Medical device construction using radiopaque nitix alloy

Abstract

The present teaching provides medical devices having a wire mesh structure formed by interweaving a plurality of NiTiX alloy wires. The NiTiX alloy material used for the wire is an alloy which is a general uniform mixed crystal of the intermetallic phase Nickel, Titanium and at least one radiopaque element, which allows the entire medical device to be visible under X-ray. The present teaching further provides a medical device designed for good self-expansion capability while exhibiting strong X-ray visibility throughout the entire device body.

Description

PATENT Attorney Docket No. PWAL-028PCTMedical Device Construction Using Radiopaque NiTiX AlloyFIELD

[0001] The present teaching relates to a medical device designed to be visible under X-ray throughout in its entirety. Such medical device has a wire mesh structure constructed with a Nickel, Titanium and at least one radiopaque element in order to achieve desired self-expansion capability as well as strong X-ray visibility.BACKGROUND

[0002] When introducing a medical device into a small blood vessels, preferably in the neurovascular application, self-expansion capability is desirable in order to avoid the need for a balloon catheter to expand the wire mesh structure. Such a balloon catheter would limit the compression of the wire mesh structure, so that the wire mesh structure cannot be introduced into particularly small blood vessels. Miniaturization of the wire mesh structure, particularly in its compressed state, is therefore desirable.

[0003] The shape memory and superelastic nature of the NiTi alloy makes it a top choice for medical device, especially implantable device. However, the low radiopacity nature of NiTi alloy makes the implant difficult to be visualized under X-ray, during the procedure. Thus radiopaque markers are incorporated to the implant device. Since radiopaque markers are typically incorporated to limited segments on the medical device, to determine the entire devices’ position upon deployed in vivo requires a clinician’s skill and experience. This practice is not only time consuming during an active procedure, but also leaves room for error.

[0004] It is therefore desirable to provide a medical device having a wire mesh structure where the wire with a smallest possible cross-sectional diameter could be used for vascular application. It is also desirable for such medical device is designed to have good self-expansion capability, and at the same time exhibits a strong X-ray visibility throughout its entire device body.PATENT Attorney Docket No. PWAL-028PCT SUMMARY OF THE INVENTION

[0005] One aspect of the present teachings provides a radially self-expandable medical device having a generally tubular profile. In various embodiment, the medical device comprises a wire-mesh structure formed by a plurality of NiTiX alloy (alloy of Nickel, Titanium and at least one radiopaque element) wires interwoven together. Each NiTiX alloy wire has a wire diameter and forms an angle with a tubular axis of the wire mesh structure. The NiTiX alloy wire is made of an alloy which is a general uniform mixed crystal of the intermetallic phase Nickel, Titanium and at least one radiopaque element with atomic number greater than 71. And the wire mesh structure has an outer diameter. A visibility of the medical device under X-ray is characterized by a visibility factor. The visibility factor of the medical device is a function of the atomic percentage of the radiopaque element (or elements) of the NiTiX alloy, the number of NiTiX alloy wires used forming the wire mesh structure, the wire diameter, the outer diameter of the wire mesh structure, and the angle between the wire and the tubular axis of the wire mesh structure.

[0006] Another aspect of the present teaching provides that the visibility factor of the medical device is characterized asa ■ n ■ df = - D ■ cos 0where / is the visibility factor, a is the atomic percentage of the radiopaque element (or elements) in the NiTiX alloy, n is the number of wires formed the wire mesh structure, d is the wire diameter, D is the outer diameter of the wire mesh structure (in its maximum recommended vessel diameter for use), and 0 is the angle between the wire and the longitudinal tubular axis of the radially expanded wire mesh structure (in its maximum recommended vessel diameter for use).

[0007] Another aspect of the present teaching provides that the visibility factor is between 0.04-0.18.

[0008] Another aspect of the present teaching provides that the outer diameter of the wire mesh structure is between 2mm and 6 mm (when implanted in its maximum recommended vessel diameter for use).PATENT Attorney Docket No. PWAL-028PCT

[0009] Another aspect of the present teaching provides that the angle between the wire and the tubular axis of the wire mesh structure is between 40-70° (when implanted in its maximum recommended vessel diameter for use).

