A blood flow imaging system and method based on light field modulation technology

Abstract

The present invention relates to the field of biological imaging technology, and in particular to a blood flow imaging system and method based on light field modulation technology. The system calculates a deviation value based on the position of a modulated light field focal plane; feeds back the deviation value to a servo system, and drives a stepper motor to move a loading platform to adjust a sample position by an output control amount; performs feature imaging on the sample based on compressed sensing image reconstruction theory and multidimensional vector matrix theory, and then obtains a two-dimensional distribution of red blood cell movement velocity in a tissue distinguished by image grayscale through contrast analysis technology. The present invention adopts light field modulation technology and combines compressed sensing theory to realize high-resolution non-invasive blood flow imaging, which greatly improves imaging resolution and anti-disturbance. The blood flow imaging device based on light field modulation technology meets the real-time, high-resolution, label-free, non-invasive blood flow imaging requirements urgently needed in clinical practice, thereby solving the problem of low image resolution of existing blood flow imaging methods.

Description

Technical Field

[0001] The present invention relates to the field of biological imaging technology, and in particular to a blood flow imaging system and method based on light field modulation technology. Background Art

[0002] Laser Doppler flowmeter and laser speckle flowmeter are two non-invasive blood testing devices that are gradually being used in clinical medicine. Although laser speckle flowmeter makes up for the defect of laser Doppler flowmeter without spatial resolution, there are still technical bottlenecks. In laser speckle imaging, in terms of scattering models, due to the complexity of biological tissues, different biological tissues may obey different flow velocity distribution models.

[0003] At present, the effectiveness of a single scattering model in actual measurement needs to be further verified. The accuracy of speckle contrast data directly affects the quality of imaging and further analysis of data. In addition, in in vivo imaging experiments, an unavoidable problem is that the breathing and heartbeat of the imaging object itself will produce jitter effects in the original speckle image, and the direct result of these effects is the reduction of image resolution. Summary of the invention

[0004] The purpose of the present invention is to provide a blood flow imaging system and method based on light field modulation technology, aiming to solve the problem of low image resolution of existing blood flow imaging methods.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a blood flow imaging method based on light field modulation technology, comprising the following steps:

[0006] Design the receiving system to match the position and size of the modulated light field, and record the focal plane position of the modulated light field;

[0007] Calculating a deviation value based on the focal plane position of the modulated light field;

[0008] Feeding back the deviation value to the servo system, and using the output control quantity to drive the stepping motor to move the loading platform to adjust the position of the sample;

[0009] Based on the theory of compressed sensing image reconstruction and multi-dimensional vector matrix theory, the sample is imaged, and then the two-dimensional distribution of the red blood cell movement velocity in the tissue distinguished by the image grayscale is obtained through contrast analysis technology.

[0010] The step of calculating the deviation value based on the focal plane position of the modulated light field includes:

[0011] Calculating the actual distance from the optical splitting system to the transmission layer of the sample;

[0012] A deviation value is calculated based on the actual distance and the focal plane position of the modulated light field.

[0013] The step of calculating the actual distance from the spectroscopic system to the transmission layer of the sample comprises:

[0014] Calculate the penetration depth of the light source in the sample based on the light source and sample conditions;

[0015] Testing the distance data from the spectroscopic system to the sample through a laser ranging module;

[0016] The actual distance from the spectroscopic system to the transmission layer of the sample is calculated based on the penetration depth and the distance data.

[0017] If the deviation value is a positive value, the deviation position is above the transmission layer of the sample; if the deviation value is a negative value, the deviation position is below the transmission layer of the sample.

[0018] In the second aspect, a blood flow imaging system based on light field modulation technology adopts the blood flow imaging method based on light field modulation technology described in the first aspect.

[0019] The invention comprises a host computer, a laser light source, a spatial light modulator, a detector, a servo control system, a lifting control platform, a laser ranging module and a spectroscopic system. The spatial light modulator, the detector and the servo control system are respectively connected to the host computer, the lifting control platform and the laser ranging module are respectively connected to the servo control system, the laser light source is connected to the spatial light modulator, and the spectroscopic system is connected to the laser light source and the laser ranging module.

