Stent weave pattern with enhanced radiopacity

Abstract

An implantable metallic braid is formed from a group of filaments of a first material, a group of filaments of a second material different from the first material, and a group of filaments of a third material different from the first and second materials. The filaments are braided together by a braiding machine and arranged on the braiding machine in a starting filament arrangement before braiding begins. The first material is a radiopaque material, the second material is a support material, and the third material is a DFT comprising the first and second materials. The different filament arrangements in the starting filament arrangement and throughout the braid allow for different levels of detail to be observed in images of the braid, wherein the specific filament arrangements achieve enhanced radiopacity without affecting the braid's other mechanical properties.

Description

Technical Field

[0001] The present invention relates generally to medical devices implantable in the body and, more particularly, to stents having enhanced radiopacity and favorable mechanical properties. Background Art

[0002] Self-expanding medical prostheses, commonly referred to as stents, are well known and commercially available. These types of devices are used within body vessels for a variety of medical applications. Examples include intravascular stents for treating stenosis, stents for maintaining patency in the urinary, biliary, esophageal, and renal tracts, and vena cava filters for trapping emboli. Furthermore, stents placed in blood vessels where aneurysms are developing are now well known and widely used. Stents with particularly fine mesh are often made into braided stents, for example for use as flow diverters.

[0003] Self-expanding stents are formed by a number of elastic filaments that are spirally wound and interwoven in a braided configuration. These stents take a generally tubular form in their unloaded or expanded state when not subjected to external forces. When subjected to an inwardly directed radial force, these stents are forced into a loaded or compressed state that reduces their radius and extends their length. A delivery device that holds the stent in its compressed state is used to deliver the stent to the treatment site through blood vessels within the body. The flexibility and reduced radius of the compressed stent enable it to be delivered through relatively small and tortuous blood vessels. After the stent is positioned at the treatment site, the delivery device is activated to release the stent, thereby allowing the stent to self-expand within the body's blood vessels. The delivery device is then removed from the stent and removed from the patient. The stent remains in the blood vessel at the treatment site.

[0004] However, a significant problem remains during stent placement and subsequent examination of the patient: due to their small size, these stents are extremely difficult to locate using X-rays. The only parts of the stent that appear on imaging are those that are sufficiently radiopaque, and the mass and thickness of these radiopaque parts decrease with the diameter of the treated vessel. Accurate placement of the stent is crucial to its effective performance. Therefore, it is necessary to visually perceive the stent as it is placed in a vessel or other body cavity. In addition, it is advantageous to visually locate and inspect previously deployed stents. Typically, increasing the radiopaqueness of a stent is achieved by sacrificing other desired mechanical properties such as strength, ductility, fatigue resistance, size, etc.

[0005] It is an object of the present invention to provide a stent having significantly enhanced radiopacity without significantly reducing the advantageous mechanical properties of the stent. Summary of the Invention

[0006] The present invention relates to a tubular metal braid for implantation in a human body. The braid comprises a plurality of groups of first filaments of a first material, a plurality of groups of second filaments of a second material different from the first material, and a plurality of groups of third filaments of a third material different from the first and second materials. The first, second, and third filaments are braided together by a braiding machine and arranged on the braiding machine in a starting filament arrangement before braiding begins. In the starting filament arrangement, the first, second, and third filaments are positioned so that each group of the second filaments is directly adjacent to one of the plurality of groups of the first filaments, each group of the third filaments is directly adjacent to one of the plurality of groups of the second filaments, both sides of each group of the first filaments are directly adjacent to one of the plurality of groups of the second filaments, and each group of the second filaments is directly adjacent to one of the plurality of groups of the first filaments on one side and directly adjacent to one of the plurality of groups of the third filaments on the other side.

