A method for preparing a scattering-based optical mold and a human tissue simulation device

Abstract

The application discloses a preparation method of a scattering-based light mold and a human tissue simulation device, which comprises the following steps: initially constructing a relation model of each mold unit in the light mold to be prepared and different human tissues; constructing an absorption coefficient expression of a graphite powder model; constructing a complete relation model of each mold unit in the light mold to be prepared and different human tissues; according to the measurement results in steps two and three, taking μ a and μ s of different human tissues as target values, calculating the data required in the mold unit for simulating the human tissues; preparing the mold unit according to the related data obtained in the above step; repeating the above steps to obtain a second light absorption mold unit for simulating human tissues to be prepared until a predetermined number of mold units are obtained, and a light mold is formed. The model is a solid model, which is not deformed, not deteriorated, has good toughness, is resistant to pulling, and can be stored for a long time.

Description

Technical Field

[0001] This invention relates to the field of near-infrared scattering light detection technology, and in particular to a method for preparing a scattering-based light mold and a human tissue simulation device. Background Technology

[0002] Near-infrared brain imaging (NIBI) is widely used in non-invasive functional imaging and monitoring of the nervous system. It measures changes in the concentrations of oxyhemoglobin and deoxyhemoglobin in the cerebral cortex during activation, resting, or inhibition to reflect activity, cognitive function, and connectivity between relevant brain regions. However, precision issues remain in the manufacturing process of NIBI. Existing blood oxygen saturation simulation devices have short shelf lives, are prone to deformation, and are unstable, failing to meet simulation requirements and thus unable to accurately calibrate the NIBI imaging module.

[0003] Currently, there are many methods for simulating human tissue. The liquid model of Intralipid + Indian ink is currently recognized as a good model for simulating the optical properties of biological tissue. However, the properties of Intralipid produced by different manufacturers are unstable and prone to deterioration, resulting in poor consistency. The literature "Research on Tissue Oxygenation Quantitative Monitoring Method Based on Near-Infrared Multispectral Spatial Resolution Technology" proposes to add agarose to the above liquid model to turn the model into a solid to simulate the optical parameters of human brain tissue. However, this agarose model is also prone to deformation and deterioration, cannot be preserved for a long time, and has poor consistency. To simulate tissue oxygen saturation, many models use blood for simulation. For example, the literature "A Method for Non-invasive Detection of Tissue Oxygen Saturation Using Near-Infrared Spectroscopy" proposes using bovine hemoglobin to simulate the relationship between transmission spectra and oxygen saturation at different oxygen saturation levels. The paper "Near-Infrared Spatial Resolution Spectroscopy and Its Application in Non-invasive Detection of Brain Oxygen" uses whole blood from normal individuals + Intralipid + buffer solution to simulate biological tissue. Oxygen is introduced to increase the oxygen saturation of the model to 100%, and then sodium dithionate, an oxygen-consuming agent, is gradually added to simulate tissue oxygen consumption. However, the above simulation devices using blood products are also prone to deterioration, and the simulation requires oxygen and oxygen-consuming agents, making the operation process cumbersome and difficult to standardize.

[0004] In Part 2-71 of the People's Republic of China National Standard GB9706.271-2022, it is necessary to develop reflective functional near-infrared spectral phantoms with good repeatability and to invent a mechanism that allows light loss to vary between 3 dB and 4 dB. However, current functional near-infrared spectral phantoms still follow the requirements of transmission-type functional near-infrared spectral phantoms. Since functional near-infrared spectrometers are based on biological scattering for imaging, there is currently a lack of solutions for scattering-based functional near-infrared spectral phantoms. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a scattering-based light mold and a human tissue simulation device to address the above-mentioned shortcomings, thereby solving the problem that existing near-infrared brain functional imaging instruments lack scattering-type near-infrared spectral phantoms with good repeatability.

