Optimization design method and processing method for improving fatigue performance of interventional medical device

Abstract

The invention relates to the technical field of medical instruments, and discloses an optimization design method and a processing method for improving the fatigue performance of an interventional medical device.The optimization design method for improving the fatigue performance of the interventional medical instrument comprises the following steps that S1, physiological load conditions and geometric conditions are determined, s2, performing preliminary structural design according to the physiological load condition and the geometric condition, determining a key working area of the interventional medical device according to an intermediate structural design result, the physiological load condition and the geometric condition, and continuing to perform the step S2 by taking the preliminary structural design as the intermediate structural design; s2, strain distribution is obtained through calculation, the average strain of the key working area is output, and it is judged that the design process is ended or the step S3 is continued according to the average strain result; s3, iteration is carried out, and the step S2 is carried out again. The problems that when the fatigue performance of the interventional medical device is improved, the original key performance and the fatigue performance improvement effect of the interventional medical device cannot be considered at the same time, and the cost is high are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to an optimization design method and a processing method for improving fatigue performance of interventional medical devices. Background Art

[0002] Interventional medical devices refer to a general term for instruments, equipment, and implants that enter the human body through natural cavities or tiny incisions and are delivered to specific locations for the purpose of diagnosing, treating, or alleviating diseases. Common interventional medical devices include vascular stents, vena cava filters, guidewires, and the like. Due to the fact that interventional medical devices enter the human body directly and may remain in the body for a long time, they are subject to complex physiological circulatory loads after entering the body. Long-term use can easily lead to accumulated fatigue damage to the structure of the interventional medical devices, resulting in structural damage. Fragments of the damaged structure may puncture human tissue, causing complications and posing a threat to the health and safety of patients. Therefore, many interventional medical devices are made of nickel-titanium alloy materials with superelasticity and shape memory effects. By improving the manufacturing process of interventional medical devices, interventional medical devices have sufficient fatigue performance and can withstand complex stress conditions in the human body for a longer period of time, thereby increasing the service life of interventional medical devices.

[0003] In related technologies, in order to increase the service life of interventional medical devices in the human body, methods such as adjusting the structural shape of the interventional medical devices, reducing the size of material impurities, improving heat treatment processes, and surface treatment are generally used.

[0004] However, in the actual application of interventional medical devices, it is not difficult to find that these methods have great limitations. For example, when the structural shape of the interventional medical device is changed simply to improve the structural fatigue performance, the shape and size of the interventional medical device are constrained by conditions such as the clinical application scenario and the size of the delivery system. It is impossible to effectively improve the fatigue resistance of the interventional medical device, and the original radial force or flexibility of the interventional medical device may be sacrificed, thereby reducing the safety and medical effect of the interventional medical device; the cost of reducing the size of material impurities is too high and the effect is very limited, which is not conducive to the actual use and promotion of interventional medical devices; it is difficult to achieve the best balance in material performance in the heat treatment process; the surface treatment process can make the surface of the material smooth, but the improvement in fatigue performance is also very limited. Summary of the Invention

[0005] In view of this, the present invention provides an optimization design method and processing method for improving the fatigue performance of interventional medical devices, so as to solve the problem that the improvement of the fatigue performance of interventional medical devices cannot take into account the original key performance of the interventional medical devices and the fatigue performance improvement effect, and the cost is high.

[0006] In the first aspect, the present invention provides an optimization design method for improving the fatigue performance of interventional medical devices, comprising the following steps: S1: determining the physiological load conditions and geometric conditions of the interventional medical device according to the target implantation site of the interventional medical device, performing a preliminary structural design on the interventional medical device according to the physiological load conditions and the geometric conditions, determining the key working area of ​​the interventional medical device according to the intermediate structural design results and the physiological load conditions and the geometric conditions, taking the preliminary structural design as the intermediate structural design, and proceeding to step S2; S2: calculating the strain distribution of the intermediate structural design and outputting the average strain of the key working area; if the average strain result is between 1.5% and 6%, taking the intermediate structural design as the final structural design and ending the design; if the average strain result deviates from the range between 1.5% and 6%, taking the intermediate structural design as the process design and proceeding to step S3; S3: iterating the process structural design and outputting the new intermediate structural design, and re-performing step S2.

