A method for preparing a customized mitral annuloplasty ring

Abstract

The present invention relates to the field of medical device technology, and discloses a method for preparing a customized mitral valve forming ring. The method aims to solve the technical problem in the prior art that the selection of specifications and models of mitral valve forming rings is limited, and the valve ring cannot fully match the patient's physiological structure. The present invention includes the following steps: obtaining the shape parameters of the mitral valve forming ring at the patient's lesion site through multimodal imaging; constructing a three-dimensional model of the lesion site, and reconstructing the lesion model to obtain a healthy mitral valve forming ring structure model; and forming through micro-scale laser powder bed melting printing, scanning the laser beam according to a certain strip width, and during the melting process of each layer, the laser scanning path rotates a certain angle relative to the substrate or the scanning path of the previous layer. The present invention ensures that the artificial mitral valve ring can perfectly match the patient's physiological structure and reduce individual differences.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a method for preparing a customized mitral valve forming ring. Background Art

[0002] Mitral valve disease ranks first in prevalence among heart valve diseases. Mitral valve disease primarily includes mitral regurgitation, mitral stenosis, and mitral valve prolapse. Mitral regurgitation accounts for 65% of cases and is primarily caused by mitral valve lesions in the mitral valve leaflets, annulus, papillary muscles, and chordae tendineae. This causes the mitral valve to not close properly during cardiac contraction, allowing blood to flow from the left ventricle into the left atrium.

[0003] Mitral valvuloplasty and mitral valve replacement are the two main surgical procedures used by cardiac surgeons to treat mitral valve disease. Previously, prosthetic valve replacement was the primary surgical treatment for mitral valve disease. However, studies have shown that mitral valvuloplasty, which preserves the valve and subvalvular structures, can effectively maintain left ventricular morphology and function, significantly reduce surgical mortality, and prevent the risk of long-term anticoagulation after surgery. Literature reports that the mortality rate of mitral valve replacement is 1.8% to 18.1%, higher than that of mitral valvuloplasty (0% to 6.1%). Mitral valvuloplasty now accounts for 41% of mitral valve surgeries. Consequently, it has gradually become widely used in cardiac surgery. Currently, the number of mitral valvuloplasty procedures is increasing annually.

[0004] Currently, commercially available mitral annuloplasty rings in my country are all fixed in size, with a very limited selection of specifications across brands. Physicians can only select the "appropriate" size of annuloplasty ring based on the patient's anatomy. This results in a failure to fully match the patient's anatomy, leading to some patients experiencing persistent regurgitation after treatment due to loose leaflet closure. Furthermore, in recurrent patients, the annuloplasty ring may change shape again, requiring a second surgery to replace the ring, creating a vicious cycle. Therefore, there is an urgent need for customized mitral annuloplasty rings.

[0005] The choice of material is extremely important for the development of such a mitral annuloplasty ring. Because the mitral annuli are a saddle-shaped, non-planar spatial conformation, and their three-dimensional shape and size change with the cardiac cycle, the use of commercial fixed-size mitral annuloplasty rings can lead to left ventricular outflow tract obstruction in some patients. Through extensive research and testing, we found that NiTi shape memory alloy, which is widely used in clinical treatment of cardiac implants, not only has excellent corrosion resistance and biocompatibility, but also has unique shape memory effect (SME) and superelasticity (SE). The use of NiTi shape memory alloy to prepare mitral annuloplasty rings can greatly compensate for the shortcomings of existing mitral annuloplasty rings and is an ideal material for manufacturing new mitral annuloplasty rings. However, due to the poor machinability of NiTi shape memory alloy, the traditional process of melting and casting followed by machining makes it difficult to form complex structures, which greatly limits the promotion and application of NiTi shape memory alloys.

[0006] The prior art Chinese patent document 201610754840.6 discloses a method for preparing a valvuloplasty ring, comprising: using a clamp to sleeve a suture layer on a metal part covered with a silicone layer on its circumference; the clamp comprises a guide segment and a main body segment, the guide segment being conical and the main body segment being hollow and tubular, the main body segment being arranged at the end of the guide segment with a larger diameter, and the internal dimensions of the main body segment being slightly larger than the outer circumference of the silicone layer so that the silicone layer can be inserted into the inner cavity of the main body segment.

