A method for diffuse optical tomography of blood oxygenation concentration and saturation based on voxels

Abstract

The application discloses a kind of diffuse light blood oxygen concentration and saturation tomography method based on voxel, it is related to biological tissue blood oxygen imaging technical field, comprising: preparation phantom 1 and phantom 2;The measured tissue is divided into individual voxel unit;Light probe combination S-D is arranged respectively to phantom 1, phantom 2 and measured tissue surface on the surface of phantom 1, phantom 2 and measured tissue, and form individual light probe combination S-D array;Obtain light intensity experimental data and Monte Carlo simulation data;According to light intensity experimental data, the average absorption coefficient of measured tissue is calculated;For each light probe combination, according to Beer's law, obtain the equation set of all light probe combinations;Equation set is solved by iteration, and three-dimensional tomography of blood oxygen is obtained.The application uses the above-mentioned diffuse light blood oxygen concentration and saturation tomography method based on voxel, and can obtain the tomographic image of tissue blood oxygen concentration and saturation by twice phantom measurement calibration using a small amount of light probe combination photon signal.

Description

Technical Field

[0001] This invention relates to the field of biological tissue oxygenation imaging technology, and in particular to a voxel-based diffuse light oxygenation concentration and saturation tomographic imaging method. Background Technology

[0002] Blood oxygenation in biological tissues is an important physiological parameter. In brain tissue, stroke or central nervous system stimulation can cause changes in tissue microcirculation, leading to oxygen metabolism disorders and even symptoms of hypoxia. In breast tissue, the hypermetabolic characteristics of breast cancer in women can cause accelerated microcirculation and insufficient oxygen supply, resulting in decreased oxyhemoglobin concentration (OHCH). ) decrease, deoxyhemoglobin concentration ( ) rise and blood oxygen saturation ( The decrease in oxygen saturation. Therefore, measuring or imaging tissue blood oxygenation is an essential physiological function detection technique. Here, blood oxygen saturation is defined as the concentration of oxyhemoglobin (OHH). ) at total hemoglobin concentration ( + The percentage of [HbO2] is calculated as: StO2 = 100% × ([HbO2] / [HbO2] + [Hb]).

[0003] Near-infrared diffuse optical tomography (DOT) is an important imaging technique for detecting blood oxygenation in biological tissues. The principle involves placing multiple light sources and detectors on the surface of the tissue being measured, forming multiple light source-detector (SD) arrays. Different light sources sequentially emit a large number of photons into the tissue. After several scattering or absorption events within the tissue, some photons return to the tissue surface and are collected by the detectors, thus acquiring the photon signal. During signal processing, the light intensity data collected by the detectors is used to reconstruct the tissue. and The process of creating a three-dimensional image is called blood oxygenation tomography. Since the main absorbers in biological tissues are oxyhemoglobin, deoxyhemoglobin, and water, the absorption coefficients of two or more wavelengths are used to determine the oxygenation concentration. It can be calculated , and .

[0004] However, obtaining the concentrations of oxyhemoglobin and deoxyhemoglobin from the acquired photon information through tomographic imaging (i.e., obtaining [HbO2] and [Hb] on each three-dimensional image voxel) is a complex process; traditional DOT imaging requires extremely expensive sinusoidal modulation optical equipment and uses the finite element method (FEM) for image reconstruction (i.e., the computational process of converting photon information into blood oxygenation imaging). FEM discretizes the tissue under test into a large number of voxel units and obtains the discrete form of the differential equations of photon transmission in these voxel units, forming a solution matrix; furthermore, the blood oxygen concentration of each voxel unit is obtained by solving the matrix. and And calculate the voxel unit. Information is used to complete a three-dimensional image of blood oxygenation. Although the FEM method can obtain blood oxygenation images at different tissue depths (i.e., tomographic imaging), the discrete form based on differential equations requires a large number of SD combinations (greater than 300) to obtain a stable three-dimensional image, which greatly increases the hardware cost of the light source and detector. If a small number of SD combinations (<50) are used to obtain photon information, the blood oxygenation imaging of FEM is extremely unstable and has a large error.