[0007] Beneficial Effects: By identifying the target implant site, the permissible dimensions of the interventional medical device and the workload it will experience after implantation can be more accurately determined based on the physiological load conditions of the target implant site. This allows for targeted preliminary structural design, improving design feasibility and the controllability of various mechanical performance parameters, effectively reducing the number of possible structural design iterations. Identifying the critical working area of ​​the interventional medical device can reduce the required calculations, narrow the structural scope that designers need to focus on, and reduce design difficulty, facilitating control of average strain levels during subsequent design processes. Through design and design iteration, the average strain result is made between 1.5% and 6%. At this time, in the titanium alloy used as the material of the interventional medical device, the average strain is in the austenite-martensite mixed zone, which can enable the key working area of ​​the interventional medical device to obtain good fatigue performance, and the fatigue damage accumulation caused by the physiological cycle load of the part of the interventional medical device other than the key working area is itself small. Therefore, by improving the fatigue performance of the key working area, the fatigue life of the entire interventional medical device can be improved. In addition, since the key working area of ​​the interventional medical device is determined, the design iteration can be carried out around the key working area in combination with the average load of the key working area, thereby improving the overall fatigue life of the interventional medical device while retaining key performance for the interventional medical device, such as superelasticity, sufficient overall radial support force, and good biocompatibility, and saving costs compared to reducing impurity size, improving heat treatment process or improving surface treatment process.

[0008] In an optional embodiment, the method of calculating the strain distribution of the intermediate structure design and outputting the average strain of the key working area includes manually calculating or setting the boundary conditions of computer simulation according to the workload, and obtaining it through the computer simulation.

[0009] Beneficial effects: Strain distribution can be determined in a variety of ways. For simple structures, it can be quickly obtained by manual calculation, empirical estimation, querying relevant data, etc., or more accurate data can be obtained through computer simulation based on the actual structure and actual working conditions of the interventional medical device.

[0010] In an optional embodiment, in step S2, the strain distribution of the intermediate structural design is calculated and the average strain of the critical working area is output. If the average strain result is between 2% and 3%, the intermediate structural design is used as the final structural design. If the average strain result deviates from between 2% and 3%, the intermediate structural design is used as the process design and step S3 is continued.

[0011] Beneficial effects: Since there is a certain error between the calculated strain distribution and the average strain of the key working area and the actual average strain of the interventional medical devices actually processed and produced, by controlling the average strain result between 2% and 3%, the optimization effect of the austenite-martensite dual-phase region can be fully utilized, and the risk of potential damage to the interventional medical devices caused by excessive average strain can be avoided, so as to obtain the best long-term fatigue performance.

[0012] In an optional embodiment, in step S1, the method of determining the geometric condition and the physiological load condition includes one or more of medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching.

[0013] Beneficial effects: By observing and analyzing the geometric conditions and stress conditions of the target implantation location through one or more methods including medical image analysis, hemodynamic measurement, direct sensor monitoring and biomechanical database matching, the target value such as the physiological circulatory stress condition of the location can be obtained more accurately, thereby facilitating the acquisition of more accurate average strain results, making the design of interventional medical devices more reliable.

[0014] In an optional embodiment, in step S3, the method of iterating the process structure design and outputting the new intermediate structure design includes one or more of modifying the geometric shape of the interventional medical device, modifying the geometric size of the interventional medical device, and adjusting the type of the interventional medical device.

[0015] Beneficial effects: In order to adjust the average strain in the key working areas of interventional medical devices, a variety of methods can be used to iteratively improve the specific form of interventional medical devices. It is not limited to adjusting the overall or local mechanical properties only by geometric shape, but it is possible to consider replacing different types of interventional medical devices, which expands the design concept and helps to adjust the average strain more accurately.

[0016] In the second aspect, the present invention provides a processing method for improving the fatigue performance of interventional medical devices, comprising the following steps: A1: calculating the local strain distribution of each part of the interventional medical device under different deformation conditions and obtaining the relationship between the deformation size and strain amount of each part of the device; A2: determining the overall deformation size that makes the maximum local strain of the key working area reach 6% to 10.5% based on the relationship between the deformation size and the strain amount, and taking the overall deformation size as the target size; A3: applying a load to the interventional medical device by simulating the physiological load application method of the target implant site, so that the interventional medical device is deformed to the target size and then releasing the interventional medical device to a free state.

[0017] Beneficial Effects: Because interventional medical devices are made of superelastic nickel-titanium alloy, applying a large strain more than once to the interventional medical device induces and stabilizes the material's internal residual stress, dislocations, and twinning microstructure, inducing multiple positive changes in the material to improve fatigue resistance and extend high-cycle fatigue life. By identifying key areas of the interventional medical device, attention can be focused, reducing unnecessary design and computational workload. By pre-understanding the relationship between deformation size and strain, the degree of strain applied can be controlled in subsequent processes. Loading the maximum local strain to 6% to 10.5% of the deformation size causes local plastic deformation, inducing residual stress and increasing the twinning structure within the material. Compared to untreated interventional medical devices, fatigue life can be increased by 20% to 50%. At the same time, the cyclic modulus is reduced by approximately 10% to 20%. Furthermore, at the same strain amplitude, stress amplitude can be reduced and crack propagation can be delayed. This promotes the coordinated adjustment of microstructure and residual stress without excessive material damage, significantly improving the cyclic fatigue life of interventional medical devices.

