Delivery system for deploying a self-expanding tube and method for deploying a self-expanding tube

Abstract

In one arrangement, a delivery system for deploying a self-expanding tube into a blood vessel is provided, comprising: a tubular member configured to be inserted into the blood vessel, an elongated body extending within a lumen of the tubular member, and the self-expanding tube disposed radially between the tubular member and the elongated body. The delivery system is configured to operate in a deployed mode in which, after at least a portion of the self-expanding tube has been deployed, during retraction of the elongated body in use, there is longitudinal relative movement between the elongated body and a portion of the self-expanding tube that remains engaged with the elongated body, the retraction of the elongated body comprising longitudinal movement of the elongated body relative to the tubular member toward a proximal end of the delivery system.

Description

Technical Field

[0001] The present invention relates to systems and methods for deploying self-expanding tubes, particularly self-expanding tubes for redirecting blood flow away from an aneurysm sac. Background Art

[0002] An intracranial aneurysm is an area of ​​weakness in the wall of a cerebral artery where dilation or bulging of the artery wall may occur. Histologically, a reduction in the tunica media, the muscularis media, and the internal elastic lamina of the artery creates a structural defect. These defects, combined with hemodynamic factors, lead to aneurysm exstrophy. Intracranial aneurysms are fairly common conditions with a prevalence of 1% to 5% in the adult population, based on autopsy studies. In the United States alone, 10 to 12 million people may have an intracranial aneurysm.

[0003] Current methods for treating intracranial aneurysms include surgical clipping and endovascular coil embolization. In the surgical clipping method, the patient's skull is opened and surgical clips are placed at the neck of the aneurysm to stop blood from flowing into the aneurysm sac. This method is relatively risky, especially for elderly or medically complex patients. Endovascular coil embolization is a less invasive method that involves placing one or more coils delivered through a catheter into the aneurysm until the aneurysm sac is completely filled with coils. It helps trigger a blood clot within the aneurysm. Although endovascular coil embolization is considered safer than surgical clipping, it has its own limitations. First, after the aneurysm is filled with coils, it will retain its original size. As a result, the pressure exerted by the aneurysm on the surrounding tissue is not eliminated. Second, this procedure is not very effective for wide-necked aneurysms because the coils may extend into the parent vessel. This problem can be alleviated by using a stent combined with coil embolization, but the procedure is difficult and time-consuming.

[0004] The use of self-expanding tubes (sometimes called stents) alone to treat aneurysms is a promising approach to avoid the above problems. In this approach, a tube with a relatively low porosity area is placed at the neck of the aneurysm in such a way that the blood flow is redirected away from the aneurysm sac and the formation of thrombi within the aneurysm is triggered. Because the aneurysm itself solidifies naturally, the risk of rupture is low. In addition, because this method does not involve coils, the aneurysm gradually shrinks as the thrombus is absorbed. Therefore, the pressure applied to the surrounding tissue can be eliminated. However, it is difficult to optimally deploy the self-expanding tube in this case. The tube must be flexible enough to pass through and adapt to the shape of the very tortuous blood vessels in the brain, while providing sufficient coverage (low porosity) to redirect blood flow away from the aneurysm to a sufficient extent. The tube needs to be deployed reliably and controllably with minimal risk of damage to the tube or surrounding tissue.

[0005] Some current methods of deploying a self-expanding tube or stent into a blood vessel involve the use of a catheter and a guidewire, wherein the stent in its compressed form is wrapped around the guidewire within the catheter. Once the catheter is positioned approximately in the correct position relative to the aneurysm, the stent is deployed from the catheter by extending the guidewire beyond the end of the catheter.

[0006] A deployed stent expands radially and contracts longitudinally relative to its compressed state, so the guidewire must typically be extended beyond the catheter tip, well beyond the final position of the stent end. This introduces the risk that the guidewire could damage the vessel or temporarily occlude a perforator vessel during deployment if it is extended far beyond the final stent position, particularly if applied to very narrow and tortuous vessels of the brain. Summary of the invention

[0007] One object of the present invention is to provide a device and a method for improving the process of deploying a self-expanding tube, in particular in the case of treating an intracranial aneurysm. In particular, one object of the present invention is to provide a device and a method for deploying a self-expanding tube, wherein the risk of damaging the vessel caused by the guidewire of the delivery system is reduced. Another object of the present invention is to provide a device and a method that allows a self-expanding tube to be deployed more accurately into a vessel.

[0008] According to a first aspect of the present invention, there is provided a delivery system for deploying a self-expanding tube into a blood vessel, comprising: a tubular member configured to be inserted into the blood vessel, an elongated body extending within the lumen of the tubular member, and a self-expanding tube radially disposed between the tubular member and the elongated body, wherein the delivery system is configured to operate in a deployment mode, in which a first longitudinal engagement force acting between the self-expanding tube and the tubular member and a second longitudinal engagement force acting between the self-expanding tube and the elongated body are such that: during deployment of the self-expanding tube in use, there is substantially no longitudinal relative movement between the elongated body and any portion of the self-expanding tube that remains engaged with the elongated body, deployment of the self-expanding tube comprising longitudinal movement of the tubular member relative to the elongated body toward a proximal end of the delivery system; and after at least a portion of the self-expanding tube has been deployed, during retraction of the elongated body in use, there is longitudinal relative movement between the elongated body and a portion of the self-expanding tube that remains engaged with the elongated body, retraction of the elongated body comprising longitudinal movement of the elongated body relative to the tubular member toward a proximal end of the delivery system.

[0009] By configuring the delivery system so that the elongated body (guidewire) can move relative to the self-expanding tube when the guidewire is retracted, an incremental deployment method is enabled, wherein during deployment of the self-expanding tube, the guidewire is prevented from extending a significant distance beyond the end of the delivery system.

[0010] In one embodiment, for reverse retraction of the self-expanding tube relative to the tubular member, the first longitudinal engagement force is greater after a portion of the self-expanding tube has been deployed out of the tubular member than when the self-expanding tube has not been deployed out of the tubular member. This configuration enables the self-expanding tube to be more easily positioned within a delivery catheter by allowing the self-expanding tube to be easily moved distally and proximally prior to deployment.

[0011] In one embodiment, the self-expanding tube is configured to self-expand from a radially contracted state to a radially expanded state in a process involving longitudinal shortening of the self-expanding tube relative to the longitudinal axis of the tubular member, and a greater first longitudinal engagement force is achieved by engagement of the radially expanded and longitudinally contracted portion of the self-expanding tube with the distal end of the tubular member. By configuring the delivery system so that movement of the guidewire relative to the self-expanding tube is achieved by expansion of a portion of the self-expanding tube, it is ensured that the self-expanding tube and the elongated body can freely move back and forth in the proximal and distal directions within the tubular member before expansion begins.

