Portable probe-based optical coherence elastography system and method

Abstract

The application relates to a portable probe-based optical coherence elastography system and method, which comprises an OCT imaging unit and an excitation device; the OCT imaging unit comprises a light source, an optical fiber, a coupler, a circulator, a balanced detector, a computer and a data acquisition card; the excitation device comprises a function generator, a signal amplifier and a probe; light emitted by the light source is divided into two paths by the first coupler according to a 90 / 10 ratio, wherein 10% of the light in one path is irradiated on a reference mirror through the first circulator; 90% of the light in the other path is irradiated on the surface of a measured object through a ball lens optical fiber in the second circulator and the probe; the signal light returned from the measured object and the reference light returned from the reference mirror are combined and interfered according to a 90 / 10 ratio in the second coupler; the interference signal is collected by the balanced detector and transmitted to the acquisition card of the computer; the waveform output by the function generator is adjusted by the signal amplifier and transmitted to the probe, and the probe is driven by the piezoelectric ceramic to excite the measured object.

Description

Technical Field

[0001] This invention belongs to the field of medical testing equipment technology, specifically relating to an optical coherence elastography system and method based on a portable probe. Background Technology

[0002] Pathological changes in biological tissues are often accompanied by changes in mechanical properties such as elasticity and stiffness. Elastography technology has advanced to the point of visualizing the distribution of strain and elastic modulus within soft tissues. Among various elastography methods, optical coherence elastography (OCE) stands out for its superior resolution and sensitivity to deformation, surpassing the capabilities of ultrasound and magnetic resonance elastography. With continuous advancements in experimental techniques and OCE algorithms, the development of portable devices is increasingly facilitating the non-destructive testing of tissue biomechanical properties.

[0003] Optical coherence tomography (OCT) utilizes the interference principle of near-infrared low-coherence light to generate high-resolution images, enabling radiation-free, non-invasive, and real-time imaging of living tissues. This technology is widely used in the detection of ophthalmic diseases, and its application in cardiovascular and other medical fields is also gradually increasing. Optical coherence elastography (OCE) is a technique that uses optical coherence tomography to capture signals of tissue deformation under stress, thereby obtaining information about the tissue's deformation or mechanical properties such as elastic modulus. Compared to traditional strain and mechanical model calculation methods, elastography directly obtains the tissue's elastic modulus by measuring the propagation velocity of elastic waves, avoiding errors that may occur during calculation.

[0004] Handheld OCE probes have great advantages in clinical applications. Kennedy et al.[1][2][3] combined fiber optic lens optical coherence tomography (OCT) with a needle to measure tissue displacement in front of the tip during needle insertion. Although the probe is designed to be thin enough to penetrate deep into the tissue, the lack of force sensing limits its ability to measure mechanical parameters such as Young's modulus. To address this limitation, Qiu et al.[4][5] developed a miniature OCE probe equipped with an integrated Fabry-Perot force sensor. This probe can apply compressive force to induce tissue deformation at its tip. By correlating the applied force with the resulting tissue deformation, it provides a way to quantify the biomechanical response of tissue to external stimuli. This probe can measure force and displacement simultaneously. However, force detection is complex and error-prone due to the complexity of biological tissues. Wang et al.[6] fabricated a lateral intravascular probe that is adept at detecting the deformation of vascular tissue as vascular pressure changes. This probe has no force-applying mechanism and is specifically designed for scanning vascular samples. Qu et al.[7] introduced an acoustic radiation force OCE probe that integrates a miniature ultrasonic transducer with an OCT probe to acquire displacement data caused by acoustic radiation force. The displacement is extracted by phase analysis of the OCT interference signal. These displacement-based measurement techniques typically require additional equipment to measure the applied force, which can complicate the instrumentation. Furthermore, these methods require complex inverse calculations to determine mechanical parameters, such as the elastic modulus, when considering the strain-dependent material properties inherent in biological tissues.

