A method for manufacturing a high-stability photoacoustic imaging phantom

Abstract

The application discloses a kind of high stability photoacoustic imaging phantom's manufacturing method, comprising the following steps: preparation initial acoustic phantom, and the acoustic parameter of initial acoustic phantom is detected, and the relationship between the added medicament concentration and each acoustic parameter is constructed; according to the detection result, the proportion of medicament is adjusted, so that the acoustic parameter is consistent with the acoustic parameter of the required simulated human tissue; preparation initial optical phantom, and the optical parameter of initial optical phantom is detected; the relationship between the added medicament concentration and each optical parameter is constructed; according to the detection result, the proportion of medicament is adjusted, so that the optical parameter is consistent with the acoustic parameter of the required simulated human tissue;Step five: according to the proportion of each medicament finally determined, mixed preparation photoacoustic imaging phantom;The scheme can change its properties by adding optical and acoustic scatterer, and high temperature, oxidation, yellowing resistance, has good softness and plasticity, can simulate the photoacoustic characteristics of tissue.

Description

Technical Field

[0001] This invention relates to the field of photoacoustic imaging image detection technology, and in particular to a method for fabricating a highly stable photoacoustic imaging phantom. Background Technology

[0002] In the field of medical imaging technology, phantom-based testing methods are an important part of optimizing equipment performance and image quality, as well as refining clinical imaging paradigms. Photoacoustic imaging, a novel biomedical imaging method developed in recent years, combines laser beams and ultrasound to non-invasively observe and image the structure and function of biological tissues. Combining the advantages of optics and acoustics, it not only provides high-resolution images but also information on the content of metabolites in vivo, thus holding broad application prospects in the biomedical field. Currently, various photoacoustic imaging phantoms have been developed, using different materials and with different shapes, but they often have limitations, such as insufficient matching of physical properties with biological tissues, low imaging resolution, complex fabrication processes, and poor stability. Furthermore, there is still a lack of commercially available testing models specifically designed for the photoacoustic (PA) field that can overcome the limitations of existing technologies, encompass optical and acoustic parameters consistent with biological tissue characteristics, and ensure long-term usability.

[0003] Currently, research on photoacoustic imaging phantom fabrication mainly involves two types of background materials: water-based and oil-based materials. However, water-based materials (such as gelatin and agar) have some drawbacks, such as amorphous shape, easy deterioration, poor material homogeneity, and high sensitivity to physical damage, making it difficult to prepare stable phantoms. On the other hand, commonly used oil-based materials include gel wax and polyvinyl chloride plastisol (PVCP). However, gel wax is often brittle and prone to breakage or deformation. In addition, gel wax is very sensitive to temperature changes and may melt or soften at higher temperatures. In some solvents, gel wax melts, and its acoustic properties do not match human tissue well. As for polyvinyl chloride plastisol (PVCP), although it has high plasticity, it is easily deformed. Furthermore, under certain environments (such as high temperatures), PVCP can release toxic gases, posing a potential hazard to experimenters. Several studies have proposed novel materials for fabricating phantoms. For example, Christopher D. Nguyen et al. used silk as the phantom material, which eliminates the need for additional absorbers and scatterers. However, the material processing steps are extremely cumbersome, and the reproducibility of the technology is poor. Another example is styrene-ethylene / butene-styrene copolymer (SEBS), which has emerged in recent years. Although it maintains property stability for a relatively long time, its widespread production is difficult due to the heterogeneity of product composition among different manufacturers. Furthermore, the inherently low sound velocity of SEBS material limits its usability.

