System and method for evaluating microvascular calcification of diabetic foot based on photoacoustic viscoelasticity imaging

Abstract

The application discloses a kind of based on photoacoustic viscoelasticity imaging's diabetic foot microvessel calcification evaluation system and method, the method includes: pulsed laser of laser is emitted by focusing objective lens, is irradiated on the foot surface tissue of diabetic patient and generates photoacoustic signal;Using phase-locked amplifier extraction photoacoustic signal's phase delay;Computer control motor scans foot surface tissue and saves photoacoustic signal data and photoacoustic signal's phase delay data.Photoacoustic signal is processed to extract the time width information of wave crest, the wave crest time width data of each point photoacoustic signal and phase delay data are respectively mapped to image in the form of gray value, and the image about the elasticity and viscoelasticity of diabetic foot surface tissue is reconstructed.Calcification threshold and inflammation threshold are set, and the imaging area is divided into different elastic regions using threshold segmentation method, and then the vascular calcification of diabetic foot is evaluated using viscoelasticity parameters, to detect whether there is calcification and inflammation in the microvessel of diabetic foot.

Description

Technical Field

[0001] This invention belongs to the field of photoacoustic microscopy imaging technology, and relates to a system and method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging. Background Technology

[0002] With improved living conditions and an aging population, the number of diabetic patients in my country is gradually increasing. Currently, the prevalence of diabetes in my country is as high as 11.2%. Among those who have had diabetes for more than 10 years, 15% to 20% will develop diabetic foot, and the amputation rate above the ankle for diabetic foot patients is 4%. These data show that diabetic foot is extremely harmful, characterized by high incidence, poor treatment outcomes, recurrent attacks, high treatment costs, and a high amputation rate. Long-term hyperglycemia in diabetic patients can cause endothelial cell dysfunction, changes in blood viscosity and arterial wall tension, leading to systemic vascular damage and foot ulcers. Abnormal vascular networks cause problems with oxygen delivery, and the excessive angiogenesis in the corresponding areas due to hypoxia can worsen the condition of diabetic foot patients and lead to numerous complications. For example, vascular calcification is a common complication of diabetes. As a major manifestation of the end stage of atherosclerosis, vascular calcification is a process in which calcium salts are actively deposited in vascular tissue under the mediation of various cells. It can cause increased vascular wall stiffness, decreased compliance, plaque rupture, and thrombosis. Vascular calcification is also an important marker for predicting cardiovascular and cerebrovascular events in diabetic patients. Therefore, monitoring calcification information of the vascular network system can reveal the development and risk factors of diabetic foot, which is of great significance for its clinical screening, prevention, treatment and prognostic assessment.

[0003] Currently, the main methods for assessing vascular calcification include imaging techniques such as CT angiography (CTA), conventional X-ray imaging, and ultrasound. CT can quantitatively detect vascular calcification. The Agatston calcification scoring method is currently the most commonly used. However, the high cost and limited availability of CT scans restrict their widespread use in vascular calcification detection. X-ray imaging is advantageous for detecting vascular calcification due to its simplicity and low cost, but it is not suitable for detecting early-stage vascular calcification. Vascular ultrasound is mainly used to detect atherosclerotic lesions and calcifications in superficial arteries such as the carotid artery. This method is low-cost and radiation-free. However, the accuracy of the detection is affected by factors such as the skill of the examiner. Summary of the Invention

[0004] This invention proposes a microvascular calcification assessment system for diabetic foot based on photoacoustic viscoelastic imaging.

[0005] The technical solution to achieve the purpose of this invention is: a microvascular calcification assessment system for diabetic foot based on photoacoustic viscoelastic imaging, the system comprising: a photoacoustic excitation module, a signal detection module, a scanning module, a data acquisition module, an assessment module, and a control module.

[0006] The photoacoustic excitation module is used to emit laser light onto the surface tissue of the foot to generate photoacoustic signals;

[0007] The signal detection module is used to receive and amplify the photoacoustic signals from the surface tissue of the foot.

[0008] The control module is used to control the photoacoustic excitation module to generate corresponding lasers and to control the scanning module to drive the data acquisition module to collect photoacoustic signals of the foot surface tissue point by point.

