A method for evaluating bone tissue composition and structural mechanical properties based on photoacoustic guided waves

Abstract

The application discloses a kind of bone tissue component and structural mechanical property evaluation method based on photoacoustic guided wave, comprising the following steps:S1, bone is processed into plate type standard part;Step S2, different wavelength laser is used to excite guided wave in bone, and the signal of multiple wavelength photoacoustic guided wave is collected based on axial propagation method;Step S3, signal processing technique is used to extract photoacoustic guided wave signal characteristic parameter;Step S4, the head wave amplitude ratio or power spectral density slope of each mode of multiple wavelength photoacoustic guided wave is drawn to draw photoacoustic guided wave parameter spectrum;Step S5, the optical and structural mechanical property and tissue component of bone standard part are measured;Step S6, S1-S5 is repeated to obtain the characteristic parameters of photoacoustic guided wave, bone property data of different bone standard parts, and the mapping information base of photoacoustic guided wave parameters and bone tissue component, structural mechanical property is established;Step S7, the bone to be measured is processed into standard part, and the characteristic parameters of multiple wavelength photoacoustic guided wave signal are tested;It is brought into the information base in S6, and the acoustic evaluation of bone tissue component and structural mechanical property to be measured is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of medical ultrasound, in particular to a method for evaluating bone tissue composition and structural mechanical properties based on photoacoustic guided waves. BACKGROUND

[0002] Ultrasound detection has the characteristics of non-invasiveness and non-radiation, and is widely used in clinical medical diagnosis and industrial non-destructive testing. It is difficult to characterize bone tissue components such as hydroxyapatite and lipids using ultrasonic waves excited by piezoelectric sensors, which restricts the early and quantitative evaluation of bone diseases such as osteoporosis and abnormal bone healing.

[0003] In recent years, scholars have explored methods for evaluating bone structural mechanical properties using ultrasonic guided waves. For example, in the field of osteoporosis detection, the bone thickness and elastic modulus are evaluated by the dispersion parameters of guided waves (see reference: Tran TNHT, Le LH, Ta DA, Ultrasonic guided waves in bone: A decade of advancement in review. IEEE Trans. Ultrason. Freq. Control, 2022, 69(10): 2875-2895), or the bone marrow tissue composition is analyzed according to the wave speed of photoacoustic guided waves excited by different wavelengths of laser in bone (see reference: Steinberg I, Shiloh L and Eyal A., First-in-human study of bone pathologies using low-cost and compact dual-wavelength photoacoustic system. IEEE J Sel Top Quantum Electron, 2018, 25(1): 7201908).

[0004] The existing methods have the following disadvantages: 1. Photoacoustic guided waves cannot evaluate the optical properties related to bone tissue composition; 2. Existing acoustic detection techniques cannot comprehensively evaluate the composition and structural mechanical properties of long bone tissue. SUMMARY

[0005] In order to overcome the deficiencies in the prior art, the present application provides a method for evaluating bone tissue composition and structural mechanical properties based on photoacoustic guided waves, which solves the problem of quantitative ultrasonic evaluation of in vitro cortical bone tissue composition and structural mechanical properties.

[0006] In order to achieve the above application purposes and solve the technical problems, the technical solutions adopted are as follows:

[0007] A method for evaluating bone tissue composition and structural mechanical properties based on photoacoustic guided waves, comprising the following steps:

[0008] Step S1: Process the cortical bone into a certain size of plate type standard part, and then enter step S2;

[0009] Step S2: Based on the axial propagation method, use different wavelength lasers to excite photoacoustic guided waves in long bones, collect multi-wavelength photoacoustic guided wave signals, and then enter step S3;

[0010] Step S3: Use signal processing techniques to extract photoacoustic guided wave signal characteristic parameters: head wave arrival time, wave number dispersion, and different guided wave mode head wave amplitude ratio, and then enter step S4;

[0011] Step S4: Draw a laser wavelength-photoacoustic guided wave mode amplitude ratio spectrum based on the amplitude ratio of each mode of photoacoustic guided waves excited by different wavelength lasers, and then enter step S5;

[0012] Step S5: Measure the optical properties, tissue composition and structural mechanical properties of the bone standard part, and then enter step S6;