[0020] The present invention discloses a blood flow imaging method based on light field modulation technology, comprising the following steps: designing a receiving system to match the position and size of a modulated light field, and recording the position of a focal plane of the modulated light field; calculating a deviation value based on the position of the focal plane of the modulated light field; feeding back the deviation value to a servo system, and driving a stepper motor to move a loading platform to adjust the position of the sample by an output control quantity; performing feature imaging on the sample based on compressed sensing image reconstruction theory and multidimensional vector matrix theory, and then obtaining a two-dimensional distribution of red blood cell movement velocity in a tissue distinguished by image grayscale through contrast analysis technology. The present invention adopts light field modulation technology and combines compressed sensing theory to realize high-resolution non-invasive blood flow imaging, which greatly improves imaging resolution and anti-disturbance. The blood flow imager based on light field modulation technology meets the real-time, high-resolution, label-free, non-invasive blood flow imaging requirements urgently needed in clinical practice, thereby solving the problem of low image resolution of existing blood flow imaging methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further illustrated by means of the non-limiting examples given in the accompanying drawings.

[0022] Figure 1The present invention is a flow chart of a blood flow imaging method based on light field modulation technology.

[0023] Figure 2 It is a structural schematic diagram of a blood flow imaging system based on light field modulation technology of the present invention.

[0024] 1-host computer, 2-laser light source, 3-spatial light modulator, 4-detector, 5-servo control system, 6-lifting control platform, 7-laser ranging module, 8-spectroscopy system. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0026] See also Figure 1 In a first aspect, the present invention provides a blood flow imaging method based on light field modulation technology, comprising the following steps:

[0027] S1 designs the receiving system to match the position and size of the modulated light field, and records the focal plane position of the modulated light field;

[0028] Specifically, the receiving system is designed to match the position and size of the modulated light field, and the focal plane position c of the modulated light field is recorded and used as the sample reference position.

[0029] S2 calculates a deviation value based on the focal plane position of the modulated light field;

[0030] S21 calculates the actual distance from the light splitting system 8 to the transmission layer of the sample;

[0031] S211 calculates the penetration depth of the light source in the sample based on the light source and the sample conditions;

[0032] Specifically, the penetration depth a of the light source in the sample is calculated based on the light source and sample conditions.

[0033]

[0034] Where k represents the backscattering factor, μ 1 , μ 2 and g represent the absorption coefficient, scattering coefficient and scattering mean cosine of biological tissue respectively, and these parameters are all related to the wavelength of light.

[0035] S212 tests the distance data from the light splitting system 8 to the sample through the laser distance measuring module 7;

[0036] Specifically, the laser ranging module 7 designed in the imaging system is used to test the spectroscopic system 8 ( Figure 1 ) to the sample and record the exact distance b.

[0037] S213 calculates the actual distance from the spectroscopic system 8 to the transmission layer of the sample based on the penetration depth and the distance data.

[0038] Specifically, in step 1, the focal plane position c of the modulated light field has been measured. At this time, the distance a+b is inconsistent with c, and the sample is in a defocused state.

[0039] S22 calculates a deviation value based on the actual distance and the focal plane position of the modulated light field.

[0040] Specifically, the distance from the focal plane at this time is calculated, that is, the deviation value d=a+bc, where d may be a positive value or a negative value, indicating that the deviation position may be above or below the sample transmission layer at this time.

[0041] S3 feeds back the deviation value to the servo system, and the output control quantity drives the stepping motor to move the loading platform to adjust the position of the sample;

[0042] Specifically, the deviation value d is fed back to the servo system, and the output control quantity drives the stepper motor to move the loading platform, automatically adjusting the sample position to ensure that the modulated light field is clearly projected onto the sample to be tested, thereby ensuring the imaging effect.

[0043] S4 performs characteristic imaging of the sample based on compressed sensing image reconstruction theory and multi-dimensional vector matrix theory, and then obtains the two-dimensional distribution of red blood cell movement velocity in the tissue distinguished by image grayscale through contrast analysis technology.

[0044] Specifically, under the premise of ensuring the quality of feature imaging, we improve the software and hardware and optimize the reconstruction algorithm, combine the compressed sensing image reconstruction theory and multi-dimensional vector matrix theory to achieve low-sampling and high-speed feature imaging, and then use contrast analysis technology to obtain the two-dimensional distribution of red blood cell movement velocity in the tissue distinguished by image grayscale.

