embodiment, the light source driver sets the operating temperature of the laser to 25°C, so that the working efficiency is the highest, the light source output is the most stable, and the actual output power of the laser is 10 mW.

[0015] In the embodiment disclosed herein, the single-mode fiber beam splitter has a splitting ratio of 1:9, which splits a path of laser light transmitted from the first single-mode optical fiber output by the laser into two paths, one of which is local oscillator light with a splitting ratio of 10%, transmitted by the second single-mode optical fiber, and used to generate coherence with the signal light as a reference; the other is excitation light with a splitting ratio of 90%, transmitted by the third single-mode optical fiber, and used for signal collection.

[0016] In the embodiment disclosed herein, the multimode fiber coupler has a splitting ratio of 1:1, and couples a reference light with a splitting ratio of 50% transmitted through the fourth single-mode fiber of the single-mode fiber variable optical attenuator and a signal light with a splitting ratio of 50% transmitted through the first multimode fiber of the optical fiber probe to output a coherent light transmitted through the second multimode fiber, which is used to be output to the photosensitivity surface of the CMOS camera to generate a laser speckle image.

[0017] In the disclosed embodiment, optionally, the local brain tissue of the biological being to be tested and the source-detection optical fiber probe are covered with a layer of light-shielding material.

[0018] In the disclosed embodiment, optionally, the rotating measuring rod is used to change the source-detection distance, and the optimal source-detection distance for detecting local cerebral blood flow is obtained to be 0-4 cm through Monte Carlo simulation analysis.

[0019] In another aspect of the present disclosure, a method for detecting near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging is provided, and imaging is performed using the near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device described above; the method for detecting near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging comprises: step A: using the laser to emit laser light, the laser light is transmitted to the optical fiber splitter via the first single-mode optical fiber and is divided into two transmission paths by the second single-mode optical fiber and the third single-mode optical fiber, namely, local oscillator light and excitation light; step B: the excitation light in step A is transmitted from the source optical fiber probe to the surface of the local tissue of the biological brain to be tested, and then the probe optical fiber probe collects the excitation light passing through the local tissue of the biological brain to be tested. The signal light diffused on the surface after being scattered by the tissue; step C: the signal light collected in step B is transmitted from the first multimode optical fiber of the optical fiber probe to the optical fiber coupler to couple with the reference light, and a diffuse coherent light is output from the second multimode optical fiber; step D: the diffuse coherent light output in step C is transmitted to the optical collimator for focusing processing, and then photographed by a high-speed CMOS camera to obtain a laser speckle image with a certain exposure time; step E: the laser speckle data in step D is sent to a computer for image processing, and the relative velocity index is obtained by using the near-infrared diffuse coherent spectral speckle contrast analysis algorithm to complete the two-dimensional relative flow velocity imaging of the local cerebral blood flow and reconstruct the relative flow velocity and flow size information.

[0020] In the disclosed embodiment, step A comprises: step A1: the local oscillator light is transmitted to a single-mode optical fiber variable optical attenuator and attenuated into a coherent reference light; and step A2: the reference light described in step A1 is transmitted from a fourth single-mode optical fiber to the optical fiber coupler described in step C.

[0021] In the disclosed embodiment, the shooting parameter setting of the high-speed CMOS camera in step D can be achieved by presetting the measurement parameters on the computer; the maximum resolution of the CMOS camera is 1088×2048 pixels, and the pixel size is 5.5×5.5 μm.

[0022] Technical Effects

[0023] It can be seen from the above technical solutions that the near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device and detection method disclosed in the present invention have at least one or part of the following technical effects:

[0024] With flexible and variable source detection distance, it can determine the optimal detection distance for local blood flow velocity detection of brain tissue of the tested organism at different detection depths;

[0025] The use of optical heterodyne detection technology can effectively avoid the interference of scalp blood flow in the head of the organism to be tested, and improve the sensitivity and detection accuracy of non-invasive spectrum detection;

[0026] Based on the improved laser speckle imaging technology, the near-infrared diffuse coherent spectroscopy speckle contrast analysis algorithm can be used to reconstruct the relative velocity index of the cross-section of the blood vessels at different detection depths in the local brain tissue of the tested organism, and obtain two-dimensional relative flow velocity imaging and local flow information;

[0027] The short measurement cycle makes it possible to quickly, non-invasively, in real time and accurately detect the relative velocity and flow size information of local cerebral blood flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained according to the drawings provided by the present invention without paying creative labor.