[0012] In one embodiment, the distal end of the elongated body includes a distal engagement member configured to detachably engage the self-expanding tube. Providing an engagement member allows the self-expanding tube to be retrieved even after it has been substantially expanded if any deployment error or other event occurs during the deployment process that necessitates completely aborting insertion of the self-expanding tube.

[0013] In one embodiment, at least a portion of the self-expanding tube engages outwardly with the tubular member and inwardly with the elongated body over at least 50% of the length of the self-expanding tube. The engagement of the self-expanding tube with the tubular member and the elongated body over most of its length distributes the engagement forces applied to the self-expanding tube over a greater length. This reduces the likelihood of damaging the self-expanding tube due to excessive force applied to a small area of ​​the tube.

[0014] In one embodiment, one or both of the composition and surface texture of the inner surface of the tubular member is uniform over the length of the tubular member in contact with the self-expanding tube. In one embodiment, one or both of the composition and surface texture of the outer surface of the elongated body is uniform over the length of the elongated body in contact with the self-expanding tube. These embodiments ensure consistent behavior during all stages of deployment and reduce the possibility of damaging the self-expanding tube.

[0015] In one embodiment, the self-expanding tube has a porosity of less than 85% when deployed. This embodiment allows the self-expanding tube to effectively redirect blood flow away from the aneurysm once deployed.

[0016] According to a second aspect of the present invention, there is provided a delivery system for deploying a self-expanding tube into a blood vessel, comprising: a tubular member configured to be inserted into the blood vessel, an elongated body extending within the lumen of the tubular member, a self-expanding tube radially disposed between the tubular member and the elongated body, and a retaining member configured to selectively apply a retaining force longitudinally to a proximal region of the self-expanding tube, wherein the delivery system is configured to operate in a retraction mode, in which application of the retaining force allows longitudinal relative movement between the elongated body and a portion of the self-expanding tube that remains engaged with the elongated body during longitudinal movement of the self-expanding tube in a proximal direction relative to the elongated body.

[0017] In some cases, it may be necessary to recover the self-expanding tube after it has been at least partially deployed, for example if the self-expanding tube has been deployed in an incorrect position. Another example is if the self-expanding tube moves significantly in the vessel after deployment has begun, deployment must be initiated again to ensure correct placement of the self-expanding tube. In such cases, it is advantageous to provide a delivery system with an operating mode in which additional force can be applied to the self-expanding tube to pull it back into the tubular member by sliding it relative to the elongated body. This means that the self-expanding tube can be retracted and redeployed even if the elongated body has not been fully extended below the deployed portion of the expansion tube due to the use of a deployment mechanism as described above.

[0018] In one embodiment, in the retraction mode, the retention force is applied such that: during longitudinal movement of the elongated body relative to the tubular member toward the proximal end of the delivery system in use, there is substantially no longitudinal relative movement between the elongated body and any portion of the self-expanding tube that remains engaged with the elongated body. This embodiment reduces the likelihood of damage to the self-expanding tube due to relative movement between the tube and the elongated body during retraction.

[0019] In one embodiment, the retaining member is configured to detachably engage with the proximal region of the self-expanding tube. By applying additional retaining force using a detachable retaining member, the self-expanding tube can be more easily released from the delivery system when deployment has been successfully completed.

[0020] In one embodiment, the proximal region of the self-expanding tube includes a proximal engagement member, and the retaining member is configured to detachably engage with the proximal engagement member. This embodiment provides a convenient way to apply a retaining force to the self-expanding tube. It also provides flexibility in the mechanism for applying the force.

[0021] In one embodiment, the retaining member comprises a retaining tube radially disposed between the elongated body and the self-expanding tube, and at least a portion of the self-expanding tube engages inwardly with the retaining tube and outwardly with the tubular member. An engaging tube is a convenient and easy to implement way to engage the self-expanding tube. Because the retaining tube engages with other cylindrical members of the delivery system, it further reduces the possibility of misalignment.

[0022] In one embodiment, the engagement of the proximal region with the retaining member is such that when the proximal region is deployed beyond the distal end of the tubular member, the proximal region disengages from the retaining member. In this embodiment, when the self-expanding tube is deployed far enough, the self-expanding tube automatically disengages from the retaining member. This further simplifies the process of releasing the stent from the rest of the delivery system when deployment of the self-expanding tube is complete.

[0023] According to a third aspect of the present invention, there is provided a delivery system for deploying a self-expanding tube into a blood vessel, the delivery system being configured to operate in a deployment mode and comprising: a tubular member configured to be inserted into the blood vessel, an elongated body extending within the lumen of the tubular member, and a self-expanding tube radially disposed between the tubular member and the elongated body, wherein the self-expanding tube comprises an elongated frame capable of reversibly converting from a radially expanded and longitudinally contracted state to a radially contracted and longitudinally expanded state, and a distal region of the elongated body comprises two end markers.

[0024] The two end markings on the elongated body can be used to guide an operator of the delivery system during deployment of the self-expanding tube. The end markings are spaced apart at predetermined distances that can be selected to correspond to characteristic lengths as part of the deployment process. This provides an in-situ distance measurement for the operator to more clearly and accurately determine these distances, simplifying operation of the delivery system and allowing the operator to obtain more consistent and accurate results.

[0025] In one embodiment, the distance between the end markers is equal to within 20% of the length of the self-expanding tube in a radially expanded and longitudinally contracted state. An important measurement during deployment is the final expanded length of the self-expanding tube. Since the self-expanding tube is maintained in its longitudinally expanded state prior to deployment, this is not typically easily determined in situ by an operator. Spacing the end markers by a predetermined distance corresponding to or within a fraction of the final length of the self-expanding tube allows the operator to more easily determine this distance during operation of the delivery system.

[0026] In one embodiment, the self-expanding tube includes markings at the distal end of the self-expanding tube. In addition to the markings on the guidewire, the markings on the self-expanding tube improve the ability to correctly set the self-expanding tube and the ability to judge the movement and positioning of the self-expanding tube relative to the elongated body.

[0027] In one embodiment, the tubular member includes markings located at the distal end of the tubular member. Including markings on the tubular member also allows for easier determination of the position of the elongated body and / or the self-expanding tube relative to the tubular member.