[0010] Another aspect of the present teaching provides that the wire diameter is between 25-35 pm.

[0011] Another aspect of the present teaching provides that the atomic percentage of the radiopaque element or elements of the NiTiX alloy is between 7-17 %.

[0012] Another aspect of the present teaching provides that the NiTiX alloy is a general uniform mixed crystal of the intermetallic phase Nickel, Titanium and at least one radiopaque element with atomic number greater than 71. In one aspect, the NiTiPt alloy is a general uniform mixed crystal of Nickel, Titanium and platinum.

[0013] Another aspect of the present teaching provides that the medical device is radially compressible to fit inside a microcatheter.

[0014] One aspect of the present teachings provides a medical device configured to be visible under X-ray throughout its entirety. In various embodiments, the medical device has a wire mesh structure with a general tubular profile, and formed by a plurality of NiTiX alloy wire interweaving together. The NiTiX alloy wire is made of an alloy which is a general uniform mixed crystal of the intermetallic phase NiTi and at least one radiopaque element with atomic number greater than 71. A visibility of the medical device under X-ray is characterized by a visibility factor. The visibility factor of the medical device is a function of the atomic percentage of the radiopaque element or elements of the NiTiX alloy, the number of NiTiX alloy wires used forming the wire mesh structure, the wire diameter, the outer diameter of the wire mesh structure (when implanted in its maximum recommended vessel diameter for use), and the angle between the wire and the tubular axis of the wire mesh structure (when implanted in its maximum recommended vessel diameter for use).

[0015] Another aspect of the present teaching provides that the medical device is configured to be radially compressible to fit inside a catheter and self-expandable radially upon releasing from the catheter.PATENT Attorney Docket No. PWAL-028PCT BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 A is a schematic view of X-ray projecting perpendicularly onto a wire in accordance with the present teachings.

[0017] Fig. IB is a schematic view of X-ray projecting onto a wire in a nonperpendicular direction in accordance with the present teachings.

[0018] Fig. 2 is a schematic view of X-ray projecting perpendicularly onto a medical device of wire mesh structure in accordance with the present teachings.

[0019] Figs. 3A-3B are schematic views of X-ray projecting perpendicularly onto a wire in its final shape as formed in the medical device of wire mesh structure in accordance with the present teachings.

[0020] Fig. 4A-4C are schematic views of X-ray projecting perpendicularly onto a medical devices of wire mesh structure with different geometrical construction in accordance with the present teachings.

[0021] Fig. 5 is a schematic view of X-ray projecting onto a medical device of wire mesh structure in a non-perpendicular direction in accordance with the present teachings.DETAILED DESCRIPTION

[0022] The present teachings are described more fully hereinafter with reference to the accompanying drawings, which show certain embodiments of the present teachings. The present teachings may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to illustrate various aspects of the present teachings. Like numbers refer to like elements throughout.

[0023] In some embodiments, the medical device, according to the present teachings, may be extended into an elongated profile for percutaneous delivery and resume to a radially expanded deployment profile upon release from the delivery system. As used in this application, unless otherwise indicated, the term “vessel” refers to a blood vessel, including an artery, an arteriole, a capillary, a venule, a vein, or a network of any of the combinations of the foregoing.PATENT Attorney Docket No. PWAL-028PCT

[0024] As explained in further detail below, various embodiments of the present teachings provides a medical device having a wire mesh structure and is designed for maximum visibility under X-ray or fluoroscopy throughout its entire device body without compromising the desirable self-expansion capability. According to one embodiment of the present teaching, the medical device has a general tubular configuration. Such device structure could be used for endovascular treatment of intracranial aneurysms such as a flow diverter for diverting the blood flow away from the diseased vascular area, thrombectomy device for removing blood clots / thrombi from blood vessels, stent for treating wide-necked intracranial aneurysms, and etc.