[0006] This invention is achieved through the following scheme:

[0007] A method for fabricating a scattering-based optical mold, comprising the following steps:

[0008] Step 1: Preliminary construction of a model showing the relationship between each mold unit in the optical mold to be prepared and different tissues in the human body:

[0009] Step 2: Construct the expression for the absorption coefficient of the graphite powder model;

[0010] Step 3: Construct a complete model showing the relationship between each mold unit in the optical mold to be prepared and different tissues in the human body;

[0011] Step 4: Based on the measurement results in Steps 2 and 3, calculate the μ value for different human tissues. a and To find the target value, calculate the data required in the current simulated human tissue mold unit;

[0012] Step 5: Based on the data obtained in Step 4, prepare the mold unit;

[0013] Step 6: Repeat steps 1 to 5 to obtain the second type of light absorption mold unit for simulating human tissue, until a predetermined number of mold units are obtained to form a light mold.

[0014] Step one specifically involves:

[0015] Based on diffuse reflection theory, the light energy flux generated by a continuous point light source in a medium is:

[0016]

[0017] In the formula It is the light energy flux at a distance L from the point light source. Indicates the diffusion coefficient of the medium. It is the effective scattering coefficient. Where g is the scattering coefficient and g is the anisotropy factor. Where L is the absorption coefficient and L is the distance from the detector point to the point light source; multiplying both sides of the equation by L and taking the natural logarithm, we can transform it into:

[0018]

[0019] From the above equation, we can see that when D remains constant, It is a constant. The line has a linear relationship with L, and its slope is K= By changing L, the light energy flux of the measured model changes with L. Plotting this value allows us to determine the slope K of the straight line with respect to L, thus obtaining the value:

[0020]

[0021] Wherein, the absorption coefficient of the model have:

[0022]

[0023] Here and Each is added to the model And the absorption coefficient of graphite powder (cm) -1 ).

[0024] Step two specifically involves the calculation of the absorption coefficient of graphite powder concentration, as follows:

[0025]

[0026] Where μ a-gp The absorption coefficient is the concentration of graphite powder, expressed in cm⁻¹. -1 T is the model thickness in cm, and I0 and I represent the incident and emitted light intensities, respectively; after transformation, we get:

[0027]

[0028] in, The specific value can be directly measured by the spectrophotometer reading, and the absorption coefficient of the graphite powder model with a known thickness can be obtained by the above formula.

[0029] Step three can be specifically derived by combining the formulas from steps one and two:

[0030]

[0031] As can be seen from the above equation, if the concentration of TiO2 in the absorption medium in the model remains constant, For a constant value, and The relationship is linear, and the slope of the straight line is The intercept is It can be changed Draw multiple straight lines, and obtain the slope and intercept of each line. From these, calculate the... The value of .

[0032] Step three can specifically involve: making at least 20 changes. The value of TiO2 was determined, and the concentration was varied at least five times to reduce the prediction error. The root mean square value of the fitting residuals was calculated to ensure the accuracy of the measurement results. Finally, the accurate value was calculated. The value of .

[0033] In step four, the specific data required in the current simulated human tissue mold unit are calculated as follows: the concentration of graphite powder and TiO2 to be added to the current simulated human tissue mold unit, as well as the thickness of the mold unit.

[0034] In step five, the preparation of the mold unit specifically involves adding TiO2 and graphite powder to highly transparent silicone, stirring thoroughly with a shear force mechanical rotor, pouring the mixture into a mold, defoaming under negative pressure, and solidifying at room temperature to ultimately form a light absorption mold unit that simulates human tissue.

[0035] The present invention also discloses a near-infrared human tissue simulation device based on scattering, including a base, a light mold, an incident light source and a detector; the base is provided with a fixed cavity adapted to the shape of the light mold, the light mold is disposed on the fixed cavity, the light mold includes multiple mold units, and each mold unit can simulate the light absorption effect of different components of the human body by adding different concentrations of TiO2 and graphite powder.