[0018] In an optional embodiment, in step A2, the overall deformation size that makes the maximum local strain of the key working area reach 6% to 9% is determined based on the relationship between the deformation size and the deformation amount, and the overall deformation size is used as the target size.

[0019] Beneficial effects: In order to further avoid damage to the structure of interventional medical devices caused by excessive loading, the maximum local strain is further limited to 6% to 9%, while ensuring the treatment effect and improving safety.

[0020] In an optional embodiment, in step A3, after the interventional medical device is deformed to a target size and maintained for 10 to 15 seconds, the interventional medical device is released to a free state.

[0021] Beneficial effects: By maintaining the deformation state of the interventional medical device, the structure of the interventional medical device is given sufficient time to induce residual stress inside the material and reshape the microstructure, thereby improving the treatment effect and ensuring the fatigue life of the interventional medical device.

[0022] In an optional embodiment, step A2 is cyclically performed two to five times.

[0023] Beneficial effect: By performing step A2 multiple times and applying the same load multiple times and maintaining it for a certain period of time, the treatment effect is consolidated.

[0024] In an optional embodiment, in steps A1 to A3, the temperature of the interventional medical device is controlled between 15°C and 35°C.

[0025] Beneficial effect: By limiting the temperature of the interventional medical device during the treatment process, excessive temperature rise during loading is avoided, which causes changes in the microstructure of the interventional medical device and thus has an unstable effect on fatigue performance, avoiding the situation where fatigue performance cannot be reliably improved.

[0026] In an optional embodiment, the following steps are also included: S1: determining the physiological load conditions and geometric conditions of the interventional medical device according to the target implantation site of the interventional medical device, performing preliminary structural design on the interventional medical device according to the physiological load conditions and the geometric conditions, determining the critical working area of ​​the interventional medical device according to the intermediate structural design results and the physiological load conditions and the geometric conditions, taking the preliminary structural design as the intermediate structural design, and proceeding to step S2; S2: calculating the strain distribution of the intermediate structural design and outputting the average strain of the critical working area; if the average strain result is between 1.5% and 6%, taking the intermediate structural design as the final structural design and ending the design; if the average strain result deviates from the range between 1.5% and 6%, taking the intermediate structural design as the process design and proceeding to step S3; S3: iterating the process structural design and outputting the new intermediate structural design, and re-performing step S2.

[0027] Beneficial Effects: By identifying the target implant site, the permissible dimensions of the interventional medical device and the workload it will experience after implantation can be more accurately determined based on the physiological load conditions of the target implant site. This allows for targeted preliminary structural design, improving design feasibility and the controllability of various mechanical performance parameters, effectively reducing the number of possible structural design iterations. Identifying the critical working area of ​​the interventional medical device can reduce the required calculations, narrow the structural scope that designers need to focus on, and reduce design difficulty, facilitating control of average strain levels during subsequent design processes. Through design and iteration, the average strain was optimized to between 1.5% and 6%. At this point, the average strain in the titanium alloy used as the material for the interventional medical device is in the austenite-martensite mixed region, enabling excellent fatigue performance in the critical working area of ​​the interventional medical device. Furthermore, the fatigue damage accumulation caused by physiological cyclic loading in the device's components outside the critical working area is relatively small. Therefore, by improving the fatigue performance of the critical working area, the fatigue life of the entire interventional medical device can be improved. Furthermore, since the critical working area of ​​the interventional medical device is identified, design iterations can be focused around the critical working area, taking into account the average load. This improves the fatigue life of the interventional medical device while retaining key performance attributes such as superelasticity, sufficient overall radial support, and good biocompatibility. This also saves costs compared to reducing impurity size, improving heat treatment processes, or improving surface treatment processes. Furthermore, by iteratively controlling the average strain in the critical working area under cyclic loading at the target implant location, combined with preloading the interventional medical device during processing, the fatigue life of the interventional medical device is further improved.

[0028] In an optional embodiment, the method of calculating the strain distribution of the intermediate structure design and outputting the average strain of the key working area includes manually calculating or setting the boundary conditions of computer simulation according to the workload, and obtaining it through the computer simulation.