[0005] Another relatively simple method is to collect the light intensity of the SD array at different times, obtain the change in light intensity, and estimate the change in the absorption coefficient within the tissue based on the modified Beer-Lambert (MBL) law. ), and further calculate the changes in the concentrations of oxyhemoglobin and deoxyhemoglobin at two different time points (i.e. and However, this method cannot obtain the absolute values ​​of oxyhemoglobin and deoxyhemoglobin concentrations (i.e., and Furthermore, it is impossible to obtain blood oxygen saturation ( ).

[0006] Another relatively simple method is to obtain the blood oxygen saturation (including oxygen saturation) of the area covered by each SD array based on the light intensity data collected from each SD array. , and The average value of blood oxygenation in a given area is used as the local oxygenation value. By stitching together the oxygenation values ​​of all local areas, a global blood oxygenation image, i.e., a two-dimensional blood oxygenation topography map, can be obtained. This method is simple to calculate and produces stable results. Furthermore, it requires only a small number of SD combinations (less than 50) to achieve imaging, resulting in low equipment costs. However, this method only produces a two-dimensional blood oxygenation topography map and cannot reflect the changes in blood oxygenation at different depths within the tissue. Summary of the Invention

[0007] The purpose of this invention is to provide a voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, this invention provides a voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method, comprising the following steps: S1. Prepare two solid or liquid phantoms with similar absorption and scattering coefficients to the tissue, and name them phantom 1 and phantom 2; S2, the tissue to be tested is divided into Individual element unit; S3. The optical detection array SD is respectively placed on the surfaces of phantom 1, phantom 2, and the tissue to be tested, forming... A combined optical detector SD array; S4. Optical intensity experimental data of each optical probe combination on phantom 1, phantom 2 and the tested tissue are obtained by optical experiment measurement, and Monte Carlo simulation data of each optical probe combination is obtained by Monte Carlo simulation. S5. For each optical probe combination, the average absorption coefficient of the tested tissue is calculated based on the light intensity experimental data obtained from phantom 1, phantom 2, and the tissue under test. ; S6. For each optical detector combination, according to Beer's Law, obtain the equation system for all optical detector combinations; S7. Solve the equations in S6 using an iterative method to calculate the imaging parameters of each voxel unit, thereby obtaining three-dimensional tomographic imaging of blood oxygenation.

[0009] Preferably, the optical detector assembly SD in S3 includes a light source S and a detector D.

[0010] Preferably, the Monte Carlo simulation data in S4 includes photon packet energy and transmission path length; A photon packet is a combination of photons on the same path.

[0011] Preferably, the average absorption coefficient in S5 Obtained through the following formula: ; in, and The absorption coefficients are those of phantom 1 and phantom 2, respectively. , and The light intensity signals obtained from phantom 1, phantom 2, and the tissue under test are respectively.

[0012] Preferably, the average absorption coefficient This includes the absorption coefficients of water and hemoglobin in the tested tissue, with the water absorption coefficient being... Given the parameters, the absorption coefficient of hemoglobin in the tested tissue is obtained using the following formula: ; In the formula, The absorption coefficient of hemoglobin in the tested tissue.

[0013] Preferably, S6 includes: S61. For each photodetector combination, according to Beer's Law, obtain a linear equation containing the concentration of oxyhemoglobin, the concentration of deoxyhemoglobin, the known extinction coefficient, the photon path weight, and the average absorption coefficient of hemoglobin in the tissue being tested for each voxel unit. S62, Obtained from the linear equation in S61 The equations for the optical detector combination are as follows: ; In the formula, and The first The concentrations of oxyhemoglobin and deoxyhemoglobin in individual docitocytes; and Oxyhemoglobin and deoxyhemoglobin respectively The known extinction coefficient of the wavelength; It is the first Under the combination of optical detectors, the photon at the first Path weights of individual units; It is the first The average absorption coefficient of hemoglobin in the tested tissue obtained under a combination of optical detectors.

[0014] Preferably, the path weight It can be obtained through the following two formulas: ; ; In the formula, Representative at the k Under the SD combination of the first optical detector combination, the first The photon packet passed through the first Normalized photon path of individual units, Representing the The energy of each photon packet is total. A photon packet.

[0015] Preferably, the normalized photon path Obtained through the following formula: ; In the formula, This is the photon path.

[0016] Preferably, the imaging parameters in S7 include oxyhemoglobin concentration, deoxyhemoglobin concentration, and blood oxygen saturation.