[0028] In one embodiment, the marker comprises a radiopaque marker. A radiopaque marker is a particularly convenient form of marker that can be easily detected using X-ray imaging during deployment of the self-expanding tube in a patient. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which like reference numerals indicate like parts, and in which:

[0030] Figure 1 is a schematic side cross-sectional view of a distal portion of a delivery system for deploying a self-expanding tube into a blood vessel according to an embodiment of the first aspect of the present invention;

[0031] Figure 2 for Figure 1 A schematic end-on cross-sectional view of a delivery system of ;

[0032] Figure 3 is a schematic side cross-sectional view depicting a deployment stage of a self-expanding tube, wherein the tubular member is longitudinally retracted relative to the elongated body;

[0033] Figure 4 To depict Figure 3 a schematic side cross-sectional view of a deployment stage subsequent to the stage depicted in , wherein the elongated body is retracted relative to the tubular member;

[0034] Figure 5 Depicted Figure 4 The deployment stage follows the stage depicted in , in which the self-expanding tube is almost fully deployed;

[0035] Figure 6 is a schematic side cross-sectional view of a distal portion of a delivery system for deploying a self-expanding tube into a blood vessel according to an embodiment of the second aspect of the present invention;

[0036] Figure 7 is a schematic side cross-sectional view of a distal portion of a delivery system for deploying a self-expanding tube into a blood vessel according to an embodiment of the third aspect of the present invention. DETAILED DESCRIPTION

[0037] Embodiments of the present disclosure provide a delivery system 2 for deploying a self-expanding tube 6 into a blood vessel. The self-expanding tube 6 may be referred to as a stent. In a preferred embodiment, the tube 6 is configured to be positioned above the opening of an aneurysm sac to redirect blood flow away from the aneurysm sac. The redirection of blood flow is preferably sufficient to promote the formation of a thrombus within the aneurysm sac.

[0038] According to an embodiment of the first aspect, the delivery system 2 comprises a tubular member 4 configured to be inserted into a blood vessel. The distal end of the tubular member 4 is depicted at Figure 1 and Figure 2 The tubular member may be referred to as a catheter. Tubular members 4 configured for such use are well known in the art of minimally invasive surgery. The tubular member 4 is typically cylindrical and sized so that its distal end can be brought to the area to be treated within the body. In the case of treating a cerebral aneurysm, the tubular member 4 will be configured so that it can be guided to the opening of the aneurysmal sac in the vasculature of the brain. This is typically achieved by providing a flexible tubular member that can be bent or flexed to conform to the patient's vasculature.

[0039] The delivery system 2 also includes an elongated body 8 extending within the lumen of the tubular member 4. The elongated body 8 may be hollow or solid. In an embodiment, the elongated body 8 is a wire.

[0040] The self-expanding tube 6 to be deployed by the delivery system 2 is radially disposed between the tubular member 4 and the elongated body 8. The self-expanding nature of the tube 6 causes the tube 6 to engage (i.e., squeeze) the tubular member 4 outwardly. In addition, at least a portion of the tube 6 engages inwardly with the elongated body 8 over at least a defined length of the tube 6. Thus, at least a portion of the tube 6 engages (e.g., directly or indirectly contacts radially) both the tubular member 4 and the elongated body 8 over at least a defined length of the tube 6. In an embodiment, the defined length is 50%, optionally 60%, optionally 70%, optionally 80%, optionally 90%, optionally 95%, optionally all, or substantially all of the length of the tube 6.

[0041] The delivery system 2 is configured to operate in a deployment mode in which the self-expanding tube can be deployed out of the tubular member and released into a patient's blood vessel. Deployment of the tube 6 is achieved by longitudinal retraction of the tubular member 4 relative to the elongated body 8 or longitudinal advancement of the elongated body 8 relative to the tubular member 4, which allows the tube 6 to expand outward on its own and leave the delivery system 2 by disengaging from the elongated body 8. The tubular member 4 and the elongated body 8 are configured such that: in the deployment mode of the delivery system 2, a first longitudinal engagement force acting between the self-expanding tube 6 and the tubular member 4 and a second longitudinal engagement force acting between the self-expanding tube 6 and the elongated body 8 are such that during deployment of the self-expanding tube 6 in use, there is substantially no longitudinal relative movement between the elongated body 8 and any portion of the self-expanding tube 6 that remains engaged with the elongated body 8, and deployment of the self-expanding tube 6 includes longitudinal movement relative to the elongated body 8 toward the proximal end of the tubular member 4 of the delivery system 2.

[0042] In order to achieve the required functionality, for the reverse deployment of the self-expanding tube 6, the first longitudinal engagement force between the tubular member 4 and the self-expanding tube 6 is weaker than the second longitudinal engagement force between the self-expanding tube 6 and the elongated body 8 at each position along the length of the self-expanding tube 6. In its simplest form, this can be achieved by providing a relatively low friction connection between the self-expanding tube 6 and the tubular member 4 and a relatively high friction connection between the self-expanding tube 6 and the elongated body 8. Alternatively or in addition, the outer surface of the elongated body 8 can be provided with a plurality of preformed or rigid protrusions 14. In use, the protrusions 14 engage with the pores of the self-expanding tube 6, thereby increasing the longitudinal engagement force acting between the self-expanding tube 6 and the elongated body 8. For example, the preformed protrusions can be formed by molding or wire forming. In an embodiment, the outer surface of the elongated body 8 is formed of a material that is soft above a predetermined temperature, the tube 6 is placed against the elongated body 8, and the surface is soft, thereby forming the protrusions, and the assembly is cooled until the protrusions harden and become rigid (self-supporting). In one exemplary embodiment, the protrusions 14 are provided by a plurality of ring elements 12, each ring element having protrusions 14 regularly spaced along the circumference of the ring element 12. However, it will be appreciated that many other configurations may be used.

[0043] In one embodiment, for reverse deployment of the self-expanding tube 6 relative to the tubular member 4, the maximum first longitudinal engagement force achievable is less than the maximum second longitudinal engagement force achievable. This ensures that the self-expanding tube 6 does not slide relative to the tubular member 4 during deployment.

[0044] The maximum force available as described herein refers to the static friction between the elements when they are not moving. Once the elements of the delivery system 2 begin to move relative to each other during deployment or retraction, the friction will change depending on the speed of movement and any other forces applied. Therefore, the maximum force available between two elements refers to the static force that resists the change of the state of the delivery system 2 from the state where the two elements are stationary relative to each other to the state where the elements move relative to each other.

[0045] The engagement between the tubular member 4 and the self-expanding tube 6 can be achieved by direct contact between the two elements or through an intermediate element (such as a coating or other structure). The engagement between the self-expanding tube 6 and the elongated body 8 can be achieved by direct contact between these elements or through an intermediate element (such as a coating or structure).

[0046] The tubular member 4 and the slender body 8 are further configured so that: a first longitudinal engagement force acting between the self-expanding tube 6 and the tubular member 4 and a second longitudinal engagement force acting between the self-expanding tube 6 and the slender body 8 cause: after at least a portion of the self-expanding tube 6 has been deployed, during the retraction of the slender body 8 during use, there is a longitudinal relative movement between the slender body 8 and a portion of the self-expanding tube 6 that remains engaged with the slender body 8, and the retraction of the slender body 8 includes a longitudinal movement of the slender body 8 relative to the tubular member 4 toward the proximal end of the delivery system 2.