[0029] Figure 1 It is a block diagram of a near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging system according to an embodiment of the present disclosure.

[0030] Figure 2 It is a flow chart of a detection method for near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging according to an embodiment of the present disclosure.

[0031] Figure 3 Schematic diagram of the experimental structure of the brain local blood flow phantom model of the local brain tissue of the biological body to be tested in the embodiment of the present disclosure; Figure 3 (a) is a schematic diagram of the composition of the local brain blood flow phantom model; Figure 3 (b) is a schematic diagram of the local blood flow phantom model of the cerebral cortex of the head.

[0032] Figure 4 It is a flow chart of the near-infrared diffuse coherent spectroscopy speckle contrast analysis algorithm of the embodiment of the present disclosure.

[0033] Figure 5 It is a schematic diagram comparing the relative velocity index of the phantom model at different source detection distances and the fitting curve of the calibrated flow velocity in the embodiment of the present disclosure.

[0034] Figure 6 It is a schematic diagram comparing the relative velocity index of different local cross sections of the phantom model and the fitting curve of the calibrated flow velocity in the embodiment of the present disclosure.

[0035] Figure 7 is a schematic diagram of the original speckle imaging and two-dimensional relative flow velocity imaging of the local brain blood flow phantom experiment in the embodiment of the present disclosure; wherein Figure 7 (a) is the original speckle image obtained by computer processing in the phantom experiment; Figure 7(b) is a schematic diagram of the two-dimensional relative flow velocity imaging corresponding to a region of interest with a size of 100×100 pixels in the phantom experiment. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] The present invention proposes a near-infrared diffuse coherent spectroscopy local cerebral blood flow speckle imaging device and a detection method thereof, which can non-invasively detect the local cerebral blood flow in the deep tissue of the head, and realize the reconstruction of its relative velocity index and two-dimensional flow velocity imaging. The device has a flexible and variable source detection distance, and can determine the optimal detection distance for the local blood flow velocity detection of the brain tissue of the biological being to be tested at different detection depths. The purpose of the present invention is to propose an optical heterodyne detection technology to overcome the problems of sensitivity and scalp blood flow interference in traditional blood flow detection methods, and reconstruct the actual relative flow velocity and flow information from the speckle formed by diffuse coherent light based on laser speckle imaging technology.

[0038] In order to make the above-mentioned objectives, technical solutions and advantages of the present invention more obvious and understandable, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0039] In the embodiment of the present disclosure, a near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device is provided. Figure 1 The system block diagram of the near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device is shown in FIG. Figure 1 As shown, the near-infrared diffuse coherent spectroscopy local cerebral blood flow speckle imaging device includes: a light source module, an optical heterodyne detection module, and an imaging acquisition module.

[0040] Wherein, the light source module includes:

[0041] A laser 1, one end of which is connected to the first single-mode optical fiber and is used to emit laser light;

[0042] The light source driver 2 is connected to the laser 1 and is used for supplying power and adjusting the operating temperature and actual output power of the laser 1 .

[0043] Wherein, the optical heterodyne detection module includes:

[0044] A single-mode fiber beam splitter 3, one input end of which is connected to the first single-mode fiber outputted by the laser 1, and is used to split one light source into two paths, namely, local oscillator light and excitation light, and two output ends of which are connected to the other two single-mode fibers, namely, the second single-mode fiber and the third single-mode fiber;

[0045] A single-mode fiber variable optical attenuator 4, one input end of which is connected to the second single-mode optical fiber split by the single-mode fiber beam splitter 3, and one output end of which is connected to the fourth single-mode optical fiber, for attenuating the local oscillator light into a reference light with a smaller power than the signal light;

[0046] A source optical fiber probe 5, which is connected to the third single-mode optical fiber split by the single-mode optical fiber beam splitter 3, and is used to transmit the excitation light to the local brain tissue 6 of the biological being to be tested;

