An electrolytic vascular occlusion device with improved delivery and enhanced MRI tracking capabilities.

Abstract

The vascular occlusion assembly comprises a vascular occlusion device configured to be placed within an aneurysm sac. The vascular occlusion device assumes a delivery configuration when confined within a delivery catheter and a deployed configuration when released from the delivery catheter into the aneurysm sac. The vascular occlusion assembly further comprises a delivery wire having a distal end to which the vascular occlusion device is attached. The delivery wire has an electrolytically separable joint proximal to the vascular occlusion device. At least a portion of the electrolytically separable joint is made of molybdenum (Mo) or an alloy thereof.

Description

Technical Field

[0001] The present disclosure generally relates to medical devices and endovascular medical procedures, and more specifically, to devices and methods for occluding vascular lesions such as aneurysms.

Background Art

[0002] Vascular occlusion devices or implants are used for various purposes including the treatment of endovascular aneurysms. An endovascular aneurysm is a local dilation of a blood vessel filled with blood, generally presenting a sac-like or balloon-like form protruding from the blood vessel, caused by disease, blood flow / blood pressure acting within the blood vessel, and / or weakening of the blood vessel wall. Endovascular aneurysms can pose a risk to the health of patients because they can have serious adverse effects on patients, such as bleeding, stroke (e.g., intracranial aneurysms), due to rupture, thrombosis, or dissection. In North America, approximately 25,000 intracranial aneurysm ruptures occur each year.

[0003] Generally used vascular occlusion devices include soft helically wound coils formed by winding platinum (or platinum alloy) wire strands around a "primary" mandrel. Subsequently, this coil is wound around a larger "secondary" mandrel and a secondary shape is imparted by heat treatment. For example, U.S. Patent No. 4,994,069, assigned to Ritchart et al. (which is hereby incorporated by reference in its entirety), describes a vascular occlusion device that takes on a linear helical primary shape when stretched for placement through the lumen of a delivery catheter and a complex secondary shape that folds when released from the delivery catheter and deployed into the vascular system. A complex three-dimensional secondary shape can be imparted to the vascular occlusion device to better fill along the contour of the aneurysm, and the rigidity / flexibility of the vascular occlusion device can be adjusted.

[0004] Various approaches exist to treat ruptured or unruptured aneurysms, including endovascular approaches that involve delivering occlusive devices into the aneurysm via an intravascular catheter. Occlusive devices are generally composed of self-expanding materials, and once deployed from the delivery system to the patient's target site, the unrestrained device expands without assistance. Self-expanding occlusive devices may be pre-energized to expand when released from the delivery catheter and / or may include shape-memory elements that allow the device to expand when exposed to pre-defined conditions. Some occlusive devices may be characterized as hybrid devices that possess the properties of both self-expanding and non-self-expanding materials.

[0005] A typical endovascular approach to deliver a vascular occlusion device into an aneurysm involves two main steps.

[0006] The first step involves using a guidewire to position a small-diameter delivery catheter or microcatheter at the aneurysm site. Typically, the distal end of the delivery catheter is given a predetermined curve of a selected shape, such as 45°, 26°, "J"-shaped, "S"-shaped, or other curved shape, depending on the patient's specific anatomical structure, by the attending physician or manufacturer. This allows the delivery catheter to remain in the desired position for releasing one or more vascular occlusion devices into the aneurysm sac after the guidewire is withdrawn. It is also desirable to make the lumen, and therefore the outer diameter, of the delivery catheter as small as possible to allow access to the aneurysm through a very narrow vascular system.

[0007] The second step involves loading the vascular occlusion device into a delivery catheter in a folded or radially compressed delivery configuration via a delivery device (e.g., a delivery wire), and then introducing it into the aneurysm sac. In some embodiments, multiple vascular occlusion devices (e.g., two) can be loaded simultaneously and then introduced sequentially into the aneurysm sac. Once delivered into the aneurysm sac, the vascular occlusion device becomes an expanded configuration and can fill and occlude the sac. The vascular occlusion device can be deformed or bent to allow for more efficient and complete filling. The vascular occlusion device is then released or "separated" from the distal end of the delivery assembly, and the delivery assembly is retracted via the delivery catheter. Depending on the patient's specific needs, one or more additional vascular occlusion devices can be pushed through the delivery catheter and released into the same aneurysm sac until the aneurysm sac is completely filled with vascular occlusion devices.

[0008] In particular, it is desirable that the occlusive device delivered into the aneurysm sac be as long as possible. That is, smaller (shorter) occlusive devices are less desirable because they may take longer and require more complex procedures to be delivered into the aneurysm sac. For example, filling a 7mm diameter nerve aneurysm sac typically requires 5 to 7 individual occlusive coils, making the procedure longer and more complex compared to reducing the number of devices. Therefore, it is important to make the occlusive device as long as possible to reduce the number of occlusive devices required to treat the aneurysm, thereby reducing the time and complexity of the procedure.

[0009] Fluoroscopy is typically used to visualize the occlusion device during delivery into the aneurysm sac, while magnetic resonance imaging (MRI) is commonly used to visualize the treatment site and confirm that the aneurysm sac is properly occluded after the procedure (e.g., several weeks after initial treatment of the aneurysm). Therefore, it is important that occlusion devices, such as occlusion coils, are configured to minimize susceptibility (i.e., be MRI compatible) to ensure radiopaqueness during aneurysm treatment while minimizing artifacts that would impair visibility on post-treatment MRI. It is also crucial that such occlusion devices are "soft" (i.e., laterally flexible and highly conformable) and therefore non-traumatic to prevent rupture of the fragile tissue of the aneurysm.