[0017] Preferably, S7 includes: right By substituting variables into the equations for the optical detector combination, we obtain the following equation: ; In the formula, ( k =1,.., MJ ; j =1,...,2 n ) is in S62 or and The combination; For S62 or Variable substitution; Blood oxygen measurement requires Near-infrared light of various wavelengths is used to detect the tissue being tested. All the above equations are arranged vertically to form... L The system of equations in the above form can be summarized as follows: ; In the formula, The coefficients of the above system of equations The matrix formed represents the near-infrared light of the first wavelength. 1~ MJ The coefficient of the row is ,... For the second wavelength of near-infrared light, of MJ +1~2 MJ The coefficient of the row is ,... ; and so on, for the first L Near-infrared light of various wavelengths, of MJ ( L -1)+1~ MJL The coefficient of the row is ,... ; For the above variables A column vector composed of elements indicates that the elements of the vector are... ,... ; Let be the vector formed by the right-hand terms of the above system of equations, representing the near-infrared light for the first wavelength. 1~ MJ Vector elements are ,... For the second wavelength of near-infrared light, of MJ +1~2 MJ Vector elements are ,... ; and so on, for the first L Near-infrared light of various wavelengths, of MJ ( L -1)+1~ MJL Vector elements are ,... ; The above equation is solved using the following iterative method: Let's first simplify this system of equations as follows: ; In the formula, * denotes matrix multiplication; The first of which The equations are: ; In the formula, For the above matrix The k Line number j Column elements represent the S62 or and The combination; Unknown variables The initial value is: ; The initial values ​​are defined in the following form: ; In the formula, The term on the right-hand side of the above system of equations is the first... k The element represents the element. The average absorption coefficient of hemoglobin in the tested tissue obtained under a single optical detection combination; After determining the above initial values, let And perform the following algebraic calculations: ; in, Represents the current value; Represents the updated value; represent The first of the matrix OK; The above calculation traversal Matrix 1~ MJL Okay, the specific expression for the second-order modulus square is: ; In a definite As Perform recursive calculations; The above calculation traversal Matrix 1- MJL Line up, and repeat this process until all are finished. When the following formula is satisfied: ; Then stop the recursive calculation and obtain Let be the blood oxygen concentration of each voxel unit to be determined; where, 1 to The component numbered 1~ The concentration of oxyhemoglobin in voxel unit 1; of +1 to 2 The component numbered 1~ The deoxyhemoglobin concentration [Hb] of voxel unit number, and the oxygen saturation of each voxel as the percentage of oxyhemoglobin in the total hemoglobin of that voxel number, are shown in the following formula: ; In the formula, Blood oxygen saturation This refers to the concentration of oxyhemoglobin. This refers to the concentration of deoxyhemoglobin. The above voxel unit results are mapped to any 3D visualization platform to obtain 3D tomographic imaging of blood oxygen.

[0018] Therefore, the present invention employs the above-mentioned voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method, which has the following beneficial effects: (1) Compared with the existing FEM method, this method can use fewer optical probe combinations (less than 50) to obtain tomographic imaging of tissue blood oxygen concentration and saturation, which greatly saves equipment costs.

[0019] (2) This method, through two phantom measurements and calibrations, compared with the existing MBL method, uses the same optical array to not only obtain tomographic imaging of absolute blood oxygen concentration, but also to calculate tomographic imaging of blood oxygen saturation.