[0029] Beneficial effects: Strain distribution can be determined in a variety of ways. For simple structures, it can be quickly obtained by manual calculation, empirical estimation, querying relevant data, etc., or more accurate data can be obtained through computer simulation based on the actual structure and actual working conditions of the interventional medical device.

[0030] In an optional embodiment, in step S2, the strain distribution of the intermediate structural design is calculated and the average strain of the critical working area is output. If the average strain result is between 2% and 3%, the intermediate structural design is used as the final structural design. If the average strain result deviates from the range between 2% and 3%, the intermediate structural design is used as the process design and step S3 is continued.

[0031] Beneficial effects: Since there is a certain error between the calculated strain distribution and the average strain of the key working area and the actual average strain of the interventional medical devices actually processed and produced, by controlling the average strain result between 2% and 3%, the optimization effect of the austenite-martensite dual-phase region can be fully utilized, and the risk of potential damage to the interventional medical devices caused by excessive average strain can be avoided, so as to obtain the best long-term fatigue performance.

[0032] In an optional embodiment, in step S1, the method of determining the geometric condition and the physiological load condition includes one or more of medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching.

[0033] Beneficial effects: By observing and analyzing the geometric conditions and stress conditions of the target implantation location through one or more methods including medical image analysis, hemodynamic measurement, direct sensor monitoring and biomechanical database matching, the target value such as the physiological circulatory stress condition of the location can be obtained more accurately, thereby facilitating the acquisition of more accurate average strain results, making the design of interventional medical devices more reliable.

[0034] In an optional embodiment, in step S3, the method of iterating the process structure design and outputting the new intermediate structure design includes one or more of modifying the geometric shape of the interventional medical device, modifying the geometric size of the interventional medical device, and adjusting the type of the interventional medical device.

[0035] Beneficial effects: In order to adjust the average strain in the key working areas of interventional medical devices, a variety of methods can be used to iteratively improve the specific form of interventional medical devices. It is not limited to adjusting the overall or local mechanical properties only by geometric shape, but it is possible to consider replacing different types of interventional medical devices, which expands the design concept and helps to adjust the average strain more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 This is a schematic diagram of the direction of applying a load to an interventional medical device in a method for improving fatigue performance of an interventional medical device according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of strain distribution when a stent is compressed to 3.6 mm, calculated by finite element analysis software simulation in a method for improving fatigue performance of an interventional medical device according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of fatigue test results of grouped products in a processing method for improving fatigue performance of interventional medical devices according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0041] The following combination Figures 1 to 3 , describing embodiments of the present invention.

[0042] According to an embodiment of the present invention, on the one hand, an optimization design method for improving the fatigue performance of an interventional medical device is provided, comprising the following steps: S1: determining the physiological load conditions and geometric conditions of the interventional medical device according to the target implantation site of the interventional medical device, performing a preliminary structural design on the interventional medical device according to the physiological load conditions and geometric conditions, determining the key working area of ​​the interventional medical device according to the intermediate structural design results and the physiological load conditions and geometric conditions, taking the preliminary structural design as the intermediate structural design, and proceeding to step S2; S2: calculating and obtaining the strain distribution of the intermediate structural design and outputting the average strain of the key working area; if the average strain result is between 1.5% and 6%, taking the intermediate structural design as the final structural design and ending the design; if the average strain result deviates from the range between 1.5% and 6%, taking the intermediate structural design as the process design and proceeding to step S3; S3: iterating the process structural design and outputting a new intermediate structural design, and re-performing step S2.

[0043] Specifically, the geometric conditions of an interventional medical device refer to the geometric conditions, such as shape and size, that enable the device to reach its target position and function properly. Physiological load conditions refer to the loads exerted by human tissue on the device at the target implantation site, such as compression from the vessel wall, impact from blood flow, and the pull of the heartbeat. Generally speaking, physiological loads occur cyclically, for example, with the rhythm of the heartbeat. Therefore, physiological loads are also called physiological cyclic loads. Under physiological cyclic loads, interventional medical devices are periodically subjected to loads, accumulating fatigue damage. This is one of the reasons why interventional medical devices require good fatigue performance.

[0044] It should be noted that the critical working area is different in different types of medical devices. The method for determining the critical working area can be obtained through experience, or it can be determined by manual calculation or computer simulation output of the stress distribution. The specific method is a skill that technical personnel in this field should master and will not be repeated in this embodiment.

