Stent Delivery Catheter Shape-Memory Retraction Mechanism
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Solution Overview
Problem
Existing stent delivery devices, particularly 'Flow-Diverters' made of many wires, face issues with increased friction and damage due to cut ends forming 'needles' that scratch the catheter's inner surface, and they cannot be easily retracted once partially deployed, limiting stent positioning accuracy.
Innovation Solution
A device featuring a catheter with a through-hole and a shape-memory part that changes dimensions to accommodate the stent, allowing smooth insertion and retraction by translating the stent relative to the catheter using a central core and coupling mechanism, preventing friction and enabling precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the stent is made of many wires braided together and cut at the ends, then the stent can be compressed into a catheter for delivery, but the cut ends form aggressive needles that scratch the catheter inner surface, causing increased friction and damage
Solution Approach 1:
A protective sheath or coating is introduced as an intermediary element between the stent wires and the catheter inner surface. This protective layer prevents the cut wire ends from directly contacting and scratching the catheter, thereby reducing friction and damage while maintaining the compressibility needed for delivery.
Solution Approach 2:
The aggressive needle-like cut ends of the wires, which initially cause harm by scratching the catheter, are converted into a beneficial feature by using them as anchoring points. The wires are designed so that these sharp ends can embed into the vessel wall upon deployment, providing secure fixation of the stent in place.
2Ease of operation
If the hole in the delivery device is dimensioned to match the catheter internal dimension for smooth sliding, then the stent can be delivered easily, but the stent cannot be retracted back into the catheter if positioning needs adjustment
Solution Approach 1:
The delivery device incorporates a dynamic expansion mechanism where the holding structure can transition between a compressed state (allowing stent insertion) and an expanded state (allowing stent release and potential retraction). This dynamic behavior enables both smooth delivery and adaptability for repositioning.
Solution Approach 2:
The delivery device is segmented into multiple functional zones: a distal expansion zone that can open to release the stent, a middle translation zone for controlled movement, and a proximal compression zone for holding the stent during delivery. This segmentation allows the device to perform multiple functions including delivery, positioning adjustment, and retraction.
3Manufacturing precision
If the delivery device includes means for translating the stent relative to the catheter, then the stent can be positioned precisely, but the device complexity increases
Solution Approach 1:
Complex mechanical translation mechanisms are replaced with simpler systems based on material properties. Shape memory alloys or elastic materials are used to provide controlled expansion and contraction, eliminating the need for complex mechanical gears, linkages, or actuators while maintaining precise positioning capability.
Solution Approach 2:
The delivery device utilizes changes in physical parameters (such as temperature, pressure, or material phase) to control stent positioning. For example, shape memory materials change their dimensional parameters in response to temperature changes, enabling controlled expansion and retraction without complex mechanical systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates the smooth sliding and retraction of the stent within the catheter, reducing friction and allowing precise positioning of the stent within the blood vessel, while minimizing damage and enabling effective deployment and repositioning.
Implementation Method 1
The part is made of a shape memory material, so that it is capable of taking two forms, a stable form Fst in which it has an overall transverse dimension at most equal to the difference between the internal transverse dimension of the catheter 20 and twice the thickness of the side wall of the stent 10, and, an unstable shape Fin in which it has an overall transverse dimension at most equal to the internal transverse dimension of the catheter 20
Data Source
Figure 1~3
Figure 4~8
AI summary
The present invention relates to devices for placing a stent (10) in a blood vessel or similar. The device according to the invention has a catheter (20) with a continuous passage (24), a component (30) which is mounted slidably in this passage, a hole (32) formed in the component and having an opening (33) in that face of the component directed toward the end (22) of the catheter, this hole (32) receiving a part 12-1 of the end (12) of the stent (10) in the folded form Fr of the latter, the component (30) being made of a shape-memory material such that it is able to assume two shapes, namely a stable shape, in which its transverse dimenion is at most equal to the difference between the internal transverse dimension of the catheter (20) and twice the thickness of the lateral wall of the stent (10), and a nonstable shape, in which its overall transverse dimension is equal to the internal transverse dimension of the catheter (20). Application in particular to the treatment of cerebral or intracranial aneurysms.