[0013] Step S6: Repeat steps S1-S5 to obtain different bone standard part measurement photoacoustic guided wave signal characteristic parameters, bone property data, and establish a photoacoustic guided wave characteristic parameter-photoacoustic guided wave mode relative parameter spectrum-bone structural mechanical property-optical property-tissue composition mapping information base, and then enter step S7;

[0014] Step S7: Process the cortical bone to be measured into a standard part, test the multi-wavelength photoacoustic guided wave signal characteristic parameters, and input them into the cortical bone photoacoustic guided wave mapping information base in step S6 to realize acoustic evaluation of the optical properties, tissue composition and structural mechanical properties of the cortical bone to be measured.

[0015] Further, in step S3, first, the upper side detection signal and the lower side detection photoacoustic signal of the bone plate are normalized to obtain signals s u , s d ; then the symmetric mode and the antisymmetric mode components of the photoacoustic guided wave are extracted through s s = 0.5 × (s u + s d ), s a = 0.5 × (s u - s d ); subsequently, the mode guided wave first arrival wave maximum and minimum value point amplitude information s max , s min , a max , a min are obtained by using a signal extreme value extraction algorithm, and the different mode guided wave head wave extreme point amplitude ratio is calculated.

[0016] Further, in step S3, the photoacoustic signals on the upper and lower surfaces of the bone plate are first normalized, and the signal power spectral density is calculated; then, the first-order Taylor fitting is used to analyze the slope of the power spectral density, and the slope of the fitting curve is extracted for bone tissue composition and related optical property evaluation.

[0017] Further, in step S3, the threshold method is used to extract the head wave velocity of the guided wave, and the wave inversion method is used to extract the photoacoustic guided wave number, which is used for elastic dispersion theory bone structure mechanical property evaluation.

[0018] Further, in step S4, the head wave amplitude ratio spectrum of the photoacoustic guided wave is obtained by using the head wave amplitude ratio of the guided wave mode of the laser excitation photoacoustic guided wave at different wavelengths.

[0019] Further, in step S6, the mapping relationship between the bone optical property, tissue composition and structure mechanical property parameters and the head wave amplitude ratio spectrum, wave number and head wave velocity of different guided wave modes is established by using a deep neural network model, and a mapping information library of the bone optical property and tissue composition and structure mechanical property and the photoacoustic guided wave parameters is established.

[0020] Further, in step S6, the following structure mechanical property and tissue composition step-by-step evaluation steps are also implemented:

[0021] Step S61: The relationship between the guided wave head wave arrival time, wave number dispersion and bone structure mechanical property, density and thickness is established, the bone structure mechanical property parameters are evaluated, and step S62 is entered;

[0022] Step S62: On the basis of step S61, the relationship between the amplitude ratio spectrum of the head wave extreme point of different guided wave modes and the bone optical property is established, and step S63 is entered;

[0023] Step S63: On the basis of step S61, the relationship between the bone optical property and the tissue composition is established, and step S64 is entered;

[0024] Step S64: On the basis of steps S62 and S63, the relationship between the head wave extreme point amplitude ratio spectrum of different guided wave modes and the bone tissue composition is established.

[0025] Further, in step S7, the multi-wavelength photoacoustic guided wave signal characteristic parameters of the to-be-tested cortical bone are input into the deep learning neural network model of the photoacoustic guided wave characteristic parameters and the bone optical property, tissue composition and structure mechanical property, and the evaluation of the to-be-tested cortical bone tissue composition and structure mechanical property is realized.

[0026] Further, in step S7, the multi-wavelength photoacoustic guided wave signal characteristic parameters of the to-be-tested cortical bone are input into the structure mechanical property and tissue composition step-by-step evaluation steps, and the evaluation of the to-be-tested cortical bone tissue composition and structure mechanical property is realized.

