MEDICAL DEVICE, IN PARTICULAR A STENT

Abstract

The invention relates to a medical device, in particular a stent, having a radially self-expandable lattice structure (10) which is tubular at least in some sections and which is made of a single wire (11), which is interwoven with itself and which comprises a core material (11a) which is visible under X-ray and a superelastic jacket material (11b) and forms meshes (12) of the lattice structure (10). The invention is characterised in that a plurality of meshes (12) arranged directly adjacently in the circumferential direction of the lattice structure (10) form a mesh ring (13), and the lattice structure (10), in a fully self-expanded state, has an expansion diameter D.sub.exp, the mesh ring (13) having a mesh number n, and the core material (11a) having a core diameter d.sub.Kern, and the following being true for the core diameter d.sub.Kern: d.sub.Kern=f.Math.(D.sub.exp/n), with the following being true for a visibility factor f: 0.05≤f≤0.08.

Claims

1-15. (canceled)

16. A medical device comprising: a radially self-expandable lattice structure made of a single wire interwoven with itself, the wire having a superelastic jacket material and a core material visible under X-ray, the wire forming meshes of the lattice structure divided into one or more tubular sections, wherein the lattice structure includes a plurality of directly neighboring meshes in a circumferential direction of the lattice structure to form a mesh ring, and wherein in a fully self-expanded state, a core diameter (d.sub.core) of the lattice structure equals a visibility factor (f) multiplied by a ratio of an expansion diameter D.sub.exp over a mesh number (n) of the mesh ring, expressed as d.sub.core=f.Math.(D.sub.exp/n), wherein the visibility factor is varies in a range from 0.05 to 0.08.

17. The medical device according to claim 1, wherein the expansion diameter is in a range between 2.5 mm and 7 mm.

18. The medical device according to claim 1, wherein a width ratio between the expansion diameter and the mesh number is one of, between 0.3 mm and 0.5 mm, in case of the expansion diameter being between 2.5 mm and 3.5 mm, and between 0.35 mm and 0.7 mm, in case of the expansion diameter being between 3.5 mm and 7 mm.

19. The medical device according to claim 1, wherein a braid angle of the lattice structure is between 60° and 70°.

20. The medical device according to claim 1, wherein a wire diameter of the wire is one of, between 40 μm and 55 μm, in case of the expansion diameter being between 2.5 mm and 3.5 mm, and between 45 μm and 65 μm, in case of the expansion diameter being between 3.5 mm and 7 mm.

21. The medical device according to claim 1, wherein the superelastic jacket material has a thickness of at least 10 μm.

22. The medical device according to claim 1, wherein a volume of the core material constitutes a percentage proportional to the overall volume of the wire selected from one of, between 13% and 32%, in case of the visibility factor being 0.05, and between 25% and 45%, in case of the visibility factor being 0.08.

23. The medical device according to claim 1, wherein the lattice structure in a fully compressed state has a compression diameter of at most 0.7 mm.

24. The medical device according to claim 1, wherein the lattice structure has closed loops at each of two axial longitudinal ends.

25. The medical device according to claim 1, wherein longitudinal ends of the lattice structure are widened in a funnel shape.

26. The medical device according to claim 1, wherein the core material comprises one of platinum, a platinum alloy, tantalum, and a tantalum alloy.

27. The medical device according to claim 1, wherein the superelastic jacket material comprises a nickel-titanium alloy.

28. The medical device according to claim 1, further comprising a catheter, wherein in a compressed state, the medical device can be configured and arranged in the catheter in a longitudinally displaceable manner.

29. The medical device according to claim 28, wherein the medical device is one of detachably connectable, firmly connectable, and connected to a transport wire.

