CN116530949B - Subcutaneous blood vessel parameter measurement method and device - Google Patents
Subcutaneous blood vessel parameter measurement method and deviceInfo
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- CN116530949B CN116530949B CN202310729961.5A CN202310729961A CN116530949B CN 116530949 B CN116530949 B CN 116530949B CN 202310729961 A CN202310729961 A CN 202310729961A CN 116530949 B CN116530949 B CN 116530949B
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- A61B5/02—Detecting, measuring or recording for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
- A61B5/02007—Evaluating blood vessel condition, e.g. elasticity, compliance
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/01—Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue
- A61B5/015—By temperature mapping of body part
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Abstract
A method and a device for measuring subcutaneous vascular parameters, wherein the measuring method comprises the steps of irradiating a skin surface layer with a plurality of lasers with different pulse widths, and simultaneously collecting temperature signals of the skin surface. And drawing a temperature distribution curve graph under each pulse width laser irradiation. The temperature distribution curve graph shows temperature peaks, after the number of the temperature peaks is stable, stable temperature peaks are obtained, the number of the stable temperature peaks is the number of blood vessels, and the depth corresponding to the stable temperature peaks is the depth of the centers of the blood vessels. Further, the fitting relation is obtained by obtaining and fitting different temperature peak information under the irradiation of laser with different pulse width at the same depth, and the diameter of the blood vessel is calculated by the principle and definition of thermal relaxation. The measuring device comprises a power supply, a display screen, a laser emitting part, a temperature acquisition part and a control part, wherein the control part is electrically connected with the power supply, the display screen, the laser emitting part and the temperature acquisition part, and the control part controls the measuring device to work.
Description
Technical Field
The invention relates to the field of blood vessel measurement, in particular to a noninvasive subcutaneous blood vessel parameter measurement method and device.
Background
Vascular skin diseases are abnormal agglomerates of blood vessels on the skin or other parts of the body, which appear as red or purple clusters. Hemangiomas are a benign hamartoma formed by residual embryonic vascular cells, and are generally classified clinically into three types, namely, nevus ruber, simple hemangiomas and cavernous hemangiomas. Based on the selective photothermal effect of biological tissues, the laser treatment can realize the selective damage of subcutaneous lesion blood vessels, so that normal tissues are reserved to the maximum extent, and the method is the only effective method for treating vascular dermatosis clinically. At the same time, however, the clinical rough, empirical treatment technique of laser radiation has reached the "ceiling". Taking laser treatment of nevus roseus as an example, due to the lack of effective nondestructive detection means of skin tissue structures and on-line monitoring of lesion vascular thermal injury, the current clinical actual treatment is mainly based on the experience of doctors, and the complete cure rate is maintained at a level lower than 20% for nearly 10 years.
The skin tissue structure comprises the number of subcutaneous blood vessels, the depth of the subcutaneous blood vessels, the diameter of the subcutaneous blood vessels and other blood vessel parameters, and has important significance for the parameter selection of laser treatment. The traditional pulse photothermal radiation method can achieve the purpose of noninvasively measuring subcutaneous blood vessel parameters, the principle of the method is that firstly, laser with specific wavelength is emitted to the surface of the skin, the laser energy can be selectively absorbed by subcutaneous lesion blood vessels, the generated heat energy is conducted to the surface of the skin under the heat conduction effect, then, a thermal infrared imager is adopted for collecting surface temperature signals, the numerical value and the change trend of the temperature signals comprise the temperature and tissue structure information of the lesion blood vessels, and therefore, the structure and the temperature numerical value of the subcutaneous blood vessels can be solved through a heat conduction inverse method.