[0020] (3) This method can make full use of the path weight of each voxel unit in the tissue during photon transmission and separate the blood oxygen concentration of different voxels by solving a system of linear equations. Compared with the existing two-dimensional blood oxygen topography method, it can obtain three-dimensional images of blood oxygen concentration and blood oxygen saturation at different depths of the tissue.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a flowchart of a voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to the present invention. Figure 2 A schematic diagram of a three-dimensional organization model divided into voxel units is provided for an embodiment of the present invention; Figure 3 A schematic diagram showing the distribution of the optical detection assembly on the surface of the tissue being tested, provided in an embodiment of the present invention; Figure 4 The following are schematic diagrams of oxyhemoglobin concentration in breast tissue at different depths, provided for embodiments of the present invention: (a) is a schematic diagram of oxyhemoglobin concentration in breast tissue at a depth of 0.5 cm; (b) is a schematic diagram of oxyhemoglobin concentration in breast tissue at a depth of 1.0 cm; (c) is a schematic diagram of oxyhemoglobin concentration in breast tissue at a depth of 1.5 cm; (d) is a schematic diagram of oxyhemoglobin concentration in breast tissue at a depth of 2.0 cm; (e) is a schematic diagram of oxyhemoglobin concentration in breast tissue at a depth of 2.5 cm; and (f) is a schematic diagram of oxyhemoglobin concentration in breast tissue at a depth of 3.0 cm. Figure 5 The following are schematic diagrams of deoxyhemoglobin concentration in breast tissue at different depths, provided for embodiments of the present invention: (a) is a schematic diagram of deoxyhemoglobin concentration in breast tissue at a depth of 0.5 cm; (b) is a schematic diagram of deoxyhemoglobin concentration in breast tissue at a depth of 1.0 cm; (c) is a schematic diagram of deoxyhemoglobin concentration in breast tissue at a depth of 1.5 cm; (d) is a schematic diagram of deoxyhemoglobin concentration in breast tissue at a depth of 2.0 cm; (e) is a schematic diagram of deoxyhemoglobin concentration in breast tissue at a depth of 2.5 cm; and (f) is a schematic diagram of deoxyhemoglobin concentration in breast tissue at a depth of 3.0 cm. Figure 6The following are schematic diagrams of blood oxygen saturation concentration in breast tissue at different depths, provided for embodiments of the present invention: (a) is a schematic diagram of blood oxygen saturation concentration in breast tissue at a depth of 0.5 cm; (b) is a schematic diagram of blood oxygen saturation concentration in breast tissue at a depth of 1.0 cm; (c) is a schematic diagram of blood oxygen saturation concentration in breast tissue at a depth of 1.5 cm; (d) is a schematic diagram of blood oxygen saturation concentration in breast tissue at a depth of 2.0 cm; (e) is a schematic diagram of blood oxygen saturation concentration in breast tissue at a depth of 2.5 cm; and (f) is a schematic diagram of blood oxygen saturation concentration in breast tissue at a depth of 3.0 cm. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] Example Please see Figures 1-6 This invention provides a voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method, comprising the following steps: S1. Prepare two solid or liquid phantoms with absorption and scattering coefficients similar to those of the tissue, named Phantom 1 and Phantom 2. The main components of Phantom 1 and Phantom 2 are: carbon black or black ink (providing the medium for photon absorption), titanium dioxide or fat emulsion (providing the medium for photon scattering), and distilled water. The absorption coefficients of Phantom 1 and Phantom 2 can be obtained through calculations of the standard formulation and measurements using a spectrometer. and ,here It refers to a specific wavelength in the near-infrared light band (i.e., 650nm~900nm); and > .

[0026] S2, the tissue to be tested is divided into Individual unit, ,in, , and The number of units in the three spatial directions of the tested tissue is determined respectively.

[0027] In this embodiment, the tissue being tested is the subject's left breast, such as... Figure 2 As shown, the tissue under test was divided into 1536 (16×6×6) voxel units. Eight × 6 photodetector assemblies were placed on the surface of the tissue, divided into eight groups. Each group included one light source and six detectors surrounding that light source. During data acquisition, the eight light sources emitted light sequentially, and the six detectors simultaneously collected photons emitted from the tissue surface, thus completing the data acquisition for the eight × 6 photodetector assemblies.

[0028] S3. The optical detector assembly SD is deployed onto the surfaces of phantom 1, phantom 2, and the tissue to be tested, respectively. The optical detector assembly SD includes a light source S and a detector D, and has a total of [number missing]. A combination of optical detectors is deployed on it, forming A combined optical detector SD array, the combined optical detector SD array includes Each light source is surrounded by [number] light sources. Each detector has a light source, and the distance between each detector varies (typically 1-4 cm). For example... Figure 3 The diagram shown is a schematic representation of the distribution of the light source and detector (i.e., the optical detector assembly) on the surface of the tissue being tested in this embodiment. The position of the light source. This indicates the location of the detector.

[0029] S4. Optical intensity experimental data for each photodetector combination on phantom 1, phantom 2, and the tested tissue were obtained through optical experiments. Monte Carlo simulation data for each photodetector combination was obtained through Monte Carlo simulation. The Monte Carlo simulation data includes photon packet energy and transmission path length. A photon packet is a combination of photons with the same path.

