Delivery Wire Stiffness Gradient for Aneurysm Coil Placement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current vaso-occlusive coil delivery systems face issues with the detachment zone bending due to orthogonal forces and the stiffness of pusher wires, which can affect the accurate placement and release of embolic coils within aneurysms, leading to potential complications.
Innovation Solution
A delivery wire assembly with a distal coil portion that gradually decreases in stiffness along its length, featuring varying coil pitches, diameters, and tensile strengths, along with an electrolytically severable junction or thermally responsive detachment mechanism, to minimize bending and improve trackability and deployment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stiff pusher wire is used to deliver the vaso-occlusive coil, then the wire can push the coil through the micro-catheter, but the detachment zone bends due to orthogonal forces from catheter bends
Solution Approach 1:
The pusher wire is divided into multiple segments with different stiffness characteristics: a stiffer proximal section for pushing force and a more flexible distal section with the detachment zone to accommodate catheter bends without excessive bending
Solution Approach 2:
Different sections of the pusher wire have locally optimized properties - the proximal section has higher stiffness for effective coil delivery, while the distal section has lower stiffness to reduce orthogonal bending forces on the detachment zone
2Shape
If a stiff distal section of the pusher wire is used, then the wire can maintain its shape, but it causes the pre-shaped micro-catheter to kick back or recoil from the aneurysm upon coil deployment
Solution Approach 1:
The pusher wire is segmented into a stiff proximal portion for shape retention and a compliant distal portion that allows the micro-catheter to maintain its pre-shaped configuration without kicking back during coil deployment
Solution Approach 2:
The stiffness parameter of the pusher wire is varied along its length, with the distal section having reduced stiffness to minimize kickback forces on the micro-catheter while the proximal section maintains sufficient stiffness for effective coil delivery
3Reliability
If the detachment zone is made of stainless steel for electrolytic severing, then it can be electrically charged for detachment, but it is susceptible to electrolysis and disintegration in ionic solutions
Solution Approach 1:
The detachment zone uses a composite or coated structure where a biocompatible, corrosion-resistant outer layer protects the inner conductive core, enabling electrolytic severing while minimizing harmful interactions with ionic solutions
Solution Approach 2:
The detachment zone is designed as a sacrificial, disposable element that is intentionally consumed through controlled electrolysis to achieve coil release, accepting some degree of disintegration as part of its intended function
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 solution enhances the precision and reliability of embolic coil placement by reducing bending and kickback during deployment, ensuring accurate positioning and release within the vasculature.
Implementation Method 1
An electrolytically severable junction is susceptible to electrolysis and disintegrates when the pusher wire is electrically charged in the presence of an ionic solution, such as blood or other bodily fluids.
Implementation Method 2
The distal coil portion of the delivery wire assembly includes a plurality of coils formed from coil wire, including one or more respective proximal, middle and distal coils, which decrease in stiffness distally along the length of the distal coil portion of the delivery wire assembly.
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A delivery wire assembly for delivery of an occlusive device to a location in a patient's vasculature includes a delivery wire conduit having a proximal tubular portion connected to a distal coil portion, and a conduit lumen extending through the proximal tubular portion and the distal coil portion. The delivery wire assembly also includes a core wire disposed in the conduit lumen and having a distal end coupled to an occlusive device. The distal coil portion of the delivery wire assembly includes a plurality of zones and the plurality of zones decrease in stiffness distally along the length of the distal coil portion of the delivery wire assembly.