The traditional pulse photothermal radiation method mainly adopts a mode of obtaining a tissue structure after laser pulse irradiation with single pulse width (duration of laser irradiation once), for example, thomas et al adopts single pulse width laser irradiation of 0.1ms to reconstruct temperature distribution by adopting a conjugate gradient method, and adopts a full width half maximum estimation method to calculate the diameter of a blood vessel according to the temperature distribution. (the algorithm of related literature ：Thomas,E,Milner,et al.Depth profiling of laser-heated chromophores in biological tissues by pulsed photothermal radiometry[J].Journal of the Optical Society of America A,1995,12(7):1479-1488.); such as Wim et al is to irradiate the skin with a single pulse width laser of 3ms, reconstruct a temperature distribution using a non-negative constraint and truncated singular value back calculation algorithm, and calculate a vessel diameter from the temperature distribution using a full width at half maximum estimation algorithm (related literature ：VERKRUYSSE W,MAJARON B,CHOI B,et al.Combining singular value decomposition and a non-negative constraint in a hybrid method for photothermal depth profiling[J].Review of Scientific Instruments,2005,76(2):4301-1-4301-6-0.).
The traditional pulse photothermal radiation method has extremely large error and lacks scientific basis for measuring the diameter of the blood vessel. This is mainly because the single laser pulse measurement method only can obtain one temperature distribution, but the temperature distribution of the subcutaneous tissue is a changing process and is related to the change of the pulse width, so that the estimated subcutaneous tissue structure by single laser pulse irradiation is also single, has occasional occurrence, has huge errors, and cannot obtain an accurate structure. In addition, during the measurement process, the signal response of the tissue surface after irradiation is fast, so the thermal radiation energy of the tissue surface is already dissipated to a certain extent when the thermal infrared imager starts to acquire the signal. Which can result in a thermal radiation signal acquired by the thermal infrared imager that is so low that the error of the final measurement increases.
Disclosure of Invention
In view of the defects of the prior art, the invention provides a subcutaneous blood vessel parameter measuring method and device, which can accurately measure the parameters of the subcutaneous blood vessel in a non-invasive manner.
In order to achieve the above object, the present invention provides a method for measuring subcutaneous blood vessel parameters, comprising:
the method comprises the steps of irradiating a skin surface layer by using a plurality of lasers with different pulse widths, collecting temperature signals on the skin surface, and drawing a temperature distribution curve showing the relation between the depth of subcutaneous tissue and the temperature under the irradiation of each pulse width laser, wherein a temperature peak is generated on the temperature distribution curve:
irradiating the surface layer by adopting a plurality of depth pulse width lasers until the number of the temperature peaks in the temperature distribution curve is stable, wherein the temperature peaks are stable temperature peaks;
Acquiring temperature peak depths corresponding to a plurality of temperature peaks by adopting a plurality of diameter pulse width laser irradiation surface layers, collecting temperature peak information under the irradiation of different diameter pulse width lasers according to each temperature peak depth, acquiring a temperature peak with the highest temperature as the highest temperature peak, and acquiring a fitting relation representing the relation between the temperature peak and the diameter pulse width after fitting;
bringing the thermal relaxation temperature into the fitting relation to obtain a thermal relaxation pulse width;
the subcutaneous blood vessel parameters include:
the number of the blood vessels is the same as the number of the stable temperature peaks,
The depth of the blood vessel is the same as the depth corresponding to the stable temperature peak,
The diameter of the vessel is positively correlated with the thermal relaxation pulse width.
Further, the pulse width of the depth pulse width laser is 5ms or more and 20ms or less.
Further, the pulse width of the diameter pulse width laser is less than 5ms.
Further, the pulse width of the depth pulse width laser is more than or equal to 5ms and less than or equal to 20ms, and the pulse width of the diameter pulse width laser is less than 5ms.
Further, the diameter of the blood vessel is proportional to the thermal relaxation pulse width.
Further, the variation temperature is 50% or less of a temperature difference between the highest temperature peak and the temperature of the subcutaneous tissue before the diameter pulse width laser irradiation.
Further, the variation temperature is 37% of the temperature difference between the highest temperature peak and the temperature of the subcutaneous tissue before the diameter pulse width laser irradiation.
Further, the pulse width of the laser can be replaced after the temperature signal of the skin surface is restored to the state before the laser irradiation each time after the laser irradiation is completed.