[0005] The OCE method based on elastic waves derives the elastic modulus of soft tissue from the propagation characteristics of elastic waves, thus avoiding the need to measure the applied force. Liang et al.[8] proposed to excite the skin with harmonic surface waves and measure Young's modulus by detecting the wave velocity through OCT phase analysis. Li et al.[9] introduced a surface wave OCE method to assess the biomechanical properties of the skin, using a custom exciter to generate surface waves and calculating the phase velocity dispersion curve through OCT phase measurement. Larin

[10]

[11]

[12]

[13]

[14] team developed contact and non-contact local methods to stimulate mechanical waves, using a speaker diaphragm with a thin hard wire to generate vibrations on a lenticule, and also measured the velocity of elastic waves in the cornea of ​​live mice. Recently, the team developed a focused air pulse technique to induce elastic waves, allowing the quantification of Young's modulus from the group velocity of elastic waves without physical contact. Using this air pulse OCE method, Young's modulus of diseased and normal skin was measured in vivo. Li et al.

[15] used laser-induced surface acoustic waves (saw) to measure the elastic properties of skin by detecting the wave velocity through OCT phase analysis. Singh et al.

[16] proposed a method for measuring the elasticity of soft biological tissues using Rayleigh wave tracking holographic imaging. Although previous studies have confirmed the effectiveness of surface wave imaging in characterizing the elastic properties of skin, the systems used in these studies are often bulky and not convenient for easy application.

[0006] To make OCE systems more clinically usable, Parmar et al.

[17] designed an OCE probe based on flexible co-channel fiber and piezoelectric sensor, applying the shear wave formula, where is the material density and is the surface wave velocity in the sample, to calculate the Young's modulus of the skin. This single-point detection method depends on precise synchronization between the piezoelectric transducer and OCT acquisition. To address the synchronization problem, Latus et al.

[18] proposed a dual-fiber OCE probe that estimates tissue elasticity by measuring the shear wave propagation time between two points. The probe contains two optical fibers, allowing the time difference to be measured in the form of waves as it moves between the two detection points. This approach simplifies the process by focusing only on local wave propagation. However, combining shear wave-excited ultrasound probes with fiber alignment results in larger and more complex wave generation and detection components. In these studies, the assumption that the soft tissue is homogeneous limits the accuracy of the derived mechanical parameters. The elastic wave has been simplified to a shear wave or surface wave, but this has not been validated.

[0007] The properties of excited elastic waves are closely related to the mechanical parameters required for OCE (Optical Coherence Theory). When a half-space medium is vertically excited, three types of elastic waves are typically generated: shear waves, longitudinal waves, and surface waves. Of these, surface waves account for approximately 70% of the total energy, and their decay rate is much slower than the other wave types. Previous studies have shown great potential in using piezoelectric ceramics to drive probes to excite surface waves in bilayer biomaterials. The Young's modulus of each layer was measured based on Rayleigh wave propagation. However, further in-depth research into the wave characteristics is still needed to measure the mechanical properties of multilayer biomaterials. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention proposes an optical coherent elastic imaging system and method based on a portable probe.

[0009] One of the above-mentioned objectives of the present invention is achieved by the following technical solution:

[0010] An optical coherent elastography system based on a portable probe includes an OCT imaging unit and an excitation device;

[0011] The OCT imaging unit includes a light source, optical fiber, coupler, circulator, balanced detector, computer, and data acquisition card; the excitation device includes a function generator, signal amplifier, and probe.

[0012] The light source is used to generate high-speed scanning laser; the coupler includes a first coupler and a second coupler; the circulator includes a first circulator and a second circulator; and the balanced detector is used to convert optical signals into electrical signals.

[0013] The light emitted from the light source is split into two paths by the first coupler at a ratio of 90 / 10. One path of light (10%) passes through the first circulator and illuminates the reference mirror; the other path (90%) passes through the second circulator and the spherical lens fiber inside the probe and illuminates the surface of the object being measured. The signal light returning from the object being measured and the reference light returning from the reference mirror converge at the second coupler at a ratio of 90 / 10 and interfere. The interference signal is collected by the balanced detector and transmitted to the computer's acquisition card.