[0027] Compared with the prior art, the present application has the following advantages and positive effects:

[0028] According to the method for evaluating the cortical bone tissue composition and structural mechanical property based on photoacoustic guided waves, the dispersion parameters of the guided waves in the elastic wave theory are combined with the characterization of the bone structural mechanical property parameters, the head wave amplitude ratio of different guided wave modes excited by different wavelength pulsed lasers is combined with the sensitivity of the power spectrum of the tissue composition to the optical property, and the quantitative evaluation of the long bone apatite matrix, collagen content, bone thickness, density and elastic modulus is realized. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. In the drawings:

[0030] Figure 1 is a schematic diagram of a long bone plate standard part in the embodiment of the present application;

[0031] Figure 2 is a schematic diagram of a photoacoustic guided wave detection experiment in the long bone in the embodiment of the present application;

[0032] Figure 3 is a flowchart of the method for evaluating the cortical bone tissue composition and structural mechanical property based on photoacoustic guided waves of the present application;

[0033] Figure 4 is a comparison diagram of photoacoustic guided wave signals excited by different wavelength lasers in the embodiment of the present application;

[0034] Figure 5 is a comparison diagram of symmetric mode and antisymmetric mode components of photoacoustic guided waves excited by different wavelength lasers in the embodiment of the present application;

[0035] Figure 6 is a schematic diagram of (a) extraction of the maximum and minimum points of the symmetric mode guided wave head wave and (b) extraction of the maximum and minimum points of the antisymmetric mode guided wave head wave in the photoacoustic guided wave excited by a 2400nm laser in the embodiment of the present application;

[0036] Figure 7 is a comparison diagram of the amplitude ratio spectrum of the head wave of different photoacoustic guided wave modes excited by different wavelength lasers and the light transmittance in the embodiment of the present application;

[0037] Figure 8 is a diagram of the amplitude ratio of the head wave of different photoacoustic guided wave modes changing with the light transmittance in the bone in the embodiment of the present application. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] like Figure 3 As shown, this embodiment discloses a method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves, including the following steps:

[0040] Step S1: Process the cortical bone into a standard plate of a certain size, and then proceed to step S2;

[0041] In step S1 of this embodiment, cortical bone can be processed into bone plates by mechanical cutting and sandpaper surface polishing.

[0042] Step S2: Based on the axial propagation method, use lasers of different wavelengths to excite photoacoustic guided waves into the long bone, collect multi-wavelength photoacoustic guided wave signals, and then proceed to step S3;

[0043] In step S2 of this embodiment, the acquisition method for receiving photoacoustic signals can be achieved by scanning the photoacoustic guided wave field using a laser vibrometer.

[0044] Step S3: Use signal processing technology to extract the characteristic parameters of the photoacoustic guided wave signal: head wave arrival time, wave number dispersion, and head wave amplitude ratio of different guided wave modes, and then proceed to step S4;

[0045] In step S3 of this embodiment, the upper and lower detection photoacoustic signals of the bone plate are first normalized to obtain signals s. u s d Then through s s =0.5×(s) u +s d ), s a =0.5×(s) u -s d The symmetric and antisymmetric modes of the photoacoustic guided wave are extracted; subsequently, a signal extremum extraction algorithm is used to obtain the amplitude information s of the first arrival wave maxima and minima of the guided wave. max s min a max a min Calculate the amplitude ratio of wavefront poles in different modes. Used for evaluating bone tissue composition and related optical properties.

[0046] In the step S3, the photoacoustic signals on the upper and lower surfaces of the bone plate are normalized, and the signal power spectral density is calculated; then, the slope of the power spectral density is analyzed by using the first-order Taylor fitting, and the slope of the fitting curve is extracted for evaluating the bone tissue composition and related optical properties.

[0047] In the step S3, the threshold method is used to extract the head wave velocity of the guided wave, and the wave inversion method is used to extract the photoacoustic guided wave number, which is used for evaluating the bone structure mechanical properties based on the elastic dispersion theory.

[0048] Step S4: Based on the amplitude ratio of each mode of the photoacoustic guided wave excited by different wavelengths of laser, a laser wavelength-photoacoustic guided wave mode amplitude ratio spectrum is drawn, and then step S5 is entered;

[0049] In the step S4 of the embodiment, the head wave amplitude ratio spectrum of the photoacoustic guided wave is obtained by using the head wave amplitude ratio of each guided wave mode of the photoacoustic guided wave excited by different wavelengths of laser.

