Stent Lattice Core Diameter Optimization for X-Ray Visibility
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Solution Overview
Problem
Existing medical stents face challenges in achieving both high X-ray visibility and self-expansion properties, particularly when inserted into small intracranial blood vessels, due to the conflicting requirements of X-ray visible core materials and superelastic jacket materials, which affect compressibility and expansion forces.
Innovation Solution
A stent design with a radially self-expandable lattice structure made from a single wire comprising a core material visible under X-ray and a superelastic jacket material, where the core diameter is optimized based on the expansion diameter and mesh number to balance visibility and self-expansion, allowing for miniaturization and easy insertion through small catheters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If the proportion of core material visible under X-ray is increased to improve visibility, then X-ray visibility is improved, but self-expandability deteriorates because core materials do not have superelastic properties
Solution Approach 1:
The wire is constructed as a composite material with a core material (platinum or platinum alloy) that provides X-ray visibility and a superelastic jacket material (nitinol) that provides self-expandability. This composite structure allows both properties to coexist in the same wire, resolving the contradiction between visibility and self-expandability.
2Ease of operation
If the wire diameter is reduced to improve compressibility for insertion into small blood vessels, then compressibility is improved, but structural integrity deteriorates
Solution Approach 1:
The composite wire structure with superelastic jacket material provides both compressibility for miniaturization and structural integrity. The superelastic properties of the jacket material allow the wire to be compressed to small diameters for insertion into small blood vessels while maintaining sufficient strength to provide self-expandability forces.
3Ease of operation
If the lattice structure is compressed to a very small cross-sectional diameter for insertion into small blood vessels, then insertability is improved, but X-ray visibility deteriorates due to plastic deformation of core material
Solution Approach 1:
The superelastic jacket material allows the lattice structure to be compressed to small diameters for insertion into small blood vessels without causing plastic deformation of the core material. The jacket material elastically deforms during compression and recovery, preserving the core material's X-ray visibility properties.
Solution Approach 2:
The core diameter is optimized based on the expansion diameter and mesh number using the relationship dcore = f·(Dexp/n) where f is between 0.05 and 0.08. This parameter optimization ensures sufficient X-ray visibility while maintaining compressibility for insertion into small blood vessels.
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 optimized stent achieves high X-ray visibility and sufficient self-expansion forces for secure anchoring in blood vessels while being compressible enough to navigate through small catheters, ensuring stable placement and effective treatment of intracranial conditions like aneurysms and stenoses.
Implementation Method 1
the wire's jacket material should cause the stent to expand by itself, i.e. to be self-expandable
Implementation Method 2
the core material, which is visible under X-ray, should allow the stent to be seen during X-ray monitoring
Data Source
AI summary
The invention relates to a medical device, in particular a stent, having a radially self-expandable lattice structure (10) which is tubular at least in some sections and which is made of a single wire (11), which is interwoven with itself and which comprises a core material (11a) which is visible under X-ray and a superelastic jacket material (11b) and forms meshes (12) of the lattice structure (10). The invention is characterised in that a plurality of meshes (12) arranged directly adjacently in the circumferential direction of the lattice structure (10) form a mesh ring (13), and the lattice structure (10), in a fully self-expanded state, has an expansion diameter Dexp, the mesh ring (13) having a mesh number n, and the core material (11a) having a core diameter dKern, and the following being true for the core diameter dKern: dKern=f·(Dexp/n), with the following being true for a visibility factor f: 0.05≤f≤0.08.