[0045] In this embodiment, by identifying the target implantation site, the permissible dimensions of the interventional medical device and the workload to which it will be subjected after implantation can be more accurately determined based on the physiological load conditions of the target implantation site. This allows for targeted preliminary structural design, improving the feasibility of the design and the controllability of various mechanical performance parameters, effectively reducing the number of possible structural design iterations. Identifying the critical working area of ​​the interventional medical device can reduce the required computational effort, narrow the structural scope that designers need to focus on, and reduce design difficulty, facilitating control of average strain levels during subsequent design processes. Through design and design iteration, the average strain result is made between 1.5% and 6%. At this time, in the titanium alloy used as the material of the interventional medical device, the average strain is in the austenite-martensite mixed zone, which can enable the key working area of ​​the interventional medical device to obtain good fatigue performance, and the fatigue damage accumulation caused by the physiological cycle load of the part of the interventional medical device other than the key working area is itself small. Therefore, by improving the fatigue performance of the key working area, the fatigue life of the entire interventional medical device can be improved. In addition, since the key working area of ​​the interventional medical device is determined, the design iteration can be carried out around the key working area in combination with the average load of the key working area, thereby improving the overall fatigue life of the interventional medical device while retaining key performance for the interventional medical device, such as superelasticity, sufficient overall radial support force, and good biocompatibility, and saving costs compared to reducing impurity size, improving heat treatment process or improving surface treatment process.

[0046] It should be noted that the effects produced by the technical solution of this embodiment are different from the methods of adjusting the structural shape of the interventional medical device, reducing the size of material impurities, improving the heat treatment process, and surface treatment in related technologies. The specific differences include but are not limited to:

[0047] Compared to related art techniques that adjust the structural shape of interventional medical devices, this embodiment focuses structural changes on critical working areas, aiming to control the average strain in these areas rather than changing the overall structure. This maintains properties such as superelasticity and sufficient overall radial support, while avoiding significant adjustments to the overall geometry and dimensions. Furthermore, because structural design changes are based on target average strain results and critical working areas, the design can be completed more accurately, on a smaller scale, and quickly.

[0048] Compared to related techniques for reducing material impurity size, this embodiment does not involve steps related to smelting processes, material purity, and thermomechanical treatment, resulting in lower costs and greater improvements in fatigue performance of interventional medical devices. It should be noted that impurity size generally refers to non-metallic particles such as oxides, nitrides, and carbides introduced during the alloy smelting and casting process, and can also refer to other related impurities.

[0049] Compared with the improvement of heat treatment process and surface treatment, the effect produced by this embodiment is more significant, and since it does not change the main chemical properties of the material itself and does not involve other chemical substances that may be exposed during the heat treatment process, it has better biocompatibility.

[0050] In one embodiment, the method of calculating the strain distribution of the intermediate structure design and outputting the average strain of the key working area includes manually calculating or setting the boundary conditions of the computer simulation according to the working load, and obtaining it through computer simulation.

[0051] Specifically, this embodiment does not limit the specific method of computer simulation, and finite element analysis simulation software may be used, or other software or equipment may be used.

[0052] In this embodiment, the strain distribution can be determined in a variety of ways. For simple structures, it can be quickly obtained by manual calculation, empirical estimation, querying relevant information, etc., or more accurate data can be obtained through computer simulation based on the actual structure and actual working conditions of the interventional medical device.

[0053] In one embodiment, in step S2, the strain distribution of the intermediate structural design is calculated and the average strain of the critical working area is output. If the average strain result is between 2% and 3%, the intermediate structural design is used as the final structural design. If the average strain result deviates from the 2% to 3% range, the intermediate structural design is used as the intermediate design and the process proceeds to step S3.

[0054] In this embodiment, since there is a certain error between the calculated strain distribution and the average strain of the key working area and the actual average strain of the interventional medical device actually processed and produced, by controlling the average strain result between 2% and 3%, the optimization effect of the austenite-martensite two-phase region can be fully utilized, and the risk of potential damage to the interventional medical device caused by excessive average strain can be avoided, so as to obtain the best long-term fatigue performance.

[0055] In one embodiment, in step S1 , the method of determining the geometric conditions and the physiological load conditions includes one or more of medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching.

[0056] It should be noted that medical imaging analysis methods include but are not limited to angiography and CT / MRI dynamic scanning to obtain the shape changes and movement trajectories of blood vessels during the cardiac cycle; hemodynamic methods include but are not limited to direct measurement of blood flow velocity and pressure waveform through ultrasound Doppler or 4D Flow MRI; direct sensor monitoring methods include but are not limited to inserting micro pressure sensor guidewires into blood vessels to record the pressure distribution on the vessel wall; biomechanical database matching methods include but are not limited to matching the vascular mechanical parameters of similar people through public biomechanical databases.