[0010] One highly desirable means of delivering a vascular occlusion device (e.g., a vascular occlusion coil) into an aneurysm sac is to use an electrolytic separation procedure, such as that described in U.S. Patent No. 5,122,136, expressly incorporated herein by reference. Such an electrolytic separation procedure involves loading a conductive delivery wire (e.g., made of stainless steel (e.g., SS316)) to which the vascular occlusion coil is attached into a delivery catheter, advancing the delivery wire distally to insert the vascular occlusion coil into the aneurysm sac, and then separating the vascular occlusion coil from the distal end of the delivery wire by passing a small current through the delivery wire to an electrolytically separable junction exposed to intravascular blood between the vascular occlusion coil and the distal end of the delivery wire. In a typical embodiment, the conductive delivery wire is coated with an electrically insulating material (e.g., stainless steel (e.g., SS316) coated with polyimide). However, a small portion of the delivery wire immediately proximal to the vascular occlusion device (e.g., less than 0.15 inches in length) is not electrically insulating, and this portion forms an electrolytically separable junction. Because the electrolytically detachable junction is not electrically insulated, it is more susceptible to electrolysis in the blood than the electrically insulating portion of the delivery wire or the occluding device. As a result, the electrolytically detachable junction dissolves substantially or completely, thereby releasing the occluding device into the aneurysm sac.

[0011] To maximize the rate of electrolysis and, consequently, the electrolytic separation performance, it is crucial that the electrical resistivity of the electrolytically separable junction is as low as possible, and that the electrochemical potential of the electrolytically separable junction is as negative as possible. Furthermore, since a portion of the electrolytically separable junction usually remains with the vascular occlusion device even after it has been electrolytically separated from the delivery wire, it is important that the electrolytically separable junction, like the vascular occlusion device itself, is configured to minimize artifacts that impair visibility during post-procedure MRI.

[0012] In particular, minimizing the lumen size of the delivery catheter while increasing the length of the vascular occlusion device, ensuring the radiopaqueness required for the vascular occlusion device during aneurysm treatment, minimizing artifacts that impair visibility during post-procedure MRI, providing the vascular occlusion device with sufficient flexibility to prevent tissue damage, and providing the minimum electrical resistivity and negative electrochemical potential to the electrolytically separable joint are all conflicting factors, presenting challenges regarding the material composition of the vascular occlusion device, and more specifically, the material composition of the electrolytically separable joint, which is crucial to this invention.

[0013] In particular, increasing the length of the occlusive device inevitably increases the friction of the occlusive device and / or the lumen size of the delivery catheter. Therefore, in order to maintain the relatively small lumen size and thus outer diameter of the delivery catheter, it is necessary to increase the column strength (buckling resistance) of the occlusive device and the unsupported electrolytically separable junction (i.e., increase Young's modulus and mechanical strength) to ensure that the occlusive device is reliably delivered into the aneurysm sac. Materials that can deliver relatively long occlusive devices via relatively small diameter delivery catheters while simultaneously satisfying other conflicting requirements such as radiopaqueness (for the occlusive device) and MRI compatibility (for both the occlusive device and the electrolytically separable junction), flexibility (for the occlusive device), low electrical resistivity and negative electrochemical potential (for the electrolytically separable junction), and biocompatibility are extremely limited.

[0014] An advantageous embodiment of a vascular occlusive device disclosed in U.S. Patent Application No. 16 / 208,860, “Vaso-Occlusive Device” (expressly incorporated herein by reference), is constructed from a gold-platinum (AuPt) alloy. Such a vascular occlusive device can be relatively long while allowing the diameter of the delivery catheter to remain relatively small, and can also provide the necessary radiopaqueness during aneurysm treatment, minimize artifacts that impair visibility during post-procedure MRI, and have the flexibility necessary to prevent tissue trauma.

[0015] However, the column strength of current electrolytically separable junctions, such as those made of SS316, is limited, and as a result, the lengthening of vascular occlusion devices achieved by using AuPt alloy in the structure of the vascular occlusion device is at least partially offset. Furthermore, the remaining portion of such electrolytically separable junctions on the vascular occlusion device side after electrolytic separation has a relatively high magnetic susceptibility, causing residual MR artifacts. This partially cancels out the MR artifact reduction effect of MRI-compatible vascular occlusion devices, potentially making post-procedure MRI difficult even when MRI-compatible vascular occlusion devices (such as those made of AuPt alloy) are used.

[0016] Therefore, there remains a need to provide electrolytically detachable junctions for relatively long vascular occlusion devices that have relatively high column strength, relatively low magnetic susceptibility, relatively low electrical resistivity, and a negative electrochemical potential. [Overview of the project]

[0017] According to the present invention, a vascular occlusion assembly comprises a vascular occlusion device (e.g., a vascular occlusion coil) configured to be placed in an aneurysm sac. The vascular occlusion device takes a delivery configuration when confined within a delivery catheter and a deployed configuration when released from the delivery catheter into the aneurysm sac. The vascular occlusion device may have a suitable length, for example, more than 5 cm. The delivery catheter may have an internal lumen (e.g., less than 0.020 inches in diameter) to which the vascular occlusion device is confined. The vascular occlusion assembly further comprises a delivery wire having a distal end to which the vascular occlusion device is attached. The delivery wire has an electrolytically separable junction proximal to the vascular occlusion device. In one embodiment, a vascular occlusion treatment system comprises a vascular occlusion assembly, a delivery catheter, and an electrolytic separation device configured to electrically connect the proximal end of the delivery wire of the vascular occlusion assembly. The electrolytic separation device is configured to supply current to the electrolytically separable junction of the vascular occlusion assembly while the vascular occlusion device is placed in the aneurysm sac, thereby electrolytically separating the vascular occlusion device from the distal end of the delivery wire.