[0007] The second material may be a monofilament or a drawn filled tube (DFT) wire comprising a core and a sheath surrounding the core. The third material may be the other of a monofilament and a DFT wire. In one embodiment, the second material is a monofilament and the third material is a DFT wire. The first material may be a radiopaque material. The monofilament may be a support material having a tensile strength greater than that of the radiopaque material. The DFT wire may include a radiopaque material and a support material having a tensile strength greater than that of the radiopaque material. The core of the DFT wire may be made of a radiopaque material and the sheath of the DFT wire may be made of a support material. The radiopaque material may be platinum and the support material may be a cobalt chromium alloy. The cobalt chromium alloy may be a 1058CoCr alloy and Each group of first filaments may include two filaments of the first material, each group of second filaments may include two filaments of the second material, and each group of third filaments may include two filaments of the third material. Each filament forming the braid is made of one of the first, second, and third materials. In one exemplary embodiment, the first material is platinum, the second material is a monofilament of a cobalt-chromium alloy, and the third material is a DFT wire including a platinum core and a sheath made of a cobalt-chromium alloy.

[0008] Another embodiment of the present invention relates to a tubular metal braid for implantation in the human body. The braid includes multiple groups of first filaments of a first material and multiple groups of second filaments of a second material different from the first material. One of the first and second materials is drawn filler tube (DFT) wire. The first and second filaments are braided together using a braiding machine and arranged on the braiding machine in a starting filament arrangement before braiding begins. In the starting filament arrangement, each group of second filaments is positioned directly adjacent to one of the multiple groups of first filaments. The first material may be a radiopaque material, and the second material may be DFT wire. The DFT wire may include a core and a sheath surrounding the core. One of the sheath and the core may be made of a radiopaque material, while the other may be made of a support material having a higher tensile strength than the radiopaque material. The DFT wire may include a platinum core and a sheath surrounding the platinum core, the sheath comprising a cobalt-chromium alloy. The cobalt-chromium alloy may be alloy L605. The cross-sectional area of ​​the platinum core may be 20% to 30% of the total cross-sectional area of ​​the DFT wire. In one embodiment, each filament forming the braid is made from either the first material or the second material.

[0009] Other and further aspects and features of the disclosed embodiments will become apparent from the following detailed description based on the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other aspects of the embodiments are described in more detail with reference to the accompanying drawings, wherein like reference numerals refer to like elements and, whenever relevant, the description of like elements shall apply to all described embodiments, in which:

[0011] Figure 1A 、 Figure 2A 、 Figure 3A and Figure 4A It is an image of two sizes of tubular metal braids formed by different arrangements of filaments in the braid;

[0012] Figure 1B 、 Figure 2B 、 Figure 3B and Figure 4B It is the beginning of weaving to form Figure 1A 、 Figure 2A 、 Figure 3A and Figure 4A A cross-sectional view of the filament arrangement of the tubular metal braid shown in FIG, previously taken from the front of the braiding machine;

[0013] Figure 5-Figure 7 is a cross-sectional view of an alternative embodiment of a filament arrangement taken from the front of a braiding machine before braiding begins;

[0014] Figure 8 and Figure 9is a graph depicting a comparison of radial pressure performance of tubular metal braids according to exemplary embodiments;

[0015] Figure 10A and Figure 10B These are images of a conventional stent and a stent according to embodiments herein being deployed in a body lumen, respectively. DETAILED DESCRIPTION

[0016] The present invention generally relates to an implantable, radially expandable stent having a unique braid pattern that enhances the radiopacity of the stent without negatively impacting the mechanical properties of the stent. The stent can be a flow-diverting stent for treating an aneurysm, or can be used for other intraluminal applications such as treating stenosis, maintaining patency, etc. The unique braid pattern provides enhanced radiopacity while maintaining or improving the mechanical properties of the tubular stent compared to existing stents formed from the same or similar materials. Thus, the unique radiopaque pattern of the disclosed device provides additional information to the physician because the physician can more easily determine length, compaction, diameter reduction, etc.