[0057] In this embodiment, the geometric conditions and stress conditions of the target implantation position are observed and analyzed by one or more methods including medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching, so that target values ​​such as the physiological circulatory stress conditions of the position can be obtained more accurately, thereby facilitating the acquisition of more accurate average strain results, making the design of interventional medical devices more reliable.

[0058] In one embodiment, in step S3 , the method of iterating the process structure design and outputting a new intermediate structure design includes one or more of modifying the geometric shape of the interventional medical device, modifying the geometric size of the interventional medical device, and adjusting the type of the interventional medical device.

[0059] Specifically, specific forms of modifying the geometric shape of the medical device include but are not limited to modifying the rib width, thickness, unit length, and connection bridge design.

[0060] In this embodiment, in order to adjust the average strain of the key working area of ​​the interventional medical device, a variety of methods can be used to iteratively improve the specific form of the interventional medical device. It is not limited to adjusting the overall or local mechanical properties only by the geometric shape, but it is possible to consider replacing different types of interventional medical devices, which expands the design concept and helps to more accurately adjust the average strain.

[0061] According to an embodiment of the present invention, on the other hand, a processing method for improving the fatigue performance of an interventional medical device is also provided, comprising the following steps: A1: calculating the local strain distribution of each part of the interventional medical device under different deformation conditions and obtaining the relationship between the deformation size and strain amount of each part of the device; A2: determining the overall deformation size that makes the maximum local strain of the key working area reach 6% to 10.5% based on the relationship between the deformation size and the strain amount, and taking the overall deformation size as the target size; A3: applying a load to the interventional medical device by simulating the physiological load application method of the target implant site, so that the interventional medical device is deformed to the target size and then releasing the interventional medical device to a free state.

[0062] Specifically, the physiological load application method that simulates the target implantation site may be to use a medical crimping machine to crimp the interventional medical device, or other dedicated equipment.

[0063] In this embodiment, since the interventional medical device is made of a superelastic nickel-titanium alloy, applying a large strain to the device more than once induces and stabilizes the material's internal residual stresses, dislocations, and twinning microstructures, inducing multiple positive changes in the material to improve fatigue resistance and extend high-cycle fatigue life. By identifying key areas of the interventional medical device, attention can be focused, reducing unnecessary design and computational workload. By pre-understanding the relationship between deformation size and strain, the degree of applied strain can be controlled in subsequent processes. Applying a maximum local strain of 6% to 10.5% of the deformation size causes local plastic deformation, induces residual stress, and increases the twinning structure within the material. Compared to untreated interventional medical devices, fatigue life can be improved by 5% to 50%, while the cyclic modulus is reduced by approximately 10% to 20%. Furthermore, at the same strain amplitude, stress amplitude can be reduced, slowing crack propagation. This promotes a coordinated adjustment of microstructure and residual stress without excessive material damage, significantly improving the cyclic fatigue life of the interventional medical device.

[0064] In one embodiment, in step A2, the overall deformation size that enables the maximum local strain of the key working area to reach 6% to 9% is determined based on the relationship between the deformation size and the deformation amount, and the overall deformation size is used as the target size.

[0065] In this embodiment, in order to further avoid damage to the structure of the interventional medical device caused by excessive loading, the maximum local strain is further limited to 6% to 9%, thereby improving safety while ensuring the treatment effect.

[0066] In one embodiment, in step A3 , after the interventional medical device is deformed to a target size and maintained for 10 to 15 seconds, the interventional medical device is released to a free state.

[0067] In this embodiment, by maintaining the deformation state of the interventional medical device, the structure of the interventional medical device is given sufficient time to induce residual stress inside the material and reshape the microstructure, thereby improving the treatment effect and ensuring the fatigue life of the interventional medical device.

[0068] In one embodiment, step A2 is looped and executed two to five times.

[0069] In this embodiment, step A2 is performed multiple times, and the same load is applied multiple times and maintained for a certain period of time to consolidate the treatment effect.

[0070] In one embodiment, in steps A1 to A3, the temperature of the interventional medical device is controlled between 10°C and 40°C.

[0071] In this embodiment, by limiting the temperature of the interventional medical device during the processing, excessive temperature rise during loading is avoided, which causes changes in the microstructure of the interventional medical device and thus has an unstable impact on the fatigue performance, thereby avoiding the situation where fatigue performance cannot be reliably improved.

[0072] Specifically, see Figure 1 The technical solutions in the above embodiments are explained below with reference to specific examples. Taking a laser-cut nickel-titanium alloy iliac vein stent as an example, the design process involves using medical-grade superelastic nickel-titanium alloy tubing (e.g., SE508) that complies with ASTM F2063, with a diameter of 3.0 mm. The iliac vein stent is initially formed by laser cutting. The stent is then placed on a heat treatment mold and placed in a heat treatment furnace (500°C ± 10°C) for 5 ± 1 minutes, followed by cooling to room temperature in water. After two heat treatments, the stent has a diameter of 10.1 mm.

