Compact Fiber Optic Force Sensor for Catheters
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Solution Overview
Problem
Existing catheter systems for medical procedures lack the ability to accurately sense contact forces with vessel or organ walls, leading to imprecision and potential tissue damage due to excessive force, and are often complex, prone to electromagnetic interference, and susceptible to thermal errors.
Innovation Solution
A compact fiber optic force sensor system with passive or active temperature compensation, featuring a structural member with flexures and slots that change dimension in response to contact forces, using fiber optics and reflecting members with different thermal expansion coefficients to enhance sensitivity and reduce thermal errors, while maintaining a compact profile and immunity to electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical, capacitive, inductive or resistive pressure sensing devices are used to measure contact force, then force measurement capability is provided, but device complexity increases and electromagnetic interference susceptibility increases
Solution Approach 1:
The patent replaces mechanical, capacitive, inductive or resistive pressure sensing devices with an optical sensing system using fiber optic cables and Fabry-Perot interferometers. This substitution eliminates electromagnetic interference susceptibility and reduces device complexity while maintaining force measurement capability through optical path length changes caused by structural member deformation.
Solution Approach 2:
The patent introduces fiber optic cables as intermediaries to transmit force information from the distal extremity to the proximal end. The optical fibers act as mediators that convert mechanical deformation into optical signal changes without requiring complex electronic sensors at the distal tip, thereby reducing device complexity.
2Measurement precision
If mechanical pressure sensing devices are used to measure contact force, then force measurement is enabled, but the devices must be sealed to prevent blood or liquids from disturbing measurements, increasing device complexity
Solution Approach 1:
The patent replaces mechanical pressure sensing devices that require sealing with an optical sensing system using fiber optic cables and Fabry-Perot interferometers. This substitution eliminates the need for sealing mechanisms while maintaining force measurement accuracy in wet medical environments.
3Stability of the object's composition
If expandable baskets or hooks are used to stabilize the distal extremity, then contact stability is improved, but the systems cannot sense the load applied by tissue wall movement
Solution Approach 1:
The patent integrates multiple functions into the structural member: it provides mechanical stabilization through its rigid configuration while simultaneously serving as the sensing element for force measurement. The structural member's deformation under load directly modulates the optical path length, enabling load sensing without requiring separate sensing components.
Solution Approach 2:
The patent merges the stabilization function and force sensing function into a single integrated structural member. The rigid structure provides both mechanical stability and the sensing capability through its deformation characteristics, eliminating the need for separate expandable baskets or hooks and sensing devices.
4Productivity
If the end effector contacts the tissue wall with excessive force, then treatment effectiveness may be improved, but inadvertent puncturing of the tissue resulting in cardiac tamponade can occur
Solution Approach 1:
The patent implements real-time force feedback by measuring contact forces between the end effector and tissue wall using the optical sensing system. This feedback enables closed-loop control of contact force, allowing the system to maintain treatment effectiveness while preventing excessive force that could cause tissue puncture or cardiac tamponade.
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 system provides accurate and uniform force sensing with reduced thermal errors, enhancing the precision and safety of medical procedures by allowing real-time feedback on contact forces, improving maneuverability, and minimizing tissue damage.
Implementation Method 1
The fiber optic and the reflecting member define a gap that creates an interferometric cavity
Implementation Method 2
the structural member is configured to produce a change in the dimension of at least one of the respective gaps in response to a force exerted on the distal tip of the catheter
Implementation Method 3
A person skilled in the art will appreciate that the force sensor of the present invention may be configured to compensate, passively or actively, for changes in dimension of the respective gaps that are caused by temperature changes
Data Source
AI summary
An ablation catheter system configured with a compact force sensor at a distal end for detection of contact forces exerted on an end effector. The force sensor includes fiber optics operatively coupled with reflecting members on a structural member. In one embodiment, the optical fibers and reflecting members cooperate with the deformable structure to provide a variable gap interferometer for sensing deformation of the structural member due to contact force. In another embodiment, a change in the intensity of the reflected light is detected to measure the deformation. The measured deformations are then used to compute a contact force vector. In some embodiments, the force sensor is configured to passively compensate for temperature changes that otherwise lead to erroneous force indications. In other embodiments, the system actively compensates for errant force indications caused by temperature changes by measuring certain local temperatures of the structural member.