[0014] The function generator is used to generate elastic waves according to experimental requirements; the signal amplifier is used to adjust the voltage and control the signal strength; the probe is an excitation execution end component, which includes a stainless steel shell, a spherical lens fiber encased in the stainless steel shell, and an axially movable probe disposed in the stainless steel shell. The tip of the probe is pointed, and the tail end of the probe is attached to a piezoelectric ceramic, which is electrically connected to the signal amplifier; an indirect connection is left between the probe tip and the spherical lens fiber.

[0015] The waveform output from the function generator is adjusted by the signal amplifier and transmitted to the probe, where the piezoelectric ceramic drives the probe to excite the measured object.

[0016] Moreover, the light source uses a high-speed sweep laser with a scanning frequency of 100KHz and a center wavelength of 1310nm.

[0017] Furthermore, the probe tip has a diameter of 0.5 mm, and the probe tip extends 0.2 mm from the bottom of the housing.

[0018] Furthermore, the working distance of the spherical lens fiber is 5mm, and the waist diameter is 20μm.

[0019] Furthermore, the maximum depth of the piezoelectric ceramic produced at a voltage of 150V is 8.5μm.

[0020] Furthermore, the distance between the probe tip and the spherical lens fiber is 1.8 mm.

[0021] The second objective of this invention is achieved through the following technical solution:

[0022] A method for measuring the elastic modulus using the aforementioned optical coherent elastography system based on a portable probe, capable of performing in vivo equivalent elasticity measurements of multilayer skin tissue, includes the following steps:

[0023] Step 1: Given a known interval between the excitation point and the detection point, measure the time required for the elastic wave to pass through the interval, where the excitation point is the position where the probe is applied and the detection point is the position detected by the spherical lens fiber.

[0024] Step 2: Calculate the average velocity of the elastic wave based on the propagation time of the elastic wave between the two points measured in Step 1.

[0025] Step 3: Calculate the Young's modulus of the object under test based on the average propagation velocity of the elastic wave obtained in Step 2.

[0026] Moreover, step 1 includes:

[0027] 1.1 The displacement caused by the propagation of the elastic wave is confirmed by phase analysis of the OCT signal, as shown in the following formula:

[0028]

[0029] Where d(z,t) represents the displacement at depth z at time t; ΔΦ(z,t) represents the phase difference between the phase at time t and the phase before excitation; n is the refractive index of the object being measured, and λ0 is the center wavelength of the laser source; n and λ0 are set to be constants, and the displacement d(z,t) is proportional to the phase difference ΔΦ(z,t);

[0030] 1.2 The phase difference is calculated by cross-correlating the phase of each subsequent line scan with the phase of the initial scan, as shown in the following formula:

[0031]

[0032] In the formula, I(z,t) is the composite OCT A-scan signal at time t, and I(z,t0) * It is the conjugate of the pre-excitation composite OCT A scan signal, which occupies the first line in the M-mode image.

[0033] 1.3. The phase difference in 1.2 is unpacked using the minimum cost flow phase expansion method. The unpacked phase difference is then substituted into the formula in 1.1 to obtain the displacement profile. The displacement-time curve shows the vibration of the detection point caused by the elastic wave. The time of the first sharp drop in the displacement curve is determined as the time when the elastic wave arrives at the detection point.

[0034] Furthermore, in step 2, the average velocity of the elastic wave is calculated using the following formula:

[0035]

[0036] In the formula, Δx is the preset distance from the detection point to the excitation point, and Δt is the time it takes for the elastic wave to travel that distance.

[0037] Moreover, in step 3:

[0038] The propagation speed of a shear wave is related to the material properties of the medium, as shown in the following formula:

[0039]

[0040] Where E is Young's modulus, v is Poisson's ratio, and p is density; surface wave velocity C R It is 0.946 times Cs; the velocity obtained from equation (3) is set to be the same as the surface wave velocity C of the skin-like layered tissue. R Equivalently, the Young's modulus of the equivalent elasticity of the multilayer structure is obtained by substituting the surface wave velocity into equation (4).

