CN102058393B - Method for measuring skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement - Google Patents

Abstract

The invention provides a method for measuring based on reflection spectrumThe invention relates to a method and a system for measuring skin physiological parameters and optical characteristic parameters. The invention provides more accurate corresponding data of the reflected light intensity and the skin optical characteristic parameters by an analysis method combining experimental data and Monte Carlo simulation, the skin physiological parameters and the optical characteristic parameters based on the reflection spectrum measurement are obtained by calculating and fitting the data and a plurality of physiological parameters on the basis of the actually measured reflection spectrum when the skin of a sample is actually measured, and finally the skin absorption coefficient mu is measured in a non-invasive way in a nondestructive and real-time manner_aAnd reduced scattering coefficient mu_s' etc. and physiological information such as melanin content, deoxyhemoglobin, oxyhemoglobin content, moisture content, etc.

Description

Measuring method of skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement

technical field

The invention belongs to the fields of spectral technology application and biomedical engineering, and relates to a method for measuring skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement. the

Background technique

In recent years, the use of optical means for medical diagnosis and treatment has gradually attracted widespread attention from biomedical researchers. Compared with other medical detection technologies such as X-ray, CT, and nuclear magnetic resonance, optical technology can implement non-destructive structural and functional detection of tissues in a non-invasive manner, and has the advantages of wide application range, high portability, and low cost. The parameters of tissue optical properties describe the response of biological tissue to incident light of different wavelengths by evaluating the optical properties of tissue such as absorption and scattering. Quantitative evaluation of optical characteristic parameters in tissue will help to optimize the diagnostic depth of optical diagnostic methods in biological tissue and the imaging quality of optical imaging technology in biological tissue. On the other hand, quantitative analysis can be given to the energy intensity of optical therapy reaching the treatment site, which is helpful to optimize the treatment dose of optical therapy. In addition, the tissue optical characteristic parameters are determined by the physiological state of the tissue. For example, the absorption of visible and near-infrared wavelengths in skin tissue is mainly contributed by melanin, oxygenated hemoglobin, deoxyhemoglobin and water in the skin. The level of absorption intensity in this wavelength range reflects the level of these substances. Therefore, the measurement results of skin optical parameters can further reflect changes in skin physiological parameters, thereby giving an objective and scientific evaluation of the physiological state of the skin surface. the

As the largest and most important organ of the human body, the thickness of the skin is about 0.5-4mm, and the total weight accounts for about 8% of the human body. The skin contains about 1/3 of the circulating blood and about 1/4 of the water in the human body. Optical characteristic parameters such as absorption coefficient μa and reduced scattering coefficient μ's of skin tissue are of great significance to theoretical research and clinical practice of laser diagnosis, laser therapy, and light dosimetry. Melanin is the main absorbing substance in the epidermis of the skin, and its concentration is directly related to the degree of fairness of the skin and the formation of pigmentation spots. An appropriate concentration of melanin can block the impact of excessive ultraviolet radiation on the skin. The concentration of melanin in the epidermis of healthy people is between 1% and Between 10% (see S.L.Jacques, "Origins of tissue optical properties in the UVA, visible, and NIR regions," in Advances in Optical Imaging and PhotonMigration, R.R.Alfano and J.G.Fujimoto, eds. (Optical Society of America), 1996) . Oxygenated hemoglobin and deoxygenated hemoglobin in the skin are related to the microcirculation state of the skin tissue, reflecting the strength of tissue metabolism. The total concentration of oxygenated hemoglobin and deoxygenated hemoglobin in the skin of healthy people, that is, the total hemoglobin content, is between 0.2% and 7% ( See E. Angelopoulou, "Understanding the color of human skin," Proc. SPIE 4299, 243-251, 2001), and the proportion of oxygenated hemoglobin in total hemoglobin, that is, the blood oxygen saturation is between 0% and 100%. (see D. Yudovsky and L. Pilon, "Rapid and accurate estimation of bloodsaturation, melanin content, and epidermis thickness from spectral diffuse reflection", Applied Optics, 2010). The moisture content in the skin is an important indicator that affects skin elasticity and physiological state, and the moisture content of healthy human skin is between 15% and 70% (see R.R.Warner, M.C.Myers and D.A.Taylor, "Electron Probe Analysis of Human Skin: Determination of the Water Concentration Profile", Journal of Investigative Dermatology, 1988). the

There are two main methods for measuring tissue optical characteristic parameters. One is to measure the spatial distribution of light after passing through the tissue. By analyzing the spatial distribution information of light, the contribution of the reduced scattering coefficient of the tissue to the light intensity attenuation is calculated from the tissue absorption coefficient to the light intensity attenuation. Separated from the attenuation of light intensity. The other is to use the pulsed laser as the light source, and use the time-domain light intensity signal obtained by the detector to calculate the degree to which the received signal is affected by tissue scattering, so as to determine the optical characteristic parameters of the tissue. The method of measuring tissue optical characteristic parameters by using light intensity distribution requires multiple detectors to receive the attenuated light intensity transmitted by the light source through the tissue at different distances, and the tissue optical characteristic parameters must be consistent within the distance range. (See F. Bevilacqua, D. Piguet, etc., "In vivolocal determination of tissue optical properties: applications to human brain". Applied Optics, 1999) In order to obtain better absorption and scattering resolution, a larger measurement range is required, but The complexity of skin tissue structure makes it impossible for large-scale measurements to meet the conditions of tissue homogeneity. Therefore, it is difficult to apply to skin tissue. The time-domain method for measuring tissue optical properties requires the use of pulsed lasers and detectors with a time resolution of picoseconds (see B.J.Tromberg, N.Shah et al., "Non-Invasive In Vivo Characterization of Breast Tumors Using Photon Migration Spectroscopy" , Neoplasia, 2000) equipment is expensive and poor in implementability. the

Contents of the invention

In view of the limitations of the above-mentioned prior art methods for the measurement of skin optical characteristic parameters, the technical problem to be solved by the present invention is to provide more accurate reflection light intensity and skin optical characteristic parameters through an analysis method combining experimental data and Monte Carlo simulation. Corresponding data, based on the actual measured reflectance spectrum when actually measuring the sample skin, calculate and fit the data with multiple physiological parameters to obtain skin physiological parameters and optical characteristic parameters based on reflectance spectrum measurement, and finally in a non-invasive way Non-destructive, real-time measurement of optical characteristic parameters such as skin absorption coefficient μ _a and reduced scattering coefficient μ _s ', as well as physiological information such as melanin content, deoxygenated hemoglobin, oxygenated hemoglobin content, and water content.