30. The medical device according to claim 28, wherein the catheter has an inner diameter of at most 0.7 mm.

31. A medical device comprising: a radially self-expandable lattice structure made of a single wire interwoven with itself, the wire having a superelastic jacket material and a core material visible under X-ray, the wire forming meshes of the lattice structure divided into one or more tubular sections, wherein the lattice structure includes a plurality of directly neighboring meshes in a circumferential direction of the lattice structure to form a mesh ring, wherein in a fully self-expanded state, a core diameter (d.sub.core) of the lattice structure equals a visibility factor (f) multiplied by a ratio of an expansion diameter D.sub.exp over a mesh number (n) of the mesh ring, expressed as d.sub.core=f.Math.(D.sub.exp/n), wherein the visibility factor varies in a range from 0.05 to 0.08, and wherein a width ratio between the expansion diameter and the mesh number is one of, between 0.3 mm and 0.5 mm, in case of the expansion diameter being between 2.5 mm and 3.5 mm, and between 0.35 mm and 0.7 mm, in case of the expansion diameter being between 3.5 mm and 7 mm.

32. The medical device according to 31, wherein a wire diameter of the wire is one of, between 40 μm and 55 μm, in case of the expansion diameter being between 2.5 mm and 3.5 mm, and between 45 μm and 65 μm, in case of the expansion diameter being between 3.5 mm and 7 mm.

33. The medical device according to claim 31, wherein a wire diameter (d.sub.wire) of the wire is at least 60 μm and a thickness of the superelastic jacket material is at least 15 μm.

34. The medical device according to claim 31, wherein a volume of the core material constitutes a percentage proportional to the overall volume of the wire selected from one of, between 20% and 30%, in case of the visibility factor being 0.05, and between 30% and 42%, in case of the visibility factor being 0.08.

35. A medical device comprising: a radially self-expandable lattice structure made of a single wire interwoven with itself, the wire having a superelastic jacket material and a core material visible under X-ray, the wire forming meshes of the lattice structure divided into one or more tubular sections, wherein the lattice structure includes a plurality of directly neighboring meshes in a circumferential direction of the lattice structure to form a mesh ring, wherein in a fully self-expanded state, a core diameter (d.sub.core) of the lattice structure equals a visibility factor (f) multiplied by a ratio of an expansion diameter D.sub.exp over a mesh number (n) of the mesh ring, expressed as d.sub.core=f.Math.(D.sub.exp/n), wherein the visibility factor varies in a range from 0.05 to 0.08, wherein a width ratio between the expansion diameter and the mesh number is one of, between 0.4 mm and 0.5 mm, in case of the expansion diameter being between 2.5 mm and 3.5 mm, and between 0.38 mm and 0.7 mm, in case of the expansion diameter being between 3.5 mm and 7 mm, and wherein a volume of the core material constitutes a percentage proportional to the overall volume of the wire selected from one of, between 25% and 30%, in case of the visibility factor being 0.05, and between 35% and 42%, in case of the visibility factor being 0.08.

Description

[0041] The invention will be described below in more detail with the aid of an example of embodiment with reference to the accompanying schematic drawings. In these:

[0042] FIG. 1 shows a perspective view of a medical device according to the invention in accordance with the preferred example of embodiment;

[0043] FIG. 2 shows a side view of the device according to FIG. 1;

[0044] FIG. 3 shows a schematic view of a mesh of the lattice structure of the medical device according to FIG. 1; and

[0045] FIG. 4 shows a schematic view of a cross-sectional profile of the wire of the medical device according to FIG. 1.

[0046] The medical device according to the invention which is shown in the example of embodiment in figures, involve, in particular, a stent which is suitable for treatment in intracranial blood vessels.

[0047] Fundamentally, the medical device can be in the form of a medical instrument or a medical implant. In all cases, it is preferably envisaged that the medical device can be guided in a minimally invasive manner by way of catheter to a treatment location, in particular within a blood vessel. As a medical instrument, the device according to the invention can, for example, constitute a thrombectomy device. The thrombectomy device can have a lattice structure 10, which is tubular at least in sections. At a distal end, the lattice structure 10 can be closed, in order to thus form a catching basket which can collect the thrombus material. The thrombectomy device is preferably firmly connected to a transport wire and for the treatment of a vascular disease does not remain in the body permanently. Instead, the thrombectomy device, like other medical instruments, is only used for short time.