[0007] However, the implementation of the above solution presents at least the following technical issues: the limited selection of mitral annuloplasty ring specifications and models, and the inability of the ring to fully match the patient's anatomy. Therefore, a method for preparing a customized mitral annuloplasty ring is urgently needed. Summary of the Invention

[0008] In view of the above technical problems, the present disclosure provides a method for preparing a customized mitral annuloplasty ring, which solves the technical problems in the prior art of limited selection of specifications and models of mitral annuloplasty rings and the inability of the rings to fully match the patient's physiological structure.

[0009] According to one aspect of the present disclosure, a method for preparing a customized mitral annuloplasty ring is provided, characterized in that it comprises the following steps:

[0010] (1) Data acquisition: Obtain the shape parameters of the mitral annuloplasty ring at the patient's lesion site through multimodal imaging;

[0011] (2) Model processing: Based on the shape parameters of the mitral annuloplasty ring at the lesion site collected in step (1), a three-dimensional model of the lesion site is constructed, and the lesion model is reconstructed to obtain a healthy mitral annuloplasty ring structure model; reconstruction of the lesion model includes the following steps: a. determining the influence of the shape and size of the mitral annuloplasty ring structure on the opening and closing of the valve leaflets; b. based on the mitral annuloplasty ring structure model, using a macro-scale numerical simulation method to analyze the mechanical characteristics of the mitral annuloplasty ring in the human body environment, revealing the evolution law of the stress field and deformation field, so as to establish a three-dimensional model;

[0012] (3) Model forming: The healthy mitral valve annulus structure model reconstructed in step (2) is formed by micro-scale laser powder bed fusion printing. The fusion printing includes the following steps: (3.1) Strip scanning: The laser beam is scanned according to a certain strip width. During the fusion printing process, an ultra-narrow single-pass fusion width is achieved through an ultra-thin powder layer thickness and an ultra-small spot diameter. The calculation formula of the laser spot diameter after the focusing lens is as follows:

[0013] ;

[0014] Where, is the focal spot diameter, is the focused spot size, is the laser wavelength, is the focal length of the focusing lens, is the laser spot size at the time of incidence, is the beam quality factor of the laser;

[0015] From the above formula, we can conclude that: by a. reducing the focal length ; b. Select high-quality lasers to make the beam quality factor Close to 1; c. Expand the laser spot size when incident by using a large-aperture scanning galvanometer These three methods work together to reduce the focus spot diameter to achieve an ultra-small spot.

[0016] The focusing lens is a telecentric field lens to avoid the distortion of the light spot shape at the edge of the forming chamber;

[0017] (3.2) Layer-by-layer rotation: During the melting process of each layer, the laser scanning path is rotated by a certain angle relative to the substrate or the scanning path of the previous layer; the above steps (3.1) to (3.2) are repeated until a customized mitral annuloplasty ring is obtained.

[0018] In some embodiments of the present disclosure, the data acquisition method in step (1) is CT imaging.

[0019] In some embodiments of the present disclosure, the strip width in step (3) is 0.1-10 mm, and the rotation angle is 10-90°.

[0020] In some embodiments of the present disclosure, the process conditions adopted for microscale laser powder bed melting in step (3) are: laser power 10-100 W, laser spot diameter 10-30 μm, laser scanning speed 100-2000 mm / s, laser spot spacing 10-100 μm, and powder layer thickness 5-20 μm.

[0021] In some embodiments of the present disclosure, the process conditions adopted for microscale laser powder bed melting in step (3) are: laser power of 30-40 W, spot diameter of 20-25 μm, laser scanning speed of 600-1000 mm / s; laser spot spacing of 30-50 μm; and powder layer thickness of 5-15 μm.

[0022] In some embodiments of the present disclosure, the powder raw material used in the microscale laser powder bed melting in step (3) is a pre-alloyed NiTi powder prepared by a vacuum induction atomization method, and the particle size of the pre-alloyed NiTi powder is 0-45 μm, wherein more than 50% of the powder particle size is less than 15 μm.

