Bone health evaluation system and method based on photoacoustic guided wave frequency-wave number spectrum

Abstract

The invention discloses a bone health evaluation system and method based on a photoacoustic guided wave frequency-wave number spectrum. The bone health evaluation system comprises a computer, a transmitting and receiving control circuit, an analog-to-digital converter, a broadband tunable laser, a laser beam focusing light spot dynamic focusing system, a laser output head, a bone tissue to be detected, an ultrasonic array transducer and a multi-channel signal amplifier. The computer controls the wavelength and energy of a laser beam output by the broadband tunable laser through the transmitting and receiving control circuit, and meanwhile controls the laser beam focusing spot dynamic focusing system to adjust the spot size of the laser beam output to the bone tissue to be detected, so that photoacoustic guided wave excitation under different laser beam radiuses and wavelengths is realized; the transmitting and receiving control circuit synchronously controls the analog-to-digital converter to perform analog-to-digital conversion on the signal from the multi-channel signal amplifier, and inputs the signal into the computer for processing; the ultrasonic array transducer detects and obtains a photoacoustic guided wave time-space wave field signal matrix; and the computer performs frequency wave number spectrum processing on the received laser excitation photoacoustic guided wave signals with different beam radiuses and wavelengths, and executes a multi-mode photoacoustic bone quality evaluation method to realize bone health diagnosis.

Description

Technical Field

[0001] This invention relates to the field of bone structure and function evaluation, and in particular to a bone health evaluation system and method based on photoacoustic guided wave frequency-wavenumber spectrum. Background Technology

[0002] Ultrasound testing, characterized by its non-radiation and non-invasive nature, is a crucial tool for bedside ultrasound and bone health monitoring in infants, young children, and the elderly. Photoacoustic waves excited by a photothermal-structural coupling mechanism are sensitive to the optical and structural mechanical properties of bone tissue components, aiding in the accurate diagnosis of bone diseases. Existing ultrasound or photoacoustic methods for evaluating osteoporosis mainly include: photoacoustic backscattering method using in-situ detection to evaluate the composition and structural mechanical properties of calcaneal tissue for diagnosing osteoporosis; ultrasound guided wave detection technology based on guided wave dispersion theory, using piezoelectric sensors to establish the relationship between the dispersion characteristics of different modes of guided waves and the mechanical properties of bone structure, enabling quantitative assessment of parameters such as bone thickness, Young's modulus, and density; and quantitative assessment of the structural mechanical and optical properties of long cortical bone based on the relative changes in the amplitude of different modes of photoacoustic guided waves.

[0003] Existing photoacoustic backscattering methods are mainly used for detecting osteoporosis in the calcaneus. Ultrasonic guided wave detection technology based on piezoelectric sensor excitation is primarily used for detecting structural mechanical properties such as bone thickness, density, and Young's modulus, but it is insensitive to optical properties related to tissue composition, making it unsuitable for a comprehensive evaluation of tissue composition and structural mechanical properties. Existing axial propagation photoacoustic guided wave bone detection technology evaluates bone optical and structural mechanical properties by establishing a model of the rate of change of guided wave amplitude in different modes and the light transmission depth in bone. However, it lacks specificity for detecting the bone light absorption coefficient and reduced scattering coefficient, affecting the stability of the evaluation of bone tissue composition and structural mechanical properties. Furthermore, changes in laser beam size affect the amplitude information of the photoacoustic guided wave modes. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a bone health assessment system and method based on photoacoustic guided wave frequency-wavenumber spectrum, which has important clinical value and social significance for achieving accurate diagnosis of bone diseases.

