Method for optimizing weaving silk in weaving intravascular stent, weaving silk and intravascular stent

Abstract

According to the method for optimizing the weaving wires in the weaving intravascular stent, three-dimensional simulation is carried out on the weaving wires with different cross sections in a three-dimensional modeling mode, and the weaving wires with different cross sections are used for establishing an intravascular stent model in three-dimensional modeling software; blood flow velocity in a tumor-carrying blood vessel and an aneurysm in a human body is simulated through three-dimensional modeling software and mechanical analysis software, and then the cross section of the weaving wire suitable for weaving the intravascular stent is determined, so that the clinical experiment frequency is reduced, the research time is shortened, the research cost is reduced, and the selection range of the weaving wire is greatly reduced; the injury to a patient in an experiment process is reduced.

Description

Technical Field

[0001] The invention relates to the field of medical devices, and in particular to a method for optimizing braided wires in a braided vascular stent and a vascular stent braided by the braided wires obtained by the method. Background Art

[0002] In the field of medical devices, vascular stents, as key devices in the field of vascular interventional treatment, have attracted much attention in recent years. They are mainly used to treat aneurysms and prevent rupture by diverting blood from entering the aneurysm cavity.

[0003] Traditional vascular stent structures usually adopt a relatively simple circular braided cross-sectional shape. With the deepening of clinical practice and the pursuit of higher treatment effects, traditional stent structures have gradually exposed some limitations. When the stent is implanted, the vascular stent is loaded onto the delivery system, and it is sent to the diseased blood vessel along the guide wire and catheter. After reaching the predetermined position, the stent is slowly and accurately released to expand in the blood vessel and adhere to the blood vessel wall. When the blood vessel is more curved and there are multiple lesions, it is difficult for the traditional circular cross-section vascular stent to completely follow its direction, and it is easy to have poor fit in the transition area of ​​the lesion site; from the above, it can be seen that to a certain extent, the shape of the cross-section of the braided wire can affect the flexibility of the vascular stent, and the flexibility of the vascular stent can be changed by changing the cross-section of the braided wire of the vascular stent. In addition, in terms of hemodynamics, the traditional vascular stent structure may have an adverse effect on local blood flow. For example, new vortices are induced near the stent or in the aneurysm cavity, causing the blood flow to form a rotational flow in the local area, increasing the impact and shear force of the blood flow on the blood vessel wall, or pressure concentration or abnormal pressure gradient occurs near the aneurysm body and neck, increasing the risk of aneurysm rupture. Therefore, there is a need for a braided wire that can both improve the flexibility of the vascular stent and eliminate the adverse effects of the vascular stent on local blood flow after implantation into the blood vessel.

[0004] The present invention aims to provide a method for optimizing the cross-section of braided wires. By studying the effect of vascular stents formed by braided wires with different cross-sections on the blood flow rate in the tumor-bearing blood vessel and the aneurysm after implantation into the tumor-bearing blood vessel, a suitable cross-section can be determined in a short time, thereby shortening the research time and reducing the research cost. Summary of the invention

[0005] The purpose of the present invention is to provide a method for optimizing the braided wires in a braided vascular stent to solve the problems existing in the above-mentioned prior art, select a suitable cross-section in a short time, shorten the research time and reduce the research cost.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a method for optimizing braided wires in a braided vascular stent, comprising the following steps:

[0007] S1: Determine the braided wire parameters;

[0008] Select braided wires with cross-sections of circular, square, regular hexagon, regular octagon, and regular decagon respectively, and use braided wires with different cross-sections to braid a vascular stent; control the porosity of the vascular stent to be consistent by controlling the size of the cross-section of the braided wire and the number of braiding turns of the braided wire;

[0009] S2: Establish a three-dimensional model of the vascular stent and analyze the force condition of the vascular stent using mechanical analysis software;

[0010] Use 3D modeling software to establish a three-dimensional model of the vascular stent formed by braided wires determined in S1; apply a rotational torque to the reference points at both ends of the vascular stent model to make the vascular stent model bend, and form a stress nephogram of the vascular stent model in the mechanical analysis software. According to the stress nephogram and the bending moment-angle curve graph, judge the force condition of each vascular stent model under the same rotational torque.

[0011] S3: Establish three-dimensional models of the aneurysm and the vascular stent, and analyze the hemodynamic changes using mechanical software;

[0012] Establish an aneurysm model, assemble it with the established vascular stent model, extract the fluid domain model, apply a velocity curve of one cardiac cycle at the inlet of the aneurysm model, and apply a pressure curve of one cardiac cycle at the outlet to test the hemodynamic changes caused by implanting the vascular stent model into the aneurysm model, and obtain a blood velocity nephogram. Judge the blood velocity in the parent artery and the aneurysm in the model according to the velocity nephogram.

[0013] In one embodiment, the material of the braided wire is nitinol.