[0073] Through simulation calculations using finite element analysis software, it was found that when the stent was compressed to 3.6 mm, the maximum local strain in the key area of ​​the stent reached approximately 9%.

[0074] It should be noted that Figure 1 The direction of the middle arrow is the compression direction of the bracket, that is, the direction in which the load is applied.

[0075] After heat treatment and shaping, the stent is pre-deformed and crimped. The processing method is as follows: the iliac vein stent with a free diameter of approximately 10.1 mm is radially and uniformly compressed to a target diameter of 3.6 mm using a radial crimping device. After reaching the target size, the crimping state is maintained for 7 seconds. The "crush-hold-release" cycle is repeated twice. Each cycle releases to the free state and stays for approximately 2 seconds. The crimping-release speed is controlled at 1 mm / s. The processing process is carried out at room temperature.

[0076] After the pre-strain treatment, the stent is routinely subjected to precision electrolytic polishing, ultrasonic cleaning, passivation (optional), and then final testing, packaging and sterilization.

[0077] Also, see Figures 1 to 2Specifically, the combined technical solution of the optimization design method and the processing method in the above embodiment is explained in conjunction with another specific example, taking a braided titanium alloy iliac vein stent as an example. The specific process is: the braiding structure, wire diameter, etc. of the stent are optimized and designed through tools such as finite element analysis (FEA). The stent has an unfolded diameter of approximately 16.1mm and is implanted in a 14mm vessel. When subjected to typical physiological loads, the average strain in the key working area of ​​the stent can be stabilized at around 2.0-2.5%, which is within the theoretical optimal fatigue performance range of nickel-titanium alloy (2%-3%).

[0078] Medical-grade nickel-titanium alloy wire (e.g., wire diameter 0.22 mm) that complies with ASTM F2063 standards is used to initially form the iliac vein stent through a braiding process. The stent is then heat-treated in a heat treatment furnace (500°C±10°C) for 15±5 minutes and then placed in water to cool to room temperature.

[0079] After heat treatment and shaping, the stent is subjected to pre-deformation and crimping treatment. It is expected that the maximum local strain of the key parts of the stent will reach a target pre-strain of about 7.5% ± 0.2% through crimping, which is within the range of 6% to 10.5% (preferably 6% to 9%) recommended in the embodiment of the present invention. Through FEA simulation calculation, when compressed to 4.0mm, the maximum local strain of the key area of ​​the stent reaches about 7.6%. The specific operation is to use a radial crimping device to radially and uniformly compress the above-mentioned stent with a free diameter of about 16.1mm to a target diameter of 4.0mm. After reaching the target size, maintain the crimping state for 10 ± 5 seconds. Repeat the "crush-hold-release" cycle twice. Release to the free state and stay for about 2 seconds in each cycle. The treatment process is carried out at room temperature. After that, the stent is electrolytically polished and cleaned as usual, and then inspected and put into storage.

[0080] The fatigue performance test results of the untreated stent, the stent with the gripping treatment in the above embodiment, and the stent with the optimized design and gripping treatment are shown in the table. Figure 3 It can be seen that the crimping treatment improves the fatigue performance of the bracket. After design optimization and crimping treatment, the fatigue performance of the bracket is further improved.

[0081] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An optimization design method for improving fatigue performance of interventional medical devices, characterized in that: The following steps are involved: S1: determining physiological load conditions and geometric conditions of the interventional medical device according to a target implantation site of the interventional medical device, performing a preliminary structural design of the interventional medical device according to the physiological load conditions and the geometric conditions, determining a key working area of ​​the interventional medical device according to the intermediate structural design result and the physiological load conditions and the geometric conditions, and proceeding to step S2 using the preliminary structural design as the intermediate structural design; S2: Calculate the strain distribution of the intermediate structural design and output the average strain of the key working area. If the average strain result is between 1.5% and 6%, use the intermediate structural design as the final structural design and end the design. If the average strain result deviates from the range between 1.5% and 6%, use the intermediate structural design as the process design and continue to step S3. S3: Iterate the process structure design and output the new intermediate structure design, and repeat step S2.

2. The optimization design method for improving fatigue performance of interventional medical devices according to claim 1, characterized in that: The method of calculating the strain distribution of the intermediate structure design and outputting the average strain of the key working area includes obtaining it by manual calculation or setting the boundary conditions of computer simulation according to the working load and obtaining it through the computer simulation.