In addition, to achieve the above object, the present invention also provides a device for measuring subcutaneous blood vessel parameters, comprising:
The power supply is provided with a power supply,
The display screen is used for outputting a result;
a laser emitting part for emitting laser of different pulse widths;
A temperature acquisition part for acquiring a temperature signal of the skin surface;
The control component is electrically connected with the display screen, the laser emission component and the temperature acquisition component;
The control part is connected with the control part to supply power for the device, the control part controls the laser emitting part to emit laser with various pulse widths to irradiate the skin surface layer, the control part controls the temperature acquisition part to acquire temperature signals on the skin surface after each irradiation is completed and transmits the temperature signals to the control part, and the control part performs data processing on the signals and outputs the obtained subcutaneous blood vessel parameters to the display screen.
The invention has the advantages that:
1. the measuring method of the invention avoids the problem that the traditional measuring method (single pulse width laser irradiation method) has serious differentiation of different temperature distribution curves due to the selection of pulse width, and the measuring result is more stable and accurate. And simultaneously, a scientific basis is provided for measuring the diameter of the blood vessel.
2. The measuring device integrates the functions of subcutaneous blood vessel parameter measurement and laser treatment, improves the automation level of the measuring process and the treatment process, saves the manpower labor, improves the working efficiency, and can effectively avoid the heat radiation energy loss caused by slow manual response in the measuring process.
Drawings
Fig. 1 is a schematic view of the temperature distribution at the initial time when the pulse laser is irradiated to the multilayer skin model.
Fig. 2 to 11 are graphs of temperature distribution at the time of pulse width laser irradiation of 20ms, 10ms, 5ms, 0.1ms, 0.2ms, 0.4ms, 0.6ms, 0.8ms, 1ms, and 1.2ms, respectively.
Fig. 12 is a graph of peak blood vessel center temperature versus pulse width for three blood vessels.
Fig. 13 is a graph of fitted temperature peak pulse widths for three vessels.
Fig. 14 is a schematic diagram of the operation of the subcutaneous vascular parameter measurement device of the present invention.
FIG. 15 is a graph comparing the error in measuring the diameter of a blood vessel by the method of the present invention with the error in measuring the diameter of a blood vessel by the conventional calculation method.
Fig. 16 is a schematic diagram of the temperature distribution curve optimized by the reverse-pushing based on the information such as the diameter depth of the blood vessel.
FIG. 17 is a graph comparing temperature distribution curves of 0.1ms laser irradiation with reverse optimization
FIG. 18 is a graph showing the error in the center temperature of blood vessels of different diameters
Detailed Description
The technical means adopted by the invention to achieve the preset aim are further described below by matching with the drawings and the preferred embodiments of the invention.
The skin layer is irradiated by using single pulse width laser, and meanwhile, temperature signals of the skin surface are collected, so that a temperature distribution curve graph of the relation between the depth of subcutaneous tissue and the initial temperature can be drawn, and the specific drawing principle is as follows:
The problem of solving the temperature distribution of subcutaneous blood vessels by using a pulse photothermal radiation method belongs to the inverse problem of heat conduction, and specifically, the temperature distribution in the skin is solved in reverse by collecting temperature signals (time evolution of temperature near the skin surface) through the diffusion of heat generated by absorption of light by a blood vessel layer in the skin to the surface.
More specifically, as shown in fig. 1, the inverse problem of heat conduction relates the pulse photothermal radiation signal Δs (T) to the initial temperature distribution T (z, t=0), an integral equation is established, and the unknown subcutaneous initial temperature distribution T (z, t=0) is solved by a truncated singular value decomposition algorithm of a custom truncated parameter.