[0025] According to some embodiments, the medical device with a wire mesh structure is flexible and atraumatic and is available in various lengths and diameters, thin-walled, and radiopaque throughout the entire device body. In some embodiments, the medical device is configured to be precisely delivered, deployed, retrieved, and repositioned. In some embodiments, the medical device is flexible enough to be delivered via a microcatheter and to be placed in a small vessel but has sufficient radial forces to conform to the vessel wall geometry when deployed.

[0026] According to one embodiment of the present teaching, the medical device has a general tubular profile, with a radially self-expandable wire mesh structure. The structure of the medical device is formed of a woven, knitted, or braided tubular metallic fabrics made out of metallic strands / wires. As used in this application, the phrase “a wire-mesh structure formed with a plurality of NiTiX alloy wires interwoven together” includes wire mesh structure formed by weaving, knitting, and braiding.

[0027] According to one embodiment of the present teaching, the metallic strands / wires forming the medical device are NiTiX alloy which not only exhibit superelastic and shape memory property similar to the conventional NiTi alloy wire, but also exhibit radiopaque property under X-ray / fluoroscopy. In another word, the metallic strands / wire forming the medical device according to one embodiment of the present teaching is visible under X-ray. According to one embodiment of the present teaching, the NiTiX alloy wires are made of a general uniform mixed crystal of the intermetallic phase NiTi and at least one radiopaque element with atomic number greater than 71.PATENT Attorney Docket No. PWAL-028PCT

[0028] In general, the present teaching provides that the medical device is configured to self-expand relying on the superelastic and / or thermal shape memory properties of the material that forming the medical device. Thus, the medical device can automatically assume a radially expanded state upon deployed in vivo. The medical device is also configured to be converted into a radially compressed state which allows the device to fit inside a catheter and to be delivered into a blood vessel by the catheter. In one embodiment, the medical device of present teaching can be used with catheters or microcatheter providing an inner diameter of 0.40 mm to 0.72 mm.

[0029] According to one embodiment of the present teaching, the medical device constructed with the NiTiX alloy is designed to maximize visibility under X-ray / fluoroscopy so that the doctor can assess the entire device body of the medical device during delivery, deployment and implantation. For example, the doctor can assess that the medical device is securely attached to a blood vessel wall along its entire length. Additionally, the medical device constructed with the NiTiX alloy is configured to self-expand upon deployment, so that the medical device can be used in very small blood vessel, such as those in the neurovascular application.

[0030] According to one embodiment of the present teaching, the NiTiX alloy used to construct the medical device is an alloy which is a general uniform mixed crystal of the intermetallic phase NiTi and at least one radiopaque element with atomic number greater than 71. Such NiTiX ternary or quarternary alloy significantly absorbs X-ray radiation, prevents most of it from passing through, and appears as a white or light area on the X-ray. Such "blocking" the X-ray and making it visible on the radiograph is typically due to the presence of elements with high atomic numbers, such as platinum, gold, tungsten, tantalum, niobium, as well as alloys thereof, which readily absorb X-ray. According to one embodiment of the present teaching, the atomic percentage of radiopaque element in the NiTiX alloy, i.e. the percentage of the total number of atoms present in the NiTiX alloy, directly affects the properties of the NiTiX alloy. NiTiX alloy with a greater atomic percentage of radiopaque element or elements would achieve higher visibility under X-ray, but at the expense of the superelasticity of material. NiTiX alloy with a lesser atomic percentage of radiopaque element or elements would preserved the superelasticity of the alloy, while sacrificing the visibility under X-ray.PATENT Attorney Docket No. PWAL-028PCT

[0031] According to one embodiment of the present teaching, the medical device has a radially collapsed elongated profile, suitable to be positioned inside a catheter and / or a microcatheter; and a radially expanded deployed configuration which adapts to the blood vessel diameter when being placed at implantation site.

[0032] Present teaching provides a medical device construction using NiTiX alloys. In one embodiment of the present teaching, the medical device is configured to have a maximized X-ray visibility while balancing between the material choice of the NiTiX alloy and the shape and design of the deployed (i.e. radially expanded) medical device; specifically a balance between the atomic percentage of radiopaque element (or elements) in the NiTiX alloy, the post implantation size of the medical device, the size and number of the metallic strands / wires used in constructing the medical device, as well as the other geometrical construction factors. In another embodiment of the present teaching, an optimized visibility perimeter is provided for the purpose of leading to a balance of self-expandability and the X-ray visibility of the medical device.

