Nested Spool Tensioning for Steerable Catheter Deflection
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Solution Overview
Problem
Existing intravascular catheters lack precise control over the deflection of their distal ends, leading to inefficiencies in positioning medical devices within the body, particularly during procedures like heart valve replacement, due to issues with cable slack and lack of active return mechanisms.
Innovation Solution
A catheter system with a steering assembly featuring dual spool assemblies and tension cables, allowing for precise control over the distal end deflection in opposite directions through a mechanism that prevents rotation of inner spools relative to outer spools, and includes a drive gear and actuator shaft for controlled steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional cable tensioning mechanisms are used in catheters, then the structure is simple, but cable slack causes imprecise control of distal end deflection
Solution Approach 1:
The patent implements a nested spool configuration where an inner spool is positioned within an outer spool. The inner spool handles the steering cable while the outer spool provides structural support and guidance. This nesting arrangement minimizes cable slack through precise geometric alignment and mechanical constraints, achieving accurate distal end deflection control without requiring overly complex external mechanisms.
2Reliability
If active return mechanisms are added to eliminate cable slack, then control precision improves, but device complexity increases
Solution Approach 1:
The patent pre-configures the spool assemblies during the manufacturing process with specific geometric relationships and initial cable tensions. The lumens, spools, and cables are arranged to automatically eliminate slack and maintain optimal tension throughout the catheter's operational range. This preliminary configuration ensures reliable steering control without requiring complex active adjustment mechanisms during use.
3Ease of operation
If multiple spool assemblies are used to control deflection in opposite directions, then steering accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The patent employs asymmetric spool designs where the inner and outer spools have different geometric characteristics optimized for their specific functions. The inner spool is configured to handle cable tension and rotation, while the outer spool provides structural support and cable guidance. This asymmetric configuration enables effective bidirectional steering control while maintaining manufacturing feasibility through clear functional differentiation of each component.
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
Enhances the precision and efficiency of catheter steering by minimizing cable slack and ensuring active return, thereby improving the accuracy and reliability of medical device placement within the body.
Implementation Method 1
rotation of the spool shaft about a longitudinal axis thereof transmits torque to the first inner spool to cause rotation of the first inner spool about the longitudinal axis of the spool shaft
Implementation Method 2
the plurality of splines engage the complementary shape of the recess of the first outer spool to prevent rotation of the first inner spool relative to the first outer spool about the longitudinal axis of the spool shaft
Implementation Method 3
The first steering cable may be fixed to the first outer spool and configured to be wound around the first spool assembly upon rotation of the first outer spool about the longitudinal axis
Data Source
AI summary
A catheter system may include a steering catheter and a steering cable extending through a lumen in the wall of the steering catheter. A steering assembly may include a spool assembly having an outer spool, an inner spool received within the outer spool, and a spool shaft received within the inner spool. The spool shaft and a recess of the inner spool may be shaped so that rotation of the spool shaft causes rotation of the inner spool. The inner spool may include splines that engage with complementary recesses of the inner spool, such that the outer spool is prevented from rotating relative to the inner spool. The steering cable may be fixed to the outer spool and may be configured to be wound around the spool assembly upon rotation of the outer spool about the longitudinal axis of the spool shaft.