[0004] According to the latest consensus on photoacoustic imaging standardization from the International Photoacoustic Standardization Consortium (IPASC), the fabrication of photoacoustic phalluses that meet standardization requirements is considered necessary. Photoacoustic imaging phalluses need to effectively characterize their optical and acoustic properties, and the relevant parameters must be within reasonable ranges to simulate the characteristics of human tissue. The acoustic parameters mainly include sound velocity, sound attenuation coefficient, and acoustic impedance, while the optical parameters mainly include absorption coefficient and reduced scattering coefficient. Furthermore, the materials used for photoacoustic phalluses must also possess the following properties: 1. High degree of tunability in optical and acoustic properties; 2. It can be safely prepared in a laboratory environment and the preparation process requires no professional training; 3. The ingredients are widely available from commercial chemical suppliers; 4. Under real-world ambient temperature (18-25°C) and humidity (30-80%) ranges, the optical, acoustic, and mechanical properties (structural robustness and durability) exhibit long-term stability (>6 months) for storage in various environments; 5. With proper transportation and handling procedures, it can withstand short-term temperatures ranging from 4°C to 40°C and maintain structural integrity. 6. It maintains the integrity of its structure and materials when in contact with aqueous media; 7. During imaging, processing and storage, it exhibits photostability in the visible to near-infrared (NIR) wavelength range (532nm - 1064nm) and can maintain this stability within safe exposure limits.

[0005] However, the materials used in photoacoustic imaging phantoms are often insufficient to meet all the above requirements, and are often limited by cumbersome manufacturing processes, poor stability, and easy deterioration. Summary of the Invention

[0006] The purpose of this invention is to provide a method for fabricating a highly stable photoacoustic imaging phantom, addressing the aforementioned shortcomings. This method solves the problems that the materials used in current photoacoustic imaging phantoms often fail to adequately meet the requirements of the latest version of the photoacoustic imaging standardization consensus of the International Photoacoustic Standardization Consortium (IPASC), and are often limited by cumbersome fabrication processes, poor stability, easy deterioration, and inability to simulate human blood vessels.

[0007] This invention is achieved through the following scheme: A method for fabricating a highly stable photoacoustic imaging phantom includes the following steps: Step 1: Prepare the initial acoustic phantom and test its acoustic parameters to establish the relationship between the concentration of the added agent and each acoustic parameter; Step 2: Adjust the dosage of the reagent according to the test results so that the acoustic parameters match the acoustic parameters of the human tissue to be simulated; Step 3: Prepare the initial optical phantom and detect its optical parameters; construct the relationship between the concentration of the added reagent and each optical parameter; Step 4: Adjust the dosage of the reagent according to the test results so that the optical parameters match the optical parameters of the human tissue to be simulated. Step 5: Prepare the photoacoustic imaging phantom by mixing the various reagents according to the final proportions determined in Steps 2 and 4.

[0008] In step one, specifically, the base material of the phantom is polydimethylsiloxane high-transparency silicone rubber; a predetermined concentration of sodium-calcium glass microspheres is added to the main agent, and the mixture is thoroughly stirred using a shear force mechanical rotor, then a curing agent is added, and after thorough stirring, it is poured into a mold, defoamed under negative pressure, and a pressure plate is placed on the surface to ensure its surface flatness. It is then solidified at room temperature to produce an acoustic phantom, which is used to characterize the acoustic properties of the phantom; the relationship between sodium-calcium glass microsphere concentration and sound velocity, as well as the relationship between sound attenuation coefficient and ultrasonic frequency under different sodium-calcium glass microsphere concentrations, are calculated.

[0009] The ratio of the added curing agent to the main agent is 1:5.

[0010] In step one, the acoustic parameters being tested include sound velocity, sound attenuation coefficient, and acoustic impedance.

[0011] In step one, the following methods are used to calculate the sound velocity, sound attenuation coefficient, and sound impedance: The sound velocity measurement of the phantom is based on the pulse substitution method. First, the propagation speed of ultrasound in degassed water at 22°C is measured; then the sound velocity in the water is calculated. Further, the fabricated phantom is placed in the sound beam propagation path, and the sound velocity of the ultrasound in the phantom sample is calculated. The acoustic attenuation coefficient of the phantom sample was obtained using relevant formulas. (dB / cm); The acoustic impedance of the phantom sample was calculated using relevant formulas. ); Finally, the ultrasonic backscattering characteristics of the phantoms were characterized by comparing B-mode ultrasound images and signal intensity analysis between phantoms or with reference materials.