[0050] Step S5: Measure the optical properties, tissue composition and structural mechanical properties of the bone standard part, and then enter step S6;

[0051] In the step S5 of the embodiment, the Fourier spectrum technology is used to measure the light absorption, transmission and scattering coefficients of the bone structure, and the contents of hydroxyapatite, lipids and collagen in the bone; the optical properties and tissue composition of the bone are measured by a transmittance and reflectance spectrum test system, the elastic modulus and Poisson's ratio of the bone are measured by a three-point stress test, and the density is measured by a bone mass and volume ratio measurement.

[0052] Step S6: Repeat steps S1-S5 to obtain the photoacoustic guided wave signal characteristic parameters and bone property data of different bone standard parts, and establish a mapping information library of the photoacoustic guided wave characteristic parameters, the photoacoustic guided wave mode relative parameter spectrum, the bone structure mechanical properties, the optical properties and the tissue composition, and then enter step S7;

[0053] In the step S6 of the embodiment, the mapping relationship between the bone optical properties, tissue composition and structural mechanical property parameters and the head wave amplitude ratio spectrum, the wave number and the head wave velocity of different guided wave modes is established by using a deep neural network model, and a mapping information library of the bone optical properties and tissue composition and the structural mechanical properties and the photoacoustic guided wave parameters is established.

[0054] Step S7: The to-be-measured cortical bone is processed into a standard part, the multi-wavelength photoacoustic guided wave signal characteristic parameters are tested, and are input into the cortical bone photoacoustic guided wave mapping information library in step S6 to realize acoustic evaluation of the optical properties, tissue composition and structural mechanical properties of the to-be-measured cortical bone.

[0055] In the step S7 of the embodiment, the multi-wavelength photoacoustic guided wave signal characteristic parameters of the to-be-measured cortical bone are input into a deep learning neural network model of the photoacoustic guided wave characteristic parameters and the bone optical properties, tissue composition and structural mechanical properties to realize evaluation of the tissue composition and structural mechanical properties of the to-be-measured cortical bone.

[0056] Further, in the step S7, the step of inputting the feature parameters of the multi-wavelength photoacoustic guided wave signals in the to-be-tested cortical bone into the structural mechanical property and tissue composition step-by-step evaluation step, realizes the evaluation of the structural mechanical property and tissue composition of the to-be-tested cortical bone.

[0057] Embodiment:

[0058] Figure 1 is a schematic diagram of a long bone plate type standard part in the embodiment of the present application. In the embodiment, the long bone is first processed into a plate type standard part of l×w×h mm 3 by mechanical processing and sandpaper polishing.

[0059] Figure 2 is a schematic diagram of a photoacoustic guided wave detection experiment in the long bone in the embodiment of the present application. In the embodiment, a multi-wavelength laser is used to excite photoacoustic guided waves in the plate type bone standard part; sensors are symmetrically pasted on the upper and lower surfaces of the bone plate to detect guided wave signals, and an oscilloscope is used to receive; then data processing is performed.

[0060] Figure 3 is a flow chart of a method for evaluating the structural mechanical property and tissue composition of the cortical bone based on photoacoustic guided waves in the embodiment of the present application, comprising the following steps:

[0061] Step S1: The long bone is processed into a plate type standard part of a certain size, and then step S2 is entered.

[0062] As shown in Figure 1 , in the embodiment, the long bone is first processed into a plate type standard part of l×w×h mm 3 by mechanical processing and sandpaper polishing.

[0063] Step S2: A wavelength adjustable pulsed laser is used to excite photoacoustic guided waves in the bone plate, and a piezoelectric sensor symmetrically pasted on the upper and lower surfaces of the bone plate is used to receive photoacoustic guided wave signals, and then step S3 is entered.

[0064] As shown in Figure 2 , in the embodiment, a multi-wavelength laser is used to excite photoacoustic guided waves in the plate type bone standard part; sensors are symmetrically pasted on the upper and lower surfaces of the bone plate to detect guided wave signals of the bone plate, and an oscilloscope is used to store the upper and lower surface detected guided wave signals s u and s d ; then data processing is performed.