[0036] Based on the structure of the aforementioned near-infrared human tissue simulation device based on scattering, both the base and the optical mold are made of highly transparent silicone, and the incident light source and detector are respectively set on opposite end faces of the optical mold.

[0037] Based on the structure of the above-mentioned near-infrared human tissue simulation device based on scattering, the base is hemispherical, and the fixing cavity is located at the center of the arc surface of the hemispherical base.

[0038] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0039] 1. This method uses transparent silicone as the base material, adding TiO2 to simulate the optical scattering properties of tissues. By changing the concentration of graphite powder (gp), different absorption coefficients are simulated, thereby simulating the optical properties of different human tissues. This model is a solid model, non-deformable, non-deteriorating, with good toughness and tensile strength, and can be preserved for a long time. It solves the problems of current near-infrared brain functional imaging devices for simulating blood oxygen saturation, such as easy deterioration, poor consistency, and cumbersome operation.

[0040] 2. The high-transparency silicone in this solution has excellent transparency, can transmit light without causing light scattering and absorption, and is resistant to high temperature, oxidation, and yellowing. It also has good softness and plasticity, and can simulate the hardness of tissues.

[0041] 3. This method adds light absorbers and scatterers to highly transparent silicone and adjusts the concentration to simulate the optical properties of tissues.

[0042] 4. This scheme uses special model properties to simulate the optical propagation characteristics of the imaging process of a functional near-infrared spectrometer based on light scattering. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the near-infrared human tissue simulation device based on scattering according to the present invention;

[0044] The markings in the diagram are: 1. Base; 2. Optical mold; 3. Incident light source; 4. Detector; 5. Fixing cavity; 6. Mold unit; 7. Optical path. Detailed Implementation

[0045] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0046] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0047] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a predetermined orientation, or be constructed and operated in a predetermined orientation. Therefore, they should not be construed as limitations on this invention.

[0048] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0049] Example 1

[0050] like Figure 1 As shown, the present invention provides a technical solution:

[0051] A near-infrared human tissue simulation device based on scattering includes, but is not limited to, a base 1, a light mold 2, an incident light source 3, and a detector 4. The base 1 is provided with a fixed cavity 5 adapted to the shape of the light mold 2. The light mold 2 is disposed on the fixed cavity 5. The light mold 2 includes multiple mold units 6. Each mold unit 6 can simulate the light absorption effect of different components of the human body by adding different concentrations of TiO2 and graphite powder. Both the base 1 and the light mold 2 are made of highly transparent silicone. The incident light source 3 and the detector 4 are respectively disposed on opposite end faces of the light mold 2.

[0052] Based on the above structure, the fixed cavity 5 is used to fix the optical mold 2, and the incident light source 3 is used to emit light. When the light passes through the mold unit 6 at different positions on the optical mold 2, different absorption rates will be generated. Finally, the light is detected by the detector 4 to complete the entire measurement process. This can effectively improve the accuracy of the near-infrared brain functional imaging system. The solid-state reflective near-infrared spectral phantom in this solution is non-deformable, non-deteriorating, has good toughness, and is resistant to tension. It can be stored for a long time and can solve the problems of easy deterioration, poor consistency, and cumbersome operation of the current near-infrared brain functional imaging simulated human tissue optical mold device.

[0053] As an example, the base 1 can be hemispherical, and the fixing cavity 5 is located at the center of the arc surface of the hemispherical base 1.