[0045] The low-order Walsh matrix is ​​Kronnick product to obtain a high-order matrix.

[0046]

[0047] Represents the Kronecker product, N represents the Walsh matrix dimension, and the data sampling process is expressed as follows

[0048]

[0049] Perform a two-dimensional Walsh transform on the target object

[0050]

[0051] A square matrix representing the stacked vector mapping, using the orthogonality of the Walsh matrix to achieve image reconstruction

[0052] O=W T ΔD N×N W

[0053] The multidimensional Walsh vector matrix is ​​derived from the definition of the two-dimensional Walsh transform kernel

[0054]

[0055] H represents the order of the multidimensional Walsh vector matrix

[0056] H=2 n , x=0,1,2,…,H-1, y=0,1,2,…,H-1, u=0,1,2,…,H-1, v=0,1,2,…,H-1

[0057] The matrix representation of the multidimensional Walsh vector transform is

[0058] F=W H f

[0059] WH represents the H-order multidimensional Walsh vector matrix, and F represents the multidimensional Walsh vector transformation of the matrix f. Following the multidimensional vector matrix multiplication calculation rules, the calculation process of the elements in F is as follows:

[0060]

[0061] Where x = 1, 2, ..., H, y = 1, 2, ..., H

[0062] Using a multidimensional Walsh vector matrix as the measurement matrix, the sampling process is equivalent to performing a multidimensional Walsh vector transformation on the target object.

[0063] B=W N O

[0064] B and O represent the detection value matrix and the multidimensional representation of the target object, respectively. Therefore, the last two dimensions of the multidimensional Walsh matrix can be used as the rows and columns of the base pattern, and the orthogonality of the multidimensional Walsh matrix can be used to reconstruct the target object image at high speed.

[0065] O=W N B

[0066] When multiple speckle patterns are collected at high speed and reconstructed, the standard deviation and average value of the speckle signal intensity at a specific point in the image and its adjacent positions are calculated to obtain the speckle contrast ratio.

[0067]

[0068] Where K is the speckle contrast ratio, σ is the standard deviation of speckle intensity, is the average speckle intensity. Using the dynamic light scattering approximation model, K is expressed as

[0069]

[0070] T represents the exposure time, τ c represents the decorrelation time, and the speed of the scattering particles can be expressed by τ c The scattering particles in the blood flow are red blood cells, and the movement speed of the scattering particles represents the blood flow speed.

[0071] See also Figure 2 In a second aspect, a blood flow imaging system based on light field modulation technology adopts a blood flow imaging method based on light field modulation technology described in the first aspect,

[0072] It includes a host computer 1, a laser light source 2, a spatial light modulator 3, a detector 4, a servo control system 5, a lifting control platform 6, a laser ranging module 7 and a spectroscopic system 8. The spatial light modulator 3, the detector 4 and the servo control system 5 are respectively connected to the host computer 1, the lifting control platform 6 and the laser ranging module 7 are respectively connected to the servo control system 5, the laser light source 2 is connected to the spatial light modulator 3, and the spectroscopic system 8 is connected to the laser light source 2 and the laser ranging module 7.

[0073] In this embodiment, a laser light source 2 is used, and a spatial light modulator 3 (digital micromirror device) is used to control the illumination light field, breaking through the limitation of the optical diffraction limit on the spatial resolution of the instrument. The receiving system is designed to match the position and size of the modulated light field, and the focal plane position of the modulated light field is recorded as the sample reference position. The main body of the blood flow imaging system is controlled by a computer, and the control linkage of all configuration devices in the main body is realized through the electrical control system. The main configuration devices include spatial light modulation equipment (digital micromirror device), high-precision digital signal acquisition card, timing control circuit, high-precision motor and controller, and high-precision single pixel detector 4, and finally the complete optomechanical function of the blood flow imaging system is realized. The upper computer 1 controls the system software, completes the driving of various configuration devices, and realizes the image display, marking, analysis, storage and other functions of the blood flow imaging system through joint debugging and testing. Combining the compressed sensing image reconstruction theory and the multi-dimensional vector matrix theory, low-sampling high-speed feature imaging is realized, and then the contrast analysis technology is used to obtain the two-dimensional distribution of the red blood cell movement velocity in the tissue distinguished by the image grayscale.