[0005] To achieve the aforementioned objectives of the invention, the technical solution adopted to solve its technical problems is as follows: This invention discloses a bone health assessment system based on photoacoustic guided wave frequency-wavenumber spectrum, comprising a computer, a transmit-receive control circuit, an analog-to-digital converter, a wideband tunable laser, a laser beam focusing spot dynamic focusing system, a laser output head, the bone tissue to be tested, an ultrasonic array transducer, and a multi-channel signal amplifier, wherein: The computer is used to send instructions to the transmit and receive control circuit to control the wavelength, energy and frequency of the wideband tunable laser to excite the output laser beam, and simultaneously control the laser beam focusing spot dynamic focusing system to adjust the size of the laser beam spot output to the bone tissue to be tested. The transmit and receive control circuit is used to receive instructions from the computer, control the radius, wavelength, energy and frequency of the output laser beam of the broadband tunable laser, and synchronously control the analog-to-digital converter to convert the output signal from the multi-channel signal amplifier into an analog-to-digital signal and input it into the computer for processing. The wideband tunable laser is used to control the laser output head to irradiate the bone tissue under test with pulsed laser beams of different wavelengths and radii through the laser beam focusing spot dynamic focusing system, thereby performing multi-mode photoacoustic excitation. The laser beam focusing spot dynamic focusing system is used to adjust the radius of the received laser beam according to the instructions of the computer, and then apply it to the bone tissue to be tested through the laser output head; The ultrasonic array transducer is used to detect the photoacoustic guided wave time-space wave field signal matrix excited by the laser output from the laser output head irradiating the bone tissue to be tested; The analog-to-digital converter is used to convert the output signal from the multi-channel signal amplifier into an analog-to-digital signal and input it into the computer for processing. The computer is also used to receive and store the digital signals output by the analog-to-digital converter, process the received multi-mode photoacoustic signals, execute the multi-mode photoacoustic bone assessment method, and realize bone health diagnosis.

[0006] This invention also discloses a bone health assessment method based on photoacoustic guided wave frequency-wavenumber spectrum, which uses the aforementioned photoacoustic guided wave frequency-wavenumber spectrum-based bone health assessment system for evaluation, including the following steps: Step S1: Collect the time-space wave field signal matrix of multi-wavelength photoacoustic guided waves excited in bone tissue by lasers with different beam radii and wavelengths; then execute steps S2 and S3. Step S2: Extract the frequency wavenumber spectrum of the time-space wavefield signal matrix of the multi-wavelength photoacoustic guided wave; then proceed to step S4; Step S3: Measure the composition, optical properties, and structural mechanical properties of bone tissue; then proceed to step S4; Step S4: Repeat steps S1~S3 to obtain batch bone tissue physical property data and frequency-wavenumber spectrum data of multi-wavelength beam guides under different beam radii; then execute step S5; Step S5: Based on the physical property data of bone tissue, calibrate the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave under different beam radii; then proceed to step S6; Step S6: Based on the inverse solution model, establish a mapping model from the guided wave frequency-wavenumber spectrum of the excitation multi-wavelength beam under different beam radii to the physical properties of bone tissue; then execute step S7; Step S7: Input the photoacoustic backscattered signal and photoacoustic guided wave parameters of the bone tissue into the inverse solution model; then execute step S8; Step S8: Output the measured physical properties of bone tissue; then proceed to step S10; Step S9: Input clinical standard data for bone health; then proceed to step S10; Step S10: Compare the data on the physical properties of bone tissue measured in Step S8 with the clinical standard data for bone health in Step S9, and give the diagnosis result of bone health.

[0007] Furthermore, in step S2, a 2D Fourier transform is used to process the time-space wave field signal matrix of the multi-wavelength photoacoustic guided wave obtained by laser excitation with different beam radii and wavelengths, so as to obtain the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave signal matrix.

[0008] Furthermore, in step S3, Fourier spectroscopy is used to test the optical properties and tissue composition of the bone tissue to be tested, and micro-CT, three-point stress test, nanoindentation or ultrasound method are used to measure the structural mechanical properties including bone structure, elastic modulus, density and Poisson's ratio.

[0009] Furthermore, in step S6, a deep learning neural network and a multi-source, multi-objective transfer learning neural network are used to train the calibration data from step S5 to establish a mapping model between the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves and the composition and physical properties of bone tissue.

[0010] Furthermore, in step S7, the bone structure function evaluation system based on multi-wavelength photoacoustic guided wave frequency-wavenumber spectrum measures and obtains the photoacoustic guided wave time-space wave field signal matrix excited by a specific beam radius and wavelength laser in the tested bone tissue according to step S1, and extracts the photoacoustic guided wave frequency-wavenumber spectrum according to step S2; then the extracted frequency-wavenumber spectrum is input into the inverse solution model to evaluate the physical properties of the bone structure.