[0012] In step three, specifically, phantoms with different concentration ratios of nano-graphite powder and nano-TiO2 are prepared. During preparation, the required amount of graphite powder and TiO2 powder is weighed and added to the PDMS main agent. The mixture is then processed using an ultrasonic crusher to ensure that the powder is completely dispersed in the medium. After cooling to room temperature, a curing agent is added at a mass ratio of 5:1. The mixture is thoroughly stirred and poured into a mold. Negative pressure is applied to remove bubbles, and the mold is placed on a horizontal table to solidify. After solidification, an optical phantom is prepared for measuring optical parameters. The relationship between graphite powder concentration and absorption coefficient, and the relationship between titanium dioxide concentration and reduced scattering coefficient are calculated.

[0013] In step three, the optical parameters include the light absorption coefficient, the scattering coefficient, and the anisotropy factor.

[0014] In step three, the following method is used to calculate the light absorption coefficient, light scattering coefficient, and anisotropy factor: The optical properties of the phantom were characterized based on the Kubelka-Munk method and measured using an integrating sphere spectrophotometer. For a finite turbid medium of thickness d, the flux loss per unit path length caused by absorption is defined as... The loss caused by scattering is defined as Then the following relationship holds:

[0015]

[0016] in, and These are the diffuse reflectance and total transmittance of the medium, respectively, and the minor coefficient. and = is defined as:

[0017] and , With the medium absorption coefficient ( ) and scattering coefficient ( They have the following relationships:

[0018]

[0019] in To reduce the scattering coefficient, through the anisotropy factor ( The scattering coefficient is defined. The extinction coefficient is the ratio of the measured parallel transmittance. By Bill-Lambert's Law Defined; Therefore, by measuring the diffuse reflectance of the phantom sample Total transmittance Parallel transmittance Then, the above three optical parameters—medium absorption coefficient, scattering coefficient, and anisotropy factor—can be obtained. , ); To meet specific usage needs, the concentration of additives can be adjusted to regulate different acoustic and optical parameters, thereby simulating different tissue types in the human body.

[0020] In step five, specifically, based on the results of steps two and four, sodium-calcium glass microspheres, graphite powder, and TiO2 of appropriate concentrations are prepared according to the requirements of the tissue to be simulated. The above three powders are added to the PDMS monomer and fully dispersed. Then, a curing agent is added and mixed thoroughly. The mixture is poured into a mold and cured to produce the final photoacoustic phantom, which is used to simulate the photoacoustic imaging of tissue.

[0021] In step five, multiple polytetrafluoroethylene (PTFE) capillaries are placed in the photoacoustic imaging phantom to simulate blood vessels. The PTFE capillaries are located at different transverse and longitudinal layers within the phantom. A light-absorbing substance solution of the same concentration is filled into the PTFE capillaries. The spacing between each pair of transversely arranged PTFE capillaries gradually increases from left to right, used to detect the transverse resolution of the photoacoustic imaging system. The spacing between each pair of longitudinally arranged PTFE capillaries is the same, used to detect the maximum imaging depth of the photoacoustic imaging system. By filling the PTFE capillaries with light-absorbing substance solutions of different concentrations, the photoacoustic imaging system is used to image the capillaries and perform photoacoustic signal intensity analysis to detect the sensitivity of the photoacoustic system to different concentrations of the substance.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This solution is the first to use PDMS high-transparency silicone as the background material for photoacoustic imaging phantoms. It has excellent transparency, can transmit light without causing light scattering and absorption, can arbitrarily change its properties by adding optical and acoustic scatterers, and is resistant to high temperature, oxidation, and yellowing. It also has good softness and plasticity and can simulate the photoacoustic properties of tissues.

[0023] 2. This solution utilizes highly transparent silicone as the base material, solving the problems of current photoacoustic imaging phantoms such as easy deterioration, poor consistency, and cumbersome manufacturing processes, and bringing a series of advantages. First, highly transparent silicone possesses excellent physical properties, will not deform or deteriorate, has good toughness and tensile strength, and can be preserved and maintain stability for a long time. Second, phantoms made using highly transparent silicone can be cast into various shapes according to molds, providing flexibility for different needs and application scenarios. Furthermore, this material has highly adjustable photoacoustic parameters; by adding acoustic scatterers, light absorbers, and scatterers, its acoustic and optical properties can be adjusted to simulate the characteristics of different tissues. In addition, highly transparent silicone has extremely high time stability; additives can be uniformly distributed within it and avoid potential gravitational sedimentation over a long time span, resulting in a long lifespan and stability for the phantom. We also achieved the ability to flexibly change the type of filling liquid by inserting polytetrafluoroethylene capillaries with negligible photoacoustic signals into the phantom to simulate the concentration of different substances in blood under different physiological states and to detect the imaging resolution and sensitivity of the photoacoustic imaging system to that substance. In summary, this invention has the potential for standardized mass production and can generate a standardized phantom solution for performance testing of photoacoustic imaging systems, which is helpful for the development and standardization of photoacoustic imaging systems. Attached Figure Description

