An OCT imaging catheter

Abstract

This invention discloses an OCT imaging catheter, relating to the field of medical device technology. The OCT imaging catheter includes a catheter body, an imaging probe, and a filling fluid. The catheter body has an inner lumen, and an imaging window and a filling space located within the imaging window are provided at the distal end of the catheter body. The imaging probe is movably inserted into the inner lumen and extends into the filling space at the imaging window. The filling fluid fills the filling space and is used to change the refraction direction of the light emitted from the lens of the imaging probe, thereby reducing astigmatism and attenuation during scanning and imaging. This invention improves the structure of the OCT imaging catheter, ensuring smooth lens rotation and retraction, improving image quality, effectively preventing lens damage, and enhancing the convenience of catheter delivery to blood vessels.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to an OCT imaging catheter. Background Technology

[0002] Because OCT (Optical Coherence Tomography) imaging technology acquires relatively clear images, allowing for complete and clear observation of the target area, it has become a mainstream method for vascular imaging. Currently, OCT imaging catheters are widely used in coronary arteries, intracranial vessels, and other fields.

[0003] However, due to the thinness and complexity of intracranial blood vessels, the distal end of the optical fiber inside the OCT imaging catheter is easily damaged during intracranial vascular imaging as it navigates through the winding, thin, and complex intracranial blood vessels, resulting in poor imaging quality or even imaging failure. Summary of the Invention

[0004] The main objective of this invention is to provide an OCT imaging catheter that aims to improve the imaging quality of OCT imaging catheters.

[0005] To achieve the above objectives, the present invention proposes an OCT imaging catheter, comprising:

[0006] The catheter body has an inner lumen, and the distal end of the catheter body is provided with an imaging window and a filling space located within the imaging window;

[0007] An imaging probe, movably inserted into the cavity and extending into the filling space at the imaging window; and

[0008] The filling liquid is used to fill the filling space.

[0009] Optionally, the filling liquid is a viscous liquid.

[0010] Optionally, the catheter body includes an outer sheath, a guidewire tip, and a spring tube. The guidewire tip is located at the distal end of the outer sheath, and the spring tube is sleeved around the outer periphery of the imaging probe and is used to drive the imaging probe to rotate and pull back under the drive of an external force. The filling space is formed by the outer sheath, the guidewire tip, and the spring tube.

[0011] Optionally, the spring tube includes an inner tube, an outer tube, and a developing ring. The outer tube is disposed on the outer periphery of the inner tube and has a peeling portion. The developing ring is disposed within the peeling portion.

[0012] Optionally, the imaging probe includes an optical fiber, a lens, and a light output control device. The lens is located at the distal end of the optical fiber, and the light output control device is located on the lens and is used to control the light output direction and protect the lens.

[0013] Optionally, the imaging probe further includes a protective element, which is disposed around the periphery of the lens and connected to the spring tube, and the protective element is used to protect the lens; the protective element is coated with a coating layer, and the material of the coating layer is polyimide.

[0014] Optionally, the surface of the light-emitting control component is provided with a first material layer, a second material layer, a third material layer and a fourth material layer from the inside out. The first material layer is made of highly elastic polyurethane, the second material layer is made of polyimide nanofibers, the third material layer is a spiral wound structure of shape memory alloy wire, and the fourth material layer is made of a biocompatible material.

[0015] Optionally, the light emission control element is a heat shrink tubing; and / or

[0016] The protective component is a crystal head.

[0017] Optionally, the outer sheath includes a proximal outer tube and a distal outer tube connected to the proximal outer tube; and / or

[0018] The proximal outer tube comprises an inner layer, a middle layer, and an outer layer stacked sequentially from the inside out. The inner layer is made of PTFE, the middle layer is made of 304 stainless steel, and the outer layer is made of PI; and / or

[0019] The material of the distal outer tube is Pebax.