[0009] The data acquisition module is used to acquire the photoacoustic signal amplified by the detection module and determine the phase delay between the photoacoustic signal and the control signal used by the control module to control the photoacoustic excitation module.

[0010] The evaluation module is used to determine the elastic modulus and viscoelastic data based on the photoacoustic signal and phase delay, and compares the elastic modulus and viscoelastic data with the calcification threshold and inflammation threshold to obtain the evaluation result.

[0011] This invention also proposes a method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging, comprising the following steps:

[0012] S1: A laser is emitted onto the surface tissue of the foot, causing the surface tissue to generate photoacoustic signals;

[0013] S2: Scan the foot surface tissue point by point to obtain photoacoustic signal data and photoacoustic signal phase delay data at different locations on the foot surface tissue;

[0014] S3: Extract the time interval between two adjacent zero points before and after the maximum value of the photoacoustic signal obtained by scanning to obtain the time width information of the peak. At the same time, map the peak time width data and phase delay data of the photoacoustic signal at each point onto the image in the form of gray values. Calculate the elastic modulus and viscoelasticity based on the peak time width information and phase delay data to reconstruct the elastic and viscoelastic images of the foot surface tissue.

[0015] S4: Replace the foot surface tissue with the foot surface tissue of a diabetic foot model with different degrees of calcification, repeat S2 and S3, obtain the elastic modulus range and viscoelastic range corresponding to different degrees of calcification, and extract the calcification threshold and inflammation threshold based on the elastic modulus range and viscoelastic range corresponding to different degrees of calcification.

[0016] S5: Using the methods in steps S2 to S3, obtain the elastic modulus and viscoelasticity of the surface tissue of the foot to be tested. Based on the elastic modulus and viscoelasticity, reconstruct an elastic image to determine whether microvascular calcification of the diabetic foot exists. Display the microvascular calcification area of ​​the diabetic foot in the elastic image of the detection area, and at the same time determine whether inflammation exists.

[0017] Preferably, the formula for calculating the viscoelasticity of the foot surface tissue is:

[0018] tanδ / ω=μ / E

[0019] Where μ is the viscosity coefficient, E is the elastic modulus, ω is the modulation angular frequency, and δ is the phase delay.

[0020] Preferably, the specific formula for calculating the elastic modulus of the foot surface tissue is as follows:

[0021] E = Kρ(R / t) 2

[0022] Where ρ is the density of the surface tissue of the diabetic foot, R is the diameter of the laser spot on the surface tissue of the diabetic foot, K is the system constant, and E is the elastic modulus of the surface tissue of the foot.

[0023] Preferably, the specific method for determining the calcification threshold is as follows:

[0024] The degree of microvascular calcification in diabetic foot was represented by a vascular calcification score A. Specifically, the degree of vascular calcification in diabetic foot was determined by a positive correlation between A and elastic modulus E. The calcification thresholds corresponding to different degrees of calcification were determined by classifying the degree of vascular calcification in the foot of diabetic foot models of the same age group into mild, moderate, and severe calcification. A=1 represented mild calcification, A=2 represented moderate calcification, and A=3 represented severe calcification.

[0025] The elastic modulus ranges corresponding to the three degrees of calcification were determined. The minimum value of the elastic modulus range corresponding to mild calcification was taken as the calcification threshold, the minimum value of the elastic modulus range corresponding to moderate calcification was taken as the moderate calcification threshold, and the minimum value of the elastic modulus range corresponding to severe calcification was taken as the severe calcification threshold.

[0026] Preferably, the specific method for obtaining the inflammation threshold is as follows: take the maximum value among the ratios of viscosity coefficient and elastic modulus of vascular tissue in healthy foot tissue of the same age group as the inflammation threshold.

[0027] Preferably, the specific method for evaluating microvascular calcification of the surface tissue of diabetic foot using elasticity information of diabetic foot is as follows: marking the area in the imaging region of the diabetic foot with an elastic modulus higher than a preset calcification threshold as the calcified area; and using the elastic modulus information to evaluate the degree and location of calcification.