[0014] In one embodiment, the porosity is 65%-75%.

[0015] A braided wire obtained by a method of optimizing the braided wire in a braided vascular stent, and the cross-section of the braided wire is a square.

[0016] A vascular stent braided with a braided wire having a square cross-section.

[0017] The present invention has achieved the following technical effects compared with the prior art:

[0018] By means of three-dimensional modeling, three-dimensional simulation is carried out on braided wires with different cross-sections, and a vascular stent model is established in three-dimensional modeling software using the braided wires with different cross-sections. The same rotational torque is applied to the reference points at both ends of the vascular stent model woven by the braided wires with different cross-sections to bend the vascular stent model. According to the judgment criterion that the greater the measured bending moment under the same rotational torque, the worse the flexibility, the vascular stent with the smallest generated bending moment is selected, and then the cross-section of the braided wire is determined; then, the blood flow in the diseased blood vessel and aneurysm in the human body is simulated through three-dimensional modeling software and mechanical analysis software, and the blood flow conditions in the diseased blood vessel and aneurysm after the vascular stent woven by the braided wires with different cross-sections is implanted into the diseased blood vessel are obtained. Based on the judgment that the blood flow velocity in the aneurysm is the lowest and the blood flow velocity in the diseased blood vessel is the highest after the vascular stent is implanted into the diseased blood vessel, a suitable vascular stent is selected, and then the cross-section of the braided wire suitable for being used as a braided vascular stent is determined, reducing the number of clinical trials, shortening the research time, reducing the research cost, greatly narrowing the selection range of the braided wire, and reducing the harm caused to patients during the experiment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 Schematic diagrams of the braided wires with different cross-sections in the present invention and the vascular stent woven by using the braided wires;

[0021] Figure 2 Schematic diagrams of the stress nephogram and bending moment rotation angle curve diagram of the vascular stent woven by the braided wires with different cross-sections under bending conditions in the present invention;

[0022] Figure 3 Schematic diagrams of the flow velocity nephogram in the artery after the vascular stent woven by the braided wires with different cross-sections in the present invention is implanted into the diseased position and the flow velocity nephogram of the blood in the artery without implanting the vascular stent;

[0023] Figure 4 Schematic diagrams of the flow velocity nephograms in three different directions in the aneurysm after the vascular stent woven by the braided wires with different cross-sections in the present invention is implanted into the diseased position and the flow velocity nephograms in three different directions in the aneurysm without implanting the vascular stent. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] The object of the present invention is to provide a method for optimizing the braided wires in a braided vascular stent.

[0026] The following further illustrates the influence of the vascular stent on blood flow velocity through software simulation. For the convenience of software simulation, the cross-section of the braided wire is a regular polygon.

[0027] S1: Determine the parameters of the braided wire.

[0028] In the prior art, the cross-section of the braided wire of the vascular stent is circular, and the diameter is 0.025 mm - 0.035 mm. Cross-sections of circular, regular quadrilateral, regular hexagon, regular octagon, and regular decagon are selected; the diameter of the inscribed circle of the cross-section of the braided wire with a regular quadrilateral and regular octagon cross-section is 0.025 mm - 0.035 mm, and the diameter of the circumscribed circle of the cross-section of the braided wire with a regular hexagon and regular decagon cross-section is 0.025 mm - 0.035 mm. The braided wire is woven into a vascular stent by using, but not limited to, double-interlaced weaving method and triple-interlaced weaving method. At the same time, the porosity on the vascular stent is further controlled by adjusting the number of braiding turns of the braided wire, so that the porosity of the vascular stent formed by braiding different cross-section braided wires is 65% - 75%.

[0029] In the vascular stent proposed in this embodiment, each braided wire is woven around a cylinder with a length of 9 mm - 11 mm for two turns, so that the coverage rate of the braided wire on the cylinder surface is 25% - 35%, and the porosity is 65% - 75%.

[0030] S2: Establish a three-dimensional model of the vascular stent and analyze the force condition of the vascular stent by a mechanical analysis software.

[0031] Use three-dimensional modeling software to establish a three-dimensional model of the vascular stent formed by braided wires with different cross-sections according to the geometric parameters determined in S1.

[0032] The established three-dimensional vascular stent model is first imported into the Hypermesh software for mesh generation, and the generated mesh is then imported into the mechanical analysis software Abaqus. A rotational torque is applied to the reference points at both ends of the vascular stent model. Theoretically, due to the isotropic structure of the circular cross-section, when an external force is applied to the reference points at both ends of the vascular stent model and the model is bent, the force is relatively evenly distributed on each braided wire. However, due to the regularity of the circular cross-section shape, during bending, the deformation of the entire cross-section is relatively consistent, lacking adjustable degrees of freedom. This relatively fixed deformation mode will reduce the flexibility and compliance of the vascular stent model. If a vascular stent woven from braided wires with a circular cross-section is placed in a curved blood vessel, the vascular stent cannot fully conform to the inner wall of the blood vessel.