[0018] According to a first aspect of the present invention, the electrolytically separable joint is composed of molybdenum (Mo) or an alloy containing more than 20% by weight of Mo. In one embodiment, the alloy contains more than 40% by weight of Mo. In another embodiment, the electrolytically separable joint is composed of a Mo alloy, for example, molybdenum (Mo)-rhenium (Re), molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), hafnium (Hf), or any combination thereof. In a particular embodiment, the Mo alloy is Mo-Re. In this case, the amount of Re contained in the Mo alloy exceeds 20% by weight, and may be, for example, 47.5% by weight. In other embodiments, the alloy may have a Young's modulus greater than 35 Msi, a mechanical strength greater than 400 Ksi, a magnetic susceptibility less than 300, an electrical resistivity less than 100 μσ·cm, and / or an electrochemical potential less than -0.1 V.

[0019] According to a second aspect of the present invention, the electrolytically separable joint is composed of an alloy containing molybdenum (Mo) and has a Young's modulus greater than 35 Msi. In one embodiment, the Young's modulus of the alloy exceeds 40 Msi, and in another embodiment, the Young's modulus of the alloy exceeds 45 Msi. In yet another embodiment, the alloy contains more than 20% by weight of Mo, and even more than 40% by weight of Mo. In yet another embodiment, the electrolytically separable joint is composed of Mo alloys, such as molybdenum (Mo)-rhenium (Re), molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), hafnium (Hf), or any combination thereof. In a particular embodiment, the Mo alloy is Mo-Re. In this case, the amount of Re in the Mo alloy is greater than 20% by weight, and may be, for example, 47.5% by weight. In other embodiments, the alloy may have a mechanical strength greater than 400 Ksi, a magnetic susceptibility of less than 300, an electrical resistivity of less than 100 μσ·cm, and / or an electrochemical potential of less than -0.1 V.

[0020] According to a third aspect of the present invention, the electrolytically separable joint is composed of an alloy containing molybdenum (Mo) and has a mechanical strength exceeding 400 Ksi. In one embodiment, the mechanical strength of the alloy exceeds 450 Ksi, and in another embodiment, the mechanical strength of the alloy exceeds 500 Ksi. In yet another embodiment, the alloy contains more than 20% by weight of Mo, and even more than 40% by weight of Mo. In yet another embodiment, the electrolytically separable joint is composed of Mo alloys, such as molybdenum (Mo)-rhenium (Re), molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), hafnium (Hf), or any combination thereof. In a particular embodiment, the Mo alloy is Mo-Re. In this case, the amount of Re in the Mo alloy is greater than 20% by weight, and may be, for example, 47.5% by weight. In other embodiments, the alloy may have a Young's modulus greater than 35 Msi, a magnetic susceptibility less than 300, an electrical resistivity less than 100 μσ·cm, and / or an electrochemical potential less than -0.1 V.

[0021] According to a fourth aspect of the present invention, the electrolytically separable joint is composed of an alloy containing molybdenum (Mo) and has a magnetic susceptibility of less than 300. In one embodiment, the magnetic susceptibility of the alloy is less than 200, and in another embodiment, the magnetic susceptibility of the alloy is less than 150. In yet another embodiment, the alloy contains more than 20% by weight of Mo, and even more than 40% by weight of Mo. In yet another embodiment, the electrolytically separable joint is composed of Mo alloys, such as molybdenum (Mo)-rhenium (Re), molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), hafnium (Hf), or any combination thereof. In a particular embodiment, the Mo alloy is Mo-Re. In this case, the amount of Re in the Mo alloy is greater than 20% by weight, and may be, for example, 47.5% by weight. In other embodiments, the alloy may have a Young's modulus greater than 35 Msi, a mechanical strength greater than 400 Ksi, an electrical resistivity less than 100 μσ·cm, and / or an electrochemical potential less than -0.1 V.

[0022] According to a fifth aspect of the present invention, the electrolytically separable joint is composed of an alloy having a Young's modulus greater than 35 Msi, a mechanical strength greater than 400 Ksi, and a magnetic susceptibility of less than 300. In one embodiment, the Young's modulus of the alloy is greater than 40 Msi, the mechanical strength of the alloy is greater than 450 Ksi, and the magnetic susceptibility of the alloy is less than 200. In another embodiment, the Young's modulus of the alloy is greater than 45 Msi, the mechanical strength of the alloy is greater than 500 Ksi, and the magnetic susceptibility of the alloy is less than 150. In yet another embodiment, the alloy contains Mo. For example, the alloy contains more than 20% by weight of Mo, and more than 40% by weight of Mo. In yet another embodiment, the alloy is composed of Mo alloys, such as molybdenum (Mo)-rhenium (Re), molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), hafnium (Hf), or any combination thereof. In a particular embodiment, the Mo alloy is Mo-Re. In this case, the amount of Re contained in the Mo alloy is greater than 20% by weight, and may be, for example, 47.5% by weight. In other embodiments, the alloy may have an electrical resistivity of less than 100 μσ·cm and / or an electrochemical potential of less than -0.1 V.

[0023] Other and further aspects and features of the embodiments will become apparent from the following detailed description with reference to the accompanying drawings. [Brief explanation of the drawing]

[0024] The drawings illustrate the design and utility of the preferred embodiments of the disclosed invention, and like elements are designated by common reference numerals. Note that the drawings are not drawn to scale, and that elements of similar structure or function are denoted by like reference numerals throughout the drawings. Also note that the drawings are intended only to facilitate the description of the embodiments. They are neither intended as an exhaustive description of the invention nor as a limitation on the scope of the invention, which is defined only by the appended claims and their equivalents. Also, exemplary embodiments of the disclosed invention need not have all of the disclosed aspects or advantages. Further, aspects or advantages described in connection with a particular embodiment of the disclosed invention are not necessarily limited to that embodiment and may be implemented in any other embodiment even if not so shown.