[0030] The photon packet energy and path are obtained through photonic Monte Carlo simulation. The process is as follows: For any given photodetector combination SD, and the optical properties of the tissue under test are set, the absorption, scattering and transmission of the photon packet in the tissue under test model are simulated by computer to obtain the energy and transmission path of the detected photon packet.

[0031] In this embodiment, near-infrared light at wavelengths of 830nm and 690nm was used to measure the left breast of the subject. The absorption coefficients of phantom 1 and phantom 2 were 0.05cm⁻¹ and 0.05cm⁻¹, respectively. -1 and 0.01cm -1 .

[0032] S5. For each optical detector combination, the average absorption coefficient of the tested tissue is calculated based on the known absorption coefficients of phantom 1 and phantom 2, as well as the experimental data of light intensity obtained on phantom 1, phantom 2, and the tested tissue. Average absorption coefficient Obtained through the following formula: ; in, and The absorption coefficients are those of phantom 1 and phantom 2, respectively. , and The light intensity signals obtained from phantom 1, phantom 2, and the tissue under test are respectively.

[0033] Average absorption coefficient This includes the absorption coefficients of water and hemoglobin within the tested tissue, due to the water absorption coefficient. Given the parameters, the absorption coefficient of hemoglobin in the tested tissue can be obtained using the following formula: ; In the formula, The absorption coefficient of hemoglobin in the tested tissue.

[0034] S6. For each optical detector assembly, using a wavelength of... Near-infrared light is used to detect breast tissue. To separate the hemoglobin concentration of different voxels (i.e., blood oxygenation imaging), a set of equations for all optical detection combinations is obtained according to Beer's Law. Specifically, these include: S61. For each photodetector combination, according to Beer's Law, obtain a linear equation containing the concentration of oxyhemoglobin, the concentration of deoxyhemoglobin, the known extinction coefficient, the photon path weight, and the average absorption coefficient of hemoglobin in the tissue being tested for each voxel unit. S62, Obtained from the linear equation in S61 The equations for the optical detector combination are as follows: ; In the formula, and The first The concentrations of oxyhemoglobin and deoxyhemoglobin in individual docitocytes; and Oxyhemoglobin and deoxyhemoglobin respectively The known extinction coefficient of the wavelength; It is the first Under the combination of optical detectors, the photon at the first The path weight of individual units (i.e., the product of normalized photon path and energy, which can be obtained through Monte Carlo simulation of photon propagation within tissues). It is the first The average absorption coefficient of hemoglobin in the tested tissue obtained under a combination of optical detectors.

[0035] Path weight Obtained through the following two formulas (two methods): The first method: ; The second method: ; In the formula, Representative at the k Under the SD combination of the first optical detector combination, the first The photon packet passed through the first Normalized photon path of individual units, Representing the The energy of each photon packet is total. Each photon packet. Among them, the photon path... Energy of photon packets All of these can be obtained through Monte Carlo simulations of photon propagation within tissues, where a photon packet is a combination of photons on the same path.

[0036] Normalized photon path Obtained through the following formula: ; In the formula, This is the photon path.

[0037] S7. Solve the equations in S6 iteratively to calculate the imaging parameters for each voxel unit, thereby obtaining a three-dimensional tomographic image of blood oxygenation. The imaging parameters include oxyhemoglobin concentration, deoxyhemoglobin concentration, and blood oxygen saturation.

[0038] The iterative process is as follows: Perform the following variable substitutions: , ; , ; , ; , ; In the formula, ( k =1,.., MJ ; j =1,...,2 n ) is in S62 or and The combination; For S62 or Variable substitution.

[0039] right By substituting variables into the equations of the optical detector combination, the equations can be rewritten as follows: ; Blood oxygen measurement requires ( ≥2) Near-infrared light of different wavelengths is used to detect the tissue being tested. All the above equations are arranged vertically to form... L The system of equations in the above form can be summarized as follows: ; In the formula, The coefficients of the above system of equations The matrix formed represents the near-infrared light of the first wavelength. 1~ MJ The coefficient of the row is ,... For the second wavelength of near-infrared light, of MJ +1~2 MJ The coefficient of the row is ,... ; and so on, for the first L Near-infrared light of various wavelengths, of MJ ( L -1)+1~ MJL The coefficient of the row is ,... ; For the above variables The column vector formed by this vector, that is, the elements of this vector are ,... ; Let the vector be the right-hand side terms of the above system of equations, that is, for the first wavelength of near-infrared light, 1~ MJ Vector elements are ,... For the second wavelength of near-infrared light, of MJ +1~2 MJ Vector elements are ,... ; and so on, for the first LNear-infrared light of various wavelengths, of MJ ( L -1)+1~ MJL Vector elements are ,... ; In this embodiment, L =2, meaning that near-infrared light at wavelengths of 830nm and 690nm was used to obtain light intensity experimental data for two phantoms and a human mammary gland, path weight. Determined according to the second method.