[0033] While a regular polygon cross-section can endow the braided wire with more corners and edges. When subjected to an external force, the corners of the polygon can serve as stress concentration points, and different degrees of deformation can occur at the positions of the corners and edges. By local deformation, the external force is absorbed and dispersed, making it easier for the vascular stent woven from braided wires with a regular polygon cross-section to bend and deform, thus improving the flexibility and compliance of the vascular stent.

[0034] During the research process, a rotational torque is applied to the reference points at both ends of the vascular stent model through the mechanical analysis software Abaqus to cause a 60° rotation angle of the vascular stent, and a force cloud diagram is formed through the mechanical analysis software Abaqus. Please refer to Figure 2 (a) to (e), and the bending moment-rotation angle curve is extracted to measure the flexibility of the vascular stent, as shown in detail in Figure 2 (f);

[0035] It can be seen from the stress cloud diagram that when the vascular stent model is bent by 60°, the stress on the five vascular stent models is mainly concentrated in the compressed and bent areas, and the stress distribution in the remaining positions is relatively uniform. When the stent rotation angle is 60°, the corresponding bending moments of the five vascular stent models (the cross-sections of the braided wires are circular, square, hexagonal, octagonal, and decagonal respectively, and the "five vascular stent models" mentioned later are all described in the above order) are 7.3 N / m, 4.5 N / m, 3.6 N / m, 4.8 N / m, and 3.9 N / m respectively. And the bending moment is negatively correlated with the flexibility. Under the same rotation angle condition, the larger the measured bending moment, the worse the flexibility. Therefore, the flexibility of the vascular stent models formed by braided wires with square, hexagonal, octagonal, and decagonal cross-sections is better than that of the vascular stent model woven from braided wires with a circular cross-section.

[0036] S3: Establish three-dimensional models of aneurysms and vascular stents, and use mechanical software to analyze the hemodynamic changes.

[0037] An aneurysm model was established in Solidworks. The aneurysm model includes an aneurysm and a parent artery, and was assembled with the established vascular stent model to extract the fluid domain model, which was then imported into the fluid dynamics software Ansys Fluent module. According to the physical properties of blood and the flow field conditions of blood vessels, the material properties and boundary conditions were set. A velocity curve of one cardiac cycle was applied at the inlet of the aneurysm model, and a pressure curve of one cardiac cycle was applied at the outlet, so as to test the hemodynamic changes caused by the implantation of the vascular stent model into the parent artery.

[0038] It can be seen from the velocity map that after the implantation of the vascular stent model, the blood flow into the aneurysm cavity was significantly blocked. The velocity in the parent artery gradually decreased from the axis to the periphery, and the velocity was the largest at the axis position. The velocity gradient change at the top of the aneurysm cavity was relatively small, while the velocity change at the bottom near the stent area was relatively large, especially at the right aneurysm neck. Combining Figure 3 with the cloud map data, the maximum velocities of the five vascular stent models in the arterial segment were 88 cm / s, 90 cm / s, 87.1 cm / s, 90 cm / s, and 84.8 cm / s respectively. A relatively high velocity in the parent artery can better maintain the patency of the parent artery, reduce intimal hyperplasia, and thus avoid the re-narrowing of the inner diameter at the site where the vascular stent model is implanted in the parent artery.

[0039] The maximum velocities in the aneurysm cavity after the implantation of the five vascular stent models were 44.32 cm / s, 43.23 cm / s, 43.64 m / s, 45.9 m / s, and 50 m / s respectively. Since the elasticity and strength of the aneurysm wall decreased compared with the parent artery wall, the ability to withstand pressure became weaker. Under the impact of a relatively high velocity in the aneurysm cavity, the aneurysm body would be further dilated, increasing the risk of aneurysm wall rupture. Therefore, after the vascular stent model was implanted into the blood vessel, it was necessary to reduce the blood flow velocity in the aneurysm. By comparing the maximum velocities in the aneurysm cavity after the implantation of the five vascular stent models, it was found that the vascular stent model woven by braided wires with a regular quadrilateral cross-section had the lowest velocity in the aneurysm cavity after implantation into the blood vessel. Therefore, through the above experiments, it can be known that the vascular stent model woven by braided wires with a regular quadrilateral cross-section has the effects of relatively high blood flow velocity in the parent artery and relatively low blood flow velocity in the aneurysm after implantation into the parent artery.