[0020] Optionally, the proximal outer tube has a recessed section on its outer surface at the connection with the distal outer tube, and the distal outer tube has a mating section on its inner surface at the connection with the proximal outer tube that is adapted to the recessed section. The mating section is arranged around the recessed section and fixed by welding or bonding.

[0021] In the technical solution of this invention, the OCT imaging catheter includes a catheter body, an imaging probe, and a filling fluid. The catheter body has an inner cavity, and an imaging window and a filling space located within the imaging window are provided at the distal end of the catheter body. The imaging probe is movably inserted into the inner cavity and extends into the filling space at the imaging window. The filling fluid fills the filling space and is used to change the refraction direction of the light emitted from the lens of the imaging probe, thereby reducing astigmatism and attenuation during scanning imaging. It can be understood that this invention improves the distal structure of the OCT imaging catheter. By placing the filling fluid in the filling space within the imaging window at the distal end of the catheter body, the lens of the imaging probe undergoes pull-back and rotational movements in the solution, effectively ensuring the smoothness of the lens rotation and pull-back, changing the refraction direction of the light emitted from the lens of the imaging probe, reducing astigmatism and attenuation during scanning imaging, and improving image quality.

[0022] In this invention, the OCT imaging probe improves the buffering and protection effect on the lens by setting a multi-layer structure, increases the tensile strength of the lens, enhances the structural support stability, reduces stress concentration, and has better biocompatibility. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of an embodiment of the OCT imaging catheter of the present invention;

[0025] Figure 2 for Figure 1 Enlarged view of section A in the middle;

[0026] Figure 3 for Figure 1 Enlarged view of section B in the middle;

[0027] Figure 4 This is a schematic diagram of the imaging probe structure in one embodiment of the OCT imaging catheter of the present invention;

[0028] Figure 5 This is a schematic diagram of the imaging probe in another embodiment of the OCT imaging catheter of the present invention;

[0029] Figure 6 This is a schematic diagram of the proximal outer tube in one embodiment of the OCT imaging catheter of the present invention;

[0030] Figure 7This is a schematic diagram showing the connection between the proximal and distal outer tubes in one embodiment of the OCT imaging catheter of the present invention;

[0031] Figure 8 This is a schematic diagram of the spring tube and a cross-sectional view of the spring tube at the imaging ring on it, according to an embodiment of the OCT imaging catheter of the present invention.

[0032] Explanation of icon numbers:

[0033] 10. Catheter body; 20. Imaging probe; 10a. Filling space; 101. Outer tube; 102. Guide wire tip; 103. Spring tube; 104. Imaging ring; 201. Optical fiber; 202. Lens; 203. Light output control component; 204. Protective component; 2411. Coating layer; 2421. First material layer; 2422. Second material layer; 2423. Third material layer; 2424. Fourth material layer; 111. Proximal outer tube; 112. Distal outer tube; 1111. Inner layer; 1112. Middle layer; 1113. Outer layer; 1131. Recessed section; 1132. Mating section; 30. Protective cover; 40. Connector; 50. Stress buffer tube; 60. Connector sleeve; 71. Pull-back mark; 72. Lens mark; 73. Axis mark strip; 221. Reflective surface; 1121. Imaging window.

[0034] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0037] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. The word "and / or" throughout the text means including three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. The technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0039] This invention proposes an OCT imaging catheter that can be applied to intracranial blood vessels, coronary blood vessels, and other fields, and is not limited to these applications.

[0040] Reference Figures 1 to 5 In one embodiment of the present invention, the OCT imaging catheter includes a catheter body 10, an imaging probe 20, and a filling fluid (not shown in the figure); the catheter body 10 forms an inner cavity, and the distal end of the catheter body 10 is provided with an imaging window 1121 and a filling space 10a located within the imaging window 1121; the imaging probe 20 is movably inserted into the inner cavity and extends into the filling space 10a at the imaging window 1121; the filling fluid fills the filling space 10a, and the filling fluid is used to change the refraction direction of the light emitted from the lens 202 of the imaging probe 20, so as to reduce astigmatism and attenuation during scanning imaging.