[0047] This can be achieved by configuring the delivery system 2 so that: for reverse retraction of the self-expanding tube 6 relative to the tubular member 4, the maximum first longitudinal engagement force that can be obtained after a portion of the self-expanding tube 6 has been deployed outside the tubular member 4 is greater than the maximum second longitudinal engagement force that can be obtained.

[0048] Figures 3 to 5 Depicted are stages in an exemplary deployment process using delivery system 2, according to an embodiment. Figure 3 Depicted is a diagram after the tubular member 4 has been longitudinally retracted relative to the elongated body 8 (indicated by the arrow showing relative movement to the left). Figure 1 and Figure 2 Delivery system 2. Relative movement can be provided by keeping elongated body 8 stationary and retracting tubular member 4, by keeping tubular member 4 stationary and advancing elongated body 8, or a combination of both. As tubular member 4 retracts, the growing distal region of tube 6 is no longer radially constrained and expands outward. As tube 6 expands outward, it also shortens longitudinally. This causes the distal end 9 of elongated body 8 to eventually protrude further from tubular member 4 than the distal end 7 of tube 6.

[0049] Protrusion of the elongated body 8 prior to deployment of the tube 6 may be undesirable. For example, protrusion may create a risk that the elongated body 8 may be undesirably advanced into tissue and cause injury. This risk may be mitigated by configuring the elongated body 8 to be relatively soft and pliable. However, this may limit the range of materials that may be used for the elongated body 8, and thus this solution may not be suitable for all situations.

[0050] Figure 4 Depicted is an exemplary deployment process using an embodiment of the delivery system 2. Figure 3 The stage after the stage shown in . In an embodiment, the problem of protrusion of the slender body 8 is solved by configuring the first longitudinal engagement force and the second longitudinal engagement force, which configuration makes: as described above, in the deployment mode of the delivery system 2, after at least a portion of the self-expanding tube 6 has been deployed, during the retraction of the slender body 8, there is a longitudinal relative movement between the slender body 8 and the self-expanding tube 6. Therefore, the longitudinal engagement force is configured so that the possibility of relative movement between the slender body 8 and the self-expanding tube 6 is asymmetric between the deployment of the self-expanding tube 6 and the retraction of the slender body 8. In an embodiment in which the slender body 8 includes a protrusion 14, this can be achieved by providing the protrusion with an asymmetric shape. As further described below, alternative embodiments are also possible.

[0051] The feature of "the first and second longitudinal engagement forces are configured such that after at least a portion of the self-expanding tube 6 has been deployed, during the retraction of the elongated body 8, there is a longitudinal relative movement between the elongated body 8 and the self-expanding tube 6" allows the elongated body 8 or the guidewire to move or slide relative to the self-expanding tube 6 when the elongated body 8 is retracted, so that the elongated body 8 can be retracted without also retracting the self-expanding tube 6. This in turn allows the elongated body 8 to be pulled back into the tubular member 4 and prevents the distal end 9 of the elongated body 8 from extending beyond the distal end 5 of the tubular member 4 by more than a predetermined distance.

[0052] exist Figure 4 In the deployment phase shown, the elongated body 8 is retracted relative to the tubular member 4, while not substantially affecting the proportion of the self-expanding expansion tube 6 beyond the distal end of the tubular member 4. However, in the deployment mode of the delivery system 2, it is not necessary that the self-expanding tube 6 does not retract during the retraction of the elongated body 8. Partial retraction of the self-expanding tube 6 is acceptable as long as the distance that the elongated body 8 is retracted relative to the tubular member 4 is greater than the distance that the self-expanding tube 6 is retracted relative to the tubular member 4. This allows the elongated body 8 to move relative to the self-expanding tube 6 in the proximal direction.

[0053] By allowing the elongated body 8 to retract relative to the tubular member 4 and the self-expanding tube 6, the likelihood that the elongated body 8 will cause damage to the blood vessel or any other surrounding tissue in which the self-expanding tube 6 is deployed is significantly reduced.

[0054] As the expansion process continues, Figure 5 As shown, more and more of the self-expanding tube 6 reaches the expanded state. However, as described above, due to the configuration of the first and second longitudinal engagement forces, the distal end 9 of the elongated body 8 can be prevented from protruding beyond the predetermined threshold before the distal end 5 of the tubular member 6.

[0055] In an embodiment, for reverse retraction of the self-expanding tube 6 relative to the tubular member 4, the first longitudinal engagement force is greater after a portion of the self-expanding tube 6 has been deployed out of the tubular member 4 than when the self-expanding tube 6 has not been deployed out of the tubular member 4. Changing the first longitudinal engagement force after a portion of the self-expanding tube 6 has been deployed provides greater flexibility in how the delivery system 2 can be handled. For example, it allows the self-expanding tube 6 to freely move forward and backward in the proximal and distal directions within the tubular member 4 with the elongated body before a portion of the self-expanding tube 6 is deployed.

[0056] In one embodiment, the first longitudinal engagement force for reverse retraction of the self-expanding tube 6 is less than the second longitudinal engagement force when the self-expanding tube 6 is not deployed. This allows the self-expanding tube 6 to be easily disposed within the tubular member 4 prior to deployment. In such an embodiment, the properties of the tubular member 4 and the elongated body 8 must be carefully designed so that the change in the first longitudinal engagement force is such that the desired asymmetry in the movement of the elongated body 8 relative to the self-expanding tube 6 between deployment of the self-expanding tube 6 and retraction of the elongated body 8 is obtained after deployment of at least a portion of the self-expanding tube 6, but not before deployment of at least a portion of the self-expanding tube 6.

[0057] In one embodiment, the self-expanding tube 6 is configured to self-expand from a radially contracted state to a radially expanded state in a process involving longitudinal shortening of the self-expanding tube 6 relative to the longitudinal axis of the tubular member 4, and to achieve a greater first longitudinal engagement force by engagement of the radially expanded and longitudinally contracted portion of the self-expanding tube 6 with the distal end of the tubular member 4. This mechanical engagement of the self-expanding tube 6 with the tubular member 4 is a convenient way to cause a change in the friction force between the self-expanding tube 6 and the tubular member 4.

[0058] In one embodiment, for reverse retraction of the self-expanding tube 6 relative to the tubular member 4, the maximum first longitudinal engagement force that can be obtained after a portion of the self-expanding tube 6 has been deployed outside the tubular member 4 is greater than the maximum second longitudinal engagement force that can be obtained. This configuration of the first and second longitudinal engagement forces allows the slender body 8 to move relative to the self-expanding tube 6.

[0059] In one embodiment, the distal end 9 of the elongated body 8 includes a distal engagement member configured to detachably engage the self-expanding tube 6. For example, the distal engagement member can be used to ensure that the self-expanding tube 6 remains in its radially contracted loaded position prior to deployment.