[0074] Beneficial effects:

[0075] 1. Compared with laser Doppler blood flow meter, the technology of the present invention has higher spatial resolution

[0076] 2. Compared with laser speckle imaging, blood flow imaging technology is complex in biological tissues. Different biological tissues may obey different flow velocity distribution models. The effectiveness of the current single scattering model in actual measurement needs to be further verified. The accuracy of the speckle contrast data directly affects the quality of imaging and further analysis of the data. In addition, in in vivo imaging experiments, an unavoidable problem is that the breathing and heartbeat of the imaging object itself will produce jitter effects in the original speckle image. The direct result of these effects is the reduction of image resolution. The present invention uses a modulated light field to illuminate the sample and finally obtains a reconstructed image. It relies on strong perturbation and can image under weak light, avoiding the phototoxicity of light to biological tissues.

[0077] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A blood flow imaging method based on light field modulation technology, characterized in that: The following steps are involved: Designing a receiving system to match the position and size of the modulated light field, and recording the position of the focal plane of the modulated light field, specifically including: designing a receiving system to match the position and size of the modulated light field, recording the position c of the focal plane of the modulated light field, and using it as a sample reference position; Calculating a deviation value based on the focal plane position of the modulated light field; Feeding back the deviation value to the servo system, the output control quantity drives the stepper motor to move the loading platform to adjust the position of the sample; Based on the theory of compressed sensing image reconstruction and multi-dimensional vector matrix theory, the sample is imaged, and then the two-dimensional distribution of the red blood cell velocity in the tissue distinguished by the image grayscale is obtained through contrast analysis technology, including: Under the premise of ensuring the quality of feature imaging, we improve the software and hardware and optimize the reconstruction algorithm, combine the compressed sensing image reconstruction theory and multi-dimensional vector matrix theory to achieve low-sampling high-speed feature imaging, and then use contrast analysis technology to obtain the two-dimensional distribution of red blood cell movement velocity in tissues distinguished by image grayscale; The calculating of the deviation value based on the focal plane position of the modulated light field comprises: Calculate the actual distance from the light splitting system to the transmission layer of the sample; Calculating a deviation value based on the actual distance and the focal plane position of the modulated light field; The calculating the actual distance from the light splitting system to the transmission layer of the sample comprises: Calculate the penetration depth of the light source in the sample based on the light source and sample conditions. Specifically, the penetration depth a of the light source in the sample is calculated based on the comprehensive light source and sample conditions. Among them, k represents the backscattering factor, μ1, μ2 and g represent the absorption coefficient, scattering coefficient and scattering mean cosine of biological tissue, respectively, and these parameters are all related to the wavelength of light; The distance data from the spectroscopic system to the sample is tested by a laser ranging module, and the precise distance b from the spectroscopic system to the sample is tested and recorded by using the laser ranging module designed in the imaging system; The actual distance from the spectroscopic system to the transmission layer of the sample is calculated based on the penetration depth and the distance data. In the step of designing the receiving system to match the position and size of the modulated light field and recording the focal plane position of the modulated light field, the focal plane position c of the modulated light field has been measured. At this time, the distance a+b is inconsistent with c, and the sample is in a defocused state.

2. The blood flow imaging method based on light field modulation technology according to claim 1, characterized in that: If the deviation value is a positive value, the deviation position is above the transmission layer of the sample; if the deviation value is a negative value, the deviation position is below the transmission layer of the sample.

3. A blood flow imaging system based on light field modulation technology, using a blood flow imaging method based on light field modulation technology as described in any one of claims 1-2, characterized in that: The invention comprises a host computer, a laser light source, a spatial light modulator, a detector, a servo control system, a lifting control platform, a laser ranging module and a spectroscopic system. The spatial light modulator, the detector and the servo control system are respectively connected to the host computer, the lifting control platform and the laser ranging module are respectively connected to the servo control system, the laser light source is connected to the spatial light modulator, and the spectroscopic system is connected to the laser light source and the laser ranging module.

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