[0011] Furthermore, in step S8, the photoacoustic guided wave frequency-wavenumber spectrum extracted from the bone to be tested in step S7 is mapped and evaluated based on the mapping model trained in step S6, so as to obtain the functional properties of the bone structure to be tested, including thickness, density, elastic modulus, and porosity, as well as the tissue components including apatite matrix, collagen, and water.

[0012] By employing the above technical solutions, this invention has the following advantages and positive effects compared with the prior art: 1. A bone health evaluation system and method based on photoacoustic guided wave frequency-wavenumber spectrum is proposed, which can be used to obtain the time-space signal matrix of laser-excited photoacoustic guided waves with different beam radii and wavelengths in long cortical bone, and to evaluate the mechanical properties of bone structure and the content of tissue components.

[0013] 2. In the proposed bone health assessment system based on the frequency-wavenumber spectrum of photoacoustic guided waves, a computer synchronously controls a wide-band tunable laser and a dynamic focusing system for the laser beam focusing spot to achieve multi-wavelength photoacoustic guided wave excitation with lasers of different wavelengths under different laser beam radii. The radius of the excitation laser beam used to excite the photoacoustic guided waves in the bone is controlled by the dynamic focusing system for the laser beam focusing spot.

[0014] 3. In the proposed method for evaluating bone structure and function based on the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves excited by lasers of different wavelengths under different beam radii, the relationship between the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves excited by lasers of different wavelengths under different laser beam radii and the physical property data of bone tissue is calibrated. This avoids the insufficient acoustic information for evaluating the mechanical properties of bone structure and the optical properties related to tissue composition caused by the limited information of guided wave modes in the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves excited by lasers of different wavelengths under a single laser beam radius, thus ensuring the stability of bone health assessment. By learning the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves excited by lasers of different wavelengths under different laser beam radii using deep learning neural networks calibrated from the physical property data of bone tissue, a mapping model between the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves under different laser beam radii and the physical properties, optical properties, and tissue composition content of bone structure is established, which can be used to realize bone health assessment. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of a bone health assessment system based on photoacoustic guided wave frequency-wavenumber spectrum according to the present invention; Figure 2 This is a flowchart of a bone health assessment method based on photoacoustic guided wave frequency-wavenumber spectrum according to the present invention; Figure 3 Here are examples of the optical property curves of cortical bone in this invention: (a) absorption coefficient spectrum, (b) reduced scattering coefficient spectrum; Figure 4This is an example of the normalized frequency-wavenumber diagram of multi-wavelength photoacoustic guided waves excited by a 0.5 mm radius laser beam in bones of different thicknesses and optical properties according to the present invention; Figure 5 This is a graph showing the relationship between pixel values ​​and light absorption coefficients of a 0.5mm radius laser beam excited in a 1mm thick bone multi-wavelength photoacoustic waveguide mode according to the present invention. Figure 6 This is a schematic diagram showing that the rate of change of pixel values ​​of different frequencies A0 and S0 modes in the frequency-wavenumber spectrum of a multi-wavelength photoacoustic waveguide excited by a 0.5mm radius beam in bones of different thicknesses varies as a power function with the light transmission depth. Figure 7 This invention presents the frequency-wavenumber spectrum of photoacoustic guided waves excited by different laser beam radii in the bone.

[0016] [Explanation of Key Symbols] 1- Computer; 2- Transmit / receive control circuit; 3-Analog-to-Digital Converter; 4- Wideband tunable laser; 5-Laser beam focusing spot dynamic focusing system; 6-Laser output head; 7 - The bone tissue to be tested; 8-Ultrasonic array transducer; 9-Multi-channel signal amplifier. Detailed Implementation

[0018] 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.