[0023] In some embodiments of the present disclosure, before the melt printing, a powder drying step is further included: the pre-alloyed NiTi powder is vacuum dried at 80-120° C. for 5-10 h to remove impurities.

[0024] In some embodiments of the present disclosure, the process conditions of the microscale laser powder bed melting also include: reducing oxygen in the forming chamber and filling it with a protective gas, the oxygen content in the forming chamber is not greater than 1000 ppm, the protective gas is argon or nitrogen, and the protective gas pressure is 10-20 mbar.

[0025] In some embodiments of the present disclosure, a NiTi substrate with the same composition is selected during the microscale laser powder bed melting process.

[0026] In some embodiments of the present disclosure, the large-aperture scanning galvanometer in step c includes a lens with a light-through hole, and the diameter of the light-through hole is 10-30 mm, so as to allow a large-diameter light beam to pass through.

[0027] The beneficial effects of the present invention are:

[0028] 1. Developing a personalized mitral valvuloplasty ring. By combining 3D printing technology with CT ultrasound imaging technology, precise manufacturing is achieved. This not only greatly reduces the production cost and cycle of the mitral valvuloplasty ring, but also significantly improves the long-term efficacy of mitral valvuloplasty, providing strong support for overcoming the major difficulties of heart valve disease.

[0029] 2. Improve the adaptability of the mitral annuloplasty ring. Utilize the superelastic properties of NiTi shape memory alloy to achieve adaptive adjustment of the mitral annuloplasty ring, thereby significantly improving its application effect.

[0030] 3. Microscale LPBF technology is used to achieve precise control of laser point energy, ensuring printing accuracy and efficiency, thereby successfully completing the manufacturing process of the mitral annuloplasty ring.

[0031] 4. Ensure that the artificial mitral valve ring can perfectly match the patient's physiological structure and reduce individual differences.

[0032] 5. The superelasticity of NiTi alloy is achieved through processing, and the superelasticity of NiTi alloy is used to achieve the application effect of adaptive adjustment of the mitral annuloplasty ring, which has a better therapeutic effect than conventional rigid and semi-rigid mitral annuloplasty rings.

[0033] 6. Microscale laser powder bed fusion technology is used to form the mitral valve forming ring, achieving precise control of phase change temperature and high-quality and high-precision forming effects.

[0034] 7. The density of NiTi prepared by the preparation process reaches more than 99% and it has super elasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of CT reconstruction imaging of the patient's lesion;

[0036] Figure 2 This is a schematic diagram of the shape extraction of the mitral annuloplasty ring at the patient's lesion;

[0037] Figure 3 Create a schematic diagram for a custom-made mitral annuloplasty ring model;

[0038] Figure 4 Schematic diagram of the deformation field of the forming ring simulated at macro scale;

[0039] Figure 5 Schematic diagram of the stress field of the forming ring simulated at macro scale;

[0040] Figure 6 Schematic diagram of the deformation field of the macro-scale simulation printing process;

[0041] Figure 7 Schematic diagram of the density of NiTi alloy under a microscope;

[0042] Figure 8 When a 6% cyclic compression test is carried out at human body temperature, the loading rate is 10 -4 s -1 Strain and stress changes of the customized mitral annuloplasty ring in the state;

[0043] Figure 9 Schematic diagram of the printed mitral annuloplasty ring;

[0044] Figure 10 A schematic diagram of the printed mitral annuloplasty ring from another perspective;

[0045] Figure 11 Schematic diagram of the printed mitral annuloplasty ring after it is removed from the forming base plate and the support is removed; DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. Example 1

[0047] This example discloses a method for preparing a customized mitral annuloplasty ring, see Figures 1 to 11 ;

[0048] The steps include:

[0049] (1) Data acquisition: Obtain the shape parameters of the mitral annuloplasty ring at the patient's lesion site through multimodal imaging;