[0041] In this embodiment, the filling fluid is a viscous liquid such as medical silicone oil. This solution not only changes the refraction direction of the light emitted from the lens 202 of the imaging probe 20, but also has a certain degree of smoothness, which helps to improve the smoothness of the imaging probe 20's pull-back and rotational movements within the cavity. Furthermore, when the lens 202 moves within the filling fluid to perform vascular segment imaging, the solution also protects the imaging components.

[0042] It is understood that the present invention improves the distal structure of the OCT imaging catheter. By setting a filling liquid in the filling space 10a within the distal imaging window 1121 of the catheter body 10, the lens 202 of the imaging probe 20 performs pull-back and rotational movements in the solution, changing the refraction direction of the light emitted from the lens 202 of the imaging probe 20. This can reduce astigmatism and attenuation during scanning imaging, eliminate the extra light halo outside the imaging probe during catheter scanning imaging due to the absence of contrast agent in the OCT imaging catheter, and reduce the resistance between the high-speed rotating core of the catheter and the inner wall of the distal outer tube 112, thereby improving image quality. It effectively ensures the smoothness of the lens 202's rotation and pull-back and improves imaging quality.

[0043] To further improve the convenience of rotating and pulling back the imaging probe 20, the following references are made: Figure 1 and Figure 2 In one embodiment, the catheter body 10 may include an outer sheath 101, a guidewire tip 102, and a spring tube 103. The guidewire tip 102 is located at the distal end of the outer sheath 101, and the spring tube 103 is sleeved on the outer periphery of the imaging probe 20 and is used to drive the imaging probe 20 to perform a rotational pull-back movement under the drive of an external force. The filling space 10a is formed by the outer sheath 101, the guidewire tip 102, and the spring tube 103.

[0044] It should be noted that the imaging window 1121 is light-transmitting, circumferentially arranged, and its length is the same as the pull-back length of the imaging probe 20, allowing light to pass through. The imaging window 1121 can be a section of the distal end of the outer sleeve 101, arranged around the outer periphery of the lens 202, or it can be embedded in a light-transmitting sheet on the distal end of the outer sleeve 101; of course, the imaging window 1121 can also be a light-transmitting tube connected to the distal end of the outer sleeve 101, which is not limited here.

[0045] Furthermore, referring to Figure 8 The spring tube 103 may include an inner tube, an outer tube, and a developing ring 104. The outer tube is located around the inner tube and has a peeling portion. The developing ring 104 is located within the peeling portion. Thus, by employing a double-layer spring tube 103 with a developing ring 104, a portion of the outer layer of the spring tube 103 is peeled off, and the developing ring 104 is welded to the peeled location. The spring tube 103 then exhibits developing marks under X-rays, and the outer diameter of the spring tube 103 at the welded location is smaller than the outer diameter of the rest of the spring tube 103, which facilitates a smaller outer diameter for the application section of the product.

[0046] In this embodiment, the developing ring 104 can be made of platinum-iridium material, but there is no limitation here.

[0047] To protect lens 202 from being squeezed by the tube and affecting image formation, or even causing damage, the following should be mainly referred to: Figure 2 , Figure 4 and Figure 5In some embodiments, the imaging probe 20 may include an optical fiber 201, a lens 202, and a light emission control component 203. The lens 202 is located at the distal end of the optical fiber 201, and the light emission control component 203 is located on the lens 202 and is used to control the light emission direction and protect the lens 202. This solves the problem that when the catheter is pushed through a narrow blood vessel, the lens 202 of the imaging probe 20 may deform or be damaged due to the compression of the catheter lumen, resulting in the catheter failing to image normally. It also solves the problem that when the catheter is pulled back through a tortuous blood vessel, the lens 202 of the imaging probe 20 may break due to the large pulling force of the proximal optical fiber 201 and friction from the inner wall of the lumen, resulting in the inability to image normally.