[0033] Fig. 1A is a schematic illustration of X-ray projecting onto a wire of a round cross-section from a position perpendicular to the longitudinal axis of the wire. In another word, the angle 0 between the longitudinal axis of the wire and the longitudinal axis of the tubular structure (not shown in this figure) is 0° (or close to 0°). Under Fig. 1 A scenario, the longest path which X-ray travels through the wire equals to the diameter (d) of the wire as illustrated.

[0034] Fig. IB is a schematic illustration of X-ray projecting onto a wire with round cross-section from a position angled to the longitudinal axis of the wire. In this illustration, the angle 0 between the longitudinal axis of the wire and the lines of the X-ray projection (which hits the longitudinal axis of the tubular structure orthogonally) is somewhere between 0° and 90°. Under Fig. IB scenario, the longest path which X-ray travels through the wire is affected by the angle 0. Specifically the longest path which X-ray crossing ( / ’) equals toco^ .

[0035] In one embodiment, the travel distance of the x-ray through a radiopaque material significantly affects the quality of an image. As the distance increases, the amount of X-ray being absorbed also increases. The travel path of the X-ray radiation through a radiopaque material directly impacts the contrast and visibility of the structure on the radiograph. Thus, a thicker radiopaque material will appear brighter and more distinct on the image due to greater X-PATENT Attorney Docket No. PWAL-028PCT ray atenuation; while a thinner material may be less visible. As such, the greater the angle 0 between the longitudinal axis and the orthogonal lines to the X-ray projection, the greater the visibility, the brighter that portion of the wire under X-ray.

[0036] Fig. 2 is a schematic illustration where X-ray projecting onto a medical device with a general tubular wire mesh structure, for example a stent. In one embodiment of the present teaching, the medical device is formed with a plurality of round wires interwoven together with each wire wound in a helical pattern. In this illustration, the longitudinal axis of the wire mesh structure is orthogonal to the lines of the X-ray projection. In another word, the angle 0 between the longitudinal axis of the tubular wire mesh structure and the orthogonal lines to the X-ray projection is 0° (or close to 0°).

[0037] Figs. 3A-3B are schematic illustrations of one wire, in a helical winding profile, among the plurality of wires forming the wire mesh structure, in its final shape (pre-defined deployment configuration) as formed onto the medical device. Fig. 3 A is a schematic illustration of the final helical shape of a wire with narrow winding pitch and a greater angles ( <9 / ) between the wire and the longitudinal axis of the radially expanded wire mesh structure. Fig. 3B is a schematic illustration of the final helical shape of a wire in the wire mesh structure with a wider winding pitch and a smaller angles (02) between the wire and the longitudinal axis of the radially expanded wire mesh structure. As shown in Figs. 3A-3B, X-ray is projected in a direction perpendicular to the longitudinal axis of the medical device.

[0038] As the wire wound in a helical fashion, X-ray travels through segments of the wire (A, A’) along the path equaling to the diameter (d) of the wire. As the wire turns along its helical path, X-ray travels through segments of the wire (C, C’, C”, C’”), along a path equaling toco^ where 0 is the angle between the longitudinal axis of that segment of the wire and the orthogonal lines to the X-ray projection. At segment (B, B’) of the wire, which is 90° from segments (A, A’), X-ray travels the longest path through the wire. Thus under X-ray, the visibility of the metallic wire illustrated in Figs. 3A-3B in one 360° revolution increases from wire segment A until reaching a maximum at segment B, then decreases from wire segment B until reaching a minimum at segment A’, then increases from wire segment B until reaching a maximum at segment B’, follow by decreases from wire segment B’ until reaching the minimumPATENT Attorney Docket No. PWAL-028PCT at segment A. In one embodiment of the present teaching, medical device with wire mesh structure, as illustrated in Fig. 2, with the X-ray projecting in a direction perpendicular to the longitudinal axis of the medical device, exhibit brightest along its outer tubular portion (E, E’) in the particular view shown in this figure.