[0040] The above equation is solved using the following iterative method: Let's first simplify this system of equations as follows: ; In the formula, * denotes matrix multiplication.

[0041] The first of which The equations are: ; In the formula, For the above matrix The k Line number j Column elements represent the S62 or and The combination; Unknown variables The initial value is: ; The initial values ​​are defined in the following form: ; In the formula, The term on the right-hand side of the above system of equations is the first... k The element, i.e., the th element The average absorption coefficient of hemoglobin in the tested tissue obtained under a combination of optical detectors.

[0042] After determining the above initial values, let And perform the following algebraic calculations: ; in, Represents the current value; Represents the updated value; represent The first of the matrix OK.

[0043] The above calculation traversal Matrix 1~ MJLOkay, the specific expression for the second-order modulus square is: ; In a definite As Perform recursive calculations.

[0044] The above calculation traversal Matrix 1- MJL Line up, and repeat this process until all are finished. When the following formula is satisfied: ; Then stop the recursive calculation and obtain Let be the blood oxygen concentration of each voxel unit to be determined; where, 1 to The component numbered 1~ The concentration of oxyhemoglobin in voxel unit 1; of +1 to 2 The component numbered 1~ The deoxyhemoglobin concentration [Hb] of voxel unit number, and the oxygen saturation of each voxel as the percentage of oxyhemoglobin in the total hemoglobin of that voxel number, are shown in the following formula: ; In the formula, Blood oxygen saturation This refers to the concentration of oxyhemoglobin. This refers to the concentration of deoxyhemoglobin.

[0045] The above voxel unit results are mapped to any 3D visualization platform to obtain 3D tomographic imaging of blood oxygen.

[0046] Therefore, the present invention employs the aforementioned voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method. Through two phantom measurements and calibrations, it can stably obtain tomographic images of tissue blood oxygen concentration and saturation using a small number of photon signals (less than 50).

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method, characterized in that, Includes the following steps: S1. Prepare two solid or liquid phantoms with similar absorption and scattering coefficients to the tissue, and name them phantom 1 and phantom 2; S2, the tissue to be tested is divided into Individual element unit; S3. The optical detection array SD is respectively placed on the surfaces of phantom 1, phantom 2, and the tissue to be tested, forming... A combined optical detector SD array; S4. Optical intensity experimental data of each optical probe combination on phantom 1, phantom 2 and the tested tissue are obtained by optical experiment measurement, and Monte Carlo simulation data of each optical probe combination is obtained by Monte Carlo simulation. S5. For each optical probe combination, the average absorption coefficient of the tested tissue is calculated based on the light intensity experimental data obtained from phantom 1, phantom 2, and the tissue under test. ; S6. For each optical detector combination, according to Beer's Law, obtain the equation system for all optical detector combinations; S7. Solve the equations in S6 using an iterative method to calculate the imaging parameters of each voxel unit, thereby obtaining three-dimensional tomographic imaging of blood oxygenation.

2. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 1, characterized in that: The optical detector assembly SD in S3 includes a light source S and a detector D.

3. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 2, characterized in that: The Monte Carlo simulation data in S4 includes photon packet energy and transmission path length; A photon packet is a combination of photons on the same path.

4. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 3, characterized in that, The average absorption coefficient in S5 Obtained through the following formula: ； in, and The absorption coefficients are those of phantom 1 and phantom 2, respectively. , and The light intensity signals obtained from phantom 1, phantom 2, and the tissue under test are respectively.

5. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 4, characterized in that: The average absorption coefficient This includes the absorption coefficients of water and hemoglobin in the tested tissue, with the water absorption coefficient being... Given the parameters, the absorption coefficient of hemoglobin in the tested tissue is obtained using the following formula: ； In the formula, The absorption coefficient of hemoglobin in the tested tissue.

6. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 5, characterized in that, S6 includes: S61. For each photodetector combination, according to Beer's Law, obtain a linear equation containing the concentration of oxyhemoglobin, the concentration of deoxyhemoglobin, the known extinction coefficient, the photon path weight, and the average absorption coefficient of hemoglobin in the tissue being tested for each voxel unit. S62, Obtained from the linear equation in S61 The equations for the optical detector combination are as follows: ； In the formula, and The first The concentrations of oxyhemoglobin and deoxyhemoglobin in individual docitocytes; and Oxyhemoglobin and deoxyhemoglobin respectively The known extinction coefficient of the wavelength; It is the first Under the combination of optical detectors, the photon at the first Path weights of individual units; It is the first The average absorption coefficient of hemoglobin in the tested tissue obtained under a combination of optical detectors.

7. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 6, characterized in that: The path weight It can be obtained through the following two formulas: ； ； In the formula, Representative at the k Under the SD combination of the first optical detector combination, the first The photon packet passed through the first Normalized photon path of individual units, Representing the The energy of each photon packet is total. A photon packet.

8. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 7, characterized in that: The normalized photon path Obtained through the following formula: ； In the formula, This is the photon path.

9. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 8, characterized in that: The imaging parameters in S7 include oxyhemoglobin concentration, deoxyhemoglobin concentration, and blood oxygen saturation.

10. The voxel-based diffuse light blood oxygen concentration and saturation tomographic imaging method according to claim 9, characterized in that, The S7 includes: right By substituting variables into the equations for the optical detector combination, we obtain the following equation: ； In the formula, ( k =1,.., MJ ; j =1,...,2 n ) is in S62 or and The combination; For S62 or Variable substitution; Blood oxygen measurement requires Near-infrared light of various wavelengths is used to detect the tissue being tested. All the above equations are arranged vertically to form... L The system of equations in the above form can be summarized as follows: ； In the formula, The coefficients of the above system of equations The matrix formed represents the near-infrared light of the first wavelength. 1~ MJ The coefficient of the row is ,... For the second wavelength of near-infrared light, of MJ +1~2 MJ The coefficient of the row is ,... ; and so on, for the first L Near-infrared light of various wavelengths, of MJ ( L -1)+1~ MJL The coefficient of the row is ,... ; For the above variables A column vector composed of elements indicates that the elements of the vector are... ,... ; Let be the vector formed by the right-hand terms of the above system of equations, representing the near-infrared light for the first wavelength. 1~ MJ Vector elements are ,... For the second wavelength of near-infrared light, of MJ +1~2 MJ Vector elements are ,... ; and so on, for the first L Near-infrared light of various wavelengths, of MJ ( L -1)+1~ MJL Vector elements are ,... ; The above equation is solved using the following iterative method: Let's first simplify this system of equations as follows: ； In the formula, * denotes matrix multiplication; The first of which The equations are: ； In the formula, For the above matrix The k Line number j Column elements represent the S62 or and The combination; Unknown variables The initial value is: ； The initial values ​​are defined in the following form: ； In the formula, The term on the right-hand side of the above system of equations is the first... k The element represents the element. The average absorption coefficient of hemoglobin in the tested tissue obtained under a single optical detection combination; After determining the above initial values, let And perform the following algebraic calculations: ； in, Represents the current value; Represents the updated value; represent The first of the matrix OK; The above calculation traversal Matrix 1~ MJL Okay, the specific expression for the second-order modulus square is: ； In a definite As Perform recursive calculations; The above calculation traversal Matrix 1- MJL Line up, and repeat this process until all are finished. When the following formula is satisfied: ； Then stop the recursive calculation and obtain Let be the blood oxygen concentration of each voxel unit to be determined; where, 1 to The component numbered 1~ The concentration of oxyhemoglobin in voxel unit 1; of +1 to 2 The component numbered 1~ The deoxyhemoglobin concentration [Hb] of voxel unit number, and the oxygen saturation of each voxel as the percentage of oxyhemoglobin in the total hemoglobin of that voxel number, are shown in the following formula: ； In the formula, Blood oxygen saturation This refers to the concentration of oxyhemoglobin. This refers to the concentration of deoxyhemoglobin. The above voxel unit results are mapped to any 3D visualization platform to obtain 3D tomographic imaging of blood oxygen.

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