[0050] (2) Model processing: Based on the shape parameters of the mitral annuloplasty ring at the lesion site collected in step (1), a three-dimensional model of the lesion site is constructed, and the lesion model is reconstructed to obtain a healthy mitral annuloplasty ring structure model; reconstruction of the lesion model includes the following steps: a. determining the influence of the shape and size of the mitral annuloplasty ring structure on the opening and closing of the valve leaflets; b. based on the mitral annuloplasty ring structure model, using a macro-scale numerical simulation method to analyze the mechanical characteristics of the mitral annuloplasty ring in the human body environment, revealing the evolution law of the stress field and deformation field, so as to establish a three-dimensional model;

[0051] (3) Model forming: The healthy mitral valve annulus structure model reconstructed in step (2) is formed by micro-scale laser powder bed fusion printing. The fusion printing includes the following steps: (3.1) Strip scanning: The laser beam is scanned according to a certain strip width. During the fusion printing process, an ultra-narrow single-pass fusion width is achieved through an ultra-thin powder layer thickness and an ultra-small spot diameter. The calculation formula of the laser spot diameter after the focusing lens is as follows:

[0052] ;

[0053] Where, is the focal spot diameter, is the focused spot size, is the laser wavelength, is the focal length of the focusing lens, is the laser spot size at the time of incidence, is the beam quality factor of the laser;

[0054] From the above formula, we can conclude that: by a. reducing the focal length ; b. Select high-quality lasers to make the beam quality factor Close to 1; c. Expand the laser spot size when incident by using a large-aperture scanning galvanometer These three methods work together to reduce the focus spot diameter to achieve an ultra-small spot.

[0055] The focusing lens is a telecentric field lens to avoid the distortion of the light spot shape at the edge of the forming chamber;

[0056] The large-aperture scanning galvanometer in step c includes a lens with a light-through hole, and the diameter of the light-through hole is 10-30 mm to allow a large-diameter light beam to pass through.

[0057] (3.2) Layer-by-layer rotation: During the melting process of each layer, the laser scanning path is rotated by a certain angle relative to the substrate or the scanning path of the previous layer; the above steps (3.1) to (3.2) are repeated until a customized mitral annuloplasty ring is obtained.

[0058] The data acquisition method in step (1) is CT imaging.

[0059] In the microscale laser powder bed melting preparation process in step (3), strip scanning and layer-by-layer rotation steps are adopted, the strip width is 0.1-10 mm, and the rotation angle is 10-90°.

[0060] The process conditions adopted for microscale laser powder bed melting in step (3) are: laser power 10-100 W, laser spot diameter 10-30 μm, laser scanning speed 100-2000 mm / s, laser spot spacing 10-100 μm, and powder layer thickness 5-20 μm.

[0061] The process conditions for microscale laser powder bed melting in step (3) are as follows: laser power of 30-40 W, spot diameter of 20-25 μm, laser scanning speed of 600-1000 mm / s, laser spot spacing of 30-50 μm, and powder layer thickness of 5-15 μm.

[0062] The powder raw material used in the micro-scale laser powder bed melting in step (3) is pre-alloyed NiTi powder prepared by vacuum induction atomization method, and the particle size of the pre-alloyed NiTi powder is 0-45 μm, wherein more than 50% of the powder particle size is less than 15 μm.

[0063] Before the melt printing, a powder drying step is also included: the pre-alloyed NiTi powder is vacuum dried at 80-120° C. to remove impurities for 5-10 hours.

[0064] The process conditions of the microscale laser powder bed melting also include: reducing oxygen in the forming chamber and filling it with a protective gas, the oxygen content in the forming chamber is not greater than 1000 ppm, the protective gas is argon or nitrogen, and the protective gas pressure is 10-20 mbar.

[0065] A NiTi substrate with the same composition is selected during the microscale laser powder bed melting process.

[0066] The strip width is 0.1-10 mm. The strip scanning method is to control the vector length of the laser scanning during the laser powder bed melting process to the set strip width. The conventional laser powder bed melting technology used in general processing NiTi memory alloys uses a strip width greater than 5 mm, while the present invention uses a micro-scale laser powder bed melting technology with a smaller laser spot, finer powder and thinner layer thickness, so the laser molten pool is finer and the strip can be narrower. Narrower strips help to reduce the residual stress in the printed component and reduce the cracking tendency of the NiTi memory alloy. At the same time, the narrow strip can suppress the powder flying phenomenon generated by ultrafine metal powder during micro-scale laser powder bed melting and forming, which can improve the printing quality. In summary, the strip width selected here helps to achieve defect-free, high-quality additive manufacturing of NiTi memory alloy.