[0065] Step S3: Based on the guided wave mode characteristics in the plate, the photoacoustic signals received on the upper and lower surfaces of the bone plate are added and subtracted to extract the symmetric and anti-symmetric mode components of the photoacoustic guided waves, and then step S4 is entered.

[0066] In this embodiment, first, the normalized processing of the photoacoustic signals on the upper and lower surfaces of the bone plate is performed to obtain the normalized signal amplitude contrast of the guided waves excited by the pulsed laser at different wavelengths Figure 4 .

[0067] As shown in Figure 5 , in this embodiment, the half of the addition result of the upper and lower surface detection signals s s = 0.5×(s u +s d ) and the half of the subtraction result s a = 0.5×(s u -s d ) are used to obtain the symmetric mode and antisymmetric mode components of the photoacoustic guided waves.

[0068] As shown in Figure 6 , in this embodiment, the signal extreme extraction algorithm is used to obtain the amplitude information s max , s min , a max , a min of the first arrival wave maximum and minimum points of the symmetric and antisymmetric modes of the photoacoustic guided waves excited by the 2400 nm laser, and the amplitude ratio of the head wave extreme points of different modes is calculated.

[0069] In this embodiment, Figure 7 the comparison shows the comparison diagram of the bone light transmittance curve in the bone plate and the amplitude ratio of the A mode and S mode of the multi-wavelength photoacoustic guided waves, which clearly shows that the bone light transmittance curve and the amplitude ratio curve of different modes of the photoacoustic guided waves are in a mirror image relationship.

[0070] Step S4: based on the photoacoustic guided wave mode amplitude ratio spectrum of the distribution of the head wave extreme point amplitude ratio p of the photoacoustic guided waves excited by the pulsed laser at different wavelengths, and then entering step S5.

[0071] In this embodiment, Figure 8 the comparison shows the fitting comparison diagram of the bone light transmittance curve in the bone plate and the head wave amplitude ratio of the A mode and S mode of the multi-wavelength photoacoustic guided waves, which clearly shows that the amplitude ratio of different modes of the photoacoustic guided waves decays exponentially with the bone light transmittance.

[0072] Step S5: the Fourier spectrum technology is used to measure the light absorption, transmittance and scattering coefficients of the bone structure, the contents of hydroxyapatite, lipids and collagen in the bone, the bone mass and volume ratio is used to measure the bone density, and the three-point stress experiment is used to detect the bone strength, elastic modulus and Poisson's ratio parameters, and then enter step S6.

[0073] Step S6: repeat steps S1-S5 to obtain the different bone standard piece measurement photoacoustic guided wave mode amplitude ratio spectrum, bone tissue composition (apatite matrix, lipid and collagen), optical properties (optical transmittance, absorption coefficient, scattering coefficient), structural mechanical properties (density, strength, elastic modulus, Poisson's ratio) data, and establish the photoacoustic guided wave head wave arrival time, guided wave wavenumber, different guided wave mode head wave amplitude ratio spectrum, power spectrum slope and bone structural mechanical properties, optical properties, tissue composition mapping information library, and then enter step S7;

[0074] Step S7: the measured cortical bone is processed into a standard piece, the photoacoustic guided wave signal dispersion parameters of different wavelengths of pulsed laser excitation are detected and obtained through steps S2-S4, the different guided wave mode head wave amplitude ratio spectrum parameters are brought into the cortical bone photoacoustic guided wave mapping information library of step S6, and the acoustic evaluation of the optical properties, tissue composition and structural mechanical properties of the measured cortical bone is realized.