[0041] The advantages and positive effects of this invention are as follows:

[0042] This invention proposes an optical coherent elastography system and method based on a portable probe, which can be used for in vivo measurement of the elasticity of multilayer superficial soft tissues. This invention integrates piezoelectric ceramics and spherical lens optical fibers into its design, replacing the excitation generator and scanning lens. By simulating waves in the multilayer structure through mechanical stimulation, the relationship between wave velocity and the equivalent Young's modulus of the sample is established, thereby enabling the measurement of the equivalent elastic modulus of multilayer tissues. This provides a convenient and effective measurement method for the non-destructive testing of the mechanical properties of biological tissues. Attached Figure Description

[0043] Figure 1This is a schematic diagram of the optical device of the handheld probe OCE system of the present invention;

[0044] Figure 2 This is an image of the handheld probe of this invention;

[0045] Figure 3 These are OCE measurement images of a single-layer phantom according to the first embodiment of the present invention;

[0046] Figure 4 This is a phase difference image measured by a single-layer phantom according to the first embodiment of the present invention;

[0047] Figure 5 This describes the displacement distribution of the surface region of a single-layer phantom in the first embodiment of the present invention.

[0048] Figure 6 It is the average displacement along the depth of the surface of the single-layer phantom in the first embodiment of the present invention;

[0049] Figure 7 This is a phase difference image measured by a three-layer phantom according to the second embodiment of the present invention;

[0050] Figure 8 This refers to the displacement distribution of the surface region of the three-layer phantom in the second embodiment of the present invention.

[0051] Figure 9 It is the average displacement along the depth of the surface of the three-layer phantom in the second embodiment of the present invention. Detailed Implementation

[0052] The structure of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that these embodiments are descriptive and not limiting.

[0053] For an optical coherent elastography system based on a portable probe, please refer to [link / reference]. Figures 1-2 The invention comprises an OCT imaging unit and an excitation device; the excitation device is used to generate elastic waves and excite the measured object; the OCT imaging unit is used to acquire surface signals of the measured object and output them as images; the OCT imaging unit includes a light source, an optical fiber, a coupler, a circulator, a balance detector, a computer, and a data acquisition card; the excitation device includes a function generator, a signal amplifier, and a probe.

[0054] Light source: High-speed sweep laser with a scanning frequency of 100KHz and a center wavelength of 1310nm.

[0055] Coupler: Includes a first coupler and a second coupler. The first coupler is used to split the optical signal of the laser emitted by the light source, and the second coupler is used to combine the reference return optical signal and the detection return optical signal.

[0056] Circulator: Ensures signals do not interfere with each other in different directions, thereby improving transmission efficiency. It includes a first circulator and a second circulator. The first circulator transmits reference optical information, and the second circulator transmits detection optical signals. The optical signals illuminating the reference mirror and returning from the first circulator are transmitted through the same optical fiber, avoiding interference by passing through the circulator. The optical signals illuminating the object and returning from the second circulator are transmitted through a single optical fiber, again avoiding interference by passing through the circulator.

[0057] Balanced detector: Used to convert optical signals into electrical signals.

[0058] The light emitted from the light source is split into two paths by the first coupler at a 90 / 10 ratio: 10% of the light passes through the first circulator and illuminates the reference mirror; the other 90% passes through the second circulator and the spherical lens fiber inside the probe and illuminates the object surface. The signal light returning from the object and the reference light returning from the reference mirror converge at the second coupler at a 90 / 10 ratio and interfere. The interference signal is collected by the balanced detector and transmitted to the computer's acquisition card.

[0059] Function generator: Used to generate elastic waves according to experimental requirements.

[0060] Signal amplifier: Used to regulate voltage and control signal strength.

[0061] Probe: The end effector component that triggers the excitation.

[0062] The probe is equipped with a spherical lens fiber and piezoelectric ceramic (DCS3-070709, DCpiezo, China). A probe with a 0.5mm tip diameter is attached to the end of the piezoelectric ceramic. A stainless steel housing encloses the spherical lens fiber and supports the probe on the surface of the object being measured. The piezoelectric ceramic is capable of producing a maximum displacement of 8.5μm at 150V, with the displacement almost proportional to the applied voltage. For all experiments, an applied voltage of 100V produces an excitation amplitude of 5.6μm. The spherical lens has a working distance of 5mm and a waist diameter of 20μm. The probe extends 0.2mm from the bottom of the housing to ensure contact with the object being measured. The distance between the probe tip and the spherical lens fiber is adjustable and set to 1.8mm to ensure the detection of a stable elastic wave signal.