[0028] Preferably, the viscoelasticity information of the surface tissue of diabetic foot is used to assess whether there is inflammation in the calcified area. Specifically, the area in the calcified area where the ratio of viscosity coefficient to elastic modulus is greater than a preset inflammation threshold is marked as an inflammatory area.

[0029] Compared with the prior art, the significant advantages of this invention are: this invention uses photoacoustic viscoelastic imaging to study the evaluation mechanism of vascular calcification assessment in diabetic foot, obtains information on the degree of calcification, and can be detected non-invasively, reducing psychological trauma to patients; by applying photoacoustic microscopy, high-resolution imaging of microvessels can be achieved, enabling the detection of microvascular calcification in diabetic foot.

[0030] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the photoacoustic viscoelastic imaging-based system for evaluating vascular calcification according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the signal detection part of the photoacoustic viscoelastic imaging-based system for evaluating vascular calcification according to an embodiment of the present invention.

[0033] Figure 3 This is a flowchart of a method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging. Detailed Implementation

[0034] As one example, such as Figure 1 As shown, a microvascular calcification assessment system for diabetic foot based on photoacoustic viscoelastic imaging is disclosed. The system includes: a photoacoustic excitation module, a signal detection module, a scanning module, a data acquisition module, an assessment module, and a control module. The photoacoustic excitation module is used to emit laser light onto the surface tissue of the foot to generate a photoacoustic signal.

[0035] The signal detection module is used to receive and amplify the photoacoustic signals from the surface tissue of the foot.

[0036] The control module is used to control the photoacoustic excitation module to generate corresponding laser pulses and to control the scanning module to drive the data acquisition module to collect photoacoustic signals of the foot surface tissue point by point.

[0037] The data acquisition module is used to acquire the photoacoustic signal amplified by the detection module and determine the phase delay between the photoacoustic signal and the control signal used by the control module to control the photoacoustic excitation module.

[0038] The evaluation module is used to determine the elastic modulus and viscoelastic data based on the photoacoustic signal and phase delay, and compare the elastic modulus and viscoelastic data with the calcification threshold and inflammation threshold to obtain the evaluation results.

[0039] In one embodiment, the photoacoustic excitation module includes a pulsed laser, a 4f system, and a focusing objective; the signal detection module includes an ultrasonic detector and a preamplifier; the signal acquisition module includes an oscilloscope and a lock-in amplifier; the scanning module includes a stepper motor; the control module includes a function generator and a computer; and the evaluation module performs corresponding functions via a computer.

[0040] In some embodiments, the laser wavelength is 532 nm;

[0041] In some embodiments, the ultrasonic detector is a hollow broadband ultrasonic detector with a bandwidth of 100 kHz to 10 MHz.

[0042] The laser emits pulsed laser light under the control of the function generator. After being collimated and filtered by a 4f system, the pulsed laser light shines through a focusing objective lens onto the foot surface tissue at the focal point, exciting a photoacoustic signal. Specifically, the foot surface tissue is in contact with a transparent coupling medium; the laser light shines through the transparent coupling medium onto the foot surface tissue, generating a photoacoustic signal.

[0043] The photoacoustic signal is received by an ultrasonic detector through a transparent coupling medium. Specifically, the ultrasonic detector is a hollow ring, and a laser beam passing through the hollow part of the ultrasonic detector via a focusing lens irradiates the surface tissue of the foot. The positions of the ultrasonic detector and the focusing lens are fixed, and the drive motor moves in response to the control signal from the computer. Each time the movement occurs, the data acquisition module acquires the photoacoustic signal and phase delay at the corresponding position.

[0044] Each time the ultrasonic detector receives a photoacoustic signal, it is amplified by an amplifier and then input to an oscilloscope and a lock-in amplifier, respectively.

[0045] The synchronization signal of the laser controlled by the function generator is input to the lock-in amplifier as a reference signal. The lock-in amplifier calculates the phase difference between the photoacoustic signal and the reference signal, i.e., the phase delay.

[0046] The oscilloscope and lock-in amplifier are connected to the computer to transmit photoacoustic signals and phase delay data to the computer.