[0048] In contrast, medical implants remain permanently at their treatment location. Such implants are, in particular, stents which are inserted into blood vessels for the treatment of aneurysms. The stents can also be used for other things. For example, such stents can also be used to treat stenoses or plaque deposits in blood vessels.

[0049] The stent shown in attached drawings is preferably suitable for the treatment of aneurysms in intracranial blood vessel.

[0050] The stent comprises a tubular, radially expandable lattice structure 10 which is formed of a single wire 11 which is interwoven with itself. At each of the longitudinal ends 14 of the lattice structure 10, the wire 11 forms loops 15. The two ends of the wire are brought together in the middle of the lattice structure 10 and are coupled to each other with a connection element 16. The connection element 16 can comprise, or be made of, a material which is visible under X-rays.

[0051] The lattice structure 10 is greatly compressible and can thus be fed to the treatment location by way of small catheters. As can also be easily seen in FIG. 1, the lattice structure 10 has a high degree of bending flexibility so that feeding into, and anchoring in, very sinuous blood vessels is easily possible.

[0052] Furthermore, it can be easily seen in FIGS. 1 and 2 that the lattice structure 10 is widened in a funnel shape at the longitudinal ends 14. Specifically, at its longitudinal ends, the lattice structure 10 has loops 15 widened in a funnel shape or opening up radially outwards.

[0053] In order to make the longitudinal ends 14 easily visible in X-ray monitoring, X-ray marker sleeves 17 are provided which are applied to the wire 11 in the area of a loop 15. Specifically, the loop 15 has a vertex and two arms, wherein the X-ray marker sleeve 17 is arranged on one of the arms. In particular, the X-ray marker sleeve 17 can be crimped onto the arm. In the shown example of embodiment, it is envisaged that only every second loop 15 carries an X-ray marker sleeve 17.

[0054] Overall, it is envisaged that three X-ray markers sleeves 17 are arranged on each longitudinal end 14. This ensures that the longitudinal ends 14 of the lattice structure 10 are easily seen in X-ray monitoring even if the lattice structure 10 has become twisted. At the same time, it makes sense to limit the number of X-ray markers sleeves 17 per longitudinal end 14 as in this way good compressibility of the lattice structure 10 is achieved. A greater number of X-ray marker sleeve 17 could lead to the X-ray marker sleeves 17 blocking each other during compressing and thereby prevent further compression of the lattice structure 10.

[0055] As can be easily seen, particularly in FIG. 2, the lattice structure 10 comprises several meshes 12, which seen in the circumferential direction of the lattice structure 10 each form mesh rings 13. A mesh ring 13 is formed from several meshes 12 which are arranged directly adjacent to each other in the circumferential direction of the lattice structure. The individual meshes are separated from each other by intersections 18 of the wire 11.

[0056] The lattice structure is built up of several mesh rings 13 arranged directly adjacent to each other in the longitudinal direction of the lattice structure 13. It is preferable if each mesh ring 13 has an even number of meshes 12. In particular, the mesh ring 13 can comprise 6, 8, 12, 14 or 16 meshes.

[0057] The lattice structure 10 is self-expandable and expends radially by itself without the effect of external forces. In this state, without forces acting on it, the lattice structure 10 assumes the expansion diameter D.sub.exp. In a fully expanded state, the lattice structure 10 consequently has the expansion diameter D.sub.exp.

[0058] By contrast, an external force effect is required to transfer the lattice structure 10 into a compressed state. A state in which the lattice structure 10 assumes its smallest possible diameter is the fully compressed state. In this fully compressed the lattice structure 10 has a compression diameter D.sub.comp. During compression of the lattice structure 10, the width of a mesh 12 reduces in the circumferential direction of the lattice structure 10. This reduction in width takes place until the wire sections, which define the mesh 12, are in contact with each other. Through this, the wire 11 blocks further compression of the lattice structure 10. For mechanical and/or geometric reasons the lattice structure 10 cannot be compressed to any desired extent, but assumes a minimum diameter, as of which no further compression is possible. This state constitutes the fully compressed state in which the lattice structure 10 has a compression diameter D.sub.comp.