The specific establishment process is as follows:
Temperature distribution Δt (z, T) for arbitrary depth z and time T according to green's solution of the one-dimensional heat transfer problem:
at any time t, the ideal pulsed photothermal radiation signal amplitude is proportional to the superposition of depth-dependent temperature variations:
Mu a -the infrared absorption coefficient of the exposed test material at the detection wavelength,
C d -proportionality constant determined by an Infrared detection System
Combining the complementary two formulas yields:
The reduced form is sorted into the first class of Fredholm integral equations:
Since most of the Fredholm integral equations of the first type have discomfort, namely that small disturbances (i.e. noise) in the measurement signal can cause the calculated solution estimation value to change greatly, and regularization can alleviate the influence of the pathological estimation problem, the basic principle is that the regularization components related to the structure are utilized to enhance the cost function usually related to the data, and a smoothness constraint is added to the input-output mapping established by the estimator, so that the solution is stabilized. Truncated Singular Value Decomposition (TSVD), one of the regularization means. The singular values obtained by Singular Value Decomposition (SVD) are non-negative and successively decreasing, with the singular values after the kth generally all tending to zero. Therefore, the TSVD principle is to intercept the first k singular values, avoid the noise of the high-frequency item from being amplified, and restore the stability of the solution by sacrificing certain solving precision. Specifically, a linear equation set obtained by discretizing an integral equation is:
ΔS(t)=KΔT
singular Value Decomposition (SVD) of the kernel function:
The core of the TSVD method is to determine a cutoff parameter k, and cut off singular values smaller than the threshold value by setting the threshold value on the singular values, so that the solution is stable and the approximate solution is ensured to be close to the true solution of the original problem.
Assuming delta is a singular value of a kernel function K, taking a threshold value as alpha, and K is a first integer which enables delta k to be less than or equal to alpha, namely:
δ1≥δ2≥…δk-1≥α≥δk≥δr≥0
The selection strategy of the cutoff parameter k is flexible and various, and the self-designed simple priori selection method-self-defined cutoff parameter method is a statistically reasonable cutoff parameter selection algorithm, so that the universality and the reliability of parameter selection can be improved. The algorithm principle formula of the self-defined cutoff parameter is as follows:
Wherein, k is a truncated parameter, m is a total number of singular values, δp is a singular value, and sigma-duty ratio threshold values (0 < sigma is less than or equal to 1) are arranged in a descending manner for each singular value. The principle meaning is that the singular value sequence number corresponding to the ratio of the selected singular value sum to the sum just exceeds the duty ratio threshold value is the cut-off parameter.
The initial temperature distribution of the subcutaneous tissue is obtained by solving based on the principle, as shown in the curve of the temperature distribution T (z, t=0) at the initial moment of the attached figure 1, wherein the curve 1 is a temperature distribution curve graph of the subcutaneous tissue in the depth direction under the irradiation of a wider pulse width, and the curve 2 is a temperature distribution curve of the subcutaneous tissue in the depth direction under the irradiation of a narrower pulse width. The skin depth is taken as the abscissa, the initial temperature is taken as the ordinate, a temperature distribution curve showing the relation between the depth of subcutaneous tissue and the temperature in fig. 2-11 can be drawn, and a temperature peak can be obtained on the temperature distribution curve as shown in fig. 2.
The invention relates to a method for measuring subcutaneous blood vessel parameters, which adopts a plurality of lasers with different pulse widths to irradiate a surface layer of a skin and collect temperature signals on the surface of the skin. The temperature distribution curve of each pulse width laser irradiation is drawn, and the specific method is as follows:
And a, collecting a temperature signal of the skin surface under the condition of not being irradiated by laser, wherein the temperature signal is a 0 pulse width temperature signal.
And b, adopting a plurality of depth pulse width laser to irradiate the surface layer, and recovering the temperature signal of the skin surface to a 0 pulse width temperature signal before each laser irradiation, so that the influence on the temperature signal acquisition during the laser irradiation is avoided. In each laser irradiation process, temperature signals of the skin surface are collected, a temperature distribution curve chart shown in fig. 2 is drawn according to the principle of solving the heat conduction inverse problem, and when the temperature peak number of the temperature distribution curve chart reaches a stable value, pulse width laser irradiation is stopped to be replaced. At this time, the temperature peaks in the temperature distribution graph are stable temperature peaks, the number of the stable temperature peaks is the number of subcutaneous blood vessels, and the depth corresponding to the stable temperature peaks is the depth of the blood vessels.