[0047] Before using this system for evaluation, N groups of diabetic foot models with different age groups and different degrees of calcification were constructed. The signal detection module collected photoacoustic signals from the surface tissues of the foot at different age groups and with different degrees of calcification. The data acquisition module collected the photoacoustic signals and the phase delay between the photoacoustic signals and the control signals used by the control module to control the photoacoustic excitation module, and transmitted them to the computer. The computer determined the elastic modulus range and viscoelastic range corresponding to different degrees of calcification based on this information, thereby determining the calcification threshold and inflammation threshold.

[0048] When using this system for evaluation, the elastic modulus and viscoelasticity of the foot detection area are obtained, an elastic image is reconstructed, the presence of microvascular calcification in diabetic foot is determined, and the microvascular calcification area of ​​diabetic foot is displayed in the elastic image of the detection area, while the presence of inflammation is also determined.

[0049] As another embodiment, such as Figure 3 As shown, a method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging includes the following steps:

[0050] The laser is activated, emitting a 532nm wavelength pulsed laser. After collimation, filtering, and focusing, the laser beam illuminates the surface tissue of the diabetic foot at the focal point of the focusing objective, exciting a photoacoustic signal. This signal is then received by an ultrasound detector via a coupling agent. The photoacoustic signal received by the ultrasound detector is amplified and input to an oscilloscope and a lock-in amplifier. A function generator controls the laser to emit pulsed laser light with a repetition frequency of up to 200kHz, and controls the laser's synchronization signal to be input to the lock-in amplifier as a reference signal. The lock-in amplifier calculates the phase delay between the photoacoustic signal and the reference signal. The oscilloscope and lock-in amplifier save the acquired photoacoustic signal and its phase delay data to a computer. The computer controls the scanning module; with each movement of the stepper motor, the computer saves the photoacoustic signal and its phase delay data. This process acquires the photoacoustic signal and its phase delay data for the detection area of ​​the diabetic foot surface tissue.

[0051] The computer processes the photoacoustic signals at each point and extracts the time difference between two adjacent zero points of the photoacoustic signal peak, which is called the peak time width. The MATLAB program maps the peak time width data and phase delay data of the photoacoustic signals at each point onto the image in the form of gray values. Based on the calculated elastic modulus and viscoelastic data, the elastic and viscoelastic information of the surface tissue of diabetic foot is reconstructed.

[0052] The specific calculation methods for elastic modulus and viscoelasticity are as follows:

[0053] 1. Calculation of viscoelasticity of diabetic foot surface tissue: The specific relationship between the viscoelasticity of diabetic foot surface tissue and the phase delay δ of photoacoustic signal is as follows:

[0054] tanδ / ω=μ / E

[0055] In the formula, μ is the viscosity coefficient of vascular tissue, E is the elastic modulus, and ω is the modulation angular frequency.

[0056] 2. Calculation of elastic modulus of surface tissue in diabetic foot: The specific formula for the elastic modulus E of surface tissue in diabetic foot and the time width t of the peak is expressed as follows:

[0057] E = Kρ(R / t) 2

[0058] In the formula, ρ is the density of the surface tissue of diabetic foot, R is the diameter of the laser spot on the surface tissue of diabetic foot focused by the laser, and K is the system constant, which is calculated from the reference data in step S1.

[0059] Using elastic and viscoelastic information of foot surface tissues from diabetic foot models of the same age but with different degrees of calcification, elastic and viscoelastic ranges corresponding to different degrees of calcification were obtained. The vascular calcification score A was used to represent the degree of microvascular calcification in diabetic feet. The specific relationship between the degree of vascular calcification and the vascular elastic modulus E in diabetic feet is as follows:

[0060] A∝E

[0061] To obtain the elastic modulus range corresponding to different degrees of calcification, the specific method is as follows: The degree of vascular calcification in the foot of diabetic foot models of the same age group is divided into mild calcification (A=1), moderate calcification (A=2), and severe calcification (A=3). The elastic modulus range corresponding to each of the three degrees of calcification is measured. The minimum value of the elastic modulus range corresponding to mild calcification is taken as the calcification threshold, the minimum value of the elastic modulus range corresponding to moderate calcification is taken as the moderate calcification threshold, and the minimum value of the elastic modulus range corresponding to severe calcification is taken as the severe calcification threshold. This obtains the elastic modulus and viscoelastic range corresponding to different degrees of calcification, preparing for the assessment of vascular calcification and inflammation.