[0054] Example 2

[0055] This invention provides a technical solution for the preparation of the optical mold 2 in Preparation Example 1;

[0056] A method for fabricating a scattering-based optical mold, comprising the following steps:

[0057] Step 1: Preliminary construction of the relationship model between each mold unit 6 in the optical mold 2 to be prepared and different human tissues:

[0058] According to the theory of diffusion, in an infinitely large medium, the light energy flux produced by a continuous point light source of unit intensity placed isotropically is:

[0059] (1)

[0060] In the formula It is the light energy flux at a distance L from the point light source. Indicates the diffusion coefficient of the medium. It is the effective scattering coefficient. Where g is the scattering coefficient and g is the anisotropy factor. Where L is the absorption coefficient and L is the distance from the detection point to the point light source; multiplying both sides of equation (1) by L and taking the natural logarithm, we can obtain:

[0061] (2)

[0062] From equation (2), we can see that when D remains constant, It is a constant. The line has a linear relationship with L, and its slope is K= Therefore, by changing L, the change in the light energy flux of the measured model with respect to L can be plotted to obtain the slope K of the straight line with respect to L, and thus the value can be obtained as follows:

[0063] (3)

[0064] Wherein, the absorption coefficient of the model have:

[0065] (4)

[0066] Here and Each is added to the model The absorption coefficient of graphite powder (GP);

[0067] Step 2: Construct the expression for the absorption coefficient of the graphite powder model;

[0068] Graphite powder is a strong absorbing medium. To control the optical absorption properties of a model, different absorption coefficients can be obtained by changing the concentration of graphite powder. The calculation method for the absorption coefficient based on graphite powder concentration is as follows:

[0069] (5)

[0070] Where μ a-gp The absorption coefficient is the concentration of graphite powder, expressed in cm⁻¹. -1 T represents the model thickness in cm, and I0 and I represent the incident and emitted light intensities, respectively. After a simple transformation, we can obtain:

[0071] (6)

[0072] in, The absorption coefficient of a graphite powder model with a known thickness can be obtained by measuring the readings of a spectrophotometer and using the above formula.

[0073] Step 3: Construct a complete model showing the relationship between each mold unit 6 in the optical mold 2 to be prepared and different tissues in the human body;

[0074] From equations (3) and (4) in the preliminary calculation process, and combined with the expressions (5) and (6) for the absorption coefficient of graphite powder, the following can be derived:

[0075] (7)

[0076] As can be seen from equation (7), if the concentration of TiO2 in the absorption medium in the model remains constant, For a constant value, and The relationship is linear, and the slope of the straight line is The intercept is It can be changed Draw multiple straight lines, and obtain the slope and intercept of each line. From these, calculate the... The value of .

[0077] Theoretically, change twice It can be concluded that The value will be changed at least 20 times to avoid instability of the light source and other systematic errors, and to ensure the accuracy of the experiment. The value of TiO2 was determined, and the concentration was varied at least five times to reduce the prediction error. The root mean square value of the fitting residuals was calculated to ensure the accuracy of the measurement results. Finally, the accurate value was calculated. The value of .

[0078] Step 4: Based on μ in Step 2 and Step 3 a and The measurement results, in μ of different human tissues a and With the target value, the specific graphite powder concentration and TiO2 concentration that need to be added to the mold unit 6 of the current simulated human tissue, as well as the thickness of the mold unit 6, can be calculated. By making the light mold 2 part that simulates different human tissues, the light loss of light in different human tissues is simulated to evaluate the optical properties of the near-infrared brain function imager.

[0079] Step 5: Based on the relevant data obtained in Step 4, add TiO2 and graphite powder to the high-transparency silicone, stir thoroughly with a shear force mechanical rotor, pour into a mold, defoam under negative pressure, and solidify at room temperature to finally form a light absorption mold unit 6 that simulates human tissue.

[0080] Step 6: Repeat steps 1 to 5 to obtain the second type of light absorption mold unit 6 for simulating human tissue, until a predetermined number of mold units 6 are obtained to form the light mold 2.