[0060] Furthermore, in some cases, it may be desirable to be able to retract the self-expanding tube 6 after at least a portion of the self-expanding tube 6 has been deployed. For example, if the self-expanding tube 6 is accidentally moved during deployment, or if the operator realizes that the self-expanding tube 6 is incorrectly placed. Therefore, in one embodiment, the distal engagement member is also configured such that: when the distal engagement member is engaged with the self-expanding tube 6, the maximum second longitudinal engagement force that can be obtained is greater than the maximum first longitudinal engagement force that can be obtained. In such an embodiment, the distal engagement member can be used to allow the self-expanding tube 6 to be recaptured or retracted into the tubular member 4 and thus removed from the blood vessel.

[0061] According to a preferred embodiment, the delivery system 2 can be used as part of a method for deploying a self-expanding tube into a blood vessel for the purpose of redirecting blood flow away from the aneurysm sac. In an embodiment of this method, deploying the self-expanding tube 6 includes: deploying a portion of the self-expanding tube 6 by longitudinally moving the tubular member 4 toward the proximal end of the delivery system 2 relative to the elongated body 8, retracting the elongated body 8 by longitudinally moving the elongated body 8 toward the proximal end of the delivery system 2 relative to the tubular member 4, and repeating the steps of deploying a portion of the self-expanding tube 6 and retracting the elongated body 8 until the self-expanding tube 6 is released from the delivery system 2 by self-expansion of the self-expanding tube 6.

[0062] This incremental deployment method afforded by the use of the delivery system 2 as described above allows for the elongated body 8 to be prevented from protruding beyond the distal end of the tubular member 4 by more than a predetermined distance at any point during deployment of the self-expanding tube 6 .

[0063] In one embodiment of the method, the self-expanding tube 6 is configured to self-expand from a radially contracted state to a radially expanded state in a process involving longitudinal shortening of the self-expanding tube 6 relative to the longitudinal axis of the tubular member 4, and the steps of deploying a portion of the self-expanding tube 6 and retracting the slender body 8 are implemented so that: during the deployment of the self-expanding tube 6, the distance that the distal end 9 of the slender body 8 extends from the distal end 5 of the self-expanding tube 6 is not greater than twice the length of the self-expanding tube 6 in the radially expanded and longitudinally contracted state at any time, and is optionally equal to the length of the self-expanding tube 6 in the radially expanded and longitudinally contracted state or half of that length.

[0064] When deployed in a self-expanded state, the delivery system 2 of the disclosed embodiments is particularly suitable for deploying a self-expanding tube 6 having a low porosity, preferably less than 85%, optionally less than 70%, optionally less than 60%, optionally less than 50%. Such porosity is effective for redirecting blood flow away from the aneurysm sac when the self-expanding tube is deployed above the opening of the aneurysm sac. Therefore, in one embodiment, the self-expanding tube 6 is configured to redirect blood flow away from the aneurysm sac when deployed above the opening to the aneurysm sac.

[0065] The term porosity p refers to the ratio of the surface area of ​​the open area to the total external surface area occupied by the material of the self-expanding tube 6, such as the frame of the interconnecting arms. The total external surface area is the sum of the surface area of ​​the open area and the surface area of ​​the area occupied by the frame material. When the frame is cylindrical, the total external surface area is only 2π.RL, where R is the radius of the cylinder and L is the length of the cylinder.

[0066] The self-expanding tube 6 may include an elongated frame. The frame may include a shape memory alloy, such as nitinol. Alternatively, the frame may include stainless steel, a polymer or other biocompatible material. The frame may include a network of interconnected arms. The frame may be formed, for example, by laser cutting a hollow tube, by 3D printing, or by other techniques known in the art for making such structures. All interconnected arms may be arranged at the same radius and without any overlap in the radial direction.

[0067] Consider a frame with porosity ρ in the fully radially expanded state. If the radius and length of the frame in the fully radially expanded state are R 0 and L 0 , then the minimum radius R that the frame can reach in the radially contracted state (defined by the state where the porosity becomes zero) is min It is specified by the following formula:

[0068]

[0069] Among them, L 1 is the length of the frame in the radially contracted state. This relationship assumes that the elements of the frame are not allowed to overlap each other in the radial direction.

[0070] This relationship states that the radius can only be reduced by a factor of ρ if the length of the frame is not allowed to change significantly. Since ρ needs to be very low (e.g., less than 80%, at least in low porosity areas such as those intended for placement above the opening to the aneurysm sac), this represents a significant limitation on the degree to which the tube can be narrowed for delivery to the region of interest. For example, if the porosity ρ of the frame is 20%, and the length of the frame is not allowed to change during radial contraction, i.e., L 1 =L 0, then the frame can only achieve a maximum radius reduction of 20%. Providing a frame that can be longitudinally expanded when in a radially contracted state is based on this understanding and allows a greater radius reduction to be achieved. For example, if the length is allowed to double, i.e. L 1 =2.L 0 , then for 20% porosity, the framework can achieve a 60% radius reduction.

[0071] In one embodiment, the longitudinal shortening of the self-expansion tube 6 includes shortening by at least 20%, optionally at least 30%, optionally at least 50%, and optionally at least 75% in a direction parallel to the longitudinal axis 10 of the tubular member 4 between a state where the self-expansion tube 6 is completely within the tubular member 4 (radially) and a state where the self-expansion tube 6 is completely out of the tubular member 4 (and has been expanded).

[0072] In some cases, it may be necessary to partially or completely recapture the self-expanding tube 6 after at least a portion of the self-expanding tube 6 has been deployed into the patient's blood vessel. This may be because, for example, the self-expanding tube 6 was initially incorrectly positioned, or if the deployed portion of the self-expanding tube 6 moved during the deployment process, it will be incorrectly positioned if deployment continues. While these situations are uncommon with the delivery system 2 operating correctly, allowing the self-expanding tube 6 to be retracted provides a failsafe in difficult situations and gives peace of mind to the patient and operator of the delivery system 2 that any errors in deployment can be more easily corrected.

[0073] According to a second aspect, a delivery system 2 for deploying a self-expanding tube 6 into a blood vessel is provided, comprising: a tubular member 4 configured to be inserted into a blood vessel, an elongated body 8 extending within the lumen of the tubular member 4, the self-expanding tube 6 radially arranged between the tubular member 4 and the elongated body 8, and a retaining member 30 configured to selectively apply a retaining force longitudinally to a proximal region of the self-expanding tube 6.

[0074] Figure 6 is a schematic side view of an embodiment of the second aspect. The tubular member 4, the self-expanding tube 6 and the elongated body 8 are substantially the same as described above. The retaining member 30 allows an additional retaining force to be applied to the self-expanding tube 6. Thus, the delivery system 2 is configured to operate in a retracted mode, in which the application of the retaining force allows longitudinal relative movement between the elongated body 8 and a portion of the self-expanding tube 6 that remains engaged with the elongated body 8 during longitudinal movement of the self-expanding tube 6 in the proximal direction relative to the elongated body 8.