[0019] Example 1 like Figure 1 As shown, this invention discloses a bone health assessment system based on photoacoustic guided wave frequency-wavenumber spectrum, comprising a computer 1, a transmit / receive control circuit 2, an analog-to-digital converter 3, a wideband tunable laser 4, a laser beam focusing spot dynamic focusing system 5, a laser output head 6, the bone tissue to be tested 7, an ultrasonic array transducer 8, and a multi-channel signal amplifier 9, wherein: The computer 1 is used to send instructions to the transmit and receive control circuit 2 to control the wavelength, energy and frequency of the output laser beam of the wideband tunable laser 4. While controlling the transmit and receive control circuit 2, it also controls the laser beam focusing spot dynamic focusing system 5 to adjust the size of the laser beam spot output to the bone tissue 7 to be tested. The transmit and receive control circuit 2 is used to receive instructions from the computer 1, control the radius, wavelength, energy and frequency of the output laser beam of the wideband tunable laser 4, and synchronously control the analog-to-digital converter 3 to convert the output signal from the multi-channel signal amplifier 9 into an analog-to-digital signal and input it into the computer 1 for processing. The wideband tunable laser 4 is used to control the laser output head 6 to irradiate the bone tissue 7 under test with pulsed laser beams of different wavelengths and radii through the laser beam focusing spot dynamic focusing system 5, thereby performing multi-mode photoacoustic excitation. The laser beam focusing spot dynamic focusing system 5 is used to adjust the radius of the received laser beam according to the instructions of the computer 1, and then apply it to the bone tissue to be tested 7 through the laser output head 6; The ultrasonic array transducer 8 is used to detect the photoacoustic guided wave time-space wave field signal matrix excited by the laser output head 6 irradiating the bone tissue 7 to be tested; The analog-to-digital converter 3 is used to convert the output signal from the multi-channel signal amplifier 9 into an analog-to-digital signal and input it into the computer 1 for processing. The computer 1 is also used to receive and store the digital signals output by the analog-to-digital converter 3, process the received multi-mode photoacoustic signals, execute the multi-mode photoacoustic bone assessment method, and realize bone health diagnosis.

[0020] Example 2 like Figure 2 As shown, this invention also discloses a bone health assessment method based on photoacoustic guided wave frequency-wavenumber spectrum, which uses the aforementioned photoacoustic guided wave frequency-wavenumber spectrum-based bone health assessment system for evaluation, including the following steps: Step S1: Collect the time-space wave field signal matrix of multi-wavelength photoacoustic guided waves excited in bone tissue by lasers with different beam radii and wavelengths; then execute steps S2 and S3. Step S2: Signal processing to extract the frequency-wavenumber spectrum of the time-space wavefield signal matrix of the multi-wavelength photoacoustic guided wave; the time-space wavefield signal matrix of the multi-wavelength photoacoustic guided wave obtained by laser excitation with different beam radii and wavelengths is processed by 2D Fourier transform to obtain the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave signal matrix; then proceed to step S4; Step S3: Measure the composition, optical properties, and structural mechanical properties of bone tissue; use Fourier transform spectroscopy to test the optical properties and tissue composition of the bone tissue to be tested, and use micro-CT, three-point stress testing, nanoindentation, or ultrasound to measure the structural mechanical properties including bone structure, elastic modulus, density, and Poisson's ratio; then proceed to step S4; Step S4: Repeat steps S1~S3 to obtain batch bone tissue physical property data and frequency-wavenumber spectrum data of multi-wavelength beam guides under different beam radii; then execute step S5; Step S5: Based on the physical property data of bone tissue, calibrate the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave under different beam radii; then proceed to step S6; Step S6: Based on the inverse solution model, establish a mapping model from the frequency-wavenumber spectrum of the multi-wavelength guided wave to the physical properties of bone tissue under different beam radii; for example, use a deep learning neural network or a multi-source multi-objective transfer learning neural network to train the calibration data in step S5 to establish a mapping model from the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave to the composition and physical properties of bone tissue; then execute step S7. Step S7: Input the photoacoustic backscattered signal and photoacoustic guided wave parameters of the bone tissue into the inverse solution model; based on the multi-wavelength photoacoustic guided wave frequency-wavenumber spectrum bone structure function evaluation system, according to step S1, measure and obtain the photoacoustic guided wave time-space wavefield signal matrix of the laser-excited specific beam radius and wavelength in the tested bone tissue, and according to step S2, extract the photoacoustic guided wave frequency-wavenumber spectrum; then input the extracted frequency-wavenumber spectrum into the inverse solution model to evaluate the physical properties of the bone structure; then execute step S8; Step S8: Output the physical property information data of the measured bone tissue; Based on the mapping model trained in step S6, perform mapping evaluation on the photoacoustic guided wave frequency-wavenumber spectrum extracted from the bone to be tested in step S7 to obtain the structural and functional properties of the bone to be tested, such as the structural mechanical shape of thickness, density, elastic modulus, porosity, etc., as well as tissue components such as apatite matrix, collagen, water, etc.; then execute step S10. Step S9: Input clinical standard data for bone health; then proceed to step S10; Step S10: Compare the data on the physical properties of bone tissue measured in Step S8 with the clinical standard data for bone health in Step S9, and give the diagnosis result of bone health.