[0024] Figure 1 This is a diagram showing the arrangement of the polytetrafluoroethylene capillaries in this invention; Detailed Implementation All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0025] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0026] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a predetermined orientation, or be constructed and operated in a predetermined orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0028] Example 1 like Figure 1 As shown, the present invention provides a technical solution: A method for fabricating a highly stable photoacoustic imaging phantom includes the following steps: Step 1: Prepare the initial acoustic phantom and test its acoustic parameters to establish the relationship between the concentration of the added agent and each acoustic parameter; Step 2: Adjust the dosage of the reagent according to the test results so that the acoustic parameters match the acoustic parameters of the human tissue to be simulated; Step 3: Prepare the initial optical phantom and detect its optical parameters; construct the relationship between the concentration of the added reagent and each optical parameter; Step 4: Adjust the dosage of the reagent according to the test results so that the optical parameters match the acoustic parameters of the human tissue to be simulated; Step 5: Prepare the photoacoustic imaging phantom by mixing the various reagents according to the final proportions determined in Steps 2 and 4.

[0029] In step one, specifically, the base material of the phantom is polydimethylsiloxane (PDMS) high-transparency silicone rubber. A predetermined concentration of soda-lime glass microspheres is added to the PDMS base, and the mixture is thoroughly stirred using a shear-force mechanical rotor. A curing agent is then added, and the mixture is stirred thoroughly before being poured into a mold. Negative pressure is applied to remove bubbles, and a pressure plate is placed on the surface to ensure its flatness. The mixture is then solidified at room temperature to produce an acoustic phantom, used to characterize its acoustic properties. The relationship between soda-lime glass microsphere concentration and sound velocity, as well as the relationship between sound attenuation coefficient and ultrasonic frequency at different soda-lime glass microsphere concentrations, are calculated.

[0030] The ratio of curing agent to main agent is 1:5. A conventional ratio of curing agent to PDMS main agent of 1:10 can achieve rapid solidification. However, the addition of different powder agents can affect the curing speed. Therefore, the inventors adjusted the ratio of curing agent to main agent to 1:5 to achieve rapid solidification. At the same time, the sound attenuation of the ratio of curing agent to main agent of 1:5 is closer to that of most human tissues, which is more conducive to body simulation.

[0031] In step one, the acoustic parameters detected include sound velocity, sound attenuation coefficient, and acoustic impedance. In this scheme, different proportions and particle sizes of sodium-calcium glass microspheres are added to control the sound velocity, sound attenuation coefficient, and acoustic impedance.

[0032] In step one, the following methods are used to calculate the sound velocity, sound attenuation coefficient, and sound impedance: The sound velocity measurement of the phantom was based on the pulse substitution method. First, the propagation speed of ultrasound in degassed water at 22℃ was measured (the standard sound velocity in water at 22℃ is 1489 m / s in the literature). Sound velocity in water... The calculation method is as follows: (1) in The distance (m) from which the sound wave travels. Let be the sound wave propagation time (s). Further, if the fabricated phantom is placed in the sound beam propagation path, then the sound velocity of the ultrasound in the phantom sample is... for: (2) in, This refers to the transmission time delay between two measurements after the phantom is immersed in the propagation path of the ultrasonic beam. Let be the thickness of the phantom sample. The sound velocity of a phantom sample with a known thickness can be obtained using the above formula.