[0025] To better understand how the above and other advantages and objects of the disclosed invention are obtained, a more specific description of the disclosed invention briefly described above will be made with reference to the specific embodiments thereof shown in the accompanying drawings. It is to be understood that those drawings show only typical embodiments of the invention and are not to be considered as limiting its scope, and that the invention will be described and explained in more specific and detailed manner while using the accompanying drawings. [Figure 1] FIG. 1 is a plan view of a vascular occlusion treatment system constructed in accordance with an embodiment of the disclosed invention, particularly showing the vascular occlusion device in a delivery configuration. [Figure 2] FIG. 2 is a plan view of the vascular occlusion treatment system of FIG. 1, particularly showing the vascular occlusion device in a deployed configuration. [Figure 3] FIG. 3 is a plan view showing a state in which the vascular occlusion structure of the vascular occlusion treatment system of FIG. 1 is deployed within an aneurysm sac. [Figure 4] FIG. 4 is a partially cut-away enlarged cross-sectional view of an electrolytically detachable joint of the vascular occlusion assembly of the vascular occlusion treatment system of FIG. 1.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure is directed to a vascular occlusion assembly for use in a vascular occlusion treatment system that delivers a vascular occlusion device (e.g., a vascular occlusion coil) into a patient's vascular structure (e.g., within an aneurysm sac) via an electrolytic detachment procedure. The vascular occlusion device described herein comprises a delivery wire having an electrolytically detachable junction composed of molybdenum (Mo) or an alloy thereof, the junction having a column strength high enough to enable delivery of a relatively long vascular occlusion device with high pushing friction through a relatively small diameter delivery catheter (i.e., a microcatheter), while simultaneously having a magnetic susceptibility low enough (i.e., MRI compatibility) to minimize artifacts that would otherwise reduce visibility during postoperative MRI, and having an electrical resistivity and a negative electrochemical potential low enough to maximize electrolytic detachment performance.

[0027] Referring to FIGS. 1 and 2, an embodiment of a vascular occlusion treatment system 10 constructed in accordance with the disclosed invention will be described. The vascular occlusion treatment system 10 includes a delivery catheter 12, a vascular occlusion assembly 14 slidably disposed within the delivery catheter 12, a ground electrode 16 configured to be disposed in contact with the patient, an electrical cable 18 configured to be removably attached to the ground electrode 16, and a power source in the form of an electrolytic detachment device 20 to which the vascular occlusion assembly 14 is removably attached and to which the ground electrode 16 is removably attached via the electrical cable 18. As will be described in further detail below, the vascular occlusion assembly 14 includes a delivery wire 22 and a vascular occlusion device 24 detachably connected to the delivery wire 22 via an electrolytically detachable junction 26.

[0028] The delivery catheter 12 has a tubular structure and can take the form of, for example, a delivery catheter, a sheath, etc. The delivery catheter 12 comprises an elongated sheath body 28 having a proximal portion 30 and a distal portion 32, and an inner lumen 34 (partially shown with dashed lines) that penetrates the sheath body 28 and extends between the proximal portion 30 and the distal portion 32, and houses the vascular occlusion assembly 14. Preferably, the inner lumen 34 has a relatively small diameter, for example, less than 0.03 inches, preferably less than 0.02 inches, so that the outer diameter of the sheath body 28 can be minimized. In an alternative embodiment, the delivery catheter 12 may have a plurality of inner lumens (not shown), each housing a vascular occlusion assembly 14.

[0029] The free end of the proximal portion 30 of the sheath body 28 remains outside the patient's body and is accessible to an operator (e.g., a clinician or physician), while the rest of the sheath body 28, including the distal portion 32, is sized and sized to reach a distant site in the patient's vascular system. The sheath body 28 has a length suitable for accessing a target tissue site within the patient's body from a vascular access point. The target tissue site varies depending on the medical procedure in which the delivery catheter 12 is used. In one embodiment, the outer diameter of the sheath body 28 may be uniform along the length of the sheath body 28. In another embodiment, the outer diameter of the sheath body 28 gradually or stepwise tapers from a first outer diameter at the proximal portion 30 to a second outer diameter at the distal portion 32, thereby facilitating guidance within a winding vascular system. While the sheath body 28 is depicted as having a generally circular cross-sectional shape, it should be understood that other cross-sectional shapes or combinations of shapes, such as elliptical, rectangular, triangular, or polygonal, may also be included.

[0030] The delivery catheter 12 may include one or more regions having different configurations and / or properties along its longitudinal direction. For example, the outer diameter of the distal portion 32 of the sheath body 28 is smaller than the outer diameter of the proximal portion 30 of the sheath body 28, thereby reducing the external shape of the distal portion 32 and facilitating guidance within a tortuous vascular system. Furthermore, the distal portion 32 may be more flexible than the proximal portion 30. Generally, the proximal portion 30 is formed from a more rigid material than the distal portion 32 of the sheath body 28, so that the proximal portion 30 is easily pushed forward within the patient's vascular system, while the distal portion 32 is formed from a more flexible material, so that the distal portion 32 maintains flexibility and can more easily follow the guidewire to access remote areas within the winding regions of the vascular system. The sheath body 28 can be made from a suitable polymer material, metal and / or alloy, such as polyethylene, stainless steel, other suitable biocompatible materials, or a combination thereof. In some cases, the proximal portion 30 may include a reinforcing layer, such as a braided layer or a coiled layer, to improve the ease of inserting the sheath body 28. The sheath body 28 may include a transition region between the proximal portion 30 and the distal portion 32.

[0031] The delivery catheter 12 is equipped with a distal port 36 that communicates with the internal lumen 34 of the delivery catheter 12, from which the vascular occlusion device 24 is deployed. The delivery catheter 12 further includes a proximal adapter 38 fixed to the proximal portion 30 of the sheath body 28 by appropriate means such as adhesive or welding. The proximal adapter 38 is equipped with a central bore 40 (shown by dashed lines) that communicates with the lumen 34 of the delivery catheter 12. The central bore 40 terminates with a proximal port 42 that allows the vascular occlusion assembly 14 to be loaded into the delivery catheter 12. The proximal adapter 38 further comprises a side port 44 that communicates with the central bore 40, thereby introducing fluid into the inner lumen 34 of the delivery catheter 12, for example, to the vascular occlusion assembly 14, to introduce contrast agent into the patient's vascular system, and / or to introduce saline into the patient's vascular system, for example, to flush out the contrast agent before electrolytic separation of the vascular occlusion device 24 and delivery into the patient's vascular system.