[0059] A compression diameter D.sub.comp which is as small as possible is expedient in order to be able to feed the lattice structure 10 to the treatment location through catheters that are as small as possible. In particular, it is envisaged that the lattice structure can be compressed in such a way, or can assume a compression diameter D.sub.comp such that the lattice structure can be guided to the treatment location via a catheter with an inner diameter of at most 3 French, more particularly 2.5 French, more particularly at most 2 French. More specifically, the lattice structure can assume a compression diameter D.sub.comp which is at most 0.7 mm, more particularly 0.6 mm, more particularly at most 0.51 mm, more particularly at most 0.42 mm.

[0060] The wire 11, which forms the lattice structure 10, is preferably designed as a composite wire. For this, the wire comprises a core material 11a, which is visible under X-ray, and a superelastic jacket material 11b. The core material 11a can, in particular, comprises platinum, a platinum alloy, tantalum and/or a tantalum alloy. In all events, the core material 11a is preferably characterised by increased visibility under X-ray radiation. This means that the entire lattice structure 10 can be easily seen by the surgeon during the implantation.

[0061] The jacket material 11b on the other hand, serves to provide the self-expansion properties of the lattice structure 10. For this, the jacket material 11b has superelastic properties. More particularly, the jacket material can be formed by a shape-memory material, which under the influence of the ambient temperature assumes a previously imparted shape. A shape-memory material of this type, can, in particular, before formed of a nickel-titanium alloy. Preferably the jacket material 11b is adapted in such a way that on reaching the body temperature of a human it pushes the lattice structure 10 into the fully expanded state.

[0062] Depending on the desired size of the lattice structure 10 of the medical device, in particular the stent, it expedient to adapt the diameter of the core material, the core diameter d.sub.core accordingly. More particularly, the self-expansion properties, the compressibility and the visibility under X-ray of the lattice structure 10 should be matched to each other in the best possible way. It has been shown that for different expansion diameters D.sub.exp, a core diameter d.sub.core that results from the product of the quotient of the expansion diameter D.sub.exp and the mesh number n of the meshes 12 of the mesh ring 13 as well as a visibility factor f is advantageous. The visibility factor f is preferably at least 0.05 and at most 0.08.

[0063] It has been specifically shown that a core diameter calculated on the basis of the above parameters results in good visibility of the lattice structure 10 under X-ray, wherein the lattice structure 10 still has good self-expanding properties and can be compressed to a small compression diameter. The equation

d.sub.core=f.Math.(D.sub.exp/n)

applies for lattice structures 10 with different expansion diameters D.sub.exp.

[0064] More particular, calculating the core diameter D.sub.core using this equation results in good parameters for lattice structures 10 which have an expansion diameter D.sub.exp between 2.5 mm and 7 mm. Such lattice structures 10 are, in particular, suitable for use in intracranial blood vessels.

[0065] In order to achieve good compressibility of the lattice structure 10, it is particularly advantageous, if as in the case of the shown examples of embodiment, the wire 11 has a wire diameter d.sub.wire which is at most 65 μm more particularly at most 60 μm, more particularly at most 55 μm, more particularly at most 40 μm. The wire 11 can have a wire diameter d.sub.wire which is between 40 μm and 50 μm, preferably between 45 μm and 50 μm. Specifically, the wire diameter d.sub.wire can be 40 μm or 45 μm or 50 μm. Such thin wires allow a particularly high degree of compression of the lattice structure 10, thus also leading to a very small compression diameter D.sub.comp. This ensures that the lattice structure 10 can be easily fed to the treatment location through small catheters.

[0066] It has also been shown that for the self-expansion properties of the lattice structure 10, a wire 11 with a jacket material thickness h of at least 10 μm is advantageous. Thus, in the case of a wire diameter d.sub.wire of 40 μm a maximum possible core diameter of 20 μm results. In FIG. 4 it can be clearly seen that through a thickness h of 10 μm for the jacket material 11b, with a wire diameter d.sub.wire of 40 μm for the core material 11a, a core diameter d.sub.core of at most 20 μm remains.