[0048] In this embodiment, the thickness of the spring tube 103 can be 0.075 mm, and the diameter of the optical fiber 201 can be 0.15 mm; these are not limited here. The light output control component 203 can be made of heat shrink tubing, etc., and the material can be PET with a thickness of 0.01 mm; these are not limited here.

[0049] It should be noted that the heat shrink tubing forms the reflective surface 221 of the lens 202. During scanning and imaging, light is emitted from the optical fiber 201 and the lens 202, hits the heat shrink tubing, and then is totally reflected and emitted.

[0050] To further enhance the protection of lens 202, refer to Figure 4 In one embodiment, the imaging probe 20 further includes a protective element 204, which covers the outer periphery of the lens 202 and is connected to the spring tube 103. Specifically, the protective element 204 is attached to the tip of the optical fiber 201 lens 202 to protect the lens 202; the protective element 204 is coated with a coating layer 2411, and the material of the coating layer 2411 may be polyimide or the like.

[0051] In this embodiment, the protective component 204 can be a crystal head or similar material, made of epoxy resin, and its thickness can be 0.15mm, which is not limited here. The polyimide coating layer 2411 can have a thickness of 0.01mm, which is not limited here.

[0052] To further enhance the protection of lens 202, refer to Figure 5 In another embodiment, the surface of the light emission control component 203 may be provided with a first material layer 2421, a second material layer 2422, a third material layer 2423 and a fourth material layer 2424 from the inside out. The first material layer 2421 is made of high-elasticity polyurethane, the second material layer 2422 is made of polyimide nanofibers, the third material layer 2423 is a spiral wound structure of shape memory alloy wire, and the fourth material layer 2424 is made of biocompatible materials.

[0053] Preferably, the first material layer 2421 is made of highly elastic polyurethane with a thickness of 0.01 mm to provide initial cushioning; the second material layer 2422 is a nanofiber reinforcing layer made of polyimide nanofibers with a thickness of 0.01 mm to improve tensile strength. The third material layer 2423 can be a spiral-wound structure of shape memory alloy wire with a pitch of 0.5 mm and a thickness of 0.03 mm to provide structural support and stress dispersion. The fourth material layer 2424 can be made of medical-grade silicone with a thickness of 0.01 mm to give the lens 202 better biocompatibility.

[0054] During manufacturing, multi-layered structures should be layered sequentially, then laminated, and finally fused together at high temperature.

[0055] Main reference Figure 1 and Figure 6 In one embodiment, the outer sleeve 101 may include a proximal outer sleeve 111 and a distal outer sleeve 112 connected to the proximal outer sleeve 111. The proximal outer sleeve 111 includes an inner layer 1111, a middle layer 1112, and an outer layer 1113 stacked sequentially from the inside out. The inner layer 1111 may be made of PTFE or the like, the middle layer 1112 may be made of 304 stainless steel or the like, and the outer layer 1113 may be made of PI. The distal outer sleeve 112 has a single-layer structure and may be made of Pebax or the like.

[0056] In other words, the proximal outer tube 111 in this embodiment adopts a three-layer structure design: the inner layer 1111 is made of PTFE material, the middle layer is made of stainless steel braided wire, and the outer layer 1113 is made of PI material. This design can enhance the support strength of the proximal end of the catheter, which helps to further improve the overall pushing performance of the catheter. The inner lumen is also more lubricated, which can reduce the resistance between the catheter and the outer tube when the catheter rotates at high speed.