[0033] In addition, the acoustic attenuation coefficient of the phantom sample (dB / cm) can be obtained from the following formula: (3) in, and The ultrasonic pressure amplitude (V) received in the hydrophone before and after the phantom was placed in the water are respectively. Sound attenuation and ultrasonic frequency The correlation is given by the following formula:

[0034] in, and These are the fitting parameters.

[0035] In addition, the acoustic impedance of the phantom sample ( The calculation method for () is as follows:

[0036] The density of the phantom was measured by measuring the mass and volume of the sample at 22°C using the formula... Calculate its density, where m represents the sample mass and V represents the sample volume; Finally, the ultrasonic backscattering characteristics of the phantoms were characterized by comparing B-mode ultrasound images and signal intensity analysis between phantoms or with reference materials.

[0037] In step three, specifically, phantoms with different concentration ratios of nano-graphite powder and nano-TiO2 are prepared. During preparation, the required amount of graphite powder and TiO2 powder is weighed and added to the PDMS main agent. The powder is then processed using an ultrasonic crusher to ensure complete dispersion in the medium. After cooling to room temperature, a curing agent is added at a mass ratio of 5:1. The mixture is thoroughly stirred and poured into a mold. Negative pressure is applied to remove bubbles, and the mold is placed on a horizontal table to solidify. After solidification, an optical phantom is prepared for measuring optical parameters. The relationship between graphite powder concentration and absorption coefficient is calculated, as well as the relationship between titanium dioxide concentration, module thickness, and reduced scattering coefficient are calculated.

[0038] In step three, the optical parameters include the light absorption coefficient and the light scattering coefficient. This scheme adjusts the light absorption characteristics by adding different concentrations of graphite powder and adjusts the light scattering characteristics by adding different concentrations of nano-TiO2.

[0039] In step three, the following method is used to calculate the light absorption coefficient and light scattering coefficient: The optical properties of the phantom were characterized based on the Kubelka-Munk method and measured using an integrating sphere spectrophotometer. For a finite turbid medium of thickness d, the flux loss per unit path length caused by absorption is defined as... The loss caused by scattering is defined as Then the following relationship holds:

[0040]

[0041] in, and These are the diffuse reflectance and total transmittance of the medium, respectively, and the minor coefficient. and = is defined as:

[0042] and , With the medium absorption coefficient ( ) and scattering coefficient ( They have the following relationships:

[0043]

[0044] in To reduce the scattering coefficient, through the anisotropy factor ( The scattering coefficient is defined. The extinction coefficient is the ratio of the measured parallel transmittance. By Bill-Lambert's Law Defined.

[0045] Therefore, by measuring the diffuse reflectance of the phantom sample Total transmittance Parallel transmittance Then, the above three optical parameters—medium absorption coefficient, scattering coefficient, and anisotropy factor—can be obtained. , ); To meet specific usage needs, the concentration of additives can be adjusted to regulate different acoustic and optical parameters, thereby simulating different tissue types in the human body.

[0046] In step five, specifically, based on the results of steps two and four, sodium-calcium glass microspheres, graphite powder, and TiO2 are prepared in appropriate proportions according to the requirements of the tissue to be simulated. Sodium-calcium glass microspheres do not affect optical parameters, and graphite powder and TiO2 powder do not affect acoustic parameters. Therefore, the above materials are added to high-transparency silicone to make a phantom, thus creating a phantom that has both tissue acoustic and optical properties, used to simulate the photoacoustic imaging of tissue.

[0047] In step five, multiple polytetrafluoroethylene (PTFE) capillaries can be placed in the photoacoustic imaging phantom to simulate blood vessels. These PTFE capillaries are located at different transverse and longitudinal levels within the phantom. A light-absorbing substance solution of the same concentration (such as hemoglobin or indocyanine green) is filled into each PTFE capillary. The transversely arranged PTFE capillaries have an increasing distance between each pair from left to right, used to detect the transverse resolution of the photoacoustic imaging system. The longitudinally arranged PTFE capillaries have the same distance between each pair, used to detect the maximum imaging depth of the photoacoustic imaging system. Figure 1 Furthermore, by filling polytetrafluoroethylene capillary tubes with light-absorbing material solutions of different concentrations, imaging them with a photoacoustic imaging system and analyzing the photoacoustic signal intensity, the sensitivity of the photoacoustic system to detect different concentrations of the material was determined.