The present invention first uses Monte Carlo calculation to obtain the simulated standard data Tmc, uses the fat emulsion solution to mix India ink to simulate the biological tissue to carry out the tissue model experiment, obtains the experimental standard data Texp of the tissue reflection light intensity under the corresponding optical characteristic parameters based on the experimental records, and The simulated standard data Tmc is calibrated by the experimental standard data Texp to obtain the final optimized standard data T. the

For the actual measurement sample, obtain the sample reflectance spectrum curve, use the final optimized standard data T, and reduce the scattering coefficient μ _s ' by calculating the melanin concentration M, total hemoglobin content B, blood oxygen saturation S, water content W, and wavelength 500nm _500nm , Rayleigh scattering content f and other parameters are fitted to obtain the simulated reflectance spectrum curve closest to the sample reflectance spectrum curve. At this time, the physiological parameters melanin concentration M, total hemoglobin content B, blood oxygen saturation S, water content W, and Further obtain the absorption coefficient μa and the reduced scattering coefficient μs' of the skin at all wavelengths.

At the same time, the present invention further includes a skin physiological parameter and optical characteristic parameter measurement system with a calculation module, and the system includes: a measurement device for the skin reflectance spectrum, a calculation and display device. The measuring device of the skin reflection spectrum includes: a wide-spectrum light source, a spectrum detector, an incident optical fiber, a reflection probe, a receiving optical fiber, a reflection probe bracket, and a data transmission line. The calculation and display device includes an analog-to-digital conversion module, a calculation module, a memory, a display processing module, a display, and a data bus. The measured experimental data of the tissue model is transmitted to the calculation and display device through the data transmission line. Stored in the memory after analog-to-digital conversion, the calculation module uses Monte Carlo calculation to obtain the simulated standard data Tmc, and calls the tissue model experimental data stored in the memory to obtain the experimental standard data Texp to calibrate the simulated standard data Tmc to obtain the final The standard data T is optimized and stored in memory. the

When measuring the reflection spectrum of the skin to be tested, the reflection spectrum of the skin to be tested and the reflection spectrum of the reflection standard sheet are respectively measured, and the measurement data is transmitted to the calculation and display device through the data transmission line. Stored in the memory after analog-to-digital conversion, the calculation module calibrates the skin measurement data with the reflectance standard sheet data to obtain the measured skin reflectance spectrum. The calculation module calls the optimized standard data T, and uses a nonlinear iterative algorithm to calculate the corresponding skin fitting reflectance spectrum under different skin tissue physiological parameters. Comparing the calculated fitted reflectance spectrum with the measured skin reflectance spectrum, the physiological parameters corresponding to the measured skin reflectance spectrum are obtained, and further calculation is performed to obtain the skin optical characteristic parameters μ _a and μ _s ' at all wavelengths, and the measured results and skin The reflectance spectrum image is displayed on the monitor.

The task of the present invention is to provide a method for measuring skin physiological parameters and optical characteristic parameters and a system for measuring skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement. the

Realize the concrete technical scheme of the present invention is:

The method for measuring skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement provided by the present invention comprises the following steps:

Step 1: Calculate the optimization data T representing the functional relationship between the optical characteristic parameters and the reflected light intensity, including the following sub-steps:

a) configure standard tissue model solution;

b) measuring the optical characteristic parameters of the standard tissue model solution;

c) Place the front end of the incident fiber and the reflective fiber in parallel into the standard tissue model solution, the other end of the incident fiber is connected to the light source, the light source provides incident light covering the wavelength range of 400-1000nm, and the other end of the reflective fiber is connected to the spectrometer, record 400- The experimental data Texp of the tissue reflection light intensity corresponding to the optical characteristic parameters in the 1000nm wavelength range;

d) Using the Monte Carlo method to simulate the simulated data Tmc of the reflected light intensity under the condition of inputting the optical characteristic parameters of the tissue model solution;

e) seek the constant K value that makes the variance of K Tmc-Texp the minimum time;

f) Take K Tmc as the optimization data T of the functional relationship between the optical characteristic parameters and the reflected light intensity

Step 2: Measuring skin physiological parameters and optical characteristic parameters, including the following sub-steps:

1) Contact the front ends of the incident fiber and reflective fiber that are the same as those in step 1 c) with the clean and flat skin surface to be tested, and connect the other end of the incident fiber to the light source, which provides incident light covering the wavelength range of 400-1000nm. The other end of the optical fiber is connected to the spectrometer to record the reflected light intensity M(λ) of the skin in the wavelength range of 400-1000nm;

2) Place the front end faces of the incident optical fiber and the reflective optical fiber above the reflective standard sheet, and record the reflected light intensity M _std (λ) of the standard sheet;

3) The normalized measured skin reflectance spectrum is $\mathrm{wxya}\left(\mathrm{\λ}\right)=\frac{m\left(\mathrm{\λ}\right)}{m_{\mathrm{std}}\left(\mathrm{\λ}\right)};$

4) Set four physiological parameters and two scattering parameters: the initial value range of melanin content M0 is 1%-10%, preferably 5%; the initial value range of hemoglobin content B0 is 0.2%-7%; preferably 0.3%; blood oxygen saturation The initial value range of degree S0 is 0%-100%, preferably 75%; the initial value range of moisture content _W0 is 15%-70%, preferably ₆₀ %; 200, preferably 50; the initial value of Rayleigh scattering content f0 ranges from 0% to 100%, preferably 50%;