[0075] This allows the self-expansion tube 6 to be retracted relative to the tubular member 4. This can be accompanied by movement of the elongated body 8 relative to the tubular member 4 in the proximal direction, although this is not required, and in some embodiments, during the retraction of the self-expansion tube 6, the elongated body 8 and the tubular member 4 are substantially stationary relative to each other.

[0076] As described above, when the features of the retracted mode and the retention member 30 are provided in combination with a delivery system 2 configured to operate in the deployed mode, the asymmetry of the possible relative movement between the self-expanding tube 6 and the elongated body 8 can be reversed in the retracted mode compared to the deployed mode. This is achieved by carefully selecting the magnitude of the retention force applied using the retention member 30 relative to the first and second longitudinal engagement forces. The retention force can take the form of a tension force applied by the retention member 30 to the proximal region of the self-expanding tube 6 in the proximal direction.

[0077] In one embodiment, in the retraction mode, the application of the retaining force is such that during the longitudinal movement of the slender body 8 relative to the tubular member 4 toward the proximal end of the delivery system 2 during use, there is essentially no longitudinal relative movement between the slender body 8 and any portion of the self-expanding tube 6 that retains engagement with the slender body 8.

[0078] In such an embodiment, the lack of movement of the elongated body 8 relative to the self-expanding tube 6 reduces the likelihood of damage to the self-expanding tube 6 due to wear or deformation of any portion of the self-expanding tube 6 in an unintentional manner. It also reduces the amount of retention force that the retaining member 30 must apply to the self-expanding tube 6 because no second longitudinal engagement force must be overcome in addition to the first longitudinal engagement force to move the self-expanding tube 6 in the proximal direction. This further reduces the risk of damage to the self-expanding tube 6.

[0079] In one embodiment, in the retracted mode, for reverse deployment of the self-expanding tube 6 relative to the tubular member 4, the sum of the retention force and the first longitudinal engagement force is greater than the maximum achievable second longitudinal engagement force.

[0080] This embodiment allows the elongated body 8 to move in the distal direction relative to the self-expanding tube 6 in the retracted mode. In the case where the delivery system 2 is such that the elongated body 8 is prevented from extending beyond the end of the tubular member 4 by more than a predetermined distance, retracting the self-expanding tube 6 and the elongated body 8 together at the same rate may result in a portion of the self-expanding tube 6 not being engaged with the elongated body 8 inside the tubular member 4. This is because the self-expanding tube 6 will expand longitudinally as it is retracted into the tubular member 4 and radially contracts. The lack of support for the self-expanding tube 6 by the elongated body 8 inside the tubular member 4 may result in damage to the self-expanding tube 6, which may make it difficult or dangerous to redeploy the tube for the patient. Allowing the elongated body 8 to move distally relative to the tube 6 can be used to ensure that the tube 6 is always properly engaged with the elongated body 8 inside the tubular member 4, while maintaining the advantage of preventing the elongated body 8 from extending too far beyond the distal end of the tubular member 4.

[0081] In one embodiment, in the retraction mode, for the reverse retraction of the self-expanding tube 6 relative to the tubular member 4, the maximum first longitudinal engagement force that can be obtained is less than the sum of the retaining force and the second longitudinal engagement force. This embodiment represents the selection of the relative magnitude of the force that allows the self-expanding tube 6 to retract relative to the tubular member 4, as described above.

[0082] In one embodiment, the retaining member 30 is configured to detachably engage with the proximal region of the self-expanding tube 6. This embodiment provides the advantage of more easily completing the deployment of the self-expanding tube 6. The detachable engagement may be provided by any suitable means, for example, a hook on the retaining member 30 configured to engage with the structure of the self-expanding tube 6. Other alternatives include electrolytic attachment, in which the retaining member 30 and the self-expanding tube 6 are engaged by a dissolvable metal element that can be dissolved once the self-expanding tube 6 has been fully deployed.

[0083] In one embodiment, the proximal region of the self-expanding tube 6 includes a proximal engagement member 32, and the retaining member 30 is configured to detachably engage with the proximal engagement member 32. Figure 6 In the particular example shown, two proximal engagement members 32 are provided, but generally any number of proximal engagement members 32 may be provided.

[0084] The proximal engagement member 32 may be engaged with the retaining member 30 by any suitable mechanism. Figure 6 In an embodiment of the present invention, the proximal engagement member 32 comprises a solid block that engages with a groove in the retaining member 30. However, other mechanisms are possible, such as a hook-shaped proximal engagement member that engages with a loop on the retaining member 30, or vice versa. The separation of the proximal engagement member 32 from the retaining member 30 can be directly controlled by the operator through an actuation mechanism provided at the proximal end of the delivery system 2. Alternatively, as further described below, the separation can be substantially automatic.

[0085] In one embodiment, the retaining member 30 includes a retaining tube radially disposed between the elongated body 8 and the self-expanding tube 6, and at least a portion of the self-expanding tube 6 engages inwardly with the retaining tube and outwardly with the tubular member 4. Figure 6 As shown, providing the retaining member 30 in the form of a retaining tube provides the advantage that the retaining member 30 is securely and consistently disposed relative to the other components of the delivery system 2. Ensuring that the self-expanding tube 6 is inwardly engaged with the retaining tube provides a convenient way to allow the retaining member 30 to engage with the self-expanding tube 6 and apply a retaining force.

[0086] In one embodiment, the engagement of the proximal region of the self-expanding tube 6 with the retaining member 30 is such that when the proximal region is deployed beyond the distal end of the tubular member 4, the proximal region is disengaged from the retaining member 30. This embodiment is advantageous because it means that the operator does not need to take additional actions to complete the deployment of the self-expanding tube 6, which simplifies the deployment process and reduces the possibility of error. A variety of different mechanisms can be used to provide this feature. Figure 6 In the illustrated embodiment, as described above, the retaining tube combined with the proximal engagement member 32 means that once the proximal region of the self-expanding tube is no longer constrained outwardly by the tubular member 4, the self-expansion of the proximal region of the self-expanding tube 6 will cause the proximal engagement member 32 to detach from the retaining member 30. In an alternative embodiment, the self-expanding tube 6 and the retaining member 30 are connected by a dissolvable element, wherein the dissolvable element dissolves when exposed to the vascular environment and releases the self-expanding tube 6 from the delivery system 2.

[0087] When using a self-expanding tube 6 that can reversibly transition from a radially expanded and longitudinally contracted state to a radially contracted and longitudinally expanded state, it is helpful during the deployment process to be able to determine how far the self-expanding tube 6 has been deployed in a single motion or movement of the elongated body 8. This is because the length of a portion of the self-expanding tube 6 that is compressed prior to deployment does not correspond to the length of the same portion once deployed. This makes it difficult to keep track of how much of the tube 6 has been deployed in a single motion.