Step c:
i adopts a plurality of diameter pulse width laser irradiation surface layers, and the temperature signal of the skin surface needs to be recovered to a 0 pulse width temperature signal before each laser irradiation, so that the influence on the temperature signal acquisition during the laser irradiation is avoided. In each laser irradiation process, temperature signals of the skin surface are collected, and a temperature distribution curve chart shown in fig. 5 is drawn according to the principle of solving the heat conduction inverse problem.
And ii as shown in figures 5-11, because the diameters and pulse widths are different, a plurality of temperature peaks are generated at the same depth, the depth corresponding to the temperature peaks is the temperature peak depth, the temperature peaks at the same temperature peak depth are selected, a relationship diagram of the central temperature peak of the blood vessel and the pulse width can be drawn as shown in figure 12, wherein the abscissa of the diagram is the pulse width, the ordinate represents the temperature peak temperature of the central blood vessel under the irradiation of the corresponding pulse width, the different curves represent the blood vessels with different depths, and three blood vessels with the diameters of 30 mu m, 50 mu m and 30 mu m are respectively arranged in each diagram.
Iii as shown in fig. 12, for the same blood vessel, obtaining the temperature peak with the highest temperature as the highest temperature peak T, selecting the temperature peak temperature corresponding to the diameter pulse width, and fitting the screened diameter pulse width and the temperature peak information corresponding to the temperature peak temperature, so as to obtain a fitting temperature peak pulse width diagram showing the relationship between the temperature peak temperature and the diameter pulse width and a fitting relation between the temperature peak temperature and the diameter pulse width as shown in fig. 13, wherein each blood vessel corresponds to one curve and one fitting relation.
Iv it is understood from the definition of thermal relaxation that the thermal relaxation temperature t of a blood vessel means the temperature of the blood vessel after the temperature of the blood vessel rises to the highest temperature and falls by a change temperature during laser irradiation, and the thermal relaxation time τ of a blood vessel means the time required from the start of laser irradiation to the rise of the temperature of the blood vessel to the highest temperature and then to the thermal relaxation temperature.
In the present invention, the pulse width represents the duration of laser irradiation, the temperature peak temperature represents the initial temperature of the blood vessel under the pulse width irradiation, and the initial temperature is the final temperature of the blood vessel under the pulse width irradiation because the pulse width time is of the order of ms, as shown in fig. 12, in the range of the diameter pulse width, the temperature of the blood vessel tends to rise to the peak value and then fall with the increase of the pulse width, namely the time of laser irradiation, so that the thermal relaxation temperature T of the blood vessel can be regarded as the temperature after the peak T falls by one change temperature, the thermal relaxation time τ of the blood vessel can be regarded as the pulse width corresponding to the thermal relaxation temperature T of the blood vessel, namely the thermal relaxation pulse width τ ', and the thermal relaxation temperature T is brought into the relation shown in fig. 13, and the thermal relaxation time τ' of three blood vessels can be obtained respectively. Preferably, in the present invention, the variation temperature T is 50% or less of the temperature difference between the highest temperature peak T and the 0 pulse width temperature signal, and more preferably, the variation temperature T is 37% of the temperature difference between the highest temperature peak T and the 0 pulse width temperature signal.
It is known from the principle of thermal relaxation that the thermal relaxation time τ of a blood vessel is positively correlated with the diameter d of the blood vessel, and further that the thermal relaxation time τ of a blood vessel is proportional to the square of the diameter d of the blood vessel, namely: (α is the thermal diffusivity of the blood vessel=1.3×10 -3cm2/s), and τ=τ' in the present invention, the diameter of the blood vessel can be calculated.