5) Calculate the absorption coefficient and the reduced scattering coefficient of the skin tissue at each wavelength through the physiological parameters, and calculate the corresponding standard reflected light intensity from the optimized data T obtained in step 1 for the absorption coefficient and the reduced scattering coefficient;

6) Combination step two 1) The reflected light intensity calculated under the measured wavelength obtains the predicted reflection spectrum pSPR(λ);

7) Calculate the error u=∑|mSPR(λ)-pSPR(λ)| between the measured skin reflectance spectrum obtained by calculating the predicted reflectance spectrum and step 2 4);

8) Step 2 4)-7) is repeated cyclically to obtain the physiological parameters corresponding to the measured sample that minimizes the error u;

9) The absorption coefficient μ _a and the reduced scattering coefficient μ _s of the skin of the tested sample are calculated according to the physiological parameters corresponding to the tested sample.

The standard tissue model solution in the method of the present invention is obtained by configuring the fat emulsion solution and India ink, and the configured standard tissue model solution is composed of 32 groups of solutions with different concentrations, and the concentration of the fat emulsion in the solution is one of the following four: 20%, 5%, 1.25%, 0.3125%; the concentration of India ink in the solution is one of the following 8: 0, 0.0015%, 0.003%, 0.013%, 0.023%, 0.048%, 0.073%, 0.098%;

The present invention measures the optical characteristic parameter of standard tissue model solution and comprises the following steps:

i) Select the measurement wavelength;

ii) measuring the luminous flux M _(r) of the measurement wavelength for the standard tissue model solution at a distance from the light source position r;

iii) Change the distance r between the reflection fiber optic probe and the light source n times, and measure the luminous flux M _(r) i respectively, where i=2, 3, 4...n;

iv) Carry out linear fitting of ln(r * M _(r) ) to the distance r, and calculate the slope 1/δ ₀ of the fitted curve;

v) adding ink to the solution, the absorption coefficient in the tissue model solution increased is _Δμa , and the absorption coefficient _Δμa is obtained by measuring the absorbance of the ink with a spectrophotometer;

vi) Taking the solution added with ink as the object, re-carry out steps ii)-iv) for the wavelength, and calculate the slope 1/ _δ1 of the fitting curve at this time;

vii) Through the following equations

$\left\{\begin{array}{c}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="0"\; label="s"\; filenames="HDA0000030168970000031.png"\; state="\{\{state\}\}">s</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}\\ \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="0"\; label="s"\; filenames="HDA0000030168970000031.png"\; state="\{\{state\}\}">s</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}\\ {{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\end{array}\right.$

Calculate the optical characteristic parameters μ _a0 and μ _s0 ′ of the standard tissue model solution;

The reflection standard sheet described in the above method has a reflectivity of 99.9% at visible and near-infrared wavelengths. the

The skin physiological parameter and optical characteristic parameter measurement system provided by the present invention is composed of a skin reflection spectrum measurement device and a calculation and display device. The skin reflection spectrum measurement device is composed of a wide-spectrum light source, a spectrum detector, an incident optical fiber, a receiving optical fiber, Reflection probe, adjustable height reflection probe bracket, data transmission line, the reflection probe is composed of the front end of the incident light fiber, the front end of the receiving fiber, the metal shell located at the front end of the incident fiber and the outer periphery of the front end of the receiving fiber, and the front end of the incident light fiber and the receiving fiber. The front end of the optical fiber and the filler between the inner wall of the metal shell are composed, the front end of the receiving optical fiber is fixed at the center of the reflection probe, and the front end of the incident optical fiber is arranged in a circular ring at equal intervals around the front end of the receiving optical fiber; the calculation and display device consists of a modulus Transformation module, calculation module, memory, display processing module, display and data bus; The calculation and display device is connected to the analog-to-digital conversion module; in the calculation and display device, the calculation module is connected to the analog-to-digital conversion module, memory, and display processing module through a data bus, and the display processing module is directly connected to the display. The calculation module of the measurement system of the present invention can adopt a 32-bit microcontroller, and the display processing module can adopt a VGA drive chip. the

Measuring principle of skin physiological parameters and optical characteristic parameters of the present invention

The following is a detailed introduction to the measurement principle of skin physiological parameters and optical characteristic parameters according to the design of this system. This example is divided into three parts: reflection spectrum measurement method; establishment of final optimized standard data T; acquisition of skin physiological parameters and optical characteristic parameters. the

1. Reflectance spectrum measurement method

When measuring the skin reflectance spectrum, the reflectance probe is vertically in soft contact with the surface of the skin tissue (contact but not deformed), and the composite light generated by the light source enters the incident optical fiber through the coupler, and enters the skin tissue through the incident optical fiber. The optical fiber probe 4 is in direct contact with the surface of the skin tissue, avoiding two interface losses of the optical fiber medium/air and air/skin tissue after the incident light leaves the incident optical fiber. Simultaneously because the optical fiber probe 4 is in direct contact with the skin tissue surface, the 80 micron interval between the incident optical fiber and the receiving optical fiber makes the incident light must be transmitted through the skin tissue to enter the receiving optical fiber. In this embodiment, after the incident light enters the skin tissue through the incident optical fiber, it is received by the receiving optical fiber through the absorption of epidermal melanin, dermal oxyhemoglobin, deoxygenated hemoglobin, water and other absorbing media and the scattering of dermal collagen and other scattering media. The reflected light intensity is transmitted through the receiving optical fiber and enters the spectrometer. In the grating CCD spectrometer, the incident light is dispersed by the grating according to its wavelength, and the 3648-pixel CCD records the reflection spectrum within the wavelength range of 400-1000nm. Since the incident light of different wavelengths is fully dispersed by the high-resolution grating, each pixel detects the light intensity values at different wavelengths. The light intensity measurement data M(λ) at all wavelengths are transferred to the memory in the calculation and display device for storage. the

Because the light intensity M detected by the spectrometer is not only affected by the reflected light intensity R(λ) produced by the transmission attenuation in the skin, but also affected by the light intensity S(λ) of the light source, the collection efficiency G of the optical fiber, and the response D(λ) of the detector. influence, namely:

M(λ)＝S(λ)R(λ)GD(λ)

标准片(美国海洋光学公司)与探头表面固定距离处测量反射光强：  In order to eliminate the influence of other factors such as the dependence of light source and detector wavelength on the measurement of skin spectrum in the system, a reflectance of 99% is used.

