Flow Diverting Stent Axial Expansion Segmentation
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Solution Overview
Problem
First generation flow diverting stents face issues such as unpredictable deployed length due to variable foreshortening, increased rigidity during delivery, reduced vessel lumen size, 'fish-mouth' effect, sub-optimal anchoring, and increased stiffness with decreasing porosity, which complicates deployment and increases thromboembolic risks.
Innovation Solution
A stent design featuring radially expandable circumferential segments and axially expandable connecting members that change configuration from a relaxed, nested state for delivery to an expanded state for deployment, utilizing chevron-shaped members and sinusoid-shaped connecting segments to enhance porosity and stiffness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If first generation flow diverting stents are used, then flow diversion can be achieved, but deployed length becomes unpredictable due to variable foreshortening
Solution Approach 1:
The stent is divided into multiple circumferential segments that can independently expand radially while maintaining axial connectivity through connecting members. This segmentation allows each segment to expand uniformly without variable foreshortening, ensuring predictable deployed length while maintaining flow diversion effectiveness.
Solution Approach 2:
The connecting members are designed to be axially expandable, transitioning from a compressed state during delivery to an expanded state at deployment. This dynamic expansion mechanism ensures that the stent maintains its axial dimensions predictably while allowing radial expansion for flow diversion.
2Reliability
If stent porosity is decreased to increase therapeutic effectiveness, then flow disruption improves, but stiffness increases making delivery difficult
Solution Approach 1:
The stent structure separates the functional requirements into distinct components: circumferential segments provide flow disruption through controlled porosity, while connecting members provide structural continuity and flexibility for delivery. This segmentation allows optimized porosity in flow diversion areas without compromising deliverability.
Solution Approach 2:
Different portions of the stent have different porosity characteristics - the circumferential segments have lower porosity for flow disruption, while the connecting members have higher porosity for flexibility and ease of delivery. This local quality variation resolves the contradiction between flow disruption effectiveness and delivery ease.
3Strength
If stent radial expansion is increased to improve vessel support, then vessel reinforcement improves, but vessel lumen size is reduced
Solution Approach 1:
The stent uses circumferential segments that expand radially to provide vessel wall support while maintaining controlled porosity. The connecting members prevent excessive radial expansion that would compromise lumen size, achieving a balance between vessel reinforcement and lumen preservation.
Solution Approach 2:
The stent design allows control over expansion parameters - the circumferential segments can expand radially to a controlled degree to provide support, while the axial dimensions are maintained through the connecting members, preserving vessel lumen size while achieving adequate vessel reinforcement.
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
This design improves deployment accuracy, reduces thromboembolic complications, and allows for better anchoring in the body lumen by controlling porosity and stiffness, facilitating effective flow diversion and adjunctive stent functions.
Implementation Method 1
Self-expanding stents expand into place when unconstrained, without requiring assistance from a balloon. A self-expanding stent may be biased so as to expand upon release from the delivery catheter and/or include a shape-memory component which allows the stent to expand upon exposure to a predetermined condition.
Data Source
AI summary
A stent configured for implantation in a body lumen includes a plurality of radially expandable circumferential segments, and an axially expandable connecting member connecting adjacent circumferential segments of the plurality. The stent has a relaxed, axially contracted configuration in which the connecting member is contracted axially and each circumferential segment is nested with at least one adjacent circumferential segment. The stent also has a delivery, axially expanded configuration in which the connecting member is expanded axially, and an axial distance between adjacent circumferential segments of the plurality is greater than when the stent is in its relaxed configuration.