[0047] A fiber optic probe 7, one end of which is connected to the first multimode optical fiber and is used to collect signal light carrying flow information of the local brain tissue 6 of the biological being to be tested;

[0048] A rotating measuring rod 8, which is connected to the same end of the optical fiber probe 7, and is used to adjust the source-probe distance between the measuring rod 8 and the source optical fiber probe 5;

[0049] The multimode fiber coupler 9 has two input ends connected to the fourth single-mode fiber of the single-mode fiber variable optical attenuator 4 and the first multi-mode fiber of the fiber probe 7, and the other output end is connected to the second multi-mode fiber, and is used to couple the reference light and the signal light into one path to interfere and generate a beat frequency signal, and output multi-mode coherent light.

[0050] Among them, the imaging acquisition module includes:

[0051] An optical collimator 10, which is connected to the second multimode optical fiber output by the multimode optical fiber coupler 9, and is used to maintain the coherent laser resonant cavity and the collimation of the focused coherent light beam;

[0052] A high-speed CMOS camera 11, which is connected to the optical collimator 10, and is used to collect and record the laser speckle pattern generated by the coherence and diffusion of the signal light and the reference light on the CMOS photosensitive surface;

[0053] The computer 12 is connected to the high-speed CMOS camera 11 to analyze the laser speckle image collected by the camera and realize two-dimensional flow velocity imaging.

[0054] A plurality of lasers 1 and a plurality of optical fiber probes 7 may also be provided, and parallel measurement and imaging may be realized by time division multiplexing or multi-light source modulation and multi-detection acquisition through an optical switch.

[0055] In the disclosed embodiment, the laser 1 adopts a fiber Bragg grating (FBG) semiconductor laser with a central wavelength of 851.1 nm, and has a built-in TEC temperature-controlled near-infrared light source, and the adjustable maximum output optical power is 200 mW.

[0056] The light source driver 2 sets the working temperature of the laser 1 to 25° C., so that the working efficiency is the highest, the light source output is the most stable, and the actual output power of the laser is 10 mW.

[0057] The single-mode fiber beam splitter 3 has a splitting ratio of 1:9, and splits the laser light transmitted from the first single-mode fiber output by the laser 1 into two paths: one path is the local oscillator light with a splitting ratio of 10%, which is transmitted by the second single-mode fiber and used to generate coherence with the signal light as a reference; the other path is the excitation light with a splitting ratio of 90%, which is transmitted by the third single-mode fiber and used for signal collection.

[0058] The multimode fiber coupler 9 has a splitting ratio of 1:1, and couples a reference light with a splitting ratio of 50% transmitted through the fourth single-mode fiber of the single-mode fiber variable optical attenuator 4 and a signal light with a splitting ratio of 50% transmitted through the first multimode fiber of the optical fiber probe 7 to output a coherent light transmitted through the second multimode fiber, which is used to be output to the photosensitive surface of the CMOS camera 11 to generate a laser speckle image.

[0059] The source optical fiber in the optical heterodyne detection module adopts a single-mode optical fiber with a core diameter of 9 μm; the probe optical fiber adopts a multi-mode optical fiber with a core diameter of 62.5 μm.

[0060] The rotating measuring rod 8 changes the source-detection distance. Monte Carlo simulation analysis shows that the optimal source-detection distance for detecting local cerebral blood flow is 0-4 cm.

[0061] In the disclosed embodiment, a detection method of near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging is also provided, and imaging is performed using the near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device. Figure 2 FIG. 1 is a flow chart of a detection method for near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging according to an embodiment of the present disclosure. Figure 2 As shown, the detection method comprises:

[0062] Step A: emitting laser light by the laser 1, the laser light is transmitted to the optical fiber splitter 3 via the first single-mode optical fiber and is divided into two paths for transmission by the second single-mode optical fiber and the third single-mode optical fiber, namely, the local oscillator light and the excitation light; Step A comprises:

[0063] Step A1: the local oscillator light is transmitted to the single-mode optical fiber variable optical attenuator 4 and attenuated into a coherent reference light; and

[0064] Step A2: The reference light in step A1 is transmitted to the optical fiber coupler 9 in step C through the fourth single-mode optical fiber;