[0067] The layer-by-layer rotation angle is 10-90°, so that the printed melt paths of each layer do not overlap, thus avoiding the accumulation of residual stress. At the same time, it can also make the NiTi structure more refined and reduce the anisotropy of its performance.

[0068] The laser power is 10-100 W (preferably 30-40 W). The selection of laser power is closely related to microscale laser powder bed melting. Due to the smaller laser spot, finer powder and thinner layer thickness, the laser power required for microscale laser powder bed melting is generally much smaller than the laser power for conventional laser powder bed melting. For example, the laser power used in other conventional laser powder bed melting when printing NiTi shape memory alloy is generally greater than 100 W. In the present invention, the use of a laser power of 30-40 W can control the heat input and prevent defects such as warping, deformation, cracking, and pores caused by excessive laser energy input.

[0069] The laser spot diameter is 10-30 μm (preferably 20-25 μm). The laser spot diameter used in other conventional laser powder bed melting is generally above 80 μm, while the laser spot diameter used in the present invention is about 1 / 3 of that, which can effectively improve the precision of the NiTi shape memory alloy customized mitral valve forming ring and achieve the printing of a forming ring with a smaller limit forming size. λ 1064nm, f 170mm,D 10-12mm, M 2 is 1.05.

[0070] The laser scanning speed is 100-2000 mm / s (preferably 600-1000 mm / s). Conventional laser powder bed fusion processes typically use laser scanning speeds of 1000-1500 mm / s or below 600 mm / s. However, the laser scanning speed of the present invention falls outside this range. This characteristic is primarily driven by the material and process constraints of microscale laser powder bed fusion: fine powder, small spot size, thin layer thickness, narrow melt path, and fast cooling rate. Laser scanning speeds within this range ensure the quality of custom NiTi shape memory alloy mitral annuloplasty rings.

[0071] The laser spot spacing is 10-100 μm, and the powder layer thickness is 5-20 μm (preferably the laser spot spacing is 30-50 μm, and the powder layer thickness is preferably 5-15 μm). The laser spot spacing used in other conventional laser powder bed melting is larger, generally above 100 μm, and the powder layer thickness is 40 μm and above. This results in the NiTi memory alloy forming accuracy achieved by conventional laser powder bed melting being poor, the surface roughness being high, and the presence of a "step effect" caused by the thick powder layer. The micro-scale laser powder bed melting technology used in the present invention has smaller spot spacing and powder layer thickness than conventional laser powder bed melting, especially the powder layer thickness is reduced by more than 50%, thereby greatly improving the "step effect" and improving the printing accuracy and surface finish of the NiTi memory alloy.

[0072] The powder particle size distribution ranges from 0 to 45 μm, with the majority concentrated below 15 μm. Conventional laser powder bed fusion typically uses powder particle sizes of 15 to 53 μm, while the present invention utilizes a much smaller range. Specifically, while the majority of powder particle sizes in conventional laser powder bed fusion are around 30 μm, the majority of powder particle sizes in the present invention's microscale laser powder bed fusion are only half that size. This characteristic helps improve the surface quality of the customized NiTi shape memory alloy mitral annuloplasty ring, enabling better performance under the cyclic loading conditions of the cardiac cycle.

[0073] Vacuum drying and impurity removal at 80-120℃ for 5-10h. Other conventional laser powder bed fusion processes generally do not dry the powder, but this vacuum drying treatment before printing is more important for the microscale laser powder bed fusion process used in the present invention, because the finer powder used has a larger specific surface area and is more likely to absorb water and agglomerate. Drying and impurity removal under the conditions set in the present invention can remove moisture attached to the surface of the ultrafine powder, reduce powder agglomeration, and improve powder fluidity and spreadability, thereby ensuring the printing quality of the NiTi shape memory alloy customized mitral valve forming ring.