[0057] In this embodiment, refer to Figures 1 to 3 The OCT imaging catheter also includes a protective cap 30, a connector 40, a stress buffer tube 50, a pull-back mark 71, a lens mark 72, a connector sleeve 60, and a shaft marking band 73. The protective cap 30 protects the proximal end of the OCT imaging catheter when it is not connected to the main unit. The connector 40 resembles a handle for easy hand operation. The stress buffer tube 50 provides cushioning during catheter entry into the blood vessel and advancement. The proximal outer tube 111 is the portion entering the proximal part of the body. The distal outer tube 112 is the portion entering the distal part of the body. The guidewire tip 102 guides the catheter body 10 to the target position within the blood vessel. The pull-back mark 71 and lens mark 72 are used to observe the catheter position. The spring tube 103 drives the imaging probe 20 to rotate and pull back. The lens 202 emits laser imaging and can be formed by the end of the optical fiber 201 or by a lens mounted on the optical fiber 201. The connector sleeve 60 protects the connector 40. The axis marking band 73 is used to mark the proximal position of the catheter.

[0058] Furthermore, the effective length of the catheter can be set to 1850±50 mm, which is the length that can enter the body. The length of the hydrophilic coating is 1500±50 mm, which is the length of entry into the blood vessel, and is the distance between the axis marker 73 and the most distal end of the OCT imaging catheter. The length of the imaging window 1121 is the probe pull-back distance, which can be set to 100±5 mm, and the outer diameter of the imaging window 1121 (the outer diameter of the outer sheath 101 where the imaging window 1121 is located) can be set to 0.46±0.03 mm. The maximum outer diameter of the catheter insertion portion can be set to 0.46±0.03 mm. The distance between the pull-back mark 71 and the lens mark 72 can be 40±3 mm or 60±3 mm. The length from the lens 202 to the most distal end of the catheter can be set to 20+0 or -3 mm. The length of the guidewire tip 102 can be set to 15±3 mm.

[0059] It should be noted that blood is composed of plasma and blood cells, with plasma accounting for approximately 55% and water accounting for 90%. To reduce friction during the procedure, in this embodiment, a hydrophilic coating is applied to the outer periphery of the outer cannula 101 of the OCT imaging catheter. The hydrophilic coating can be applied by dipping in a hyaluronic acid (HA)-based solution followed by heat curing. When physiological saline is continuously applied to the hydrophilic coating during insertion into the blood vessel, the friction between the catheter and the blood is significantly reduced, greatly enhancing catheter patency.

[0060] Main reference Figure 7 In one embodiment, the proximal outer tube 111 has a recessed section 1131 on its outer surface at the connection between it and the distal outer tube 112, and the distal outer tube 112 has a mating section 1132 adapted to the recessed section 1131 on its inner surface at the connection between it and the proximal outer tube 111. The mating section 1132 is arranged around the recessed section 1131 and fixed by welding or bonding.

[0061] In this embodiment, the proximal outer tube 111 and the distal outer tube 112 employ a unique welding process. This ensures the strength of the connection between the two outer tubes while also guaranteeing that the outer diameter of the weld does not exceed the outer diameters of the proximal outer tube 111 and the distal outer tube 112. Specifically, the connection between the proximal outer tube 111 and the distal outer tube 112 is achieved through mechanical stripping. Approximately 6-7 mm of the outer surface of the proximal outer tube 111 is uniformly stripped of about half the wall thickness, forming an outer step shape, i.e., the aforementioned countersunk section 1131. Similarly, approximately 6-7 mm of the inner surface of the distal outer tube 112 is uniformly stripped of about half the wall thickness, forming an inner step shape, i.e., the aforementioned mating section 1132. After peeling off the outer layer 1113 of the proximal outer cannula 111 and the inner layer 1111 of the distal outer cannula 112, they are joined by heat fusion or adhesive bonding. The difference between the peeling thickness of the inner layer 1111 of the distal outer cannula 112 and the peeling thickness of the outer layer 1113 of the proximal outer cannula 111 is equal to the adhesive bonding thickness. This ensures the smoothness of the catheter after the proximal and distal outer cannulas 112 are bonded together, while also preventing the connection size from increasing. This design allows for a smaller outer diameter of the catheter's application segment, resulting in better passage in clinical applications.