[0065] Step B: the excitation light in step A is transmitted from the source optical fiber probe 5 to the surface of the local brain tissue 6 of the biological subject to be tested, and then the optical fiber probe 7 collects the signal light diffused on the surface after the excitation light is scattered by the local brain tissue 6 of the biological subject to be tested; and

[0066] Step C: the signal light collected in step B is transmitted from the first multimode optical fiber of the optical fiber probe 7 to the optical fiber coupler 9 to couple with the reference light in step A1, and a diffuse coherent light is output from the second multimode optical fiber; and

[0067] Step D: The diffuse coherent light outputted in step C is transmitted to the light collimator 10 for focusing, and then photographed by the high-speed CMOS camera 11 to obtain a laser speckle image with a certain exposure time;

[0068] Step E: The laser speckle data described in step D is sent to the computer 12 for image processing, and the relative velocity index of the local brain tissue 6 of the biological subject to be tested is obtained by speckle contrast analysis, and the two-dimensional relative flow velocity imaging of the local cerebral blood flow by near-infrared diffuse coherence spectroscopy is completed and its actual relative flow velocity and flow size information are reconstructed.

[0069] In the embodiment of the present disclosure, the local brain tissue 6 to be tested in step B can be verified by using a local brain blood flow phantom model for phantom experiment, and its composition diagram is shown as follows: Figure 3 (a) is shown. The local brain blood flow phantom model comprises:

[0070] The blood phantom solution is a mixed solution composed of a fat emulsion solution and India ink in a certain proportion; the fat emulsion solution is used as a scattering agent to simulate other components of blood under the cerebral cortex, and the India ink is used as an absorbent to simulate blood cells; and

[0071] A peristaltic pump, using its stable and known flow rate setting to adjust the flow rate of the phantom model; the pump head end of the peristaltic pump is connected to a latex hose with a matching inner diameter to extract the blood phantom solution to simulate the flow of blood in blood vessels in human tissue; and

[0072] A local phantom model of the cerebral cortex of the head, such as Figure 3(b) is used to simulate the physiological environment of local cerebral blood flow; it is characterized in that it presents a cubic hollow hard model, the detection surface is an agar layer simulating the skull and scalp layer, and the other side surfaces and the bottom surface are non-absorbent black hard material; the fat emulsion solution is contained in the phantom model to simulate the physiological environment of the deep blood vessels in the brain (such as the gray and white matter layers of the brain), and the latex hose supporting the peristaltic pump is U-shaped and passed through the phantom model inside, close to the agar layer, to simulate the flow of local cerebral blood vessels in the cerebral cortex.

[0073] The phantom experiment design of the local brain blood flow phantom model includes:

[0074] The blood phantom solution has a mixing ratio of 0.09% India ink and 3% fat emulsion. Its optical parameters are: absorption coefficient μ a =0.11mm -1 , reduced scattering coefficient μ′ s =0.83mm -1 .

[0075] The peristaltic pump and its matching latex hose were set to an initial flow rate of 50 mL / min, and were run for 2 min to wait for the blood phantom solution to flow stably in the soft hose before changing the flow setting to start the experiment; the peristaltic pump was randomly adjusted to measure several groups of blood phantom solutions with the same soft hose inner diameter at a rotation speed of (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100) rpm, and the calibrated flow rate was obtained based on the relationship between the calibrated rotation speed and the flow rate; and several groups of experiments with different hose inner diameters of (4.8, 6.4, 7.9) mm were also measured; and the source-probe distance was selected to be (0.6, 0.8, 1.0, 1.2) cm to compare the measurement results.

[0076] The thickness of the scalp and skull agar layer of the head cerebral cortex local blood flow phantom model is set to 1 cm to simulate the thickness of an adult skull.

[0077] In the embodiment of the present disclosure, the shooting setting of the high-speed CMOS camera 11 in step D can be preset by the computer 12 with measurement parameters, including the number of frames, exposure time, spatial resolution, and the type of data stored. In the phantom experiment, the shooting frame number of the CMOS camera is set to 1000 frames, the exposure time is 1ms, and the type of data stored is AV1 data; the highest resolution is 1088×2048 pixels, the imaging area of ​​interest can be selected for processing, and the pixel size is 5.5×5.5μm.