[0062] Diabetic foot vascular calcification was assessed using viscoelastic parameters of the foot surface tissue. Areas exceeding the calcification and inflammation thresholds were marked as calcified and inflammatory areas, respectively, and displayed in the images to identify microvascular calcification areas in the diabetic foot and determine the presence of inflammation.

[0063] Preferably, the specific method for evaluating microvascular calcification of the surface tissue of diabetic foot using elastic information of diabetic foot is as follows: marking the area in the imaging region of the diabetic foot with an elastic modulus higher than a preset calcification threshold as the calcified area;

[0064] The specific method is as follows: areas in the imaging region that are above the mild calcification threshold but below the moderate calcification threshold are marked as mild calcification areas, and so on, moderate calcification areas and moderate calcification areas are marked, thereby assessing the degree and location of calcification.

[0065] Preferably, the viscoelasticity information of the surface tissue of diabetic foot is used to assess whether there is inflammation in the calcified area. Specifically, the maximum value of the viscoelastic range of the blood vessel tissue of healthy foot is set as the inflammation threshold, and the area in the calcified area with viscoelasticity greater than the preset inflammation threshold is marked as the inflammatory area.

[0066] This embodiment utilizes photoacoustic microscopy to effectively acquire images of vascular calcification at different degrees. Because vascular calcification causes calcium ions to accumulate on the vessel wall, it increases the elastic modulus of the blood vessel, leading to arteriosclerosis and increased elastic modulus. Different elastic modulus values ​​reflect the degree of vascular calcification. Therefore, by using elastic modulus data obtained from normal blood vessel samples as a control group, and assessing the degree of vascular calcification based on photoacoustic elastic modulus data, a photoacoustic image of vascular calcification distribution can be reconstructed.

[0067] This systematic approach can non-invasively and effectively detect vascular calcification of varying degrees. It can also use the phase delay detected by the lock-in amplifier to perform viscoelastic imaging and assess whether inflammation has occurred in the calcified vascular area. In addition, the system has the capability of high-resolution imaging detection and can be applied to high-resolution detection.

[0068] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

[0069] This invention utilizes photoacoustic microscopy (PAM) technology to perform photoacoustic phase-delay imaging for the assessment of vascular calcification. By focusing a laser through a microscope objective, a smaller laser spot can be generated on the sample, enabling the detection of microvessels and achieving high-resolution imaging of microvessels within human skin. Finally, the degree of vascular calcification in diabetic foot is evaluated based on the correlation between vascular viscoelasticity information and vascular calcification. Furthermore, this method offers advantages such as safety and low cost.

[0070] The embodiments are described in more detail.

Claims

1. A method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging, wherein the method is implemented by a computer, characterized in that... Includes the following steps: S1: Emits a laser beam to the surface tissue of the foot, generating a photoacoustic signal; S2: Scan the foot surface tissue point by point to obtain photoacoustic signal data and photoacoustic signal phase delay data at different locations on the foot surface tissue; S3: Extract the time interval between two adjacent zero points before and after the maximum value of the photoacoustic signal obtained from the scan to obtain the time width information of the peak. Simultaneously, map the peak time width data and phase delay data of the photoacoustic signal at each point onto the image in grayscale form. Calculate the elastic modulus and viscoelasticity based on the peak time width information and phase delay data to reconstruct an image of the elasticity and viscoelasticity of the foot surface tissue, called the elastic image. The formula for calculating the viscoelasticity of the foot surface tissue is: in, It is the viscosity coefficient. It is the elastic modulus. It is the modulation angular frequency. For phase delay; The specific formula for calculating the elastic modulus of foot surface tissue is as follows: in, R represents the density of the surface tissue of the diabetic foot, and R is the diameter of the laser spot on the surface tissue of the diabetic foot when focused. For system constants, The elastic modulus of the surface tissue of the foot; S4: Replace the foot surface tissue with the foot surface tissue of a diabetic foot model with different degrees of calcification, repeat S2 and S3, obtain the elastic modulus range and viscoelastic range corresponding to different degrees of calcification, and extract the calcification threshold and inflammation threshold based on the elastic modulus range and viscoelastic range corresponding to different degrees of calcification. S5: Using the methods in steps S2 to S3, obtain the elastic modulus and viscoelasticity of the surface tissue of the foot to be tested. Based on the elastic modulus and viscoelasticity, determine whether microvascular calcification of diabetic foot exists, and display the microvascular calcification area of ​​diabetic foot in the elastic image of the detection area on the foot surface. At the same time, use the viscoelastic information of the surface tissue of diabetic foot to assess whether there is inflammation in the calcification area.