[0063] The waveform output from the function generator is adjusted by the signal amplifier and then transmitted to the probe, where the piezoelectric ceramic drives the probe to be excited.

[0064] Using the aforementioned optical coherent elastography system based on a portable probe, in vivo equivalent elasticity measurements of multilayer skin tissue can be performed. The steps for measuring the elastic modulus are as follows:

[0065] Step 1: Given a known interval between the excitation point and the detection point, measure the time required for the elastic wave to pass through that interval, where the excitation point is the position where the probe is applied and the detection point is the position detected by the spherical lens fiber.

[0066] Step 2: Calculate the average velocity of the elastic wave based on the propagation time of the elastic wave between the two points measured in Step 1.

[0067] Step 3: Calculate the Young's modulus of the object under test based on the average propagation velocity of the elastic wave obtained in Step 2.

[0068] In step 1:

[0069] Phase analysis of OCT signals is used to detect displacement caused by the propagation of elastic waves, as shown in the following equation:

[0070]

[0071] Where d(z,t) represents the displacement at depth z at time t; ΔΦ(z,t) represents the phase difference between the phase at time t and the phase before excitation; n is the refractive index of the object being measured, and λ0 is the center wavelength of the laser source. Assuming n and λ0 are constants, the displacement d(z,t) is proportional to the phase difference ΔΦ(z,t).

[0072] For step 1, given the known interval between the excitation and detection points, the time required for the elastic wave to cross this interval is measured. To accurately pinpoint the arrival time of the elastic wave at the detection point, a 1ms delay is programmed into the probe's excitation sequence after the OCT B scan is initiated. During the measurement, the probe is applied to the object surface. A sinusoidal pulse is input to the piezoelectric ceramic, and M-mode OCT data is captured for 20ms. To mitigate the effects of noise, each experiment is performed 20 times, and the 20 data points are summed and averaged. The phase change is calculated by cross-correlation of the phase of each subsequent line scan with the initial scan.

[0073]

[0074] In the formula, I(z,t) is the composite OCT A scan signal at time t, and I(z,t0) * It is the conjugate of the pre-excitation composite OCT A-scan signal, which occupies the first line in the M-mode image in this experiment. Since ΔΦ(z,t) is usually wrapped in [-π, π], the minimum cost flow phase expansion method is applied. Substituting the unwrapped ΔΦ(z,t) into equation (1) yields the displacement profile. The displacement versus time curve illustrates the vibration of the detection point caused by the elastic wave. The time of the first sharp drop in the displacement curve is determined to be the time when the elastic wave arrives at the detection point.

[0075] In step 2:

[0076] Once the propagation time of the elastic wave is obtained, the average velocity of the elastic wave can be easily calculated using the following formula:

[0077]

[0078] In the formula, Δx is the preset distance from the detection point to the excitation point, which is 1.8 mm according to the probe design. Δt is the time it takes for the elastic wave to travel the distance.

[0079] In step 3:

[0080] The propagation speed of shear waves is related to the material properties of the medium.

[0081]

[0082] E is Young's modulus, v is Poisson's ratio, and p is density. Surface wave velocity C R It is approximately 0.946 of Cs. The velocity obtained from equation (3) is set to be the surface wave velocity C of the skin-like layered tissue. R Therefore, the surface wave velocity can be substituted into equation (4) to solve for the Young's modulus of the equivalent elasticity of the multilayer structure.

[0083] Example:

[0084] The optical elastic imaging method proposed in this invention includes two basic components: the setup of the excitation device and the setup of the optical coherence tomography (OCT) imaging unit.

[0085] The excitation waveform is set using a function generator and a power amplifier. The function generator and data acquisition are triggered and controlled via software settings. Probe vibration and data acquisition can occur simultaneously, or a certain delay can be set according to test requirements. The portable probe is then placed on the surface of the specimen.