[0062] In addition, in some embodiments, the OCT imaging catheter may also include a guide tube for guiding the catheter body 10 into the target location within the blood vessel. Specifically, the guide tube can assist the guidewire tip 102 at the distal end of the catheter body 10 in smoothly entering other instruments and can provide support for the advancement of the catheter body 10. The guide tube is made of PTFE or similar material; its outer diameter can be 1.35±0.05mm, and its inner diameter can be 0.75±0.05mm, which is not limited here.

[0063] In summary, this invention ensures the smoothness of lens 202 rotation and retraction and imaging quality by filling the inner lumen of the catheter body 10 with liquid; the lens 202 is protected from damage by the lens 202 protective component 204; the proximal outer tube 111 adopts a three-layer structure design to ensure the rigidity of the outer tube and facilitate its insertion into the blood vessel; the proximal outer tube 111 and the distal outer tube 112 are welded or bonded to ensure the catheter's passability; in addition, the design of the spring tube 103 and the imaging ring 104 ensures a small catheter diameter.

[0064] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An OCT imaging catheter, characterized in that, include: The catheter body has an inner lumen, and the distal end of the catheter body is provided with an imaging window and a filling space located within the imaging window; An imaging probe is movably inserted into the inner cavity and extends into the filling space at the imaging window. The imaging probe includes an optical fiber, a lens, and a light emission control component. The lens is located at the distal end of the optical fiber, and the light emission control component is located on the lens and is used to control the light emission direction and protect the lens. The light emission control component is a heat shrink tubing. The surface of the light emission control component is provided with a first material layer, a second material layer, a third material layer, and a fourth material layer from the inside out. The first material layer is made of highly elastic polyurethane, the second material layer is made of polyimide nanofibers, the third material layer is a spiral wound structure of shape memory alloy wire, and the fourth material layer is made of a biocompatible material. The catheter body includes an outer tube, a guidewire head, and a spring tube. The guidewire head is located at the distal end of the outer tube. The spring tube is sleeved around the outer periphery of the imaging probe and is used to drive the imaging probe to rotate and pull back under the drive of an external force. The filling space is formed by the outer tube, the guidewire head, and the spring tube. The length of the imaging window is equal to the pull-back distance of the imaging probe. as well as The filling fluid is used to fill the filling space to change the refraction direction of the light emitted from the lens of the imaging probe, so as to reduce astigmatism and attenuation during scanning imaging.

2. The OCT imaging catheter as described in claim 1, characterized in that, The filling liquid is a viscous liquid.

3. The OCT imaging catheter as described in claim 1, characterized in that, The spring tube includes an inner tube, an outer tube, and a developing ring. The outer tube is disposed on the outer periphery of the inner tube and has a peeling portion. The developing ring is disposed within the peeling portion.

4. The OCT imaging catheter as described in claim 1, characterized in that, The imaging probe also includes a protective element, which covers the outer periphery of the lens and is connected to the spring tube. The protective element is used to protect the lens. The protective element is coated with a coating layer, and the material of the coating layer is polyimide.

5. The OCT imaging catheter as described in claim 4, characterized in that, The protective component is a crystal head.

6. The OCT imaging catheter as described in claim 1, characterized in that, The outer sheath includes a proximal outer tube and a distal outer tube connected to the proximal outer tube; and / or The proximal outer tube comprises an inner layer, a middle layer, and an outer layer stacked sequentially from the inside out. The inner layer is made of PTFE, the middle layer is made of 304 stainless steel, and the outer layer is made of PI; and / or The material of the distal outer tube is Pebax.

7. The OCT imaging catheter as described in claim 6, characterized in that, The proximal outer tube has a recessed section on its outer surface at the connection with the distal outer tube, and the distal outer tube has a mating section on its inner surface at the connection with the proximal outer tube that is adapted to the recessed section. The mating section is arranged around the recessed section and fixed by welding or bonding.

Images