Measure the reflected light intensity at a fixed distance between the standard sheet (Ocean Optics, USA) and the probe surface:

Mstd(λ)＝S(λ)Rstd(λ)Gstd D(λ)

When calibrating light source intensity and detector wavelength response, the difference from skin tissue measurement is that the position of the optical fiber probe is adjusted using prefabricated firmware so that the distance between the end face of the optical fiber probe and the upper surface of the reflection standard is a fixed value d, in this example d = 5cm. the

Then this result can be used for calibration of reflected light intensity:

$\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; GD</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; G</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}$

K is a constant that has no wavelength dependence on the fiber efficiency, and R _std (λ) is also a constant of 99% at visible and near-infrared wavelengths. Assuming the constant k=R _std (λ)/K, then the calibration of the reflected light intensity of the skin tissue is:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; std</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}$

The R(λ) curve in Figure 9 is the typical data for measuring the skin reflectance spectrum. the

2. Establishment of final optimized standard data T

In order to analyze the skin tissue reflectance spectrum, the tissue optical property parameters are measured. In this example, the final optimized standard data T is first established. In this example, the corresponding relationship between the skin absorption coefficient μ _a and the reduced scattering coefficient μ _s ' and the reflected light intensity measured by the probe is obtained through model experiments combined with monte carlo simulation analysis. The specific steps can be divided into three parts: model experiment, Monte Carlo simulation and using experimental data to calibrate the simulation results:

1) Tissue model experiment The tissue model solution prepared by fat emulsion solution (Guangzhou Baite Qiaoguang Medical Supplies Co., Ltd.) and India ink (Beijing Suolaibao Technology Co., Ltd.) was used to simulate biological tissue. The fat emulsion solution provides scattering in the tissue model solution and the India ink solution provides absorption in the tissue model solution. Standard tissue model solutions with different optical property parameters were obtained by adjusting the concentrations of fat emulsion solution and India ink. Put the reflectance fiber optic probe into multiple groups of model solutions to measure the reflectance spectrum. Because the tissue model solution has different absorption coefficients and reduced scattering coefficients at each wavelength within the spectral measurement range. Only need to configure 32 sets of model solutions (4 concentrations of fat emulsion: 20%, 5%, 1.25%, 0.3125%; 8 concentrations of India ink: 0, 0.0015%, 0.003%, 0.013%, 0.023%, 0.048%, 0.073 %, 0.098%) can cover the optical characteristic parameter range of skin tissue, so as to obtain the experimental standard data Texp based on the tissue reflected light intensity recorded in the experiment. The concentration of fat emulsion and India ink solution in each standard tissue model solution is shown in Table 1. the

Table I

For each set of configured tissue model solutions, the optical characteristic parameters of the configured tissue model solutions are determined by measuring the luminous flux combined with the method of adding absorbers:

At a specific wavelength, one end of two 400-micron core-diameter step-type multimode fibers is used to connect the light source and the spectrometer respectively, and the other end is placed in the tissue model solution in parallel at a distance r, and the measured light intensity is M _(r) , then it is calculated based on the diffuse approximation of the point light source:

${\mathrm{<span\; class="notranslate">\; m</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; *</span>\frac{{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&pi;Dr</span>}}$

The measured light intensity M _(r) and the luminous flux F (r) at a distance of r from the point light source in the solution differ by a constant K times, where K is related to the light source intensity, optical fiber collection efficiency, and spectrometer response to light intensity. D is the mean free path, and δ is the optical penetration depth. These two parameters can be calculated from the absorption coefficient μa and the reduced scattering coefficient μs':

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}}$

$\mathrm{<span\; class="notranslate">\; \&delta;</span>}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; D.</span>}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}}<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}}$

For the same sample and the same wavelength, the parameters K, D and δ are all constants that do not change with r, so the calculation formula of M _(r) can be rewritten as:

$\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="K"\; filenames="HDA0000030168970000021.png"\; state="\{\{state\}\}">K</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&pi;D</span>}}<span\; class="notranslate">\; )</span>$

For the same solution, its absorption coefficient and reduced scattering coefficient are set to μ _a0 and μ _s0 ′, change the distance r between the measuring fibers, measure the luminous flux M _(r) at different distances, set ln(r*M _(r) ) for the distance r for linear fitting, then 1/δ ₀ is the slope of the fitting curve, and because:

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="0"\; label="s"\; filenames="HDA0000030168970000031.png"\; state="\{\{state\}\}">s</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}$

After obtaining the slope 1/δ ₀ , the first equation characterizing the relationship between μ _a0 and μ _s0 ′ is determined,

And by adding ink to the solution, the absorption coefficient Δμ _a in the tissue model solution can be increased without changing its reduced scattering coefficient μ _s0 ′, where Δμ _a is the absorption coefficient produced by adding ink, which can be measured by a spectrophotometer Obtained by measuring the absorbance of the ink, then by measuring the fitting curve of M _(r) , 1/δ ₁ can be obtained, at this time:

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="0"\; label="s"\; filenames="HDA0000030168970000031.png"\; state="\{\{state\}\}">s</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}$

By solving the system of equations:

$\left\{\begin{array}{c}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="0"\; label="s"\; filenames="HDA0000030168970000031.png"\; state="\{\{state\}\}">s</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}\\ \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="0"\; label="s"\; filenames="HDA0000030168970000031.png"\; state="\{\{state\}\}">s</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}\\ {{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\end{array}\right.$

The optical characteristic parameters μ _a0 and μ _s0 ′ of each group of tissue model solutions can be calculated.