[0017] Braided stents of the same material, size, number of filaments, and filament size will produce different patterns on X-ray depending on how the wire pattern is placed on the braiding machine. Certain braid patterns produce excellent edge definition while maintaining a highly visible cross-hatching pattern. It has been discovered that the unique placement of platinum and drawn fill tube (DFT) radiopaque wires in the braided construction will produce a distinct segmented pattern on angiography. The specific alternating pattern of platinum wires, DFT wires, and support wires creates a hybrid braid that enhances radiopacity without affecting radial pressure or stent performance characteristics such as opening and apposition.

[0018] Figure 1A-Figure 7 The stents shown in the drawings are all made of the same number, size and type of filaments, but have different filament arrangements. These stents are generally tubular bodies formed by braiding the filaments according to any technique known in the art of braiding tubular bodies. Figure 1A 、 Figure 2A 、 Figure 3A and Figure 4A As shown in , in smaller diameter stents (such as Figure 1A 、 Figure 2A 、 Figure 3A and Figure 4A ) and larger diameter stents (as shown in the top portion of Figure 1A 、 Figure 2A 、 Figure 3A and Figure 4A In both cases, the arrangement of the wires in the braid has a significant impact on the level of detail that can be seen in the imaging. Figure 1B 、 Figure 2B 、 Figure 3B 、 Figure 4B and Figure 5-Figure 7 A cross-sectional view of the arrangement of the filaments, viewed from the front of the braiding machine before the start of braiding, is depicted. The properties of the resulting tubular metal braid are highly dependent on Figure 1B 、 Figure 2B 、 Figure 3B 、 Figure 4B and Figure 5-Figure 7 The starting filament arrangement shown in .

[0019] Figure 1A and Figure 1B The stent shown in FIG is a conventional stent 100 formed by weaving together a plurality of filaments. The plurality of filaments include a first material 102 and a second material 104. Figure 1B As shown in the cross-sectional view of FIG, in the initial filament arrangement, the filaments of the second material 104 are directly adjacent to the filaments of the first material 102 on both sides of the filaments of the first material 102. Figure 1A As shown in , cross-hatching and edge patterns do not appear in the imaging. Figure 1A The edges of the stent 100 shown in FIG are shown as solid lines. In contrast, the cross-hatching and edge patterns in FIG. Figure 2A 、 Figure 3A and Figure 4A This is even more visible in the images of the brackets shown in . In particular, Ref. Figure 4A , the edges of the bracket appear as alternating light and dark areas rather than solid lines.

[0020] Figures 2A-4B The bracket in Figure 1A and Figure 1B The bracket 100 shown in FIG is formed of the same material. Figures 2A-4B The stent in the embodiment includes filaments of a first material 102 and filaments of a second material 104, both of which are Figure 1A and Figure 1B The first material 102 and the second material 104 used in the stent 100 are the same. Figures 2A-4B The stent in FIG4 further includes filaments formed of a third material 106, which is a combination of the first material 102 and the second material 104. The third material 106 is a drawn filler tube (DFT) wire having a core made of the first material 102 or the second material 104, covered with a sheath made of the other of the first material 102 and the second material 104.

[0021] In an exemplary embodiment, the first material 102 is a radiopaque material, the second material 104 is a monofilament made from a support material having a higher tensile strength than the radiopaque material, and the third material 106 is a DFT wire having a core made from the radiopaque material and a sheath made from the support material. Alternatively, the DFT wire may have a core made from the support material and a sheath made from the radiopaque material. The radiopaque material may be platinum, gold, palladium, tungsten, or the like, or an alloy made from two or more of these materials. The support material has a higher tensile strength than the radiopaque material and may be a cobalt-chromium (CoCr) alloy, for example. Other materials that can be used for the support material include, but are not limited to, L605, molybdenum, titanium, or any relatively high-strength radiopaque alloy, such as platinum. The radiopaque material and support material of the DFT wire may be the same as those of the first and second materials, or they may be different radiopaque materials and support materials. Those skilled in the art will readily appreciate that the braided filaments can be made from any suitable biocompatible material and can be processed into a braid.