[0067] The best possible maximum wire diameter d.sub.wire is determined on the one hand by the expansion diameter D.sub.exp and, on the other hand, by the mesh number n of the respective lattice structure 10. For lattice structures 10 with an expansion diameter D.sub.exp between 2.5 mm and 7 mm, wire diameters D.sub.wire between 40 μm and 65 μm, more particularly between 40 μm and 60 μm, have proven to be advantageous.

[0068] From the aforementioned geometric specifications, the percentage proportion of the volume of core material 11a in relation to the overall volume of the wire 11 can be calculated. This essentially corresponds to the quotient between the square of the ratio of the product from the visibility factor f and the mesh width b to the square of the wire diameter d.sub.wire. The mesh width b results from the ratio between the expansion diameter D.sub.exp and the mesh number n. Specifically, the volume proportion φ of the core material 11a can be calculated as follows:

φ=(f.Math.D.sub.exp/n).sup.2/d.sub.wire.sup.2

[0069] Expressed in percent, in the case of a visibility factor f of 0.05, the percentage by volume of the core material 11a in relation to the overall volume of the wire 11 is preferably between 13% and 32%, more particularly between 20% and 30%, more particularly between 25% and 30%.

[0070] With a visibility factor f of 0.08, the percentage by volume φ of the core material 11a in relation to the overall volume of the wire 11 is preferably between 25% and 45%, more particularly between 30% and 42%, more particularly between 35% and 40%.

[0071] In FIG. 3, a section of the lattice structure 10 of the medical device or the stent according FIG. 1 is shown. Specifically, FIG. 1 shows a single mesh 12 of the lattice structure 10, which is delimited by several wire sections of the wire 11. As is usual in the case of lattice structures 10, the mesh 12 is rhombus-shaped.

[0072] In FIG. 3 it is again clearly shown how the wire 11 is designed as a composite wire. In particular for illustration purposes, it is shown that the core material 11a extends through the wire 11 and is surrounded by the jacket material 11b. In X-ray monitoring, the core material 11a is visible in particular, wherein the X-ray density is particularly high in the area of the intersections 18 of the wire 11. The intersections 18 are therefore particularly well seen during X-ray monitoring.

[0073] The braid angle α of the lattice structure 10 in the shown forms of embodiment is preferably between 60 and 70 degrees, preferably 65 degrees, wherein a tolerance of ±3 degrees can be envisaged. In the context of the present invention, the braid angle α is considered as the angle formed between a longitudinal axis M of the lattice structure 10 and the wire 11. The wire 11 is helically wound around the longitudinal axis M.

[0074] For clarification, the braid angle α is illustrated in FIG. 2. It is also conceivable that because of the rhomboid shape of the individual meshes 12, the braid angle α essentially corresponds to half the entire mesh angle β. The mesh angle β is formed between two intersecting wire sections of the wire 11, wherein these wire sections are arranged next to each other in the circumferential direction.

[0075] In general, the invention is based on the following considerations:

[0076] For a product series of medical devices, more particularly stents, the lattice structure of which is essentially configured in the same way, though the individual products differ in terms of their expansion diameter D.sub.exp, it is expedient to increase the mesh number n of the individual mesh rows 13 with increasing expansion diameter D.sub.exp.

[0077] The width b of an individual mesh can generally be calculated from the expansion diameter D.sub.exp and the mesh number n is as follows:

b=π.Math.D.sub.exp/n

[0078] In the context of this application, the ratio D.sub.exp/n between the expansion diameter D.sub.exp and the mesh number n, is designated as the width ratio R.sub.GS.

[0079] With a high width ratio R.sub.GS, the individual meshes are comparatively wide. This has the drawback that embolic material, such as coils in an aneurysm, can only be held back by the lattice structure 10 with difficulty.

[0080] Furthermore, a large mesh width b negatively affects the stability of the lattice structure 10.

