Radiopaque Marker Attachment to Biodegradable Stents
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Solution Overview
Problem
Biodegradable polymers used in stents are radiolucent, making it difficult to visualize them under x-ray, and attaching radiopaque markers is challenging due to deformation during crimping and expansion, leading to potential dislodgment and protrusion issues.
Innovation Solution
A method and apparatus using a cylindrical mandrel with rollers to securely attach radiopaque markers to stents, ensuring retention during deformation and minimizing protrusion, by pressing markers into engagement with the stent structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If radiopaque markers are attached to polymeric stents, then x-ray visibility is improved, but marker retention is compromised during crimping and expansion due to deformation
Solution Approach 1:
The marker is inserted into the stent strut before crimping occurs. By performing the marker attachment in advance, the marker is positioned within the Strut structure before deformation begins, allowing it to be carried along with the strut through crimping and expansion without dislodgment
Solution Approach 2:
The radiopaque marker is nested within the stent strut structure, specifically positioned inside the Strut lumen or within a recess in the strut. This nesting arrangement ensures the marker is protected and retained during deformation, as it is surrounded by the strut material throughout crimping and expansion
2Reliability
If markers are securely attached to stents, then marker retention during deformation is improved, but marker protrusion increases causing interference with blood flow and vessel walls
Solution Approach 1:
The marker is nested within the strut structure, positioned inside the Strut lumen or within a recess. This containment prevents the marker from protruding outward to interfere with blood flow or vessel walls, while still maintaining secure attachment during deformation
Solution Approach 2:
The marker is positioned at specific locations on the stent, such as at the ends or within specific struts, rather than uniformly across all struts. This localized placement minimizes overall interference with blood flow while maintaining necessary visibility for specific treatment zones
3Ease of manufacture
If conventional attachment methods are used, then manufacturing simplicity is maintained, but attachment uniformity and reliability deteriorate
Solution Approach 1:
The marker is inserted into the stent strut before crimping in a single integrated step. This preliminary insertion, combined with the subsequent crimping process, achieves both secure retention and consistent positioning without requiring separate attachment operations
Solution Approach 2:
The marker insertion process is merged with the crimping process into a single integrated operation. The marker is inserted and then the crimping action secures it simultaneously, combining two functions into one manufacturing step that improves both efficiency and consistency
Data Source
AI summary
A mandrel for supporting a stent and rollers for pressing a radiopaque marker into a stent are disclosed. The mandrel can have a forward portion for carrying the stent and a rear portion for urging the stent forward portion into a gap between the rollers. The mandrel may be pushed or pulled into the gap, which is sized to allow the rollers to press the marker into engagement with the stent. Prior to moving the mandrel into the gap, the marker may be placed on a surface of the stent or partially inside a recess in the stent. Several markers can be efficiently and uniformly pressed onto the stent by moving the mandrel into the gap in one continuous movement in an axial or lateral direction. Markers can also be pressed onto the stent by placing the stent in the gap and rotating the stent about its central axis.