Adjustable Tensioning Spool 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 of the catheter tip deflection in opposite directions through complementary spline engagement and a gear mechanism, minimizing cable slack and enabling active return.
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 occurs leading to imprecise control of catheter deflection
Solution Approach 1:
The patent employs nested spool assemblies where an inner spool is positioned within an outer spool. The inner spool handles the steering cable while the outer spool provides additional winding capacity. This nesting arrangement allows the system to maintain precise cable tension control without requiring excessively large individual spools, thus achieving better control precision while managing device complexity through compact integration.
Solution Approach 2:
The patent transitions from linear cable tensioning to rotational spool-based tensioning by adding a dimensional element. The spools rotate around an axis perpendicular to the catheter's longitudinal axis, creating a new degree of freedom for cable management. This dimensional change enables continuous cable retraction and tension adjustment, eliminating cable slack while providing precise control over catheter deflection.
2Measurement precision
If cable slack is present in the steering mechanism, then the device complexity is low, but the positioning accuracy of medical devices deteriorates
Solution Approach 1:
The spool assemblies are pre-configured with appropriate cable lengths and winding arrangements during assembly. The inner and outer spools are positioned and dimensioned beforehand to ensure that the steering cable maintains proper tension throughout the range of motion. This preliminary action prevents cable slack from developing during operation, ensuring consistent positioning accuracy without requiring complex active tensioning mechanisms.
Solution Approach 2:
The nested spool configuration creates a mechanical feedback system where the rotation of the inner spool is constrained by the outer spool's cable capacity. As the catheter deflects and the steering cable tensions, the spools rotate to take up slack automatically. This passive feedback mechanism maintains optimal cable tension and positioning accuracy throughout the steering range, eliminating the need for active sensors or motors.
3Measurement precision
If active return mechanisms are added to eliminate cable slack, then control precision improves, but device complexity and energy consumption increase
Solution Approach 1:
The nested spool assembly operates as a self-service tensioning system. The inner spool winds the steering cable while the outer spool simultaneously unwinds or stores excess cable length. This self-regulating mechanism automatically maintains cable tension without requiring external power sources, motors, or active control systems. The system uses the mechanical energy already present in the catheter deflection motion itself to manage cable tension, achieving precise control with minimal additional energy consumption.
Data Source
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Figure 3~4A
AI summary
A catheter system (100) may include a steering catheter (410a, 410b) and a steering cable (1400) extending through a lumen (412a, 412b) in the wall of the steering catheter. A steering assembly (1000) may include a spool assembly having an outer spool (1200), an inner spool (1300) received within the outer spool, and a spool shaft (1100) received within the inner spool. The spool shaft and a recess (1340) 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 (1330) that engage with complementary recesses (1220) of the outer 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.