[0039] When comparing helical wire profile illustrated in Figs. 3A and 3B, it is clear that the helical wire with narrow winding pitch and a greater angle 01 between the wire and the longitudinal axis of the radially expanded wire mesh structure would be brighter on the radiograph comparing to wire in the helical wire mesh structure with a wider winding pitch and a smaller angle (02).

[0040] Fig. 4A-4C are schematic illustrations where X-ray projecting onto medical devices with wire mesh structure of different geometrical construction. Fig. 4 A shows a wire mesh structure with a greatest angle 0 between the wire and the longitudinal axis of the radially expanded wire mesh structure among the three figures; and Fig. 4C shows a wire mesh structure with a smallest angle 0 between the wire and the longitudinal axis of the radially expanded wire mesh structure among the three figures. The angle 0 between the wire and the longitudinal axis of the radially expanded wire mesh structure shown in Fig. 4B is in between of those shown in the Figs. 4A & 4C. Applying the conclusion presented in relation to Figs 1 A-1B, 2 & 3A-3B, the wire mesh structure with the greatest angle 0 between the wire and the longitudinal axis of the radially expanded structure, as shown in Fig. 4A, provides the greatest visibility along its outer diameter under X-ray. And the smallest angle 0 between the wire and the longitudinal axis of the radially expanded structure, as shown in Fig. 4C, provides the weakest visibility along its outer diameter under X-ray.

[0041] Thus, in one embodiment of the present teaching, a medical device is designed with a balanced approach among various factors in order to optimize both self-expandability and X-ray visibility of its wire mesh structure, such as those shown in Figs 2 and 3A-3C. To achieve an optimized design, various factors are considered. A summary of such balanced approach is the following:Dd ■ a = f - cos 0nPATENT Attorney Docket No. PWAL-028PCT

[0042] where D is the outer diameter of the wire mesh structure (when implanted in its maximum recommended vessel diameter for use); d is the wire diameter; n is the number of wires formed the wire mesh structure; 0 is the angle between the wire and the longitudinal axis of the radially expanded wire mesh structure (when implanted in its maximum recommended vessel diameter for use), as shown in Figs. 4A-4C; a is the atomic percentage of the radiopaque element (or elements); and / is the visibility factor. According to one embodiment of the present teaching, the visibility factor reflects the degree of brightness of the wire under X-ray. In one embodiment of the present teaching, the visibility factor is in the range of 0.04-0.18. that is0.04 < f < 0.18

[0043] In another embodiment of the present teaching, when the goal is to maximize the visibility of the medical device on the radiograph with wire mesh structure made of NiTiX alloy wire, the previously presented design approach is applied. In one embodiment of the present teaching, the design factors that affects the visibility factor ( / ) of the medical device includes the atomic percentage (a) of the radiopaque element (or elements) presented in the NiTiX alloy, the number of wires formed the wire mesh structure (n), the diameter of a single wire formed the wire mesh structure (d), the outer diameter of the (implanted in its recommended vessel diameter for use) wire mesh structure ( / )), and the angle between the wire and the longitudinal axis of the radially expanded (implanted in its recommended vessel diameter for use) wire mesh structure (0). For ease of understanding, the above presented design approach is transformed as following:a ■ n ■ df = - D ■ cos 0

[0044] In one embodiment of the present teaching, the above presented design approach is developed to achieve the best X-ray visibility in a medical device with wire mesh structure without comprising its self-expandability. This design approach takes into account the geometrical construction requirement of the medical device, as well as the material range of the NiTiX alloy based on its atomic percentage of the radiopaque element. For example, with a given wire diameter, and an outer diameter of the medical device, a best possible choice (i.e. atomic percentage of the radiopaque element or elements) of the NiTiX alloy could be selected.PATENT Attorney Docket No. PWAL-028PCT