In step b of the present invention, the pulse width of the deep pulse width laser is preferably in the range of 5ms to 20ms (inclusive). If the pulse width is too large, skin is damaged, and if the pulse width is too small, as shown in fig. 5-11, other curve peaks affect the judgment of temperature peaks.
In step c of the present invention, the pulse width of the diameter pulse width laser is preferably in the range of 0ms to 5ms (excluding the end points), and more preferably in the range of 0ms to 1.2ms (including the end points of 1.2 ms). As shown in FIG. 12, when the pulse width is 0ms-1.2ms, the temperature of the temperature peak changes faster, which is beneficial to solving the fitted temperature peak pulse width diagram and the fitting relation. The number of diameter pulse width lasers is not limited in the invention, and the more the number is, the more accurate the result is.
In the present invention, the order of the steps a, b and c is not limited, and it is within the scope of the present invention as long as the corresponding result can be obtained.
The invention also provides a device for non-invasively measuring subcutaneous blood vessel parameters by using the measuring method. As shown in fig. 14, the apparatus includes a power source, a display screen, a laser emitting part, a temperature collecting part, and a control part. The control component is electrically connected with the display screen, the laser emission component and the temperature acquisition component, and the power supply is connected with the control component to supply power for the device.
The control part can control the laser emission device to emit laser with different pulse widths to irradiate the skin surface layer, and after each emission is completed, the control part controls the temperature acquisition part to acquire a temperature signal of the skin surface and transmit the temperature signal back to the control part, and the control part processes the temperature signal and the data. Further, the control part can control the laser emitting part and the temperature collecting part to complete the steps a, b and c, and output the number of subcutaneous blood vessels, the depth of the subcutaneous blood vessels and the diameter of the subcutaneous blood vessels to the display screen.
Further, the control component can build a skin model, a light transmission model, a biological heat transfer model and a thermal damage model according to the obtained skin vascular parameters, and simulate laser treatment processes of different parameters (including wavelength, frequency and pulse width of laser). Finally, the optimal laser treatment parameters are automatically selected and transmitted to the display screen, and the control part can control the laser emission device to treat the patient according to the optimal parameters as long as a user turns on a treatment switch on the display screen.
The subcutaneous blood vessel parameter measuring method has the advantages that:
1. In the traditional single pulse width measurement method, pulse width selection is different, and the shapes of acquired temperature distribution curves are quite different, as shown in fig. 2-11, so that the acquired temperature peak number and the acquired temperature peak position are inaccurate, and the blood vessel number and the blood vessel position are inaccurate. The method of the invention adopts a plurality of depth pulse width lasers to irradiate the epidermis layer until the temperature distribution curve is stable, and then obtains the number of stable temperature peaks and the depth of the stable temperature peaks, thereby obtaining the accurate number of blood vessels and the depth of the blood vessels.
2. The conventional single pulse width measurement method uses the full width at half maximum (FWHM) of a temperature distribution curve, i.e. a straight line parallel to the abscissa passing through the midpoint of the ordinate of a temperature peak, and the distance between the intersection of the straight line and the curves on both sides of the peak is shown as H in fig. 5) to represent the diameter of a blood vessel. The method lacks scientific basis, and the acquired blood vessel diameter is inaccurate because the acquired temperature distribution curve shape is very different due to different pulse width selections.
According to the method, through the temperature peaks irradiated by the pulse widths with the diameters, the fitting relation diagram of the temperature peaks and the pulse widths is drawn, and the relation is solved, so that errors caused by large temperature curve differences under different pulse widths are avoided, and the calculation is more accurate. Simultaneously, the definition and principle of thermal relaxation are introduced, the thermal relaxation pulse width and the thermal relaxation time are corresponding, the temperature peak of the blood vessel is converted into the temperature of the blood vessel when the blood vessel is irradiated by laser, the thermal relaxation temperature is obtained through calculation, the thermal relaxation pulse width is solved through fitting relation, the thermal relaxation time is further obtained, and finally the diameter of the blood vessel can be solved. Provides scientific basis for measuring the diameter of the blood vessel.