[0032] The delivery catheter 12 further comprises one or more radiopaque marker bands 46 (in this case, two distal bands 46a and a proximal band 46b) positioned near the distal port 36 of the distal portion 32 of the delivery catheter 12, and these marker bands can be identified using medical imaging techniques (e.g., fluoroscopy). The distal band 46a can be used to position the distal tip of the delivery catheter 12 within the patient's vascular system, while the proximal band 46b can be used to position the delivery catheter 12 relative to a partially or fully deployed vascular occlusion device 24. As a result, the delivery catheter 12 and the delivery wire 22 can be aligned longitudinally, thereby ensuring that the electrolytically detachable joint 26 is positioned immediately distal to the distal port 36 of the delivery catheter 12 in contact with the bodily fluids in the patient's vascular system, allowing for easy electrolytic separation of the vascular occlusion device 24 from the delivery wire 22, as will be described in more detail below. The radiopaque marker band 46 can be made of a suitable radiopaque material, such as gold, platinum, palladium, tantalum, tungsten alloy, or polymer material with added radiopaque fillers.

[0033] In the illustrated embodiment, the delivery wire 22 has a unipolar configuration and has only the function of supplying current from the electrolytic separation device 20 to an electrolytically separable junction 26, and the current is then returned to the electrolytic separation device 20 via a ground electrode 16 positioned in contact with the patient. In this case, the delivery wire 22 may only have a power terminal (not shown) for supplying current from the electrolytic separation device 20 to the electrolytically separable junction 26. In an alternative embodiment, the delivery wire 22 may have a bipolar configuration and have the function of supplying current to the electrolytically separable junction 26 and returning current from the junction. In this case, the delivery wire 22 has a bipolar terminal (not shown) located on the proximal portion 52 of the core wire 48, which allows for supplying current from the electrolytic separation device 20 to the electrolytically separable junction 26 and returning current from the electrolytically separable junction 26 to the electrolytic separation device 20.

[0034] Typically, the vascular occlusion device 24 can be inserted into the patient's body by first inserting the delivery catheter 12 into the patient's vascular system (e.g., minimally invasively) to reach the aneurysm site. When the delivery catheter 12 is used to access the vascular system in the brain from the femoral artery access point in the patient's groin, the total length of the sheath body 28 can be 125 cm to 200 cm. The diameter of the delivery catheter 12 is also made as small as possible. For example, the distal portion 32 of the sheath body 28 can have a relatively small outer diameter (e.g., less than 3F) and a relatively small inner diameter (i.e., the size of the lumen 28) (e.g., less than 0.020 inches, e.g., 0.015 inches to 0.025 inches, preferably 0.015 inches to 0.018 inches).

[0035] The delivery catheter 12 can be used in an "over-the-wire" manner, in which case the delivery catheter 12 is introduced into the patient's body along a pre-introduced guidewire, and the delivery catheter 12 extends along the entire length of the guidewire (not shown). Alternatively, the delivery catheter 12 can be used in a "rapid exchange" manner, in which case the guidewire extends only through the distal portion of the delivery catheter 12 from a guidewire port (not shown). In yet another alternative embodiment, after the guidewire is withdrawn, the delivery catheter 12 may be inserted into the patient's body while leaving the distal portion of the sheath or access catheter at the target site. This allows the delivery catheter 12 to navigate through the patient's blood vessels via the sheath or access catheter.

[0036] At the aneurysm site, as shown in Figure 3, the vascular occlusion device 24 can be pushed distally from the delivery catheter 12 placed in the parent vessel V via the delivery wire 22 and introduced into the aneurysm sac A through the aneurysm neck N. After being pushed out from the delivery catheter 12, the vascular occlusion device 24 can self-expand into a predetermined shape, as described later. Once the vascular occlusion device 24 is inserted into the aneurysm sac A, it can be electrolytically separated from the delivery wire 22, as described further below. A sufficient number of vascular occlusion devices 24 can be delivered to fill and occlude the aneurysm sac A. Alternatively, before its electrolytic separation, the vascular occlusion device 24 can be removed or withdrawn by pulling it proximal to the delivery wire 22 and re-stored in the delivery catheter 12.

[0037] Generally, the vascular occlusion device 24 takes a delivery configuration (Figure 1) when constrained within the delivery catheter 12, and a deployed configuration (Figure 2) that conforms to the internal shape of the aneurysm sac A when deployed from the delivery catheter 12 into the aneurysm sac A. The vascular occlusion device 24 can be pre-biased to form a cylindrical, conical, or other desired external shape. The vascular occlusion device 24 is highly flexible, and its overall shape is easily deformable. In the illustrated embodiment, the vascular occlusion device 24 is shown as a helical coil formed of wire having an appropriate diameter, for example, 1 to 6 mils. The diameter of the vascular occlusion device 24 in the delivery configuration can be, for example, 10 to 30 mils. The length of the vascular occlusion device 24 can be any desired appropriate length, for example, 1 to 60 cm, depending on the site to be occluded. In alternative embodiments, the vascular occlusion device 24 can take the form of a structure other than a coil, for example, a braid. The vascular occlusion device 24 can optionally be covered with or connected to a fibrous material tied to the outside of the coil or braid. The vascular occlusion device 24 can be made of a suitable biocompatible, radiopaque material such as platinum, gold, tungsten, iridium, or alloys thereof, or other metals. In one advantageous embodiment, the vascular occlusion device 24 is made of a gold-platinum (AuPt) alloy (e.g., AuPt34) which has been demonstrated to have good column strength, good radiopaqueness, and good MRI compatibility (disclosed in U.S. Patent Application No. 16 / 208,860, expressly incorporated herein by reference, “Vaso-Occlusive Device”). Thus, the length of the vascular occlusion device 24 can be relatively long (e.g., more than 5 cm, e.g., in the range of 5 cm to 45 cm). In the illustrated embodiment, the vascular occlusion device 24 has an end cap or tip that prevents puncture of the aneurysm sac A when delivered into the aneurysm sac A.