[0045] In one embodiment of the present teaching, the outer diameter of the medical device ( / )), is the outer diameter of the device at the any given moment. As known to those skilled in the art, a medical device assumes a smaller outer diameter when being delivered through a catheter, and then expanded into a greater outer diameter when deployed in vivo, such as inside a blood vessel. According to one embodiment, for the same device, when the outer diameter of the medical device changes, the angle between the wire and the longitudinal axis of the wire mesh structure (0 changes accordingly. And thus the visibility factor of the medical device varies according to the outer diameter of the device at the any given moment. In one embodiment of the present teaching, the outer diameter of the medical device ( / )) is between 2.0 mm and 6.0 mm. In one embodiment of the present teaching, the outer diameter of the same medical device ( / )) could expand up to 1000% from its radially collapsed delivery profile to its radially expanded deployment profile.

[0046] In one embodiments of the present teaching, the angle (0 between the wire and the longitudinal axis of the radially expanded wire mesh structure (implanted in its recommended vessel diameter for use) is between 10° and 80°. In another embodiments of the present teaching, the angle (0 between the wire and the longitudinal axis of the radially expanded wire mesh structure (implanted in its recommended vessel diameter for use) is between 40° and 70°. This angle influences the radial expansion behavior of the wire mesh structure and the porosity of the radially expanded structure. In addition, this angle (0 influences the bending flexibility and the ability of the medical device to be delivered by catheter. This angle (0 is the angle between the wire and the longitudinal axis of the radially expanded wire mesh structure, such as illustrated in Figs. 2 and 4A-4C, which is different from the angle between the wire and the longitudinal axis of the radially compressed wire mesh structure.

[0047] In one embodiment of the present teaching, the wire size / diameter also affects the radial strength and flexibility of the medical device. In order to achieve good compressibility without compromising radial strength of the final structure, the wire diameter is between 0.025 mm-0.035 mm for the medical device used in neurovascular application.

[0048] In one embodiment of the present teaching, the number of the wires forming the wire mesh structure affects the outer diameter, the radial strength, and the flexibility of thePATENT Attorney Docket No. PWAL-028PCT medical device. In one embodiment, the number of the wires forming the wire mesh structure is between 48 and 64 for device used in vascular application.

[0049] In order to ensure that the wire mesh structure of the medical device according to the present teaching has good self-expansion capabilities, the maximum atomic percentage of the radiopaque element or elements in the NiTiX alloy used for constructing the medical device should be no more than 17%. In one embodiment of the present teaching, the atomic percentage of the radiopaque element (or elements) in the NiTiX alloy is between 7.0 - 17.0%.

[0050] In another embodiment of the present teaching, the visibility factor ( / ) is in the range of 0.04-0.18.

[0051] Although it is always the best practice for a doctor to project X-ray onto a medical device in an orthogonal direction as illustrates in Fig. 2, in practice, the projection angle could ranges from 0°-90°. When checking the deployment of the medical device, the physician works along the device’s longitudinal axis and tries to adjust almost 90° (segment by segment.) Figs. 5 is a schematic illustration where the X-ray is projecting onto a medical device with wire mesh structure in a direction non-perpendicular to the longitudinal axis of the medical device. In this embodiment under fluoroscopy, the brightest part (F, F’) of the medical device remains the same as the previously presented exemplary scenario in Figs. 2, 3A-3B, while both edges (G, G’) of the medical device appears to be brighter comparing to the exemplary scenario in Figs. 2, 3A-3B due to the angled orientation of the medical device which leads to more mass within the X-ray field. In one embodiment, despite the positioning angle between the longitudinal axis of the medical device and direction where the X-ray projects, the medical device formed with NiTiX alloy is visibly through its entire length, which provides great visual aid for device delivery, deployment, and post implantation assessment.