[0022] Figure 2A The bracket 200 shown in FIG. Figure 2B . Before braiding begins, the filaments are arranged on the braiding machine so that a single filament of the third material 106 is located on either side of a single filament of the first material 102. Directly adjacent to the other side of the single filament of the third material 106 is a filament of the second material 104. The pattern of second material 104, third material 106, first material 102, third material 106, and second material 104 repeats around the stent 200. This is referred to as a "hybrid 8x" construction. Figure 2A As shown in Figure 1A The hybrid 8x weave pattern provides better visibility of weave details compared to the bracket shown in . Figure 1A The cross-hatching pattern is more visible in stent 200 having a hybrid 8x weave pattern than in conventional stent 100 shown in FIG.

[0023] In another embodiment, the stent 300 comprises filaments that are braided together, wherein the filaments are braided together before the braiding begins. Figure 3B. The starting filament arrangement has a group of filaments of a first material 102 and a group of filaments of a third material 106 positioned directly adjacent to each side of the group of filaments of the first material 102. On the other side of the group of filaments of the third material 106 is a group of filaments of a second material 104. In this example, there are two filaments in each group of filaments. However, it should be readily understood that each group can include three or more filaments. The pattern of two filaments of the second material 104, two filaments of the third material 106, two filaments of the first material 102, two filaments of the third material 106, and two filaments of the second material 104 is repeated around the stent 300. This pattern is referred to as a "hybrid double 4x" construction. As Figure 3A As shown in Figure 1A and Figure 2A Compared to the bracket in the image, the hybrid dual 4x pattern achieves better visibility and slightly better edge definition of the crosshatch pattern.

[0024] In yet another embodiment, the stent 400 comprises filaments braided together, wherein the filaments are braided together before the braiding begins. Figure 4B The starting filament arrangement is similar to the pattern arrangement shown in , except that the third material 106 and the second material 104 are exchanged. Figure 3B 104. That is, the group of filaments of the first material 102 is placed directly adjacent to the group of filaments of the second material 104 on both sides. The group of filaments of the third material 106 is placed directly adjacent to the other side of the group of filaments of the second material 104. In this example, there are two filaments in each group of filaments. The pattern of two filaments of the third material 106, two filaments of the second material 104, two filaments of the first material 102, two filaments of the second material 104, and two filaments of the third material 106 is repeated around the stent 400. This pattern is referred to as a "hybrid double 8x" construction. As Figure 4A , the hybrid double 8x pattern achieves better visibility of the cross-hatched pattern of the filaments and also achieves better edge definition along the sides of the stent 400 compared to other embodiments. That is, the edges of the stent 400 appear as alternating light and dark areas, rather than solid lines.

[0025] Figure 5Another example of a starting filament arrangement is depicted in FIG. In this example, two filaments of the second material 104 are directly adjacent to one side of a single filament of the first material 102, and two filaments of the third material 106 are directly adjacent to the other side of the single filament of the first material 102. The pattern of four filaments of the second material 104, a single filament of the first material 102, four filaments of the third material 106, and a single filament of the first material 102 repeats around the stent. This pattern is referred to as a "hybrid 4x" configuration. While the hybrid 4x braid pattern can provide a stent with enhanced radiopacity, it has been found that the braid opening and juxtaposition is awkward compared to other braid configurations.

[0026] exist Figure 6 In yet another example of a starting filament arrangement for a stent, shown in , a single filament of a first material 102 is surrounded on two sides by a single filament of a second material 104. The other side of the single filament of the second material 104 is directly adjacent to a single filament of a third material 106. The pattern of a single filament of the third material 106, a single filament of the second material 104, a single filament of the first material 102, a single filament of the second material 104, and a single filament of the third material 106 repeats around the stent. This pattern is referred to as a "hybrid 16x" configuration.