[0038] The delivery wire 22 is a coil, tendon, wire, etc. (e.g., a conventional guide wire, a torque-transmitting cable tube, or a hypo tube) and has sufficient column strength to push the vascular occlusion device 24 into the aneurysm sac A. The delivery wire 22 can have an appropriate outer diameter (e.g., 10-30 mils) and an appropriate length (e.g., 50-300 cm). The material used to construct the delivery wire 22 is selected to give different flexibility and stiffness properties to different parts of the delivery wire 22. For example, the delivery wire 22 can be formed of different materials along its length, for example, materials with different elastic moduli, resulting in differences in flexibility.

[0039] In the illustrated embodiment, the delivery wire 22 comprises a core wire 48 made of a conductive material and a sleeve 50 made of an electrically insulating material such as polytetrafluoroethylene, polyurethane, polyethylene, polypropylene, or other suitable polymer material. The core wire 48 has a proximal portion 52 that extends proximal to the proximal portion 30 of the delivery catheter 12 for manipulation by a physician, a distal portion 54 to which the vascular occlusion device 24 is attached, and an intermediate portion 56 located between the proximal portion 52 and the distal portion 54. The proximal portion 52 of the core wire 48 is enlarged to facilitate ergonomic manipulation of the delivery wire 22 by a physician. The proximal portion 52 of the core wire 48 tapers distally toward the intermediate portion 56. The distal portion 54 of the core wire 48 extends from the intermediate portion 56 and tapers further distally, providing flexibility to the distal end of the delivery wire 22. The delivery wire 22 may include a coil (not shown) attached around the distal portion 54 of the core wire 48, thereby providing some column strength to the distal end of the delivery wire 22 without adversely affecting the flexibility of the tapered distal portion 54 of the core wire 48. The sleeve 50 is positioned on the distal portion 54 of the core wire 48 and serves to electrically insulate the portion of the distal portion 54 of the core wire 48 that is proximal to the electrolytically detachable junction 26 of the delivery wire 22 from the blood in the patient's vascular system, as described later. The delivery wire 22 further comprises a radiopaque marker band 58 positioned on the sleeve 50, which can be identified using medical imaging techniques (e.g., fluoroscopy).The marker band 58 can be used to position the delivery catheter 12 relative to the partially or fully deployed vascular occlusion device 24 (by aligning it with the proximal marker 46b of the delivery catheter 12), thereby aligning the delivery catheter 12 and the delivery wire 22 longitudinally, thereby ensuring that the electrolytically detachable joint 26 is positioned in contact with the body fluids in the patient's vascular system just distal to the distal port 36 of the delivery catheter 12, and as a result, the vascular occlusion device 24 can be easily electrolytically separated from the delivery wire 22, as described later. The radiopaque marker band 58 can be made of a suitable radiopaque material, such as gold, platinum, palladium, tantalum, tungsten alloy, or polymer material with radiopaque filler added.

[0040] Referring further to Figure 4, the vascular occlusion device 24 is fixed to the distal portion 56 of the core wire 48 via an electrolytically resistant bushing 60. The electrolytically detachable junction 26 takes the form of an electrolytically detachable segment for electrolytically separating the vascular occlusion device 24 from the delivery wire 22, and is located on the core wire 48 between the electrically insulating sleeve 50 and the vascular occlusion device 24. Therefore, when current is supplied to the core wire 46, the current flows through the electrolytically detachable junction 26. However, since the electrolytically detachable junction 26 is not electrically insulated, it is more susceptible to electrolytic dissolution in the blood than the portion of the core wire 48 covered by the electrically insulating sleeve 50 and the vascular occlusion device 24. Therefore, when current is applied to the core wire 48, the electrolytically detachable junction 26 dissolves, releasing the vascular occlusion device 24. Preferably, the length of the electrolytically detachable junction 26 is not significantly greater than the diameter of the electrolytically detachable junction 26. For example, the length of the electrolytically separable joint 26 is short, at 0.001 inches, and can typically be 0.010 inches or less.

[0041] In the illustrated embodiment, the grounding electrode 16 takes the form of a metal clip configured to be detachably attached to a subcutaneous injection needle (not shown) inserted percutaneously into the patient's body, for example, in the thigh or groin, thereby electrically coupling the grounding electrode 16 to the patient and forming an electrical circuit that electrically connects the vascular occlusion assembly 14 to the grounding electrode 16 via the conductive patient.

[0042] The electrolytic separation device 20 is operated by a physician and can perform an electrolytic separation process. The electrolytic separation device 20 comprises an outer casing 62, a power terminal 64 to which a core wire 48 is electrically connected, a ground terminal 66 to which a ground electrode 16 is electrically connected via an electrical cable 18, electronic components (not shown) housed within the outer casing 62 for supplying current in a controlled manner to the electrolytically separable joint 26 of the vascular occlusion assembly 14, and an electrolytic separation actuator 70 mounted on the outer casing 62 for manually initiating the flow of current from the electrolytic separation device 20 to the electrolytically separable joint 26 of the vascular occlusion assembly 14.

