Flow Diverter Composite Wire Structure for X-Ray Visibility
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Solution Overview
Problem
Existing medical devices, particularly flow diverters, face challenges in achieving high X-ray visibility and good self-expandability, especially when miniaturized for use in small blood vessels, due to the conflict between X-ray visible core materials lacking superelastic properties and superelastic materials compromising compressibility.
Innovation Solution
A medical device with a radially self-expandable lattice structure composed of interwoven wires, where some wires have an X-ray visible core material and a superelastic mantle material, with a specific relationship between core diameter and expansion diameter to balance visibility and self-expansion properties, allowing for use through small catheters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If the proportion of X-ray visible core material is increased to improve visibility, then X-ray visibility is improved, but self-expandability deteriorates because core materials lack superelastic properties
Solution Approach 1:
The wire is constructed as a composite material with an X-ray visible core material (e.g., platinum) and a superelastic mantle material (e.g., nitinol). This composite structure allows the core to provide radiopacity while the mantle provides superelastic properties for self-expansion. The specific diameter ratio ensures both functions are optimized simultaneously.
Solution Approach 2:
The invention specifies a particular parameter relationship: the ratio between core material diameter and total wire diameter should be between 0.05 and 0.20. By controlling this dimensional parameter, the invention balances the competing requirements of visibility (requiring larger core) and self-expansion (requiring sufficient mantle thickness).
2Adaptability or versatility
If the lattice structure is compressed to a very small cross sectional diameter for feeding into small blood vessels, then adaptability to small vessels is improved, but contact with the vessel wall deteriorates
Solution Approach 1:
The invention controls the wire diameter to be between 30 μm and 65 μm, and specifies the core-to-total diameter ratio between 0.05 and 0.20. These parameter optimizations ensure the lattice can be compressed sufficiently small for delivery while maintaining enough structural integrity to establish good contact with the vessel wall upon expansion.
Solution Approach 2:
The superelastic mantle material enables the lattice structure to undergo large deformations during compression and expansion cycles while maintaining mechanical performance. This allows the device to be delivered through small catheters and then fully expand to contact the vessel wall effectively.
3Adaptability or versatility
If the wire diameter is reduced to improve compressibility, then compressibility is improved, but X-ray visibility deteriorates
Solution Approach 1:
By using a composite wire structure with a high-density X-ray visible core surrounded by a superelastic mantle, the invention achieves both small overall diameter (for compressibility) and sufficient radiopacity (from the core). The core-to-total diameter ratio of 0.05-0.20 optimizes this balance.
Solution Approach 2:
The wire structure has non-uniform composition: the core material provides localized X-ray visibility while the mantle material provides localized superelasticity. This spatial differentiation of material properties allows the wire to simultaneously achieve small diameter and high visibility.
4Ease of operation
If a balloon catheter is used to expand the lattice structure, then expansion capability is improved, but device complexity and risk of injury increase
Solution Approach 1:
The lattice structure is designed with inherent superelastic properties that enable it to self-expand upon deployment from the catheter. The stored elastic energy in the compressed state drives the expansion, eliminating the need for a balloon catheter and reducing system complexity and procedural risk.
Solution Approach 2:
The lattice structure is pre-formed with a larger diameter configuration and then compressed for delivery. The pre-stored elastic energy in the compressed state enables automatic expansion to the final configuration, eliminating the need for post-deployment expansion mechanisms.
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
The device achieves high X-ray visibility and sufficient self-expansion forces for anchoring in vessels while being compressible enough to navigate through small catheters, particularly suitable for intracranial applications.
Implementation Method 1
the superelastic properties of the mantle material of the wire are intended to ensure that the stent expands autonomously, i.e. it is self-expandable
Data Source
AI summary
The invention is directed to a medical device, in particular a flow diverter, having a radially self-expandable lattice structure which is tubular at least in some regions and which is composed of a plurality of interwoven individual wires which form meshes of the lattice structure, wherein at least some of the individual wires have an X-ray visible core material and a superelastic mantle material, wherein a plurality of directly adjacent meshes in the circumferential direction of the lattice structure form a mesh ring in a fully self-expanded state, the lattice structure has an expansion diameter Dexp, the mesh ring has a mesh number n, and the core material has a core diameter dcore, and wherein for the core diameter dcore, the following holds:dcore=f·(Dexp/n)wherein the following holds for a visibility factor f:0.08≤f≤0.15.