Connect the reflectance spectrum measuring device in this example, put the reflectance spectrum probe into the model solution, and measure the reflectance spectrum of each group of tissue model solution samples. Calibrate with a reflective standard sheet, and record the reflected light intensity at each wavelength within the measured wavelength range. Because the optical properties of the tissue model solution samples are different at each wavelength, and the optical property parameters in each group of samples overlap each other, it can be obtained by measuring the 32 groups of tissue model solutions in this example. Within the range of the skin optical property parameters, The experimental standard data Texp of tissue reflected light intensity corresponding to different absorption coefficient μ _a and reduced scattering coefficient μ _s '.

2) In this example, Monte Carlo simulation is further used to analyze the transmission distribution of the photons in the skin tissue after leaving the incident optical fiber. Figure 3 shows that when μ _a =2.1870cm ^-1 and μ _s ' = 64cm ^-1 , after the incident light enters the tissue from the incident light on the right, it leaves the Monte Caro simulation results. Calculate the total reflected light intensity that finally escapes from the range of the receiving optical fiber on the contact surface of the reflection probe, so as to obtain the received light intensity of the reflection probe for theoretical simulation.

After several simulations, the received light intensity that can be detected by the reflection probe is calculated under the conditions of different absorption coefficient μ _a and reduced scattering coefficient μ _s ' within the range of skin optical characteristic parameters. Thus, the simulated standard data Tmc obtained by Monte Carlo simulation is obtained.

Fig. 4 is the reflected light intensity standard data Tmc obtained by Monte Carlo simulation for the example of the inventive device. It can be seen from the figure that when the reduced scattering coefficient in the tissue remains constant and the absorption coefficient increases gradually, the reflected light intensity detected by the probe gradually decreases. While the absorption coefficient in the tissue remains unchanged, the reflected light intensity detected by the probe increases with the enhancement of the reduced scattering coefficient when the tissue scattering is small, and decreases with the enhancement of the reduced scattering coefficient when the tissue scattering is large. It can also be seen from the results of the standard data of reflected light intensity that the probe used in this example is more sensitive to the change of scattering, insensitive to the change of absorption when the absorption coefficient is low, and sensitive to the change of absorption coefficient when the absorption coefficient is high more sensitive. As for skin tissue, since the dermis has a large number of capillaries and is closer to the skin surface, it provides a large amount of absorption in the skin tissue within the detection range of the probe. Therefore, the probe is very suitable for detecting changes in physiological parameters of skin tissue, changing absorption and reduced scattering coefficients in the tissue. the

3) Due to the experimental error of Texp obtained by the experimental measurement has certain fluctuations, and the Tmc obtained by the Monte Carlo simulation is a theoretically perfect value, without considering the experimental attenuation such as optical fiber receiving efficiency and transmission loss in the actual experiment, resulting in the simulation The result differs from the measured result by a constant factor k. Therefore, in this embodiment, the results of the experimental standard data Texp obtained by the experimental measurement are introduced to calibrate the simulated standard data Tmc, the optimized standard data is set as T=k × Tmc, and the variance of T-Texp is obtained for all data, and the variance is obtained as The coefficient k=k' at the minimum value. the

Then the final optimized standard data is T'=k'*Tmc, and the final optimized standard data T gives the reflected light intensity measured by the probe under different skin absorption coefficient μ _a and reduced scattering coefficient μ _s '. That is, the probe measures the reflected light intensity R=T(μ _a , μ _s ').

3. Acquisition of skin physiological parameters and optical characteristic parameters

1): In the measurement of the actual sample, the CCD spectrometer obtains the reflectance spectrum curve of the skin sample, and the result is shown as the curve indicated by the point in Fig. 9 . the

Because the concentration relationship of melanin, deoxygenated hemoglobin, oxygenated hemoglobin, water and other physiological substances in the skin tissue determines the change of the absorption coefficient in the skin, and the dependence of the absorption coefficient of each component on the wavelength change is constant, so The concentration of physiological substances in the tissue can be directly used to calculate the absorption coefficient of the tissue at different wavelengths. the

The transmission of light in the skin is divided into two parts: the attenuation of the epidermis and the reflection of the dermis, so the calculation formula of the reflection spectrum of the skin sample can be expressed as:

pSPR＝T _epi '*R _derm

Where T _epi is the transmittance of light in the epidermis of the skin, and R _derm is the reflectance of light in the dermis.

The attenuation of light in the epidermis of the skin is only affected by the absorption of melanin, so the transmittance of light in the epidermis of the skin can be expressed as:

T _epi (λ)＝exp(-M*μ _{a_mel} (λ)*L _epi )

Wherein M is the concentration of melanin, Lepi is the optical thickness of the epidermis, the value of a healthy human body is 0.03cm, and μ _{a_mel} (λ) is a set of constants that vary with the wavelength of the melanin absorption coefficient (numerical reference SLJacques, "Origins of tissueoptical properties in the UVA, visible, and NIR regions," in Advances in Optical Imaging and Photon Migration, RRAlfano and JG Fujimoto, eds. (Optical Society of America), 1996).

The reflection of the dermis is determined by the absorption coefficient and the reduced scattering coefficient of the dermis, and the final optimized data T obtained by combining the previous experimental data with the Monte Carlo simulation analysis method gives the optical properties in the skin Within the range that the parameters can obtain, the reflected light intensity corresponding to all possible combinations of the absorption coefficient and the reduced scattering coefficient. the

That is, R _derm (λ)=T(μ _a (λ), μ _s '(λ))

At this time, as long as the absorption coefficient and the reduced scattering coefficient are given, the corresponding reflected light intensity data can be obtained through the final optimization data T. the

2): The absorption medium of the dermis mainly includes deoxygenated hemoglobin, oxygenated hemoglobin and water. Its absorption coefficient can be calculated as:

μ _a (λ)=B*(S*μ _{a_oxy} (λ)+(1-S)*μ _{a_deoxy} (λ))+W*μ _{a_water} (λ)