[0048] Because photoacoustic imaging functions include both qualitative (imaging) and quantitative (analyzing the content of components in tissues), different and the same concentration of substance solutions can be filled into the tube to test the performance of the photoacoustic imaging system in different dimensions.

[0049] The phantom material used in this invention is polydimethylsiloxane (PDMS) high-transparency silicone rubber, an elastic material made from organosilicon polymers. Silicone possesses many excellent properties, such as long lifespan, good stability, and adjustable hardness. It is commonly used to fabricate molds, seals, and filler materials. Silicone has the ability to embed scatterers such as glass and plastic microspheres, and is therefore considered a potential tissue substitute. Silicone has been shown to have significant similarities to tissues such as human breast tissue and skin, and has therefore been successfully used to create phantoms simulating these tissues with good simulation results. Silicone has good acoustic properties, which can simulate the acoustic characteristics of human tissue. It also has good optical transparency, and its optical properties are highly adjustable. Furthermore, due to the temperature plasticity of silicone, other light absorbers can be embedded within it to evaluate the image quality of photoacoustic imaging systems.

[0050] Based on this evidence, we propose a photoacoustic imaging phantom made of silicone. Its composition and hardness can be adjusted as needed to achieve the desired optical and acoustic properties, thereby simulating different types of tissue. Due to its simple fabrication process, it can also be cast into various shapes using different molds to meet the needs of image quality inspection and teaching training. Furthermore, polytetrafluoroethylene (PTFE) capillaries are inserted into different layers of the phantom to simulate blood vessels. This material has been shown to produce extremely low photoacoustic signals, which do not affect the photoacoustic signal magnitude of the substances filled within the capillaries. The specific arrangement of the capillaries can reflect the resolution of the photoacoustic imaging system and its sensitivity to substance concentration detection. Due to the stability of the background material, this photoacoustic imaging phantom can be reused, and liquids of different compositions can be filled into the capillaries to simulate the concentration states of substances in blood vessels under different physiological conditions.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a highly stable photoacoustic imaging phantom, characterized in that: Includes the following steps: Step 1: Prepare the initial acoustic phantom and test its acoustic parameters to establish the relationship between the concentration of the added agent and each acoustic parameter; In step one, specifically, the base material of the phantom is polydimethylsiloxane high-transparency silicone rubber; a predetermined concentration of soda-lime glass microspheres is added to the main agent, and the mixture is thoroughly stirred using a shear force mechanical rotor. Then, a curing agent is added, and the mixture is stirred thoroughly before being poured into a mold. Negative pressure is applied to remove bubbles, and a pressure plate is placed on the surface to ensure its flatness. The mixture is then solidified at room temperature to produce an acoustic phantom, used to characterize its acoustic properties. The relationship between soda-lime glass microsphere concentration and sound velocity, as well as the relationship between sound attenuation coefficient and ultrasonic frequency at different soda-lime glass microsphere concentrations, are calculated. Step 2: Adjust the dosage of the reagent according to the test results so that the acoustic parameters match the acoustic parameters of the human tissue to be simulated; Step 3: Prepare the initial optical phantom and detect its optical parameters; construct the relationship between the concentration of the added reagent and each optical parameter; Step 4: Adjust the dosage of the reagent according to the test results so that the optical parameters match the optical parameters of the human tissue to be simulated. Step 5: Based on the proportions of each agent determined in Steps 2 and 4, prepare the photoacoustic imaging phantom. Specifically, in Step 5, based on the results of Steps 2 and 4, prepare sodium-calcium glass microspheres, graphite powder, and TiO2 at appropriate concentrations according to the requirements of the tissue to be simulated. Add the above three powders to the PDMS monomer and disperse them fully. Then add the curing agent and mix thoroughly. Pour the mixture into a mold and cure it to make the final photoacoustic phantom, which is used to simulate the photoacoustic imaging of tissues.

2. The method for fabricating a high-stability photoacoustic imaging phantom as described in claim 1, characterized in that: in, The ratio of the added curing agent to the main agent is 1:

5.