[0078] In the embodiment of the present disclosure, the high-speed CMOS camera 11 in step E transmits the captured laser speckle image to the computer 12 for processing via the RJ-45 Ethernet interface. Figure 7(a) shows the original laser speckle image obtained by shooting. The near-infrared diffuse coherent spectroscopy speckle contrast analysis algorithm is used to select an area of ​​interest with a size of N×N pixels (generally N>30) to extract the velocity feature value. The algorithm flow chart is shown in Figure 4 shown.

[0079] Using the improved laser speckle contrast imaging technology, the near-infrared diffuse coherent spectroscopy speckle contrast analysis algorithm mainly includes two parts: system calibration and speckle measurement. The purpose of this algorithm is to obtain the real flow speckle contrast measured under a single exposure by estimating and correcting the system noise, so as to obtain the relative velocity index of the local blood flow in the biological tissue to be measured. By comparing the results at different source-detection distances (SD), the fitting curve with the calibrated blood flow velocity is established through the relative velocity index, and the following can be obtained: Figure 5 The normalized fitting curves of the relative velocity index and the calibrated flow velocity are shown in Figure 1. It can be seen that the relative velocity index and the calibrated flow velocity have a good linear relationship at different source-detection distances, and the average linear correlation coefficient is 0.9881. Therefore, the actual measured blood flow velocity of the phantom can be reconstructed based on the fitting curve, and two-dimensional relative flow velocity imaging can be performed in the calculation area, such as Figure 7 (b) as shown.

[0080] In addition, according to the cross-sectional area of ​​the local blood vessels in the imaging area, the blood vessel flow volume of different cross-sections can also be calculated. Figure 6 As shown, it is a schematic diagram of the normalized fitting curve comparison of the relative velocity index and the calibrated flow rate of different local cross-sections (determined by the inner diameter tubeD) of the phantom model in the embodiment of the present disclosure. It can be seen that when the flow rate is the same at 100mL / min, the relative velocity index ratio of the tube inner diameters of 4.8mm, 6.4mm and 7.9mm is 0.78:0.55:0.47. It shows that this method can better distinguish the relative flow velocity information of different tube inner diameters, and the average correlation coefficient between the relative velocity index and the actual flow velocity is 0.9801. Therefore, the relative flow velocity corresponding to the hose with different cross-sectional areas can be calculated according to the fitting curve, and its flow rate can be reconstructed by multiplying it by the cross-sectional area. Therefore, the detection method of local cerebral blood flow speckle imaging of near-infrared diffuse coherence spectroscopy proposed in the present disclosure can establish a fitting curve of the relative velocity index and flow rate as a reference for reconstructing the relative flow velocity and flow rate of the local blood flow of the brain of the tested organism.

[0081] So far, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0082] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the device and its core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

[0083] Based on the above description, those skilled in the art should have a clear understanding of the near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device and detection method disclosed in the present invention.

[0084] In summary, the present invention proposes a near-infrared diffuse coherent spectroscopy local cerebral blood flow speckle imaging device and a detection method thereof, which can non-invasively detect the local blood flow of deep head tissues, realize the reconstruction of its relative velocity index and two-dimensional flow velocity imaging. The purpose of the present invention is to propose an optical heterodyne detection technology to overcome the sensitivity and scalp blood flow interference problems in traditional blood flow detection methods, and based on the improved laser speckle imaging technology, use the near-infrared diffuse coherent spectroscopy speckle contrast analysis algorithm to reconstruct the actual relative flow velocity and flow information from the laser speckle formed by the diffuse coherent light.

[0085] The device has a flexible and variable source detection distance, and can reconstruct local blood flow velocity and flow size at different detection depths and cross-sections of the biological tissue to be tested. It has the characteristics of stability, flexibility and applicability of traditional hardware correlators and the convenience and speed of software correlators.

[0086] It should also be noted that the ordinal numbers used in the specification and claims, such as "first", "second", etc., to modify the corresponding elements, do not themselves mean that the element has any ordinal number, nor do they represent the order of one element and another element, or the order of the manufacturing method. The use of these ordinal numbers is only used to make a named element clearly distinguishable from another element with the same name.