[0081] By contrast, with a small width ratio R.sub.GS, a small mesh width b is produced. Through this the lattice structure 10 becomes less flexible, so that navigation of the medical device through a catheter becomes more difficult. A small mesh width b also means that microcatheters, which are used to insert coils into an aneurysm, can only be fed through the meshes with difficulty.

[0082] It is therefore expedient to arrive at a mesh width b which achieves a compromise between the stability and good navigability of the lattice structure 10. It has been shown that a width ratio R.sub.GS in a range of 0.4 mm to 0.5 mm leads to good results. Taking into account the circle constant n, this results in a preferred mesh width b of between 1.25 mm and 1.6 mm.

[0083] In the case of an expansion diameter D.sub.exp of 2.4 mm, a width ratio R.sub.GS of between 0.3 mm and 0.45 mm, more particularly between 0.4 mm and 0.45 mm, preferably 0.42 mm, is preferred.

[0084] Lattice structures 10 with an expansion diameter D.sub.exp of more than 2.5 mm, preferably have a width ratio R.sub.GS of between 0.35 mm and 0.7 mm, more particularly between 0.38 mm and 0.6 mm. More specifically, the width ratio R.sub.GS can be between 0.35 and 0.7 mm if the lattice structure 10 has an expansion diameter D.sub.exp of between 2.5 mm and 3.5 mm. Lattice structures 10 with an expansion diameter D.sub.exp between 3.5 mm and 7 mm preferably have a width ratio R.sub.GS of between 0.35 mm and 0.6 mm.

[0085] The braid angle α influences the mechanical expansion behaviour, the flexibility and feedability of the medical device. A braid angle α between 60° and 70°, preferably 650 has proven to be well suited for the treatment of intracranial blood vessels by way of medical devices with a lattice structure 10 having an expansion diameter D.sub.exp of between 2.5 mm and 7 mm.

[0086] A predetermined width ratio R.sub.GS and consequently a predetermined mesh width b as well as a predetermined braid angle α result in a rhomboid shape and size of the mesh 12, from which, in combination with the wire diameter d.sub.wire, a braid density or porosity results. The braid density indicates the proportion of the entire outer surface of the lattice structure that is formed by the wire 11, i.e. less the opening surface of the meshes 12. The porosity on the other hand, indicates the proportion of the overall outer surface of the lattice structure formed by the sum of the opening surfaces of the meshes 12. The width ratio R.sub.GS also influences the maximum incircle diameter of the mesh 12, which is also known as “pin opening”.

[0087] Together with the braid angle α and the width ratio R.sub.GS, the wire diameter d.sub.wire influences the braid density and the porosity of the lattice structure 10 and also affects the radial force and the feedability of the medical device. The following wire diameters d.sub.wire have proven to be advantageous for different expansion diameters D.sub.exp: [0088] In the case of an expansion diameter D.sub.exp of 2.5 mm the wire diameter d.sub.wire is preferably between 40 μm and 50 μm, more particularly between 45 μm and 50 μm. [0089] In the case of an expansion diameter D.sub.exp between 2.5 mm and 4.5 mm the wire diameter d.sub.wire is preferably between 45 μm and 60 μm, more particularly 50 μm. [0090] In the case of an expansion diameter D.sub.exp between 4.5 mm and 6 mm the wire diameter d.sub.wire is preferably between 50 μm and 65 μm, more particularly 55 μm. [0091] In the case of an expansion diameter D.sub.exp between 6 mm and 7 mm the wire diameter d.sub.wire is preferably between 50 μm and 65 μm, more particularly 60 μm.

[0092] The length of the lattice structure 10 is preferably between 10 mm and 50 mm.

[0093] For good visibility under X-ray, the wire 11 has an X-ray visible core material 11a with a core diameter d.sub.core. When selecting the core diameter d.sub.core, the size of the individual meshes 12 plays an important role. The wider and longer the meshes 12, the lower is the braid density of the lattice structure 10. A higher core diameter d.sub.core is required in order to easily see the wire 11 during X-ray monitoring.