3. The method for fabricating a highly stable photoacoustic imaging phantom as described in claim 1 or 2, characterized in that: In step one, the acoustic parameters being tested include sound velocity, sound attenuation coefficient, and acoustic impedance.

4. The method for fabricating a high-stability photoacoustic imaging phantom as described in claim 3, characterized in that: In step one, the following methods are used to calculate the sound velocity, sound attenuation coefficient, and sound impedance: The sound velocity measurement of the phantom is based on the pulse substitution method. First, the propagation speed of ultrasound in degassed water at 22°C is measured; then the sound velocity in the water is calculated. Further, the fabricated phantom is placed in the sound beam propagation path, and the sound velocity of the ultrasound in the phantom sample is calculated. ; The acoustic attenuation coefficient of the phantom sample was obtained using relevant formulas. (dB / cm); The acoustic impedance of the phantom sample was calculated using relevant formulas. ); Finally, the ultrasonic backscattering characteristics of the phantoms were characterized by comparing B-mode ultrasound images and signal intensity analysis between phantoms or with reference materials.

5. The method for fabricating a high-stability photoacoustic imaging phantom as described in claim 1, characterized in that: In step three, specifically, phantoms with different concentration ratios of nano-graphite powder and nano-TiO2 are prepared. During preparation, the required amount of graphite powder and TiO2 powder is weighed and added to the PDMS main agent. The mixture is then processed using an ultrasonic crusher to ensure that the powder is completely dispersed in the medium. After cooling to room temperature, a curing agent is added at a mass ratio of 5:

1. The mixture is thoroughly stirred and poured into a mold. Negative pressure is applied to remove bubbles, and the mold is placed on a horizontal table to solidify. After solidification, an optical phantom is prepared for measuring optical parameters. The relationship between graphite powder concentration and absorption coefficient, and the relationship between titanium dioxide concentration and reduced scattering coefficient are calculated.

6. The method for fabricating a high-stability photoacoustic imaging phantom as described in claim 5, characterized in that: In step three, the optical parameters include the light absorption coefficient, the scattering coefficient, and the anisotropy factor.

7. The method for fabricating a high-stability photoacoustic imaging phantom as described in claim 6, characterized in that: In step three, the following method is used to calculate the light absorption coefficient, light scattering coefficient, and anisotropy factor: The optical properties of the phantom were characterized based on the Kubelka-Munk method and measured using an integrating sphere spectrophotometer. For a finite turbid medium of thickness d, the flux loss per unit path length caused by absorption is defined as... The loss caused by scattering is defined as Then the following relationship holds: in, and These are the diffuse reflectance and total transmittance of the medium, respectively, and the minor coefficient. and = is defined as: and , With the medium absorption coefficient ( ) and scattering coefficient ( They have the following relationships: in To reduce the scattering coefficient, through the anisotropy factor ( The scattering coefficient is defined. The extinction coefficient is the ratio of the measured parallel transmittance. By Bill-Lambert's Law Defined; Therefore, by measuring the diffuse reflectance of the phantom sample Total transmittance Parallel transmittance Then, the above three optical parameters—medium absorption coefficient, scattering coefficient, and anisotropy factor—can be obtained. , ); To meet specific usage needs, the concentration of additives can be adjusted to regulate different acoustic and optical parameters, thereby simulating different tissue types in the human body.

8. The method for fabricating a high-stability photoacoustic imaging phantom as described in claim 7, characterized in that: In step five, multiple polytetrafluoroethylene (PTFE) capillaries are placed in the photoacoustic imaging phantom to simulate blood vessels. The PTFE capillaries are located at different transverse and longitudinal layers within the phantom. A light-absorbing substance solution of the same concentration is filled into the PTFE capillaries. The spacing between each pair of transversely arranged PTFE capillaries gradually increases from left to right, used to detect the transverse resolution of the photoacoustic imaging system. The spacing between each pair of longitudinally arranged PTFE capillaries is the same, used to detect the maximum imaging depth of the photoacoustic imaging system. By filling the PTFE capillaries with light-absorbing substance solutions of different concentrations, the photoacoustic imaging system is used to image the capillaries and perform photoacoustic signal intensity analysis to detect the sensitivity of the photoacoustic system to different concentrations of the substance.

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