[0040] To further clarify the blood flow situation in the aneurysm after the implantation of the vascular stent model woven by braided wires with a regular quadrilateral cross-section into the parent artery, combined with the study of blood flow velocity in the S3 aneurysm model, the blood flow velocity in the aneurysm was observed in three different directions, and the blood flow velocity cloud maps in the aneurysm in the XZ-1, XZ-2, and XZ-3 directions were obtained. Please refer to Figure 4 (a), (b), (c);

[0041] It can be seen from the velocity cloud map that the velocity magnitudes on the XZ-1, XZ-2 and XZ-3 planes decrease in turn. The area with a larger velocity on the XZ-1 plane is mainly concentrated near the pore area of ​​the vascular stent model and on the right side of the aneurysm. The area with a larger velocity on the XZ-2 plane is mainly concentrated in the area to the right of the center of the aneurysm. The area with a larger velocity on the XZ-3 plane is mainly concentrated on the left and right sides of the aneurysm.

[0042] After the five vascular stent models were implanted into the tumor-bearing blood vessels, the average flow velocities in the XZ-1 plane were 5.5 cm / s, 4.74 cm / s, 5.83 cm / s, 6.2 cm / s, and 7.3 cm / s, respectively; the average flow velocities in the XZ-2 plane were 1.1 cm / s, 1.0 cm / s, 1.1 cm / s, 1.2 cm / s, and 1.6 cm / s, respectively; and the average flow velocities in the XZ-3 plane were 0.1 cm / s, 0.2 cm / s, 0.2 cm / s, 0.1 cm / s, and 0.2 cm / s, respectively. Comparison of the average flow velocities on each plane confirmed that the vascular stent model woven with braided wire with a regular quadrilateral cross section had the lowest blood flow rate in the aneurysm after being implanted into the tumor-bearing blood vessel.

[0043] From the above experimental data, it can be seen that compared with the braided wire with a circular cross-section, the vascular stent woven by the braided wire with a regular polygonal shape has better flexibility, is easier to transport and release when passing through relatively curved blood vessels, reduces the risk of damage to the blood vessels, and can better conform to the physiological curvature and dynamic changes of the blood vessels after release, while reducing the impact on the normal physiological function of the blood vessels, and improves the blood flow guidance effect of the vascular stent, so that the blood flow direction can be more accurately regulated, the blood flow can be evenly dispersed, the impact of blood flow on the aneurysm wall can be reduced, thrombosis in the tumor can be promoted, the occlusion of the aneurysm can be accelerated, and at the same time, the patency of the tumor-bearing blood vessels can be maintained, and the postoperative recurrence rate can be reduced.

[0044] The present invention also protects a braided wire obtained by the above optimization method, wherein the cross section of the braided wire is a regular quadrilateral;

[0045] And a vascular stent formed by weaving a braided wire with a regular quadrilateral cross section, the diameter of the vascular stent is 4.7mm-4.8mm, and the length is 9mm-11mm.

[0046] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0047] It should be noted that for those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0048] Specific examples are used in the present invention to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for optimizing braided wires in a braided vascular stent, characterized in that: The steps include: S1: Determine braiding wire parameters; Selecting braided wires with cross sections of a circle, a regular quadrilateral, a regular hexagon, a regular octagon and a regular decagon, and using the braided wires with different cross sections to weave a vascular stent; controlling the size of the cross section of the braided wire and the number of turns of the braided wire to keep the porosity of the vascular stent consistent; S2: Establish a three-dimensional model of the vascular stent and use mechanical analysis software to analyze the stress of the vascular stent; Using three-dimensional modeling software to establish a three-dimensional model of a vascular stent formed by braided wires with different cross sections according to the parameters determined by S1; applying a rotational torque to the reference points at both ends of the vascular stent model to bend the vascular stent model, and forming a stress cloud map of the vascular stent model in the mechanical analysis software, and judging the stress conditions of each vascular stent model under the same rotational torque according to the stress cloud map and the bending moment angle curve diagram; S3: Establish a three-dimensional model of aneurysm and vascular stent, and use mechanical software to analyze the changes in blood flow dynamics; An aneurysm model was established and assembled with the constructed vascular stent model to extract the fluid domain model. A flow velocity curve of one cardiac cycle was applied at the inlet of the aneurysm model, and a pressure curve of one cardiac cycle was applied at the outlet. This was done to test the hemodynamic changes caused by the implantation of the vascular stent model into the aneurysm model, and to obtain a blood flow velocity cloud map. The blood flow velocity in the tumor-bearing vessel and the aneurysm in the model was determined by the flow velocity cloud map.

2. The method for optimizing the braided wire in the braided vascular stent according to claim 1, characterized in that: The material of the braided wire is nickel-titanium alloy.

3. The method for optimizing the braided wire in the braided vascular stent according to claim 1, characterized in that: The porosity is 65%-75%.

4. A braided wire obtained by the method for optimizing the braided wire in a braided vascular stent according to any one of claims 1 to 3, wherein the cross section of the braided wire is a regular quadrilateral.

5. A vascular stent woven using the braided wire according to claim 4.

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