3. The measuring device for subcutaneous blood vessel parameters can realize automation of subcutaneous blood vessel measurement, the control device can control the skin measuring device to detect the skin surface in real time, and automatically collect temperature data during laser irradiation, so that response time is reduced, dissipation of heat radiation energy during manual temperature signal collection is avoided, and measurement is more accurate.
4. According to the subcutaneous blood vessel parameter measuring device, the parameters of laser treatment can be optimized according to the acquired subcutaneous blood vessel parameters through the control system, and the laser emitting device is started according to the parameters, so that the skin is treated, the technical effect of measurement and treatment integrated automation is achieved, and time and labor are saved. And can improve the cure rate of vascular dermatosis.
The technical means of the invention are further elucidated and verified by the following specific examples:
Example 1
A heat transfer model of the multi-layer skin is established, including the epidermis layer, the blood vessel layer and the dermis layer. Wherein the vascular layer is composed of a whole layer of blood vessels, the diameter of each blood vessel is similar to the thickness of the vascular layer, the blood vessel is matched with the case characteristics of the actual vascular skin disease, three blood vessels in the model are respectively marked as A, B, C in sequence, and the diameters are respectively 30 mu m, 50 mu m and 30 mu m. In fig. 2-11, the black rectangle represents the epidermal layer of the skin and the light gray rectangle represents the vascular layer.
The measurement method of subcutaneous blood vessel parameters in the invention is utilized to simulate the measurement of the multi-layer skin heat transfer model:
As shown in fig. 2-4, the temperature distribution curves obtained by drawing the simulation under the irradiation of the depth pulse width of 20ms, 10ms and 5ms are respectively, and it can be seen from the graph that the temperature distribution curves are stable when the diameter pulse width is 10ms and 5ms, and three stable temperature peaks are generated. Thus, a total of 3 blood vessels were measured subcutaneously at depths of 0.2mm, 0.31mm and 0.42mm, respectively.
Fig. 5-11 are graphs of temperature distribution plotted under simulated radial pulse width irradiation of 0.1ms, 0.2ms, 0.4ms, 0.6ms, 0.8ms, 1ms and 1.2ms, respectively, and fig. 12 is a graph of a central temperature peak of a blood vessel and pulse widths (including 5ms and 10ms pulse widths), respectively, so that a fitting relation and a fitting relation of temperature peak temperatures of three blood vessels and radial pulse widths can be fitted, namely fig. 13.
Further, taking the B blood vessel as an example, the measured 0 pulse width temperature signal is 37.1 ℃, the read highest temperature peak T is the change temperature 49.91, the change temperature is (49.91-37.1) ×37% = 4.7397 ℃, and the thermal relaxation temperature is 49.91-4.7397 = 45.1703 ℃. The thermal relaxation temperature is brought into the fitting relation (45.1703 = 49.786 e-0.093x) of fig. 12, the thermal relaxation pulse width τ' =1.046ms is obtained, and the thermal relaxation pulse width is put into the thermal relaxation formula to obtain the diameter d=46.6μm of the blood vessel, and the error compared with the actual blood vessel diameter is only 6.8%.
The diameter of the A vessel was calculated to be 39.4 μm with an error of 31.3%, and the diameter of the C vessel was calculated to be 39.3 μm with an error of 31%.
Embodiment two:
A multi-layer skin heat transfer model with blood vessel diameters of 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm and 100 μm, respectively, was established as in example one. The method of the invention and the traditional method are respectively used for simulating and measuring the diameter of the blood vessel, and calculating the error value. The results are plotted as an error comparison of vessel diameter calculations as depicted in fig. 15, where the curve of the triangle represents the method of the present invention, the curve of the square represents the algorithm of Thomas et al, and the curve of the circle represents the algorithm of Wim et al.