[0043] The outer casing 62 is constructed of a suitable material, such as acrylonitrile butadiene styrene (ABS) or polycarbonate, and is shaped and sized to allow a physician to hold it ergonomically with one hand. In the illustrated embodiment, the power terminal 64 takes the form of a port (e.g., a funnel) through which the proximal portion 52 of the core wire 48 can be alternately inserted and removed, while the ground terminal 66 takes the form of a port through which the corresponding plug 88 of the electrical cable 18 can be alternately inserted and removed. The electronic components are configured to supply current to the electrolytically detachable junction 26 of the vascular occlusion assembly 14 during one or more electrolytic separation cycles until the vascular occlusion device 24 is electrolytically separated from the delivery wire 22, to detect the electrolytic separation of the vascular occlusion device 24 from the delivery wire 22, and to report various events occurring during the electrolytic separation process to the physician via various indicators 86. Further details regarding such electronic components are described in U.S. Provisional Application No. 63 / 486,183, entitled "Vaso-Occlusive Electrolytic Detachment Detection," which is expressly incorporated herein by reference.

[0044] In the illustrated embodiment, the electrolytic separation actuator 70 takes the form of a push button, which can be pressed to manually instruct the electrolytic separation device 20 to perform an electrolytic separation cycle (i.e., a period during which current is supplied from an electronic component (not shown) to the electrolytically detachable junction 26 of the vascular occlusion assembly 14). Activating the push button 70 once (i.e., pressing briefly and then releasing) starts the electrolytic separation cycle. Activating the push button 70 multiple times can start a series of electrolytic separation cycles. That is, the push button 70 can be activated to start a first electrolytic separation cycle, and then, after the first electrolytic separation cycle is completed, the push button 70 can be activated again to start a second electrolytic separation cycle, and so on.

[0045] In particular, it is important that the electrolytically detachable junction 26 has the column strength necessary to facilitate the delivery of a relatively long vascular occlusion device 24 (e.g., more than 5 cm) via a relatively small diameter delivery catheter 12 (e.g., one with a lumen 34 diameter of less than 0.03 inches). Furthermore, it is important that at least the distal portion of the electrolytically detachable junction 26 (i.e., its distal portion) is MRI compatible, as it is likely to remain with the vascular occlusion device 24 even after the vascular occlusion device 24 has been electrolytically separated from the delivery wire 22. In addition, it is important that the electrolytically detachable junction 26 has good electrolytic separation performance.

[0046] The inventors have found that molybdenum (Mo) and certain metal alloys thereof, as well as any combination thereof, can provide a column strength sufficiently high to facilitate the delivery of a relatively long vascular occlusion device 24 through a relatively small diameter delivery catheter 12 to an electrolytically separable joint 26, even if it is relatively small in diameter, while simultaneously providing MRI compatibility to minimize artifacts that impair visibility during post-treatment MRI, and providing relatively high electrolytic separation performance. Therefore, at least the distal portion of the electrolytically separable joint 26, and preferably the entire electrolytically separable joint 26 from the viewpoint of ease of manufacture, and even the entire core wire 48 in some embodiments, can be made of Mo or a specific Mo-containing alloy.

[0047] For example, compared to SS316, which has a Young's modulus of approximately 29 million pounds per square inch (29 Msi) and a mechanical strength in the range of 270,000 to 330,000 pounds per square inch (270 to 330 Ksi), molybdenum has a Young's modulus of 47.1 Msi and a mechanical strength in the range of 400 to 500 Ksi. Also, compared to SS316, which has a magnetic susceptibility in the range of 3570 to 6700, Mo has a magnetic susceptibility of 123. Furthermore, compared to SS316, which has an electrical resistivity of 74 microsiemens per centimeter (μσ·cm) and an electrochemical potential of less than -0.5 volts (V), Mo has a remarkably low electrical resistivity of 5.5 microsiemens per centimeter (μσ·cm) and an electrochemical potential of less than -0.2 volts (V). Therefore, it can be seen that the electrolytically separable joint 26 made of Mo has significantly higher column strength (approximately 50% higher strength and 62% higher rigidity) than the electrolytically separable joint 26 made of SS316, and also has superior MRI compatibility and equivalent electrolytic separation performance.

[0048] By combining specific metals with Mo, alloys can be obtained that can be used to construct electrolytically separable joints 26, which have even higher column strength and simultaneously provide the required MRI compatibility and electrolytic separation performance. For example, in order to give the electrolytically separable joints 26 the high column strength required, the alloy used to construct the electrolytically separable joints 26 must have a Young's modulus greater than 35 million pounds per square inch (35 Msi) and a mechanical strength greater than 400,000 pounds per square inch (400 Ksi), preferably a Young's modulus greater than 40 Msi and a mechanical strength greater than 450 Ksi, and more preferably a Young's modulus greater than 45 Msi and a mechanical strength greater than 500 Ksi. Furthermore, in order to give the electrolytically separable joints 26 the required MRI compatibility, the alloy used to construct the electrolytically separable joints 26 must have a magnetic susceptibility of less than 300, preferably less than 200, and more preferably less than 150. Furthermore, in order to provide the electrolytic separation performance required for the electrolytically separable joint 26, the alloy used to construct the electrolytically separable joint 26 must have an electrical resistivity of less than microsiemens (μσ·cm) per 100 centimeters, preferably less than 75 μσ·cm, more preferably less than 50 μσ·cm, and must have an electrochemical potential of less than -0.1 volts (V). The weight percentage of Mo in such an alloy is preferably greater than 20%, and more preferably greater than 40%, to ensure that the resulting electrolytically separable joint 26 has the required MRI compatibility. The alloy can be, for example, a Mo alloy, meaning that the weight ratio of Mo contained in the alloy is higher than that of any other component in the alloy.