[0021] Figure 3 The light absorption coefficients and reduced scattering coefficients of three cortical bones, S1, S2, and S3, are given. The reduced scattering coefficient of the bone tissue is also given. Comparison of absorption coefficient μ a There are greater differences. Typical optical properties (0.014 mm) were then analyzed. -1 0.498mm -1 (0.014mm) -1 4.98mm -1 (0.469mm) -1 0.8mm -1 ), Frequency-wavenumber spectrum characteristics of laser-excited photoacoustic guided waves in bones of different thicknesses.

[0022] Figure 4 Frequency-wavenumber diagrams (thickness, absorption coefficient μ) of multi-wavelength photoacoustic guided waves excited by a 0.5 mm radius laser beam in bones of different thicknesses and optical properties. a Reduced scattering coefficient (a) (1mm, 0.014mm) -1 0.498 mm -1 (b)(1mm, 0.014mm) -1 4.98mm -1 (c) (1mm, 0.469mm) -1 0.8mm -1 (d) (3mm, 0.014mm) -1 0.498mm -1 (e) (3mm, 0.014mm) -1 4.98mm -1 (f) (3mm, 0.469mm) -1 0.8mm -1 (g)(5mm, 0.014mm) -1 0.498mm -1 (h) (5mm, 0.014mm) -1 4.98mm -1 (i) (5mm, 0.469mm) -1 0.8mm -1 ). Figure 4 The modal components and their associated pixel values ​​in the normalized frequency-wavenumber plots of multi-wavelength photoacoustic guided waves excited by a 0.5 mm radius laser beam in bones of different thicknesses and optical properties exhibit specificity, for example: Figure 4 (a)~(c) In the photoacoustic guided wave frequency-wavenumber spectrum of 1mm thick bone, only A0 and S0 modes exist. The pixel value of S0 mode changes more significantly with the bone absorption coefficient and reduced scattering coefficient than the pixel value of A0 mode. Figure 4 The bone resorption coefficient in both (a) and (b) is 0.014 mm. -1 However, the pixel values ​​of the S0 mode at various frequencies change with the reduced scattering coefficient from 0.498 mm. -1 It became 4.98mm -1 And decreased by 0.014 mm. -1 Absorption coefficient, 0.498 mm -1 Reduced scattering coefficient, frequency wavenumber spectrum of photoacoustic guided waves in bone with thicknesses of 1 mm, 3 mm, and 5 mm Figure 4In (a), (d), and (g), the guided wave mode types increase with increasing bone thickness, and the changes in the pixel values ​​of each mode at different frequency points are different. The guided wave frequency-wavenumber curves in bones with other different light absorption coefficients and reduced scattering coefficients also show the above differences. In summary, this indicates that the guided wave mode dispersion characteristics and pixel value characteristics of each mode in the photoacoustic guided wave frequency-wavenumber spectrum exhibit specificity and sensitivity to the light absorption coefficient and reduced scattering coefficient related to bone tissue components.

[0023] To further verify the sensitivity of modal pixel values ​​in the photoacoustic guided wave frequency-wavenumber spectrum to the optical properties of bone tissue, pixel values ​​of the A0 and S0 modal components in the 200kHz–600kHz range were extracted from the photoacoustic guided wave frequency-wavenumber spectrum. The quantitative relationship between the pixel values ​​of each modality and the bone optical coefficient and light transmission depth was analyzed. The light transmission depth δ is related to the light absorption coefficient μ. a Reduced scattering coefficient The relationship is .