[0087] Furthermore, the shapes and sizes of the components in the figures do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present disclosure. Unless otherwise indicated, the numerical parameters in this specification and the appended claims are approximate values ​​and can be changed according to the desired characteristics obtained through the contents of the present disclosure. Specifically, all numbers used in the specification and claims to indicate the content of the composition, source detection distance, etc., should be understood to be modified by the term "approximately" in all cases. In general, the meaning of the expression refers to the inclusion of a change of ±10% in some embodiments, a change of ±5% in some embodiments, a change of ±1% in some embodiments, and a change of ±0.5% in some embodiments by a specific number.

[0088] In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0089] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and set in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition they may be divided into multiple submodules or subunits or subcomponents. All features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner may be combined in any combination, except that at least some of such features and / or processes or units are mutually exclusive. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose. Furthermore, in a unit claim that lists several devices, several of these devices may be embodied by the same hardware item.

[0090] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: the claimed disclosure requires more features than the features explicitly recited in each claim. More specifically, as reflected in the claims below, the disclosed aspects are less than all the features of the single embodiment disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present disclosure.

[0091] The specific embodiments described above further illustrate the purpose, technical solutions and technical effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device, characterized in that: It includes: A light source module, used for emitting near-infrared laser light, comprising a laser (1) and a light source driver (2); The optical heterodyne detection module is used to generate and collect beat frequency coherent signals. The source-detection distance is flexible and variable, and the optimal source-detection distance can be selected for different detection depths and cross-sections of the biological tissue to be tested, effectively avoiding interference with the scalp blood flow of the head of the biological tissue to be tested; An imaging acquisition module, used for acquiring laser speckle images; Wherein, the optical heterodyne detection module includes: A single-mode optical fiber beam splitter (3), one input end of which is connected to the first single-mode optical fiber output by the laser (1), and is used to split one light source into two paths, namely, local oscillator light and excitation light, and two output ends of which are connected to two other single-mode optical fibers, namely, a second single-mode optical fiber and a third single-mode optical fiber; A single-mode optical fiber adjustable optical attenuator (4), one input end of which is connected to the second single-mode optical fiber split by the single-mode optical fiber beam splitter (3), and one output end of which is connected to the fourth single-mode optical fiber, and is used to attenuate the local oscillator light into a reference light with a smaller power than the signal light; A source optical fiber probe (5), which is connected to the third single-mode optical fiber split by the single-mode optical fiber beam splitter (3) and is used to transmit the excitation light to the local brain tissue (6) of the biological being to be tested; A fiber optic probe (7), one end of which is connected to the first multimode optical fiber and is used to collect signal light carrying flow information of the local brain tissue (6) of the biological being to be tested; A rotating measuring rod (8) connected to the same end of the optical fiber probe (7) for adjusting the source-probe distance between the measuring rod and the source optical fiber probe (5); A multimode optical fiber coupler (9), whose two input ends are connected to the fourth single-mode optical fiber of the single-mode optical fiber variable optical attenuator (4) and the first multimode optical fiber of the optical fiber probe (7), and whose other output end is connected to the second multimode optical fiber, and is used to couple the reference light and the signal light into one path to generate a beat frequency signal through interference, and output multimode coherent light; Among them, the imaging acquisition module includes: An optical collimator (10), which is connected to the second multimode optical fiber outputted by the multimode optical fiber coupler (9) and is used to maintain the coherent laser resonant cavity and the collimation of the focused coherent light beam; A high-speed CMOS camera (11), connected to the light collimator (10), for collecting and recording a laser speckle image generated by the coherence and diffusion of the signal light and the reference light on the CMOS photosensitive surface; A computer (12) is connected to the high-speed CMOS camera (11) to analyze the laser speckle image collected by the camera and realize two-dimensional flow velocity imaging.

2. The near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to claim 1, characterized in that: The light source module includes: A laser (1), one end of which is connected to the first single-mode optical fiber and is used to emit laser light; A light source driver (2) is connected to the laser (1) and is used for supplying power and adjusting the operating temperature and actual output power of the laser (1).