As shown in FIG. 15, the overall calculation error of the conventional single laser pulse width irradiation method is larger than that of the method of the present invention, and the calculation error is increased when the diameter of the blood vessel is too small or too large, no matter the pulse width is smaller like 0.1ms or relatively larger like 3ms, but the method proposed by the present project only has larger error when measuring the blood vessel with smaller diameter (less than 40 μm), and the error is still far smaller than that of the conventional method. .
Example III
Based on the information of the diameter, the depth and the like of the blood vessel, the temperature distribution curve can be reversely deduced and optimized, the optimizing principle is shown in figure 16, wherein the dotted line is the temperature distribution calculated by the reverse problem, the temperature distribution curve is reversely deduced and reconstructed through the information of the diameter, the depth and the like of the blood vessel, and the solid line is the simulated temperature distribution curve of the skin temperature curve heat transfer model calculated by the positive problem of heat transfer after laser irradiation. The thickness of the tissue layer, defined as vessel diameter d, according to Anderson R et al, is defined as the corresponding depth spread as each temperature peak decays to half on both sides (i.e., at half peak in fig. 16). In addition, the half peak temperature value of the broken line and the full line basically coincides, so after measuring the information of the diameter d of the blood vessel and the central depth z of the blood vessel, the central depth z of the blood vessel is found in the abscissa of the temperature distribution curve, the width of d/2 is extended to the left and right sides by taking z as the center, and the intersection point of the two reconstructed temperature distribution curves (the broken line in fig. 16) is the temperature value corresponding to the half peak temperature, so that the temperature peak value can be calculated, and then the temperature distribution curve can be reversely optimized by 5 temperature points in total.
FIG. 17 is a graph of temperature distribution optimized by the above-described reverse optimization method, wherein the solid line is a skin temperature curve calculated by the positive problem of heat transfer after laser irradiation, and is a standard curve, the circular dash-dot line is a blood vessel parameter measured by the method of the present application, and the reverse optimized temperature distribution curve, and the triangular dash-dot line is a blood vessel parameter measured by the algorithm of Thomas et al under single pulse width 0.1ms laser irradiation, and the reverse optimized temperature distribution curve is obtained by the reverse optimization.
The vessel was selected to a depth of 0.3mm, the diameter of the vessel was changed, and the temperature peak of the vessel of different diameters was obtained from the depth of 0.3mm in fig. 17. The temperature peak value of the algorithm of Thomas et al and the error value of the temperature peak value and the standard value of the method of the present application were calculated, respectively, using the temperature peak value of the simulated temperature distribution curve as the standard value, as shown in fig. 18. The square dot-dash line in fig. 18 is the algorithm of Thomas et al, and the circular dot-dash line is the method of the present application.
As shown in fig. 17 and 18, the temperature distribution curve calculated by the blood vessel parameter calculated by the method of the present application is more fit to the standard curve than the temperature distribution curve calculated by the blood vessel parameter calculated by Thomas et al, and the error value of the temperature peak calculated by the blood vessel parameter calculated by the method of the present application is lower and more stable, no matter how the blood vessel diameter is changed.
The above description is only of the preferred embodiments of the present invention, and is not intended to limit the present invention in any way, although the present invention has been described above with reference to the preferred embodiments, but is not limited thereto, and any person skilled in the art will appreciate that the present invention can be embodied in the form of a program for use herein without departing from the scope of the present invention, while the above disclosure is directed to various equivalent embodiments, which are capable of being modified or varied in several ways, it is apparent to those skilled in the art that many modifications, variations and adaptations of the embodiments described above are possible in light of the above teachings.
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| CA2198826A1 (en) * | 1997-02-28 | 1998-08-28 | Denis K. Dudley | Laser treatment of telangiectasia |
| CN104323762A (en) * | 2014-12-01 | 2015-02-04 | 广州佰奥廷电子科技有限公司 | Photoacoustic microscopy imaging-based quantitative detection device for nevus flammeus blood vessel |
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| CN104323762A (en) * | 2014-12-01 | 2015-02-04 | 广州佰奥廷电子科技有限公司 | Photoacoustic microscopy imaging-based quantitative detection device for nevus flammeus blood vessel |
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