[0024] Figure 5 The relationship between the pixel value and the light absorption coefficient of the multi-wavelength photoacoustic guided wave mode excited by a 0.5 mm radius laser beam in a 1 mm thick bone is shown in the figure: (a) the pixel value of the A0 mode changes with the light absorption coefficient, and (b) the pixel value of the S0 mode changes with the light absorption coefficient. Figure 5 (a) and (b) respectively show the changes in the pixel values ​​of the A0 and S0 modes as a function of the light absorption coefficient in the frequency wavenumber spectrum of the photoacoustic waveguide excited by a 0.5 mm radius laser beam in bone with a thickness of 1 mm. At the same frequency, the pixel value of the A0 mode is higher than that of the S0 mode. The pixel value of the mode at each frequency increases with the increase of the light absorption coefficient.

[0025] Figure 6 This demonstrates the A0 mode pixel values ​​u at various frequency points from 200Hz to 600kHz in the wavenumber spectrum of a multi-wavelength beam guided by a 0.5mm radius laser-excited beam in bones of different thicknesses. a With S0 mode pixel value u s The modal pixel value change rate r=(u a -u s ) / u s The variation of light transmission depth as a power function. Figure 6 In (a), the rate of change of modal pixel values ​​at different frequencies in 1 mm thick bone decreases with the power function of light transmission depth; the median of the box plot of the rate of change of modal pixel values ​​at each frequency with the power function exponent fitted to the light transmission depth increases with increasing bone thickness.

[0026] Figure 6The rate of change of modal pixel values ​​at different frequencies (A0 and S0) in the frequency-wavenumber spectrum of multi-wavelength photoacoustic guided waves excited by a 0.5 mm radius beam in bones of different thicknesses varies with the light transmission depth as a power function: (a) Power function fitting of modal pixel value change rate with light transmission depth in 1 mm thick bone, (b) Statistical graph of modal pixel value change rate at different frequencies in bones of different thicknesses with the power function exponent of light transmission depth.

[0027] Figure 7 (a)~(c) show 0.469mm -1 Absorption coefficient, 0.8mm -1 Reduced scattering coefficient, frequency-wavenumber spectrum characteristics of laser-excited multi-wavelength beam guides with radii of 1 mm, 2 mm and 2.5 mm in a 3 mm thick bone: (a) wavenumber diagram of photoacoustic guide excited by 1 mm beam radius; (b) wavenumber diagram of photoacoustic guide excited by 2 mm beam radius; (c) wavenumber diagram of photoacoustic guide excited by 2.5 mm beam radius.

[0028] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A bone health evaluation system based on photoacoustic guided wave frequency- wavenumber spectrum, characterized by, The system comprises a computer, a transmitting-receiving control circuit, an analog-to-digital converter, a wide-band tunable laser, a laser beam focusing spot dynamic focusing system, a laser output head, a bone tissue to be measured, an ultrasonic array transducer, and a multi-channel signal amplifier. The computer is configured to send instructions to the transmitting-receiving control circuit to control the wavelength, energy and frequency of the laser beam emitted by the wide-band tunable laser, and to control the laser beam focusing spot dynamic focusing system to adjust the size of the laser beam spot output onto the bone tissue to be measured. The transmitting-receiving control circuit is configured to receive instructions from the computer, control the radius, wavelength, energy and frequency of the laser beam emitted by the wide-band tunable laser, and synchronously control the analog-to-digital converter to perform analog-to-digital conversion on the output signal from the multi-channel signal amplifier and input the computer for processing. The wide-band tunable laser is configured to control the laser output head to irradiate pulsed laser beams of different wavelengths and radii onto the bone tissue to be measured through the laser beam focusing spot dynamic focusing system to perform multi-mode photoacoustic wave excitation. The laser beam focusing spot dynamic focusing system is configured to adjust the radius of the received laser beam according to the instructions from the computer, and then act on the bone tissue to be measured through the laser output head. The ultrasonic array transducer is configured to detect the photoacoustic guided wave time-space wave field signal matrix excited by the laser irradiated by the laser output head onto the bone tissue to be measured. The analog-to-digital converter is configured to perform analog-to-digital conversion on the output signal from the multi-channel signal amplifier and input the computer for processing. The computer is further configured to receive and store the digital signal output by the analog-to-digital converter, process the received multi-mode photoacoustic signal, perform a multi-mode photoacoustic bone quality evaluation method, and realize bone health diagnosis.