3. The near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to any one of claims 1-2, characterized in that: The laser (1) adopts a fiber Bragg grating (FBG) semiconductor laser with a central wavelength of 851.1 nm, and is equipped with a TEC temperature-controlled near-infrared light source, and the adjustable maximum output optical power is 200 mW.

4. The near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to any one of claims 1-2, characterized in that: The light source driver (2) sets the working temperature of the laser (1) to 25°C, when the working efficiency is the highest, the light source output is the most stable, and the actual output power of the laser is 10 mW.

5. The near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to any one of claims 1-2, characterized in that: The single-mode fiber beam splitter (3) has a splitting ratio of 1:9, and splits a path of laser light transmitted from the first single-mode fiber output by the laser (1) into two paths, one of which is local oscillator light with a splitting ratio of 10%, transmitted by the second single-mode fiber, and used to generate coherence with the signal light as a reference; and the other is excitation light with a splitting ratio of 90%, transmitted by the third single-mode fiber, and used for signal collection.

6. The near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to claim 2, characterized in that: The multimode fiber coupler (9) has a splitting ratio of 1:1, and couples a reference light with a splitting ratio of 50% transmitted through a fourth single-mode fiber of the single-mode fiber variable optical attenuator (4) and a signal light with a splitting ratio of 50% transmitted through a first multimode fiber of a probe fiber probe (7) to output a coherent light transmitted through a second multimode fiber, which is used to be output to a photosensitive surface of the CMOS camera (11) to generate a laser speckle image.

7. The near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to any one of claims 1-2, characterized in that: The rotating measuring rod (8) changes the source-detection distance, and the optimal source-detection distance for detecting local cerebral blood flow is found to be 0-4 cm through Monte Carlo simulation analysis.

8. A method for detecting local cerebral blood flow speckle imaging using near-infrared diffuse coherence spectroscopy, characterized in that: The detection method uses the near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging device according to any one of claims 1 to 7 for imaging; the detection method comprises: Step A: emitting laser light using the laser (1), the laser light being transmitted to the optical fiber splitter (3) via the first single-mode optical fiber and being split into two paths for transmission by the second single-mode optical fiber and the third single-mode optical fiber, namely, local oscillation light and excitation light; and Step B: the excitation light in step A is transmitted from the source optical fiber probe (5) to the surface of the local brain tissue (6) of the biological subject to be tested, and then the detection optical fiber probe (7) collects the signal light diffused on the surface after the excitation light is scattered by the local brain tissue (6) of the biological subject to be tested; and Step C: the signal light collected in step B is transmitted from the first multimode optical fiber of the optical fiber probe (7) to the optical fiber coupler (9) to couple with the reference light, and a diffuse coherent light is output from the second multimode optical fiber; Step D: The diffuse coherent light outputted in step C is transmitted to the light collimator (10) for focusing, and then photographed by a high-speed CMOS camera (11) to obtain a laser speckle image with a certain exposure time; Step E: The laser speckle data described in step D is sent to a computer (12) for image processing, and a near-infrared diffuse coherent spectral speckle contrast analysis algorithm is used to obtain a relative velocity index, complete two-dimensional relative flow velocity imaging, and reconstruct the relative flow velocity and flow size information of the local cerebral blood flow, thereby effectively avoiding interference from the scalp blood flow of the head of the tested organism.

9. According to the method for detecting local cerebral blood flow speckle imaging using near-infrared diffuse coherence spectroscopy as claimed in claim 8, the step A comprises: Step A1: the local oscillator light is transmitted to the single-mode optical fiber variable optical attenuator (4) and attenuated into a coherent reference light; as well as Step A2: The reference light described in step A1 is transmitted to the optical fiber coupler (9) described in step C through the fourth single-mode optical fiber.

10. According to the detection method of near-infrared diffuse coherence spectroscopy local cerebral blood flow speckle imaging according to claim 8 or 9, the shooting setting of the high-speed CMOS camera (11) in step D can preset measurement parameters through the computer (12); the maximum resolution is 1088×2048 pixels and the pixel size is 5.5×5.5μm.

Images