[0081] Transparent silica gel can be replaced by highly transparent gel wax, agarose, and other materials that can form a matrix.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a light mold based on scattering, wherein Includes the following steps: Characterized by: Step 1: Initially construct a model showing the relationship between each mold unit in the optical mold to be prepared and different tissues in the human body; specifically, Step 1 involves: Based on diffuse reflection theory, the light energy flux generated by a continuous point light source in a medium is: In the formula It is the light energy flux at a distance L from the point light source. Indicates the diffusion coefficient of the medium. It is the effective scattering coefficient. Where g is the scattering coefficient and g is the anisotropy factor. Where L is the absorption coefficient and L is the distance from the detector point to the point light source; multiplying both sides of the above equation by L and taking the natural logarithm, we get... From the above equation, we can see that when D remains constant, It is a constant. The line has a linear relationship with L, and its slope is K= By changing L, the change in the light energy flux of the model with respect to L is measured, and the slope K of the straight line with respect to L is plotted. The obtained value is: Wherein, the absorption coefficient of the model have: Here and Each is added to the model And the absorption coefficient of graphite powder; Step 2: Construct the expression for the absorption coefficient of the graphite powder model; Step 3: Construct a complete model showing the relationship between each mold unit in the optical mold to be prepared and different tissues in the human body; Step 3 specifically involves: combining the derivation of formulas from Step 1 and Step 2: As can be seen from the above equation, if the concentration of TiO2 in the absorption medium in the model remains constant, For a constant value, and The relationship is linear, and the slope of the straight line is The intercept is By changing Draw multiple straight lines, and obtain the slope and intercept of each line. From these, calculate the... The value; Step 4: Based on the measurement results in Steps 2 and 3, calculate the μ value for different human tissues. a and To obtain the target value, calculate the data required in the mold unit of the current simulated human tissue; in step four, the data required in the mold unit of the current simulated human tissue specifically includes: the concentration of graphite powder and TiO2 to be added to the mold unit of the current simulated human tissue, as well as the thickness of the mold unit. Step 5: Based on the relevant data obtained in Step 4, prepare the mold unit; In Step 5, the preparation of the mold unit specifically involves adding TiO2 and graphite powder to high-transparency silicone, stirring thoroughly with a shear force mechanical rotor, pouring into a mold, defoaming under negative pressure, and solidifying at room temperature to finally form a light absorption mold unit that simulates human tissue. Step 6: Repeat steps 1 to 5 to obtain the second type of light absorption mold unit for simulating human tissue, until a predetermined number of mold units are obtained to form a light mold.

2. The method for preparing a scattering-based optical mold as described in claim 1, characterized in that: Step two specifically involves the calculation of the absorption coefficient of graphite powder concentration, as follows: Where μ a-gp The absorption coefficient is the concentration of graphite powder, expressed in cm⁻¹. -1 T is the model thickness in cm, and I0 and I represent the incident and emitted light intensities, respectively; after transformation, we get: in, The specific value can be directly measured by the spectrophotometer reading, and the absorption coefficient of the graphite powder model with a known thickness can be obtained by the above formula.

3. The method for preparing a scattering-based optical mold as described in claim 2, characterized in that: Step three specifically involves making at least 20 changes. The value of TiO2 was determined, and the concentration was varied at least five times to reduce the prediction error. The root mean square value of the fitting residuals was calculated to ensure the accuracy of the measurement results. Finally, the accurate value was calculated. The value of .

4. A near-infrared human tissue simulation device based on scattering, characterized in that: The device includes a base, an optical mold obtained by any one of claims 1 to 3, an incident light source, and a detector; the base is provided with a fixed cavity adapted to the shape of the optical mold, the optical mold is disposed on the fixed cavity, the optical mold includes multiple mold units, and each mold unit can simulate the light absorption effect of different components of the human body by adding different concentrations of TiO2 and graphite powder.

5. The near-infrared human tissue simulation device based on scattering as described in claim 4, characterized in that: Both the base and the optical mold are made of highly transparent silicone, and the incident light source and detector are respectively set on opposite end faces of the optical mold.

6. The near-infrared human tissue simulation device based on scattering as described in claim 5, characterized in that: The base is hemispherical, and the fixing cavity is located at the center of the arc surface of the hemispherical base.

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