2. A method for bone health evaluation based on photoacoustic guided wave frequency- wavenumber spectrum, characterized by, The bone health evaluation system based on the photoacoustic guided wave frequency-wavenumber spectrum according to claim 1 is used for evaluation, comprising the following steps: Step S1: collecting a multi-wavelength photoacoustic guided wave time-space wave field signal matrix excited by laser beams of different beam radii and wavelengths in the bone tissue; then performing steps S2 and S3; Step S2: signal processing to extract the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave time-space wave field signal matrix; then performing step S4; Step S3: measuring the composition, optical properties and structural mechanical properties of the bone tissue; then performing step S4; Step S4: repeating steps S1-S3 to obtain batch physical property data of the bone tissue and frequency-wavenumber spectrum data of the multi-wavelength beam guided wave excited under different beam radii; then performing step S5; Step S5: calibrating the frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave excited under different beam radii based on the physical property data of the bone tissue; then performing step S6; Step S6: establishing a mapping model from the frequency-wavenumber spectrum of the multi-wavelength beam guided wave excited under different beam radii to the physical properties of the bone tissue based on an inverse solution model; then performing step S7; Step S7: input the photoacoustic backscattering signal and the photoacoustic guided wave parameter of the bone tissue into the inverse solution model; then perform step S8; Step S8: output the measured bone tissue physical property information data; then perform step S10; Step S9: input the bone health clinical standard data; then perform step S10; Step S10: compare the measured bone tissue physical property information data in step S8 with the bone health clinical standard data in step S9, and give a bone health diagnosis result.

3. The method for bone health evaluation based on photoacoustic guided-wave frequency-wavenumber spectrum according to claim 2, characterized in that, In step S2, the 2D Fourier transform is used to process the multi-wavelength photoacoustic guided wave time-space wave field signal matrix obtained by laser excitation with different beam radii and wavelengths, to obtain a frequency-wavenumber spectrum of the multi-wavelength photoacoustic guided wave signal matrix.

4. The method for bone health evaluation based on photoacoustic guided-wave frequency-wavenumber spectrum according to claim 2, characterized in that, In step S3, the Fourier spectrum technology is used to test the optical properties and tissue components of the bone tissue to be measured, and the micro-CT, three-point stress test method, nano indentation or ultrasonic method is used to measure the structural mechanical properties including bone structure, elastic modulus, density and Poisson's ratio.

5. The method for bone health evaluation based on photoacoustic guided-wave frequency-wavenumber spectrum according to claim 2, characterized in that, In step S6, the deep learning neural network and multi-source multi-target transfer learning neural network are used to train the calibration data in step S5, to establish a mapping model of the multi-wavelength photoacoustic guided wave frequency-wavenumber spectrum and the bone tissue components and physical properties.

6. The method for bone health evaluation based on photoacoustic guided-wave frequency-wavenumber spectrum according to claim 2, characterized in that, In step S7, based on the bone structure function evaluation system of the multi-wavelength photoacoustic guided wave frequency-wavenumber spectrum, the photoacoustic guided wave time-space wave field signal matrix of the measured bone tissue excited by a specific beam radius and wavelength laser is obtained according to step S1, and the photoacoustic guided wave frequency-wavenumber spectrum is extracted according to step S2; then the extracted frequency-wavenumber spectrum is input into the inverse solution model for bone structure physical property evaluation.

7. The method of evaluating bone health based on photoacoustic guided-wave frequency- wavenumber spectrum according to claim 2, characterized in that, In step S8, based on the mapping model trained in step S6, the photoacoustic guided wave frequency-wavenumber spectrum extracted from the bone to be measured in step S7 is mapped and evaluated, to obtain the bone structure functional properties including thickness, density, elastic modulus and porosity, and the tissue components including apatite matrix, collagen and water.

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