[0027] It is worth noting that Figures 1A-6 All the stents shown in FIG are made of the same material and have the same number of filaments. In one example, the stent is made of platinum and cobalt-chromium alloy. Figures 2A-6 The examples shown in also include DFT wires formed by platinum and cobalt-chromium alloys. Figures 2A-6 Each filament of the stent is made of the first material, the second material or the third material. Figures 1A-6 Each of the embodiments shown in the drawings includes 40 filaments, but one of ordinary skill in the art will readily appreciate that any number of filaments may be used. Furthermore, one of ordinary skill in the art will appreciate that materials other than platinum and cobalt-chromium alloys may be used to braid the filaments of the stent. Examples of cobalt-chromium alloys that may be used to make the stent include 1058CoCr alloy, alloy L605, 35N LT Super alloys, etc.

[0028] Depending on the ultimate tensile strength of third material 106 (DFT wire), second material 104 (monofilament) may not be necessary. For example, it has been found that when the DFT wire is formed with a platinum core having a cross-sectional area of ​​20% to 30% of the total cross-sectional area of ​​the DFT wire and an outer sheath of alloy L605, monofilament is not necessary. Alloy L605 has a higher ultimate tensile strength than other alloys, such as 1058CoCr alloy. Figure 7An example of a stent comprising only the first material 102 and the third material 106 is depicted in FIG. Figure 7 Each filament of the stent in is made of the first material 102 or the third material 106. In another embodiment, it was found that when the tubular braid includes a DFT wire formed by a platinum core having a cross-sectional area of ​​28% of the total cross-sectional area of ​​the DFT wire and an outer sheath of 1058CoCr alloy, monofilaments of the second material 104 are necessary to enhance the strength of the stent and obtain sufficient radial compression.

[0029] As mentioned above, the pattern of filaments used in the braid of the stent can affect the radiopacity of the stent. Some braid patterns (e.g., Figure 4B The pattern shown in ) provides a higher definition image of the stent details. However, the weave pattern has been shown to have a negligible effect on the mechanical properties of the stent. Figure 8 and Figure 9 As shown in , the braid pattern has little, if any, effect on the radial pressure performance of the stent. Figure 8 The radial pressure of 2 mm and 2.5 mm compressed diameter stents with braid patterns according to the above embodiments is depicted. Figure 8 As shown in , the radial pressure of these stents is comparable to that of conventional stents, as depicted on the right side of the graph.

[0030] Similarly, Figure 9 Depicted are radial pressures for 3 mm and 3.5 mm compressed diameter stents having braid patterns according to embodiments described herein. Figure 9 As shown in , the radial pressure of these stents is comparable to that of conventional stents, as depicted on the right side of the graph.

[0031] Figure 10A is an image of a conventional stent 1000, such as Figure 1A and Figure 1B The stent shown in FIG. The edge 1002 of the stent 1000 is shown as a solid line, making it difficult for the physician to see the filaments and to observe whether the stent is expanding or compressing. In contrast, Figure 10B Depicted is the deployment of a stent 1010 having a braid pattern according to embodiments described herein. Figure 10BThe edges of the stent in the embodiment of the present invention are shown in Figure 1012 as alternating dark and light areas. In this way, the physician is able to see which areas of the stent 1010 are compressed and which areas are expanded. The compressed areas 1014 are shown as darker, shorter segments, while the expanded areas 1016 are shown as lighter, longer segments. This visibility is important in, for example, aneurysm treatment where a forward force can be used to longitudinally compress the stent in the neck area of ​​the aneurysm. With the enhanced radiopacity of the braid pattern disclosed herein, the physician can see that the stent is compressed to effectively divert blood flow away from the aneurysm. The enhanced radiopacity also allows the physician to see if the device is correctly deployed in terms of position or radial orientation relative to the entrance of the aneurysm.