[0075] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves, characterized in that, Includes the following steps: Step S1: Process the cortical bone into a standard plate of a certain size, and then proceed to step S2; Step S2: Based on the axial propagation method, use lasers of different wavelengths to excite photoacoustic guided waves into the long bone, collect multi-wavelength photoacoustic guided wave signals, and then proceed to step S3; Step S3: Use signal processing technology to extract the characteristic parameters of the photoacoustic guided wave signal: head wave arrival time, wave number dispersion, and head wave amplitude ratio of different guided wave modes, and then proceed to step S4; In step S3, the upper and lower detection photoacoustic signals of the bone plate are first normalized to obtain signals s. u s d Then through s s =0.5×(s) u +s d ), s a =0.5×(s) u -s d Extract the symmetric and antisymmetric modes of the photoacoustic guided wave; then, use a signal extremum extraction algorithm to obtain the amplitude information s of the first arrival wave maxima and minima of the guided wave. max s min a max a min Calculate the amplitude ratio of wavefront poles in different modes. Used for evaluating bone tissue composition and related optical properties; Step S4: Plot the laser wavelength-optical waveguide mode amplitude ratio spectrum based on the amplitude ratio of each mode of the photoacoustic waveguide excited by lasers of different wavelengths, and then proceed to step S5; Step S5: Measure the optical properties, tissue composition, and structural mechanical properties of the bone standard, and then proceed to step S6; Step S6: Repeat steps S1 to S5 to obtain the characteristic parameters of photoacoustic guided wave signals and bone property data of different bone standard parts. Establish a database of information mapping between the characteristic parameters of photoacoustic guided waves, the relative parameter spectrum of photoacoustic guided wave modes and the mechanical properties, optical properties and tissue composition of bone structure, and then proceed to step S7. Step S7: The cortical bone to be tested is processed into a standard part, and the characteristic parameters of the multi-wavelength photoacoustic guided wave signal are tested and input into the cortical bone photoacoustic guided wave mapping information database in step S6 to realize the acoustic evaluation of the optical properties, tissue composition and structural mechanical properties of the cortical bone to be tested.

2. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 1, characterized in that, In step S3, the photoacoustic signals detected on the upper and lower surfaces of the bone plate are first normalized and the signal power spectral density is calculated. Then, a first-order Taylor fitting is used to analyze the slope of the power spectral density, and the slope of the fitted curve is extracted for the evaluation of bone tissue composition and related optical properties.

3. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 1, characterized in that, In step S3, the wave velocity of the waveguide head is extracted using the threshold method and the wave number of the photoacoustic waveguide is extracted using the waveform inversion method, which are used to evaluate the mechanical properties of bone structure according to elastic dispersion theory.

4. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 1, characterized in that, In step S4, the amplitude ratio of the head wave of each waveguide mode is obtained by using lasers of different wavelengths to excite the photoacoustic guided wave to obtain the amplitude ratio spectrum of the head wave of each waveguide mode.

5. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 1, characterized in that, In step S6, a mapping relationship is established between the optical properties of bone, tissue composition and structural mechanical properties and the head wave amplitude ratio spectrum, wave number and head wave velocity of different guided wave modes through a deep neural network model, and a mapping information database of the optical properties of bone, tissue composition and structural mechanical properties and photoacoustic guided wave parameters is established.

6. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 1, characterized in that, In step S6, the following step-by-step evaluation of structural mechanical properties and microstructure composition is also performed: Step S61: Establish the relationship between waveguide head wave arrival time, wavenumber dispersion and bone structure mechanical properties, density and thickness, evaluate bone structure mechanical property parameters, and proceed to step S62; Step S62: Based on step S61, establish the relationship between the amplitude ratio spectrum of the head wave extreme points of different guided wave modes and the bone optical properties, and proceed to step S63; Step S63: Based on step S61, establish the relationship between bone optical properties and tissue composition, and proceed to step S64; Step S64: Based on steps S62 and S63, establish the relationship between the amplitude ratio spectrum of the head wave extreme points of different guided wave modes and the bone tissue composition.

7. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 5, characterized in that, In step S7, the characteristic parameters of the multi-wavelength photoacoustic guided wave signal in the cortical bone to be tested are input into a deep learning neural network model of the photoacoustic guided wave characteristic parameters and the optical properties, tissue composition and structural mechanical properties of the bone, so as to realize the evaluation of the tissue composition and structural mechanical properties of the cortical bone to be tested.

8. The method for evaluating the composition and structural mechanical properties of bone tissue based on photoacoustic guided waves according to claim 6, characterized in that, In step S7, the characteristic parameters of the multi-wavelength photoacoustic guided wave signal in the cortical bone to be tested are input into the stepwise evaluation steps of structural mechanical properties and tissue composition, so as to realize the evaluation of the tissue composition and structural mechanical properties of the cortical bone to be tested.

Images