3. The optimization design method for improving fatigue performance of interventional medical devices according to claim 2, characterized in that: In step S2, the strain distribution of the intermediate structural design is calculated and the average strain of the critical working area is output. If the average strain result is between 2% and 3%, the intermediate structural design is used as the final structural design. If the average strain result deviates from the range between 2% and 3%, the intermediate structural design is used as the process design and step S3 is continued.

4. The optimization design method for improving fatigue performance of interventional medical devices according to claim 2 or 3, characterized in that: In step S1 , the method of determining the geometric condition and the physiological load condition includes one or more of medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching.

5. The optimization design method for improving fatigue performance of interventional medical devices according to claim 2 or 3, characterized in that: In step S3, the method of iterating the process structure design and outputting the new intermediate structure design includes one or more of modifying the geometric shape of the interventional medical device, modifying the geometric size of the interventional medical device, and adjusting the type of the interventional medical device.

6. A method for improving fatigue performance of interventional medical devices, characterized in that: The following steps are involved: A1: Calculate the local strain distribution of each part of the interventional medical device under different deformation conditions and obtain the relationship between the deformation size and strain of each part of the device; A2: Determine the overall deformation size that enables the maximum local strain in the critical working area to reach 6% to 10.5% based on the relationship between the deformation size and the strain, and use the overall deformation size as the target size; A3: Apply a load to the interventional medical device in a manner that simulates the physiological load application method of the target implantation site, deform the interventional medical device to a target size, and then release the interventional medical device to a free state.

7. The method for improving fatigue performance of interventional medical devices according to claim 6, characterized in that: In step A2, the overall deformation size that enables the maximum local strain of the key working area to reach 6% to 9% is determined based on the relationship between the deformation size and the deformation amount, and the overall deformation size is used as the target size.

8. The method for improving fatigue performance of interventional medical devices according to claim 6, characterized in that: In step A3, after the interventional medical device is deformed to a target size and maintained for 10 to 15 seconds, the interventional medical device is released to a free state.

9. The method for improving fatigue performance of interventional medical devices according to claim 8, characterized in that: Repeat step A2 two to five times.

10. The method for improving fatigue performance of interventional medical devices according to claim 9, characterized in that: In steps A1 to A3, the temperature of the interventional medical device is controlled between 15°C and 35°C.

11. The method for improving fatigue performance of an interventional medical device according to any one of claims 6 to 11, characterized in that: The following steps are also included: S1: determining the physiological load conditions and geometric conditions of the interventional medical device according to the target implantation site of the interventional medical device, performing a preliminary structural design of the interventional medical device according to the physiological load conditions and the geometric conditions, determining the key working area of ​​the interventional medical device according to the intermediate structural design result and the physiological load conditions and the geometric conditions, and proceeding to step S2 using the preliminary structural design as the intermediate structural design; S2: Calculate the strain distribution of the intermediate structural design and output the average strain of the key working area. If the average strain result is between 1.5% and 6%, use the intermediate structural design as the final structural design and end the design. If the average strain result deviates from the range between 1.5% and 6%, use the intermediate structural design as the process design and continue to step S3. S3: Iterate the process structure design and output the new intermediate structure design, and repeat step S2.

12. The method for improving fatigue performance of an interventional medical device according to claim 12, characterized in that: The method of calculating the strain distribution of the intermediate structure design and outputting the average strain of the key working area includes obtaining it by manual calculation or setting the boundary conditions of computer simulation according to the working load and obtaining it through the computer simulation.

13. The method for improving fatigue performance of an interventional medical device according to claim 13, characterized in that: In step S2, the strain distribution of the intermediate structural design is calculated and the average strain of the critical working area is output. If the average strain result is between 2% and 3%, the intermediate structural design is used as the final structural design. If the average strain result deviates from the range between 2% and 3%, the intermediate structural design is used as the process design and step S3 is continued.

14. The method for improving fatigue performance of an interventional medical device according to claim 13, characterized in that: In step S1 , the method of determining the geometric condition and the physiological load condition includes one or more of medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching.

15. The method for improving fatigue performance of an interventional medical device according to claim 13, characterized in that: In step S1 , the method of determining the geometric condition and the physiological load condition includes one or more of medical image analysis, hemodynamic measurement, direct sensor monitoring, and biomechanical database matching.

16. The method for improving fatigue performance of an interventional medical device according to claim 13, characterized in that: In step S3, the method of iterating the process structure design and outputting the new intermediate structure design includes one or more of modifying the geometric shape of the interventional medical device, modifying the geometric size of the interventional medical device, and adjusting the type of the interventional medical device.

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