[0088] In particular, when using the incremental deployment mechanism described above, in which the elongated body 8 is alternately deployed and then retracted relative to the self-expanding tube 6, a balance needs to be struck between two elements. The first element is not to extend the elongated body 8 too far beyond the end of the tubular member 4 before retracting the elongated body 8 again relative to the self-expanding tube 6. As previously described, extending the elongated body 8 too far will risk damaging the blood vessel. The second element is not to extend the elongated body 8 too short a distance beyond the end of the tubular member 4 in each step, which will result in too many deployment / retraction cycles to deploy the self-expanding tube 6. A large number of deployment / retraction cycles increases the complexity and difficulty of the deployment process, thereby increasing the possibility of user error. The optimal deployment distance for each iteration of the cycle will find a balance between these two elements. Placing markings on the elongated body 8 can provide the operator with guidance on the optimal distance by which the elongated body 8 is deployed in each deployment / retraction cycle.

[0089] The markings on the elongated body 8 may also be used for other purposes, such as correctly positioning the self-expanding tube 6 during the deployment process. It is beneficial for the operator to be able to determine the position where the self-expanding tube 6 should be deployed during the deployment process to properly cover the neck of the aneurysm. In many prior art devices, since the degree of longitudinal retraction depends on the degree of radial expansion, which itself depends on the exact size and shape of the blood vessel in which the self-expanding tube 6 is deployed, it is impossible to accurately predict the final length of the self-expanding tube 6. This is particularly true when using a self-expanding tube 6 that is primarily composed of a wire mesh. Therefore, if markings are included on the elongated body 8, they are typically included only at the distal end of the elongated body 8, corresponding to the position of the distal end of the self-expanding tube 6 at the beginning of the deployment process. This generally does not provide the user with sufficient guidance for placing the self-expanding tube 6, because the position of the distal end is not a good indication of the final position of the proximal end, and therefore, the self-expanding tube 6 may be easily placed incorrectly, requiring time-consuming and potentially difficult retraction and re-deployment of the stent.

[0090] However, when using a self-expanding tube 6 design as described herein, the longitudinal contraction and radial expansion that occur upon deployment are substantially independent, and the final length of the tube 6 is more consistent and predictable. This makes it possible to include markings on the elongated body 8 at a distance that represents the final deployed length of the self-expanding tube 6. These markings help locate the self-expanding tube 6 during deployment, thereby ensuring that the self-expanding tube 6 will properly cover the neck of the aneurysm and that there is no risk of the self-expanding tube 6 later moving.

[0091] Figure 7A delivery system 2 for deploying a self-expanding tube 6 into a blood vessel is depicted, comprising: a tubular member 4 configured to be inserted into a blood vessel, an elongated body 8 extending within the lumen of the tubular member 4, and the self-expanding tube 6 radially disposed between the tubular member 4 and the elongated body 8, wherein the self-expanding tube 6 comprises an elongated frame capable of reversibly transforming from a radially expanded and longitudinally contracted state to a radially contracted and longitudinally expanded state, and a distal region of the elongated body 8 comprises two end markers 20.

[0092] In one embodiment, the distance L between the end markers 20 is equal to within 20%, optionally within 10%, optionally within 5% of the length of the self-expanding tube 6 in its radially expanded and longitudinally contracted state. Due to the fact that the self-expanding tube 6 contracts longitudinally when deployed, the distance L between the end markers 20 before the self-expanding tube is deployed is significantly less than the length of the self-expanding tube 6 in its radially contracted and longitudinally expanded state. This feature can help position the self-expanding tube 6 during deployment. In one embodiment, the optimal deployment distance for a single deployment / retraction cycle is 10% to 90%, optionally 25% to 75% of the final length of the self-expanding tube 6 in its longitudinally contracted and radially expanded state.

[0093] In one embodiment, the distance L between the end markers 20 is equal to within 2 mm, optionally within 1 mm, and optionally within 0.5 mm of the length of the self-expanding tube 6 in the radially expanded and longitudinally contracted state. In the case where the self-expanding tube 6 is used to treat cerebral aneurysms, this represents a suitable spacing of the size of the self-expanding tube 6 suitable for treating cerebral aneurysms.

[0094] In such Figure 7 In the illustrated embodiment, the self-expanding tube 6 includes a marking 22 located at the distal end 7 of the self-expanding tube 6. In one embodiment, the self-expanding tube 6 also includes a marking 24 located at the proximal end of the self-expanding tube 6. These markings 22, 24 make it easier for the operator to determine where the end of the self-expanding tube 6 is during the deployment process, and can be aligned with the end marking 20 on the elongated body 8.

[0095] In the previously described embodiments of the delivery system 2, the use of the end markers 20 is particularly advantageous, wherein the first and second longitudinal engagement forces are configured such that the elongated body 8 can be retracted relative to the self-expanding tube 6. This is because they provide a reference that allows the operator to extend the self-expanding tube 6 to a consistent and / or optimal length in each deployment / retraction cycle. In one embodiment, the tubular member 4 includes a marker located at the distal end of the tubular member 4. The marker on the tubular member 4 can be used as a reference relative to the marker on the elongated body 8, so that the elongated body 8 is retracted to the same position relative to the tubular member 4 and is deployed the same distance relative to the tubular member 4 in each deployment / retraction cycle.

[0096] The elongated body 8 can also be repositioned throughout the deployment process so that the end marker 20 can be used to monitor whether movement of the delivery system 2 during deployment has affected the final position of the self-expanding tube 6. In embodiments where the self-expanding tube 6 includes one or more markers 22, 24, the end marker 20 on the elongated body 8 can be aligned with the markers on the self-expanding tube 6 and used as a ruler to check whether the deployment of the self-expanding tube 6 has properly placed it relative to the aneurysm.

[0097] In one embodiment, the markers 20, 22, 24 include radiopaque markers. X-ray imaging is commonly used to monitor the deployment of stents in blood vessels, so radiopaque markers are particularly suitable for devices designed for such procedures. In addition, in order to improve the visibility of the delivery system 2 to the operator during the deployment process, the elongated body 8 can include a radiopaque wire, and / or at least a portion of the self-expanding tube can be composed of a radiopaque wire. The radiopaque wire can include a wire made entirely or partially of a material selected according to its opacity to the type of radiation used for imaging.

[0098] The markings 20, 22, 24 may be in the form of spots or bands placed on or within the elongated body 8 and / or the self-expanding tube 6. Alternatively, the markings may comprise rings around the circumference of the elongated body 8 or the self-expanding tube 6. The use of ring-shaped markings may be advantageous in allowing the markings to be more clearly seen regardless of the relative orientation of the delivery system 2 and the imaging system used to monitor the procedure.

[0099] In embodiments where the self-expanding tube 6 includes a marker 24 disposed at the proximal end of the self-expanding tube 6 , the marker 24 also functions as a proximal engagement member 32 .