[0052] In one embodiment of the present teaching, wires of the same cross-sectional profile are used forming of the entire wire mesh structure. In another embodiment, at least one wire of different cross-sectional profile is used in the structure. In one embodiment of the present teaching, wires of the same size are used forming of the entire wire mesh structure. In another embodiment, at least one wire of different size (diameter) is used in the structure. In one embodiment, wires forming the entire wire mesh structure has the same cross-sectional profilePATENT Attorney Docket No. PWAL-028PCT throughout its entire length. In another embodiment, at least one wire has different cross-section profiles at different portions of the wire. In one embodiment, wires forming the entire wire mesh structure has the same size throughout its entire length. In another embodiment, at least one wire has different size at different portions of the wire. In one embodiment, wires forming the entire wire mesh structure is made of NiTiX alloy which exhibit X-ray visibility. In another embodiment, at least 25% of the wires forming the entire wire mesh structure is made of NiTiX alloy which exhibit X-ray visibility.

[0053] Various embodiments have been illustrated and described herein by way of examples, and one of ordinary skill in the art will appreciate that variations can be made without departing from the spirit and scope of the present teaching. The present teaching is capable of other embodiments or of being practiced or carried out in various other ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this present teaching belongs. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present teaching. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

Claims

PATENT Attorney Docket No. PWAL-028PCT WE CLAIM:

1. A radially self-expandable medical device comprisinga wire-mesh structure formed with a plurality of NiTiX alloy wires in a helical pattern interwoven together has a generally tubular profile; wherein the wire mesh structure has an outer diameter (D), wherein each NiTiX alloy wire has a wire diameter (d); wherein each NiTiX alloy wire in its helical shape forms an angle (0) with a tubular axis of the wire mesh structure;wherein each NiTiX alloy wire contains a radiopaque element with an atomic percentage proportional to a ratio of an outer diameter (D) of the wire mesh structure to the wire diameter (d) and a cosine angle (0 between the wire and the tubular axis of the wiremesh structure by a constant factor of 0.04-0.18.

2. The medical device of claim 1, characterized in that the atomic percentage of radiopaque material is between 7 and 17.

3. The medical device of claim 1, characterized in that the outer diameter (D) of the wire mesh structure is between 2 mm and 6 mm.

4. The medical device of claim 1, characterized in that the angle (0 between the wire and the tubular axis of the wire mesh structure is between 10° and 80°.

5. The medical device of claim 1, characterized in that the diameter (d) of the NiTiX alloy wire is between 0.025 mm and 0.035 mm.

6. The medical device of claim 1, characterized in that the NiTiX alloy is a substance of a general uniform mixture of NiTi and at least one radiopaque element with atomic number greater than 71.

7. The medical device of claim 1, characterized in that the NiTiX alloy is a substance of a general uniform mixture of Nickel Titanium alloy and Platinum.PATENT Attorney Docket No. PWAL-028PCT 8. The medical device of claim 1, characterized in that the medical device is radially compressible to fit inside a microcatheter.

9. A medical device configured to be visible under X-ray, the medical device comprising,a plurality of NiTiX alloy wires in a helical pattern interwoven together forming a wire mesh structure with a general tubular profile,wherein at least one NiTiX alloy wire is made of a substance of a generally uniform atomic mixture of Nickel, Titanium and at least one radiopaque element of an atomic number greater than 71;wherein the at least one NiTiX alloy wire contains a radiopaque element with an atomic percentage (a) proportional to a ratio of an outer diameter (D) of the wire mesh structure to the wire diameter (d) and a cosine angle (0 between the wire and the tubular axis of the wire-mesh structure and the NiTiX alloy wire by a constant factor of 0.04-0.18;wherein the at least one radiopaque element has an atomic number greater than 71.

10. The medical device of claim 11, character in that the wherein the atomic percentage of radiopaque material is between 7 and 17.

11. The medical device of claim 11, characterized in that the outer diameter (D) of the wire mesh structure is between 2 mm and 6 mm.

12. The medical device of claim 11, characterized in that the angle (0 between the wire and the tubular axis of the wire mesh structure is between 10° and 80°.

13. The medical device of claim 11, characterized in that the diameter (d) of the NiTiX alloy wire is between 0.025 mm and 0.035 mm.

14. The medical device of claim 1, characterized in that the medical device is configured to be radially compressible to fit inside a catheter; and self-expandable radially upon releasing from the catheter.

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