Irrigated Ablation Catheter Contact Force Sensing via Fluid Pressure
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Solution Overview
Problem
Conventional catheters require complex and costly mechanisms, such as strain gauges, to measure contact force between the catheter and tissue, which increase the size and complexity of the device.
Innovation Solution
A catheter system that uses a deformable shaft with an inner and outer tip member configuration, where the size of the gap between the tip members varies with contact force, allowing fluid pressure differences to be measured to determine contact force, eliminating the need for conventional force sensors and associated components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force sensing mechanisms (strain gauges) are used to measure contact force, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical force sensing mechanisms (strain gauges) with a fluid pressure-based sensing system. Fluid is delivered through an inner tip member, and the pressure required to maintain a specific flow rate changes in response to contact force applied to the outer tip member. This substitution eliminates complex mechanical components while maintaining measurement capability through fluid dynamics principles.
Solution Approach 2:
The invention uses hydraulic principles by delivering fluid through the catheter tip and measuring pressure changes in the fluid column. The fluid delivery lumen in the inner tip member creates a pressure field that responds to external contact forces. By monitoring the pressure required to maintain constant fluid flow, the system indirectly measures contact force without direct mechanical sensing elements at the tip.
2Measurement precision
If strain gauges and additional components are added for force measurement, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The inner tip member serves multiple functions: it delivers irrigation fluid to the treatment site and simultaneously acts as a pressure sensor for contact force measurement. The fluid delivery system, already necessary for ablation therapy, is repurposed to provide sensing capability. This multi-functionality eliminates the need for separate sensing components, reducing manufacturing complexity and cost.
Solution Approach 2:
The catheter's own fluid delivery system provides the sensing function. The pressure changes in the fluid column, caused by contact force affecting the gap between inner and outer tip members, are self-measured through the existing fluid pathway. No external or additional sensing infrastructure is required - the system uses its own operational fluid to perform both therapy and measurement functions.
3Measurement precision
If conventional force sensors are integrated into the catheter, then measurement precision is improved, but the size of the catheter increases
Solution Approach 1:
The sensing function is merged with the fluid delivery structure. The inner tip member, which already exists as a separate component for fluid delivery, is integrated with the sensing mechanism. The gap between the inner and outer tip members serves dual purposes: it controls fluid flow for irrigation and simultaneously transduces contact force into pressure changes. This merging eliminates the need for separate sensor housings and wiring within the catheter tip.
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
Enables accurate measurement of contact force without increasing the size, cost, or complexity of the catheter, providing a simpler and more cost-effective solution for force measurement during procedures like ablation.
Implementation Method 1
A difference in fluid pressure between the first and second ports is indicative of a contact force between the catheter and the external surface
Implementation Method 2
The outer and inner tip members are configured such that a size of the gap varies in response to contact of the outer tip member with an external surface
Data Source
AI summary
A catheter is configured to indicate contact force between the catheter and tissue. The catheter includes an elongate deformable shaft having proximal and distal ends. The catheter includes an inner tip member projecting outwardly from the distal end, the inner tip member defining a fluid delivery lumen extending therethrough, and an outer tip member coupled to the distal end and disposed about the inner tip member. The inner and outer tip members define a gap therebetween in fluid communication within the fluid delivery lumen and the tip members are configured such that the size of the gap varies in response to contact of the outer tip member with the tissue. The catheter further includes first and second fluid sensing tubes defining ports upstream and downstream from the gap; wherein a difference in fluid pressure between the ports is indicative a contact force between the catheter and the external surface.