Wherein B, S, W respectively represent total hemoglobin content, blood oxygen saturation, water content, μ _{a_oxy} (λ), μ _{a_deoxy} (λ), μ _{s_water} (λ), respectively the absorption of oxygenated hemoglobin, deoxygenated hemoglobin and water coefficients, are constants that vary with wavelength (numerical references WGZijlstra, A.Buursma and OWvan Assendelft, "Visible and Near Infrared Absorption Spectraof Human and Animal Haemoglobin", VSP Publishing, Utrecht, 2000; GMHale, MRQuerry, "Optical constants of water in the 200-nm to 200-μm wavelength region" Applied Optics, 1973). The scattering of the dermis is mainly composed of Rayleigh scattering and Mie scattering with small particle size in the skin. Assuming that the reduced scattering coefficient of the dermis at a wavelength of 500nm is μ _s ' _500nm , the wavelength dependence of Rayleigh scattering and Mie scattering is respectively μ _s ' _500nm *(λ/500) ^-4 , μ _s ' _500nm *( λ/500) ^-1 . Therefore, the reduced scattering coefficient of the dermis can be calculated as: μ _s '(λ)=μ _s ' _500nm *(f*(λ/500) ^-4 +(1-f)*(λ/500) ^-1 )

Where f is a parameter representing the Rayleigh scattering content of the dermis. the

Therefore, given the three physiological parameters total hemoglobin content B, blood oxygen saturation S, water content W and two skin scattering property parameters at a wavelength of 500nm, after reducing the scattering coefficient μ _s ' _500nm , the Rayleigh scattering content f is Two optical characteristic parameters, the absorption coefficient μa and the reduced scattering coefficient μs' of the skin dermis, can be calculated.

3): According to the above-mentioned principle, when setting four physiological parameters of melanin concentration M, total hemoglobin content B, blood oxygen saturation S, water content W and two skin scattering property parameters μ _s ' _500nm , Rayleigh scattering content f Then according to the equation system:

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; pSPR</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; mel</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 0.03</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{<span\; class="notranslate">\; ,</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; oxygen</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; deoxy</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; the\; water</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\\ {{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{<span\; class="notranslate">\; ,</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{<span\; class="notranslate">\; ,</span>}}_{\mathrm{<span\; class="notranslate">\; 500</span>}\mathrm{<span\; class="notranslate">\; nm</span>}}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; *</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 500</span>}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 500</span>}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>\end{array}\right.$

That is, the fitting reflectance spectrum curve of the skin sample can be obtained, and the result is shown as the curve represented by the solid line in Fig. 9 . the

4): Through accompanying drawings 5-8, it can be seen that when other parameters are fixed values, the influence of the change of a single physiological parameter on the reflectance spectrum curve, wherein the fixed value parameters are set as: M=0.02, B=0.004, S=0.9, W = 0.60, μ _s ' _500mn = 43.6, f = 0.62.

Therefore, different settings of melanin concentration M, total hemoglobin content B, blood oxygen saturation S, water content W, skin scattering property parameters μ _s ' _500nm , and Rayleigh scattering content f will lead to changes in the fitted reflection spectrum curve. The combined algorithm uses the six parameters as variables to perform curve fitting and calculates the array variance between the fitted reflectance spectrum and the actual measured spectrum, and obtains the values of the six parameters when the variance is the smallest, thus obtaining four physiological parameters The calculated value, and the corresponding optical characteristic parameters are obtained by calculating the six parameters: skin absorption coefficient μa and reduced scattering coefficient μs'.

Description of drawings

Figure 1: It is a schematic diagram of the structure of a measurement device for skin reflectance spectroscopy, where:

1——broad-spectrum light source;

2—spectral detector;

3——Incident fiber;

4——reflection probe;

5——receiving optical fiber;

6——reflection probe bracket;

7——data transmission line;

8—calculation and display device;

Figure 2: is the structural diagram of the reflection probe in the inventive device example, wherein:

3——Incident fiber;

5——receiving optical fiber;

9——fiber cladding;

10——reflection probe;

Figure 3: Monte Carlo simulation results of the reflected light intensity distribution of the tissue in the reflective probe when μ _a =2.1870cm ^-1 and μ _s '=64cm ^-1 for the inventive device;

Figure 4: It is the simulated standard data of reflected light intensity obtained by using Monte Carlo simulation for the example of the inventive device;

Figure 5: It is a trend diagram of the change of the reflectance spectrum with the physiological parameter total hemoglobin content B;

Figure 6: It is the change trend diagram of the reflectance spectrum with the physiological parameter melanin content M;

Figure 7: It is a trend diagram of the change of the reflectance spectrum with the physiological parameter blood oxygen saturation S;

Figure 8: It is a trend diagram of the change of the reflectance spectrum with the physiological parameter water content W;

Figure 9: Spectral fitting and physiological parameter acquisition for the example of the inventive device, the reflection spectrum of this example corresponds to M=1.3% B=0.4% S=92% W=65%:

Fig. 10: Workflow diagram of obtaining skin physiological parameters and tissue optical characteristic parameters by the calculation module. the

Detailed ways

Embodiment 1: Composition of reflection spectrum measurement system

Referring to Figure 1, the structural composition of the system for measuring skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement is introduced:

The measurement system of the skin reflection spectrum includes a measurement device of the skin reflection spectrum and a calculation and display device, wherein the measurement device of the skin reflection spectrum includes 1, a wide-spectrum light source; 2, a spectrum detector; 3, an incident optical fiber; 4, a reflection probe; 5 , receiving optical fiber; 6, reflection probe bracket; 7, data transmission line; the calculation and display device is composed of an analog-to-digital conversion module, a calculation module, a memory, a display processing module, a display, and a data bus. Since the light intensity fluctuation of the halogen tungsten lamp under the stable voltage is small and the continuity with the wavelength change in the visible and near-infrared wavelength range is good, so in this example, the halogen tungsten lamp is used as a wide-spectrum light source to provide the visible and near-infrared wavelength range The continuous incident spectrum in . According to the application conditions, it can also be replaced by other broad-spectrum light sources such as xenon lamps and LED composite light sources. The incident light is connected to the light source through the SMA905 connector, and connected to the reflection probe, which transmits the wide-spectrum incident light provided by the light source to the skin surface. As shown in FIG. 2 for the reflection probe, the incident optical fiber 3 and the receiving optical fiber 5 are both step-type multimode optical fibers with a core diameter of 400 microns. The 6 incident optical fibers surround the receiving optical fiber symmetrically. The distance between the center of the incident fiber and the receiving fiber core is 480 microns, and the fiber cladding 9 is filled around the incident fiber and the receiving fiber within a radius of 740 microns from the center of the reflection probe. Outside the central radius of 740 microns is the metal shell 10 for fixing. In this example, the metal shell is made of aluminum alloy. The receiving optical fiber receives the reflected light from the skin surface from the center of the reflection probe, and transmits the reflected light to the spectral detector through the SMA905 connector. The spectrometer adopts a grating CCD spectrometer, a 3648-pixel CCD, a wavelength range of 400-1000nm, and a wavelength resolution of <1.34nm. The reflection probe bracket 6 can adjust the position of the reflection probe in the vertical direction. The spectrum detector is connected with the analog-to-digital conversion module in the calculation and display device through a data transmission line. the

In the calculation and display device, the calculation module is connected with the analog-to-digital conversion module, the memory and the display processing module through the data bus, and the display processing module is directly connected with the display. The analog-to-digital conversion module uses a 16-bit 4-channel parallel analog-to-digital conversion chip, which is responsible for the A/D conversion of the output data of the spectrometer. The memory is responsible for the storage of reflection spectrum measurement data and standard data T. The calculation module uses a microcontroller with ARM32-bit CPU as the core, which is responsible for the normalized calculation of reflection spectrum, reflection spectrum analysis, acquisition of physiological parameters and optical characteristic parameters. The display processing module uses a VGA driver chip for visual processing of experimental results. the

Embodiment 2: Measurement process of skin physiological parameters and optical characteristic parameters

In actual application, the reflected light intensity optimization data T including a large amount of experimental and Monte Carlo simulation data has been recorded and stored in the storage unit of the computing and display device. The process of using the device to measure tissue physiological parameters and optical characteristic parameters is as follows:

1) Connect the components of the device, place the reflection probe vertically on the clean and flat surface of the skin to be tested, and record the skin reflection light intensity M(λ);

2) Place the reflection probe vertically at a fixed distance d above the reflection standard sheet, and record the reflected light intensity M _std (λ) of the standard sheet;

3) Then the normalized measured skin reflectance spectrum is $\mathrm{wxya}\left(\mathrm{\&lambda;}\right)=\frac{m\left(\mathrm{\&lambda;}\right)}{m_{\mathrm{std}}\left(\mathrm{\&lambda;}\right)};$

4) Set four physiological parameters and two scattering parameters: the initial value range of melanin content M0 is 1%-10%, preferably 5%; the initial value range of hemoglobin content B0 is 0.2%-7%; preferably 0.3%; blood oxygen saturation The initial value range of degree S0 is 0%-100%, preferably 75%; the initial value range of moisture content W0 is 15%-70%, preferably 60%; the reduced scattering coefficient μs'500nm initial value range of wavelength 500nm is 20-200 , preferably 50; the initial value range of Rayleigh scattering content f0 is 0%-100%, preferably 50%;

5) Calculate the absorption coefficient and the reduced scattering coefficient of the skin tissue at each wavelength through the physiological parameters, and calculate the corresponding standard reflected light intensity from the optimized standard data T for the absorption coefficient and the reduced scattering coefficient;

6) Calculate the error u=Σ|mSPR(λ)-pSPR(λ)| between the measured skin reflectance spectrum obtained in 4) and the predicted reflectance spectrum;

7) Repeat the process 4)-6) until the error u reaches the minimum, then the physiological parameters corresponding to the measured sample are obtained: melanin concentration M, total hemoglobin content B, blood oxygen saturation S, moisture content W and skin scattering property parameter μ _s'500nm , f _.

8) Calculate the optical characteristic parameters of the tested sample through the above physiological parameters corresponding to the tested sample: skin absorption coefficient μ _a and reduced scattering coefficient μ _s '.

Figure 9 is a case of healthy male right forearm inner skin reflection spectrum measurement results R(λ) and the calculated reflection spectrum pR(λ) obtained according to the physical parameters and optical characteristic parameters obtained by the nonlinear optimization algorithm. The reflection spectrum corresponds to the obtained melanin content M=1.3%, total hemoglobin content B=0.4%, blood oxygen saturation S=92%, and water content W=65%. The reduced scattering coefficient μ _s ' _500nm = 20.5cm ^-1 at 500nm, the Rayleigh scattering content f = 46%. A total of 20 cases of healthy male right forearm inner skin reflectance spectra were measured by using the device of the example of the present invention, and the obtained skin physiological parameters all conformed to the parameter ranges recorded in the literature.

In order to realize the above method, this embodiment uses such a system for measuring skin physiological parameters and optical characteristic parameters with a calculation module, the system includes: a measurement device for skin reflectance spectrum, a calculation and display device. The measuring device of the skin reflection spectrum includes: a wide-spectrum light source, a spectrum detector, an incident optical fiber, a reflection probe, a receiving optical fiber, a reflection probe bracket, and a data transmission line. The calculation and display device includes an analog-to-digital conversion module, a calculation module, a memory, a display processing module, a display, and a data bus. Stored in the memory after analog-to-digital conversion, the calculation module uses Monte Carlo calculation to obtain the simulated standard data Tmc, and calls the tissue model experimental data stored in the memory to obtain the experimental standard data Texp to calibrate the simulated standard data Tmc to obtain the final The standard data T is optimized and stored in memory. the