[0094] More particularly, the mesh width b influences the distance between the intersections 18 of a mesh row 13. At the intersections 18, sections of the wire 11 overlap and thereby form areas with an increased X-ray density. The more the intersections 18 are distanced from each other, the greater the core diameter d.sub.core should be in order to ensure good visualisation of the lattice structure 10. More particularly, through a high number of intersections, not only is the surface of the lattice structure 10 easily seen, but also the shape of the lattice structure 10, adapting to the vascular wall.

[0095] The width ratio R.sub.GS determines the density of the intersections 18 of a mesh row 13. The smaller the width ratio R.sub.GS, the smaller is the distance between the intersections 18 and the higher the braid density of the lattice structure 10.

[0096] With a high width ratio R.sub.GS, a relatively large core diameter d.sub.core is expedient. For a small width ratio R.sub.GS, an accordingly smaller core diameter d.sub.core is sufficient.

[0097] It has been shown that a ratio between the core diameter d.sub.core and the width ratio R.sub.GS of between 0.05 und 0.08 leads to good results. In the context of the present application, the aforementioned ratio produces the thus designated visibility factor f.

[0098] In the case of a visibility factor f of 0.05, with a width ratio R.sub.GS of between 0.4 and 0.5 mm, an advantageous core diameter d.sub.core of between 20 μm and 25 μm results. For a greater width ratio R.sub.GS, the core diameter d.sub.core can increase to up to 30 μm, more particularly up to 35 μm.

[0099] In the case of a visibility factor f of 0.08, with a width ratio R.sub.GS between 0.4 mm and 0.5 mm, an advantageous core diameter d.sub.core of between 33 μm and 40 μm results. For a smaller width ratio R.sub.GS, the core diameter d.sub.core can be reduced to a value of between 30 μm and 25 μm, more particularly specifically to 30 μm, in particular 25 μm.

[0100] In order to assume sufficient torsion resistance and thereby a suitable restoring force during a spring-like deformation of the wire 11, it is advantageous if the jacket material 11b has a thickness that is at least 10 μm. In the case of a maximum wire diameter d.sub.wire, this results in an upper limit for the core diameter d.sub.core of 40 μm.

[0101] With one of 2.5 mm and a preferred wire diameter d.sub.wire of 40 μm, the core diameter d.sub.core must not be greater than 20 μm, as otherwise the proportion of jacket material 11b would be too low. In order to achieve this, a visibility factor of 0.05 should be selected. With a larger expansion diameter D.sub.exp, the preferred wire diameter d.sub.wire is at least 50 μm. For such lattice structures 10, the core diameter d.sub.core can consequently be up to 30 μm. In a lattice structure 10 with an expansion diameter D.sub.exp of 3.5 mm, a greater visibility factor f of up to approx. 0.07 is possible.

[0102] A visibility factor f of 0.08 can be used if the width ratio R.sub.GS is low or the wire diameter d.sub.wire high.

[0103] Selection of the suitable visibility factor f, results in a percentage proportion of the volume of core material 11a in relation to the overall volume of the wire 11. Preferably, the volumetric proportion of the core material 11a is between 13% and 32% in the case of a visibility factor of 0.05 and between 25% and 75% in the case of a visibility factor of 0.08. More particularly, with a visibility factor f of between 0.05 und 0.06, the volumetric proportion of the core material 11a can be between 20% and 30%, more particularly between 25% and 30%. With a visibility factor f of between 0.06 und 0.08, the volumetric proportion of the core material of the core material 11a is preferably between 25% and 45%, more particularly between 30% and 40%.

[0104] Applicable for all examples of embodiment of the invention is that through the use of a single wire 11 with a superelastic jacket material 11b, a lattice structure 10 can be formed that expands well and can be packed into miniaturised feeding systems and is also easily visible through the core material 11a that is visible under X-ray.