[0100] The delivery system including the end marker 20 is suitable for a method of deploying a self-expanding tube 6 into a blood vessel, wherein deploying the self-expanding tube 6 comprises: deploying a portion of the self-expanding tube 6 by longitudinally moving the tubular member 4 relative to the elongated body 8 toward the proximal end of the delivery system 2 (or equivalently moving the elongated body 8 longitudinally in the distal direction relative to the tubular member 4), retracting the elongated body 8 by longitudinally moving the elongated body 8 relative to the tubular member 4 toward the proximal end of the delivery system 2, and repeating the steps of deploying a portion of the self-expanding tube 6 and retracting the elongated body 8 until the self-expanding tube 6 is released from the delivery system 2 by self-expanding the self-expanding tube 6, wherein during at least one repetition of the step of deploying a portion of the self-expanding tube 6, the distance deployed by the self-expanding tube 6 is equal to within 25%, optionally within 15%, optionally within 10%, and optionally within 5% of the distance between the end markers 20. In this method, the end markers 20 provide a function as a reference for the operator so that the self-expanding tube 6 is deployed to a consistent distance. In one embodiment, the distance L between the markers 20 is selected to correspond to an optimal distance. The optimal distance may need to be equal to the distance that balances the above two factors or within the distance range that balances the above two factors, for example, within 10%, that is, avoiding extending the slender body 8 too far beyond the distal end of the tubular member 4 at each repetition of the deployment step, and avoiding too many deployment steps required to deploy the self-expansion tube 6.

[0101] In one embodiment, the optimal distance is related to the length of the self-expanding tube in the radially expanded and longitudinally contracted state. For example, as the distance between the end marks suggested above, the optimal distance can be equal to within a predetermined percentage of the length of the self-expanding tube in the radially expanded and longitudinally contracted state, such as 25%-75%.

[0102] In one embodiment, one or both of the composition and surface texture of the inner surface of the tubular member 4 is arranged to be uniform over the length of the tubular member 4 in contact with the self-expanding tube 6. Optionally, a low friction coating may be provided on the inner surface of the tubular member 4.

[0103] The elongated body 8 may also be configured such that one or both of the composition and the surface texture of the outer surface of the elongated body 8 is uniform over the length of the elongated body 8 in contact with the self-expanding tube 6. Even if the surface is uniform, it will be straightforward for a person skilled in the art to arrange for the frictional engagement force between the self-expanding tube 6 and the elongated body 8 to be higher than the frictional engagement force provided by the tubular member 4 relative to the reverse deployment of the self-expanding tube 6, for example, by providing a suitable high friction coating or surface roughening.

Claims

1. A delivery system for deploying a self-expanding tube into a blood vessel, include: a tubular member configured to be inserted into the blood vessel; an elongated body extending within the lumen of the tubular member; as well as a self-expanding tube disposed radially between the tubular member and the elongated body, wherein the delivery system is configured to operate in an expanded mode in which a first longitudinal engagement force acting between the self-expanding tube and the tubular member and a second longitudinal engagement force acting between the self-expanding tube and the elongated body are such that: substantially no longitudinal relative movement between the elongate body and any portion of the self-expanding tube that remains engaged with the elongate body during deployment of the self-expanding tube in use, the deployment of the self-expanding tube comprising longitudinal movement of the tubular member relative to the elongate body toward the proximal end of the delivery system; there is longitudinal relative movement between the elongated body and a portion of the self-expanding tube that remains engaged with the elongated body during retraction of the elongated body in use after at least a portion of the self-expanding tube has been deployed, the retraction of the elongated body comprising longitudinal movement of the elongated body relative to the tubular member toward a proximal end of the delivery system; for reverse retraction of the self-expanding tube relative to the tubular member, the first longitudinal engagement force is greater after a portion of the self-expanding tube has been deployed out of the tubular member than when the self-expanding tube has not been deployed out of the tubular member; as well as For reverse retraction of the self-expanding tube relative to the tubular member, a maximum first longitudinal engagement force achievable after a portion of the self-expanding tube has been deployed outside of the tubular member is greater than a maximum second longitudinal engagement force achievable, wherein The maximum first achievable longitudinal engagement force is a static friction force acting between the self-expanding tube and the tubular member, and the maximum second achievable longitudinal engagement force is a static friction force acting between the self-expanding tube and the elongated body.

2. The delivery system according to claim 1, in: the self-expanding tube being configured to self-expand from a radially contracted state to a radially expanded state in a process involving longitudinal shortening of the self-expanding tube relative to a longitudinal axis of the tubular member; and The greater first longitudinal engagement force is achieved by engagement of the radially expanded and longitudinally contracted portion of the self-expanding tube with the distal end of the tubular member.

3. The delivery system of claim 1 or 2, configured such that, for reverse deployment of the self-expanding tube relative to the tubular member, a maximum first longitudinal engagement force achievable is less than a maximum second longitudinal engagement force achievable.

4. The delivery system according to claim 1 or 2, in, The distal end of the elongated body includes a distal engagement member configured to detachably engage the self-expanding tube.

5. The delivery system according to claim 4, in, The distal engagement member is further configured such that, when the distal engagement member is engaged with the self-expanding tube, a maximum second longitudinal engagement force obtainable is greater than a maximum first longitudinal engagement force obtainable.

6. The delivery system according to claim 1 or 2, in, At least a portion of the self-expanding tube is engaged outwardly with the tubular member and inwardly with the elongated body over at least 50% of the length of the self-expanding tube.

7. The delivery system of claim 1 or 2, configured such that one or both of the composition and the surface texture of the inner surface of the tubular member are uniform over the length of the tubular member in contact with the self-expanding tube.

8. The delivery system of claim 1 or 2, configured such that one or both of the composition and the surface texture of the outer surface of the elongated body are uniform over the length of the elongated body in contact with the self-expanding tube.

9. The delivery system according to claim 1 or 2, in, The self-expanding tube has a porosity of less than 85% when expanded.

10. The delivery system according to claim 1 or 2, in, The self-expanding tube is configured to redirect blood flow away from the aneurysm sac when expanded over an opening to the aneurysm sac.

11. The delivery system of claim 1 , further comprising a retaining member configured to selectively longitudinally apply a retaining force to a proximal region of the self-expanding tube, the delivery system further configured to operate in a retraction mode, wherein application of the retaining force allows longitudinal relative movement between the elongated body and a portion of the self-expanding tube that is retained in engagement with the elongated body during longitudinal movement of the self-expanding tube in a proximal direction relative to the elongated body.

12. The delivery system according to claim 1 or 11, in: The self-expanding tube includes an elongated frame that is reversibly convertible from a radially expanded and longitudinally contracted state to a radially contracted and longitudinally expanded state; and a distal region of the elongated body includes two end markers.

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