2. The method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging according to claim 1, characterized in that, The specific method for determining the calcification threshold is as follows: The degree of microvascular calcification in diabetic foot was represented by the vascular calcification score A. The degree of vascular calcification in diabetic foot A was positively correlated with the elastic modulus E. The calcification threshold corresponding to different degrees of calcification was determined by classifying the degree of vascular calcification in the feet of diabetic foot models of the same age group into mild calcification, moderate calcification, and severe calcification. A=1 indicates mild calcification, A=2 indicates moderate calcification, and A=3 indicates severe calcification. The elastic modulus ranges corresponding to the three degrees of calcification were determined. The minimum value of the elastic modulus range corresponding to mild calcification was taken as the calcification threshold, the minimum value of the elastic modulus range corresponding to moderate calcification was taken as the moderate calcification threshold, and the minimum value of the elastic modulus range corresponding to severe calcification was taken as the severe calcification threshold.

3. The method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging according to claim 1, characterized in that, The specific method for obtaining the inflammation threshold is as follows: take the maximum value among the ratios of viscosity coefficient and elastic modulus of blood vessel tissue in healthy foot tissue of the same age group as the inflammation threshold.

4. The method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging according to claim 1, characterized in that, The specific method for evaluating microvascular calcification of the surface tissue of diabetic foot using elastic information of the surface tissue is as follows: the region in the elastic image with an elastic modulus higher than a preset calcification threshold is marked as the calcified region; the degree and location of calcification are evaluated using the elastic modulus information.

5. The method for assessing microvascular calcification in diabetic foot based on photoacoustic viscoelastic imaging according to claim 1, characterized in that, The specific method for assessing the presence of inflammation in calcified areas using viscoelastic information of diabetic foot surface tissue is as follows: areas in the calcified region where the ratio of viscosity coefficient to elastic modulus is greater than a preset inflammation threshold are marked as inflammatory areas.

6. A microvascular calcification assessment system for diabetic foot based on photoacoustic viscoelastic imaging, used to implement the method described in any one of claims 1 to 5, characterized in that, The system includes: a photoacoustic excitation module, a signal detection module, a scanning module, a data acquisition module, an evaluation module, and a control module. The photoacoustic excitation module is used to emit laser light to the surface tissue of the foot, and the surface tissue of the foot generates photoacoustic signals. The signal detection module is used to receive and amplify the photoacoustic signals from the surface tissue of the foot. The control module is used to control the photoacoustic excitation module to generate corresponding lasers and to control the scanning module to drive the data acquisition module to collect photoacoustic signals of the foot surface tissue point by point. The data acquisition module is used to acquire the photoacoustic signal amplified by the detection module and determine the phase delay between the photoacoustic signal and the control signal used by the control module to control the photoacoustic excitation module. The evaluation module is used to determine the elastic modulus and viscoelastic data based on the photoacoustic signal and phase delay, and compare the elastic modulus and viscoelastic data with the calcification threshold and inflammation threshold to obtain the evaluation results.

7. The microvascular calcification assessment system for diabetic foot based on photoacoustic viscoelastic imaging according to claim 6, characterized in that, The photoacoustic excitation module includes a pulsed laser, a 4f system, and a focusing objective. The pulsed laser and the 4f system are located on the same optical axis, and the 4f system and the focusing objective are connected by optical fiber coupling.

8. The microvascular calcification assessment system for diabetic foot based on photoacoustic viscoelastic imaging according to claim 6, characterized in that, The calcification threshold and inflammation threshold are determined based on the elastic modulus range and viscoelastic range corresponding to different degrees of calcification in different age groups.

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