[0086] Setup of the optical coherence tomography (OCT) setup: Upon triggering, a piezoelectric ceramic probe strikes the surface of an object to generate elastic waves. M-mode OCT imaging is performed to detect the propagation of these waves, and dynamic interactions are captured via a spherical lens fiber. For each trigger, 2000 A-scans are recorded, corresponding to a 20ms data acquisition window. The wave velocity of the elastic waves is determined by the distance between the excitation point and the measured point, as well as the time between the excitation reaching the measured point.

[0087] Single-layer and three-layer models were fabricated according to the present invention. Two portions of food-grade silica gel (Yuchen Silica Gel, China), component A and component B, were mixed uniformly in a 1:1 ratio. 0.02% TiO2 was added to the mixture as a scattering agent. These components were thoroughly mixed and subjected to vacuum treatment for one hour to remove air bubbles from the mixed solution. The resulting membrane had a diameter of 40 mm, a height of 38 mm, and a measured density of 1.17 × 10⁻⁶.3 kg / m 3 The three-layer silicone mold is made by curing two layers of silicone on top of a single layer. The top, middle, and bottom layers are made of silicone materials with Shore hardness of 35, 25, and 15, respectively, and the cumulative thickness of the mold is 6mm.

[0088] Phase difference maps acquired during the application of sinusoidal pulses to the phantom. The original M-mode OCT images, comprising 1024 pixels vertically and 2000 pixels horizontally, were converted to a depth range of 9.68 mm and an imaging time span of 20 ms. Given the limited penetration depth of OCT, deeper regions primarily exhibit noise; therefore, only the first 300 pixels were retained for analysis. For surface wave characteristics studies, the data from 10 rows adjacent to the sample surface were carefully examined. Phase difference expansion was performed in selected near-surface regions and subsequently input into equation (1) to calculate displacement.

[0089] The scanned images were processed to obtain curves showing the surface displacement of the phantom over time. In the single-layer phantom, a slight rise in the waveform occurs at approximately 1 ms before a significant drop, indicating surface wave propagation. The most abrupt drop observed at 1.18 ms was determined to be the moment the surface wave arrives at the detection point. Considering the 1 ms interval between the start of OCT imaging and actuator excitation, the propagation time Δt of the elastic wave from excitation to the detection point was calculated to be 0.18 ms. Assuming a distance Δx from excitation to the detection point of 0.18 mm, the wave velocity was determined to be 10.0 m / s, corresponding to 0.946 times the shear wave velocity. The elastic modulus can be calculated to be 389.60 kPa. This value is in excellent agreement with the 394.56 kPa obtained through tensile testing, showing only a 1.25% difference. In the curves for the three-layer phantom, the wave arrival time is 0.15 ms. Therefore, the wave velocity was determined to be 12.0 m / s. The equivalent Young's modulus of the phantom was calculated to be 561.03 kPa, which differs from the 567.70 kPa measured in the tensile test by approximately 1.17%.

[0090] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. An optical coherent elastic imaging system based on a portable probe, characterized in that: Includes an OCT imaging unit and excitation device; The OCT imaging unit includes a light source, optical fiber, coupler, circulator, balanced detector, computer, and data acquisition card; the excitation device includes a function generator, signal amplifier, and probe. The light source is used to generate high-speed scanning laser; the coupler includes a first coupler and a second coupler; the circulator includes a first circulator and a second circulator; and the balanced detector is used to convert optical signals into electrical signals. The light emitted from the light source is split into two paths by the first coupler at a ratio of 90 / 10. One path of light (10%) passes through the first circulator and illuminates the reference mirror; the other path (90%) passes through the second circulator and the spherical lens fiber inside the probe and illuminates the surface of the object being measured. The signal light returning from the object being measured and the reference light returning from the reference mirror converge at the second coupler at a ratio of 90 / 10 and interfere. The interference signal is collected by the balanced detector and transmitted to the computer's acquisition card. The function generator is used to generate elastic waves; the signal amplifier is used to adjust the voltage and control the signal strength; the probe is an excitation execution end component, which includes a stainless steel shell, a spherical lens fiber encased in the stainless steel shell, and an axially movable probe disposed in the stainless steel shell. The tip of the probe is pointed, and the tail end of the probe is attached to a piezoelectric ceramic, which is electrically connected to the signal amplifier; an indirect connection is left between the probe tip and the spherical lens fiber. The waveform output from the function generator is adjusted by the signal amplifier and transmitted to the probe, where the piezoelectric ceramic drives the probe to excite the object being measured.

