Embolic Coil Elongation-Preventing Wire Dynamics
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Solution Overview
Problem
Existing embolization coils face issues with breakage of elongation-preventing wires when wound into smaller diameters and inefficiencies in delivery and positional correction due to stress concentration and relaxation.
Innovation Solution
An embolization coil design featuring a partially or entirely pitch-wound coil with an elongation-preventing wire having an expandable/shrinkable shape, fixed at two points, which reduces breakage risk and improves delivery efficiency by dispersing forces radially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the embolization coil is wound into a shape with a smaller diameter, then delivery efficiency is improved, but the elongation-preventing wire breaks due to excessive stress
Solution Approach 1:
The elongation-preventing wire is designed with a dynamic expandable/shrinkable shape that can adapt its configuration based on the coil's diameter. When the coil is compressed to a smaller diameter for delivery, the wire can shrink accordingly; when the coil expands to its secondary shape at the target site, the wire expands to prevent elongation. This dynamic adaptability resolves the contradiction between delivery efficiency and breakage resistance.
Solution Approach 2:
The wire's shape parameters (expandable/shrinkable characteristics) are changed to match the coil's dimensional changes. The wire is configured to have different effective lengths and configurations depending on whether the coil is in its compressed delivery state or expanded deployed state, allowing it to withstand stress in both conditions without breaking.
2Strength
If the elongation-preventing wire is made rigid to prevent breakage, then wire strength is improved, but delivery efficiency deteriorates due to stress concentration
Solution Approach 1:
Rather than making the wire rigid, the invention uses a dynamic wire that changes its mechanical properties based on the coil's state. During delivery, the wire is in a flexible, shrunk state that reduces stress concentration and improves delivery efficiency. During deployment, the wire transitions to an expanded state that provides the necessary strength to prevent elongation and breakage.
Solution Approach 2:
The wire's physical parameters (shape, effective length, flexibility) are changed in response to the coil's dimensional changes. This allows the wire to exhibit different mechanical characteristics - more flexible during delivery and stronger during deployment - resolving the contradiction between strength and delivery efficiency.
3Ease of operation
If the coil is made flexible for easy placement, then placement efficiency is improved, but the coil cannot prevent unlimited elongation
Solution Approach 1:
The coil structure has different local qualities: the coil itself remains flexible for easy placement and navigation, while the elongation-preventing wire provides localized stiffness and elongation control at critical points. The wire is fixed to the coil at multiple points, creating zones of controlled rigidity that prevent unlimited elongation without compromising the overall flexibility needed for placement.
Solution Approach 2:
The embolization coil system combines two different structural elements - a flexible coil and a more rigid elongation-preventing wire - to achieve both flexibility for placement and stability for elongation control. This composite structure allows the coil to be easily placed while the wire prevents unlimited elongation.
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 design enhances resistance to breakage and maintains delivery efficiency by distributing forces radially, reducing stress concentration and fatigue, thus improving the coil's performance during placement and relocation.
Implementation Method 1
the elongation-preventing wire has a region having an expandable/shrinkable shape in the region placed between the two points different from each other
Data Source
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AI summary
An embolic coil configured in such a manner that the risk that a stretch preventing wire breaks is very small even if the embolic coil is wound to a diameter smaller than the diameter of a secondary shape of the coil imparted thereto and also in such a manner that the embolic coil has excellent deliverability. An embolic coil is configured in such a manner that a stretch preventing wire and a coil, a part or the whole of said coil being coarsely wound, are affixed to each other at at least two different points. The portion of the stretch preventing wire which is located between the two different portions is provided with a portion to which a stretchable shape has been imparted.