[0105] The particular challenge consists in producing the lattice structure by way of only a single wire 11. Single wire production requires the formation of loops 15 at the longitudinal ends 14 of the lattice structure 10. In the area of the loops 15, the wire 11 is subject to very great expansion (up to 8%, sometimes more), which when using conventional wire materials, for example cobalt-chromium alloys, can lead to plastic deformation of the wire 11 during compression of the lattice structure 10, so that at the longitudinal ends 14 the lattice structure 10 would no longer expand by itself. Instead, after implantation, the longitudinal ends 14 would remain bent radially inwards (cigar shape of the lattice structure 10) and could thereby encourage the formation of thrombi.

[0106] The superelastic jacket material 11b, envisaged in the invention, which in particular comprises nitinol, withstands such expansion. However, a precondition is also that the jacket material 11b has a corresponding thickness h in relation to the overall diameter of the wire 11. To this extent it is a question of the diameter and volume ratio between the core material 11a and the jacket material 11b.

[0107] In devices according to the invention, because of the superelastic jacket material 11b and its ratio to the X-ray visible core material 11a, the loops 15 have good elastic expansion properties and are also easily visible under X-rays. The positioning of the device in a blood vessel can therefore be easily monitored, which is also the case if the loops 15 have no additional X-ray marker sleeves 17.

[0108] In this context it has been shown that for the following wire diameters d.sub.wire the following core diameters d.sub.core are preferred:

[0109] For d.sub.wire=45 μm: d.sub.core=24.6 μm

[0110] For d.sub.wire=50 μm: d.sub.core=27.4 μm or 31.6 μm.

[0111] For d.sub.wire=55 μm: d.sub.core=30.1 μm or 34.8 μm.

[0112] A wire 11 with a wire diameter d.sub.wire of 50 μm is preferably used for lattice structures 10 with an expansion diameter D.sub.exp of between 2.5 mm and 5.0 mm.

[0113] For lattice structures 10 with an expansion diameter D.sub.exp between 2.5 mm and 3.0 mm, a wire 11 with a wire diameter d.sub.wire of 45 μm can also be used.

[0114] For lattice structures 10 with an expansion diameter D.sub.exp between 4.5 mm and 5.0 mm, a wire 11 with a wire diameter d.sub.wire of 55 μm can also be used.

[0115] The preferred thickness h of the jacket material is calculated as follows:

h=(d.sub.wire−d.sub.core)/2

[0116] The jacket material 11b consequently has a thickness h, which for the above-described, preferred wire diameter d.sub.wire is at least 9 μm (with d.sub.wire=50 μm and d.sub.core=31.6 μm) and at most 12.4 μm (with d.sub.wire=55 μm and d.sub.core=30.1 μm).

[0117] With regard to the mesh number n, it is preferably envisaged that lattice structures 10 with an expansion diameter D.sub.exp of between 2.5 mm and 7.0 mm preferably have around 6 to 16 meshes 12 per mesh ring 13.

[0118] Lattice structures 10 with an expansion diameter D.sub.exp between 2.5 mm and 3.5 mm preferably have 6 or 8 meshes 12 per mesh ring 13. In the case of lattice structures 10 with an expansion diameter D.sub.exp between 3.5 mm and 5.0 mm, mesh rings 13 can each be provided with 6 or 8 or 10 or 12 meshes.

[0119] Lattice structures 10 with an expansion diameter D.sub.exp of between 5.0 mm and 7.0 mm preferably have a mesh number n of 8 or 10 or 12 or 14 or 16.

REFERENCE NUMBERS

[0120] 10 Lattice structure. [0121] 11 Wire [0122] 11a Core material [0123] 11b Jacket material [0124] 12 Meshes [0125] 13 Mesh ring [0126] 14 Longitudinal end [0127] 15 Loop [0128] 16 Connection element [0129] 17 X-ray marker sleeve [0130] 18 Intersection [0131] D.sub.exp Expansion diameter [0132] D.sub.comp Compression diameter [0133] d.sub.core Core diameter [0134] d.sub.wire Wire diameter [0135] b Mesh width [0136] f Visibility factor [0137] h Thickness of the jacket material 11b [0138] R.sub.GS width ratio [0139] α Braid angle [0140] β Mesh angle [0141] n Mesh number [0142] φ Percent by volume