[0074] Although some preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0075] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a customized mitral annuloplasty ring, characterized in that: The steps include: (1) Data acquisition: Obtain the shape parameters of the mitral annuloplasty ring at the patient's lesion through multimodal imaging; (2) Model processing: constructing a three-dimensional model of the lesion site based on the shape parameters of the mitral annuloplasty ring at the lesion site collected in step (1), and reconstructing the lesion model to obtain a healthy mitral annuloplasty ring structure model; Reconstructing the lesion model includes the following steps: a. determining the impact of the shape and size of the mitral annuloplasty ring on the opening and closing of the valve leaflets; b. based on the mitral annuloplasty ring structure model, using macro-scale numerical simulation methods to analyze the mechanical characteristics of the mitral annuloplasty ring in the human body environment, revealing the evolution of the stress and deformation fields, and thus establishing a three-dimensional model; (3) Model forming: The healthy mitral valve annulus structure model reconstructed in step (2) is formed by micro-scale laser powder bed fusion printing. The fusion printing includes the following steps: (3.1) Strip scanning: The laser beam is scanned according to a strip width of 0.1-10 mm. During the fusion printing process, the single-pass fusion width is controlled by controlling the powder layer thickness and the spot diameter. The calculation formula of the laser spot diameter after the focusing lens is as follows: ； Where d is the focal spot diameter and the size of the focused spot. is the laser wavelength, f is the focal length of the focusing lens, D is the laser spot size at the time of incidence, M 2 is the beam quality factor of the laser; From the above formula, we can conclude that by a. reducing the focal length f; b. selecting high-quality lasers, the beam quality factor M 2 Close to 1; c. Expand the incident laser spot size D by using a large-aperture scanning galvanometer; these three methods together reduce the focused spot diameter; The focusing lens is a telecentric field lens to avoid the distortion of the light spot shape at the edge of the forming chamber; (3.2) Layer-by-layer rotation: During the melting process of each layer, the laser scanning path is rotated 10-90° relative to the substrate or the scanning path of the previous layer; the above steps (3.1) to (3.2) are repeated until a customized mitral valve forming ring is obtained; the process conditions used for microscale laser powder bed melting are: laser power 10-100 W, laser spot diameter 10-30 μm, laser scanning speed 100-2000 mm / s, laser spot spacing 10-100 μm, and powder layer thickness 5-20 μm.

2. The method for preparing a customized mitral annuloplasty ring according to claim 1, wherein: The data acquisition method in step (1) is CT imaging.

3. The method for preparing a customized mitral annuloplasty ring according to claim 1, wherein: The process conditions adopted for microscale laser powder bed melting in step (3) are as follows: laser power of 30-40 W, spot diameter of 20-25 μm, laser scanning speed of 600-1000 mm / s; laser spot spacing of 30-50 μm; and powder layer thickness of 5-15 μm.

4. The method for preparing a customized mitral annuloplasty ring according to claim 1, wherein: The powder raw material used in the microscale laser powder bed melting in step (3) is pre-alloyed NiTi powder prepared by vacuum induction atomization method, and the particle size of the pre-alloyed NiTi powder is 0-45 μm, wherein more than 50% of the powder particle size is less than 15 μm.

5. The method for preparing a customized mitral annuloplasty ring according to claim 1, wherein: Before the melt printing, a powder drying step is also included: the pre-alloyed NiTi powder is vacuum dried at 80-120° C. to remove impurities for 5-10 hours.

6. The method for preparing a customized mitral annuloplasty ring according to claim 1, wherein: The process conditions of the microscale laser powder bed melting also include: reducing oxygen in the forming chamber and filling it with a protective gas, the oxygen content in the forming chamber is not greater than 1000 ppm, the protective gas is argon or nitrogen, and the protective gas pressure is 10-20 mbar.

7. The method for preparing a customized mitral annuloplasty ring according to claim 1, wherein: The large-aperture scanning galvanometer in step c includes a lens with a light-through hole, and the diameter of the light-through hole is 10-30 mm.

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