The measuring device of the skin reflection spectrum measures the reflection spectrum of the skin to be tested, which respectively measures the reflection spectrum of the skin to be tested and the reflection spectrum of the reflection standard sheet, and the measurement data is transmitted to the calculation and display device through the data transmission line. Stored in the memory after analog-to-digital conversion, the calculation module calibrates the skin measurement data with the reflectance standard sheet data to obtain the measured skin reflectance spectrum. The calculation module calls the optimized standard data T, and uses a nonlinear iterative algorithm to calculate the corresponding skin fitting reflectance spectrum under different skin tissue physiological parameters. Comparing the calculated fitted reflectance spectrum with the measured skin reflectance spectrum, the physiological parameters corresponding to the measured skin reflectance spectrum are obtained, and further calculation is performed to obtain the skin optical characteristic parameters μ _a and μ _s ' at all wavelengths, and the measured results and skin The reflectance spectrum image is displayed on the monitor. Figure 10 shows the workflow of the calculation module for acquiring skin physiological parameters and tissue optical characteristic parameters.

In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included within the scope of protection claimed by the present invention. the

Claims (4)

1. A method for measuring skin physiological parameters and optical characteristic parameters based on reflection spectrum measurement, comprising the steps of: Step 1: Calculate the optimization data T representing the functional relationship between the optical characteristic parameters and the reflected light intensity, including the following sub-steps: a) configuring a standard tissue model solution; b) measuring the optical characteristic parameters of the standard tissue model solution; c) Place the front end of the incident fiber and the reflective fiber in parallel into the standard tissue model solution, the other end of the incident fiber is connected to the light source, the light source provides incident light covering the wavelength range of 400-1000nm, and the other end of the reflective fiber is connected to the spectrometer, record 400- The experimental data Texp of the tissue reflection light intensity corresponding to the optical characteristic parameters in the wavelength range of 1000nm; d) Using the Monte Carlo method to simulate and obtain the simulated data Tmc of the reflected light intensity under the condition of inputting the optical characteristic parameters of the standard tissue model solution; e) Find the constant K value that makes the variance of |K·Tmc-Texp| the smallest; f) taking K Tmc as the optimization data T of the functional relationship between the optical characteristic parameters and the reflected light intensity; Step 2: Measuring skin physiological parameters and optical characteristic parameters, including the following sub-steps: 1) Contact the front ends of the incident fiber and reflective fiber that are the same as those in step 1 c) with the clean and flat skin surface to be tested, and connect the other end of the incident fiber to the light source, which provides incident light covering the wavelength range of 400-1000nm. The other end of the optical fiber is connected to the spectrometer to record the skin reflection light intensity M(λ) in the wavelength range of 400-1000nm; 2) Place the front end faces of the incident optical fiber and the reflective optical fiber above the reflective standard sheet, and record the reflected light intensity M _std (λ) of the standard sheet; 3) The normalized measured skin reflectance spectrum is

4) Set four physiological parameters and two scattering parameters: the initial value range of melanin content M0 is 1%-10%; the initial value range of hemoglobin content B0 is 0.2%-7%; the initial value range of blood oxygen saturation S0 is 0% -100%; the initial value range of moisture content W0 is 15%-70%; the initial value range of the reduced scattering coefficient μ _s ' at _500nm wavelength is 20-200; the initial value range of Rayleigh scattering content f0 is 0%-100%; 5) Calculate the absorption coefficient and the reduced scattering coefficient of the skin tissue at each wavelength by the physiological parameters and the scattering parameters set in step two 4), and optimize the data T obtained from step one for the absorption coefficient and the reduced scattering coefficient Calculate the corresponding standard reflected light intensity in 6) combining the standard reflected light intensity calculated under the wavelength of 400-1000nm to obtain the predicted reflectance spectrum pSPR(λ); 7) Calculate the error u=∑|mSPR(λ)-pSPR(λ)| between the predicted reflectance spectrum and the measured skin reflectance spectrum obtained in step 2 3); 8) Repeat step 2 4)-7) cyclically to obtain the physiological parameter and the scattering parameter corresponding to the measured sample that minimizes the error u; 9) Calculate the absorption coefficient μ _a and the reduced scattering coefficient μ _s ′ of the skin of the tested sample by calculating the physiological parameters and scattering parameters corresponding to the tested sample that minimize the error u. 2. measuring method as claimed in claim 1, it is characterized in that, standard tissue model solution is to obtain with fat emulsion solution and Indian ink configuration, the standard tissue model solution of configuration is made of 32 groups of different concentration solutions, the fat emulsion in the solution The concentration is one of the following 4: 20%, 5%, 1.25%, 0.3125%; the concentration of India ink in the solution is one of the following 8: 0, 0.0015%, 0.003%, 0.013%, 0.023%, 0.048%, 0.073%, 0.098%. 3. measuring method as claimed in claim 1, is characterized in that, the optical characteristic parameter of measuring standard tissue model solution comprises the following steps: i) Select the measurement wavelength; ii) measuring the luminous flux M _(r) of the measurement wavelength for the standard tissue model solution at a distance from the light source position r; iii) Change the distance r between the reflective fiber optic probe and the light source n times, and measure the luminous flux M _(r) i respectively, where i=2, 3, 4...n; iv) Carry out linear fitting of |n(r*M _(r) ) to the distance r, and calculate the slope 1/δ ₀ of the fitted curve; v) The absorption coefficient increased in the standard tissue model solution after dripping ink into the solution is _Δμa , and the absorption coefficient _Δμa is obtained by measuring the absorbance of the ink with a spectrophotometer; vi) Taking the solution added with ink as the object, re-carry out steps ii)-iv) for the measured wavelength, and calculate the slope 1/ _δ1 of the fitting curve at this time; vii) Through the following equations $\left\{\begin{array}{c}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}\\ \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>}\\ {\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\end{array}\right.$ The optical characteristic parameters μ _a0 and μ _s0 ′ of the standard tissue model solution are calculated. 4. measuring method as claimed in claim 1, is characterized in that, reflection standard sheet has a reflectivity of 99.9% in visible near infrared wavelength.

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