[0032] Although specific embodiments illustrating variations of many aspects of the disclosed invention have been disclosed and described herein, such disclosure is provided for purposes of illustration and description only. Accordingly, various changes and modifications may be made to the disclosed embodiments without departing from the scope of the claims. For example, not all components described in the embodiments are essential for any particular embodiment, and the disclosed invention may include any suitable combination of the described components. Therefore, the disclosed invention should not be limited except as set forth in the appended claims and their equivalents.

Claims

1. An implantable braided fabric comprising: a plurality of groups of first filaments formed from a radiopaque material; a plurality of groups of second filaments, each of the second filaments being a monofilament formed from a support material having a tensile strength greater than the tensile strength of the radiopaque material; a plurality of groups of third filaments, each of the third filaments being a drawn fill line including a core and a sheath surrounding the core, the core being made of one of a radiopaque material and a support material, and the sheath being made of the other of a radiopaque material and a support material, wherein the support material of the drawn fill line has a tensile strength greater than the tensile strength of the radiopaque material of the drawn fill line, wherein the groups of the first filaments, the second filaments, and the third filaments are woven together by a braiding machine and are arranged on the braiding machine in a starting filament arrangement before braiding begins, wherein each group of the third filaments is positioned directly adjacent to one of the multiple groups of the first filaments.

2. The braid according to claim 1, wherein The core of the drawn fill line is made from the radiopaque material, and the sheath of the drawn fill line is made from the support material.

3. The braid according to claim 1, wherein: The core of the drawn fill line is made from the support material, and the sheath of the drawn fill line is made from the radiopaque material.

4. The braid according to claim 1, wherein: The radiopaque material and the support material of the third filament are different from the radiopaque material of the first filament and the support material of the second filament, respectively.

5. The braid according to claim 1, wherein The radiopaque material and the support material of the third filament are the same as the radiopaque material of the first filament and the support material of the second filament, respectively.

6. The braid according to claim 5, wherein: The radiopaque material of the first filament or the radiopaque material of the third filament is platinum, and the support material of the first filament or the support material of the third filament is cobalt-chromium alloy.

7. The braid according to claim 6, wherein: The cobalt-chromium alloy is one of 1058 CoCr alloy and 35N LT® superalloy.

8. The braid according to claim 1, wherein: The radiopaque material of the first filament or the radiopaque material of the third filament is one of the following: platinum, gold, palladium, tungsten or an alloy made of two or more of these materials; and the supporting material of the second filament or the supporting material of the third filament is one of cobalt-chromium alloy, molybdenum, and titanium.

9. The braid according to claim 1, wherein: Each group of first filaments consists of two filaments, each group of second filaments consists of two filaments, and each group of third filaments consists of two filaments.

10. The braid according to claim 1, wherein: The radiopaque material of the first filament is platinum, the support material of the second filament is cobalt-chromium alloy, and the drawn filler wire includes a platinum core and a sheath made of cobalt-chromium alloy.

11. The braid according to claim 1, wherein: The braid is tubular.

12. The braid according to claim 1, wherein The drawn filler wire includes a platinum core and a cobalt-chromium alloy sheath surrounding the platinum core.

13. The braid according to claim 12, wherein: The cobalt-chromium alloy is alloy L605.

14. The braid according to claim 12, wherein: The cross-sectional area of ​​the platinum core is 20% to 30% of the total cross-sectional area of ​​the drawn filling line.

15. The braid according to claim 1, wherein Each filament of the first set of filaments forming the braid is formed from the radiopaque material, and each filament of the second set of filaments forming the braid is formed from the support material.

16. The braid according to claim 1, wherein Each group of first filaments is located directly between two groups of third filaments, and each group of second filaments is located directly between two groups of third filaments.

17. The braid according to claim 16, wherein: The starting filament arrangement was a mixed 8x configuration.

18. The braid according to claim 16, wherein: The starting filament arrangement was a hybrid dual 4x configuration.

Images