2. The optical coherent elastic imaging system based on a portable probe according to claim 1, characterized in that: The light source uses a high-speed swept laser with a scanning frequency of 100KHz and a center wavelength of 1310nm.

3. The optical coherent elastic imaging system based on a portable probe according to claim 1, characterized in that: The probe tip has a diameter of 0.5 mm and extends 0.2 mm from the bottom of the housing.

4. The optical coherent elastic imaging system based on a portable probe according to claim 1, characterized in that: The working distance of the spherical lens fiber is 5mm, and the waist diameter is 20μm.

5. The optical coherent elastic imaging system based on a portable probe according to claim 1, characterized in that: The piezoelectric ceramic produces a maximum size of 8.5 μm at a voltage of 150 V.

6. The optical coherent elastic imaging system based on a portable probe according to claim 1, characterized in that: The distance between the probe tip and the spherical lens fiber is 1.8 mm.

7. A method for measuring the elastic modulus using an optical coherent elastic imaging system based on a portable probe as described in any one of claims 1-6, characterized in that, In vivo measurement of equivalent elasticity of multilayer skin tissue can be performed, including the following steps: Step 1: Given a known interval between the excitation point and the detection point, measure the time required for the elastic wave to pass through the interval, where the excitation point is the position where the probe is applied and the detection point is the position detected by the spherical lens fiber. Step 2: Calculate the average velocity of the elastic wave based on the propagation time of the elastic wave between the two points measured in Step 1. Step 3: Calculate the Young's modulus of the object under test based on the average propagation velocity of the elastic wave obtained in Step 2.

8. The method for measuring the elastic modulus using an optical coherent elastic imaging system based on a portable probe according to claim 7, characterized in that: Step 1 includes: 1.1 The displacement caused by the propagation of the elastic wave is confirmed by phase analysis of the OCT signal, as shown in the following formula: Where d(z,t) represents the displacement at depth z at time t; ΔΦ(z,t) represents the phase difference between the phase at time t and the phase before excitation; n is the refractive index of the object being measured, and λ0 is the center wavelength of the laser source; n and λ0 are set to be constants, and the displacement d(z,t) is proportional to the phase difference ΔΦ(z,t); 1.2 The phase difference is calculated by cross-correlating the phase of each subsequent line scan with the phase of the initial scan, as shown in the following formula: In the formula, I(z,t) is the composite OCT A-scan signal at time t, and I(z,t0) * It is the conjugate of the pre-excitation composite OCT A-scan signal, which occupies the first line in the M-mode image; 1.

3. The phase difference in 1.2 is unpacked using the minimum cost flow phase expansion method. The unpacked phase difference is then substituted into the formula in 1.1 to obtain the displacement profile. The displacement-time curve shows the vibration of the detection point caused by the elastic wave. The time of the first sharp drop in the displacement curve is determined as the time when the elastic wave arrives at the detection point.

9. The method for measuring the elastic modulus using an optical coherent elastic imaging system based on a portable probe according to claim 7, characterized in that, In step 2, the average velocity of the elastic wave is calculated using the following formula: In the formula, Δx is the preset distance from the detection point to the excitation point, and Δt is the time it takes for the elastic wave to travel that distance.

10. The method for measuring the elastic modulus using an optical coherent elastic imaging system based on a portable probe according to claim 9, characterized in that, In step 3: The propagation speed of a shear wave is related to the material properties of the medium, as shown in the following formula: Where E is Young's modulus, v is Poisson's ratio, and p is density; surface wave velocity C R It is 0.946 times Cs; the velocity obtained from equation (3) is set to be the same as the surface wave velocity C of the skin-like layered tissue. R Equivalently, the Young's modulus of the equivalent elasticity of the multilayer structure is obtained by substituting the surface wave velocity into equation (4).

Images