[0049] Certain Mo alloys (molybdenum containing 47.5 percent rhenium by weight (Mo-47.5Re)) have a Young's modulus of 52.9 Msi, a mechanical strength in the range of 600-800 Ksi, a magnetic susceptibility of 110, an electrical resistivity of 22 μσ·cm, and an electrochemical potential of less than -0.4 volts (V). Therefore, it can be seen that an electrolytically separable junction 26 composed of Mo-47.5Re has even higher column strength (more than 100% stronger and 82% harder) than an electrolytically separable junction 26 composed of SS316, while also having better MRI compatibility and at least equivalent electrolytic separation performance. Experimental studies using a prototype bipolar delivery wire have shown that an electrolytically separable joint 26 made of Mo-47.5Re with a diameter of 0.002 inches and a length of 0.002 inches has an average electrolytic separation time of 7.4 seconds, which is comparable to the electrolytic separation time of a 0.002-inch electrolytically separable joint 26 made of SS316. The electrolytic separation time of an electrolytically separable joint 26 with a diameter of 0.00175 inches made of Mo-47.5Re is expected to be reduced to 5-6 seconds. While Mo-Re alloys are described as containing 47.5 percent rhenium by weight, the weight ratio of rhenium in other Mo-Re alloys (or other Mo-containing alloys) can range, for example, from 20-60%.

[0050] Other types of Mo alloys that can satisfy the above-mentioned ranges of Young's modulus, mechanical strength, magnetic susceptibility, and electrical resistivity include molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), and hafnium (Hf). In contrast, other types of alloys that do not contain Mo (or contain only a relatively small amount of Mo by weight), such as cobalt (Co) alloys, have low Young's modulus and mechanical strength and / or relatively high magnetic susceptibility, making them unsuitable for use at certain weight ratios.

[0051] While this specification discloses and describes specific embodiments, those skilled in the art will understand that they are not intended to limit the disclosed invention. Furthermore, it will be apparent to those skilled in the art that various changes, substitutions, and modifications (e.g., dimensions of various parts, combinations of parts) can be made without departing from the scope of the disclosed invention as defined solely by the following claims and their equivalents. Therefore, this specification and the drawings should be interpreted as illustrative, not restrictive. The various embodiments disclosed and described herein are intended to encompass alternatives, modifications, and equivalents of the disclosed invention, which are included within the scope of the appended claims.

Claims

1. A vascular occlusion assembly, A vascular occlusion device configured to be placed in an aneurysm sac, having a delivery configuration when constrained within a delivery catheter and a deployment configuration when released from the delivery catheter into the aneurysm sac, A delivery wire having a distal end to which the vascular occlusion device is attached, wherein the delivery wire has an electrolytically separable joint proximal to the vascular occlusion device, the electrolytically separable joint is made of molybdenum (Mo) or an alloy thereof, and the alloy has at least one of a Young's modulus greater than 35 Msi, a mechanical strength greater than 400 Ksi, and a magnetic susceptibility less than 300. A vascular occlusion assembly characterized by comprising the following:

2. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the alloy has at least two of the following: a Young's modulus greater than 35 Msi, a mechanical strength greater than 400 Ksi, and a magnetic susceptibility of less than 300.

3. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the alloy has a Young's modulus greater than 35 Msi, a mechanical strength greater than 400 Ksi, and a magnetic susceptibility of less than 300.

4. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the alloy has a Young's modulus greater than 35 Msi.

5. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the alloy has a mechanical strength exceeding 400 Ksi.

6. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the alloy has a magnetic susceptibility of less than 300.

7. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized by containing more than 20% by weight of Mo in the alloy.

8. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized by containing more than 40% by weight of Mo in the alloy.

9. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the electrolytically separable joint portion is made of Mo alloy.

10. In the vascular occlusion assembly according to claim 9, A vascular occlusion assembly characterized in that the Mo alloy is selected from the group consisting of molybdenum (Mo)-rhenium (Re), molybdenum (Mo)-tungsten (W), molybdenum (Mo)-rhodium (Rh), molybdenum (Mo)-iridium (Ir), molybdenum (Mo)-platinum (Pt), molybdenum (Mo)-palladium (Pd), molybdenum (Mo)-gold (Au), molybdenum (Mo)-tantalum (Ta), molybdenum (Mo)-niobium (Nb), molybdenum (Mo)-zirconium (Zr), molybdenum (Mo)-cerium (Ce), hafnium (Hf), and any combination thereof.

11. In the vascular occlusion assembly according to claim 10, A vascular occlusion assembly characterized in that the Mo alloy is molybdenum (Mo)-rhenium (Re).

12. In the vascular occlusion assembly according to claim 11, A vascular occlusion assembly characterized in that the amount of Re contained in the Mo alloy exceeds 20% by weight.

13. In the vascular occlusion assembly according to claim 11, A vascular occlusion assembly characterized in that the amount of Re contained in the Mo alloy is 47.5% by weight.

14. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the alloy has an electrical resistivity of less than 100 μσ·cm.

15. In the vascular occlusion assembly according to claim 1, The aforementioned alloy is characterized by having an electrochemical potential of less than -0.1V, and is used as a vascular occlusion assembly.

16. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the length of the vascular occlusion device exceeds 5 cm.

17. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the vascular occlusion device is a vascular occlusion coil.

18. In the vascular occlusion assembly according to claim 1, A vascular occlusion assembly characterized in that the delivery catheter has an inner lumen in which the vascular occlusion device is restrained, and the diameter of the inner lumen is less than 0.020 inches.

19. A vascular occlusion treatment system, The vascular occlusion assembly according to claim 1, The delivery catheter and A vascular occlusion treatment system characterized by being equipped with the following features.

20. In the vascular occlusion treatment system according to claim 16, A vascular occlusion treatment system further comprising an electrolytic separation device configured to electrically connect the proximal end of the delivery wire of the vascular occlusion assembly, wherein the electrolytic separation device is configured to supply current to an electrolytically separable joint of the vascular occlusion assembly while the vascular occlusion device is placed in the aneurysm sac, thereby electrolytically separating the vascular occlusion device from the distal end of the delivery wire.

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