Tendon-Driven Catheter Force Control Without Tip Sensors
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Solution Overview
Problem
Existing robotic catheter intervention systems lack effective sensor-free force control, leading to challenges in maintaining optimal contact force during procedures like radiofrequency ablation, which can result in tissue perforation or inadequate treatment due to the absence of direct tactile feedback and reliance on computationally expensive or error-prone estimation methods.
Innovation Solution
A method for controlling force through position using a steerable tendon-driven catheter system, employing a combination of force-contact and kinematic models, including artificial intelligence, to determine and adjust the configuration of tendons for precise force application without sensors, utilizing a control mechanism with servo-motors and tendon encoders for real-time adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor-free force estimation methods are used, then manufacturing complexity and cost are reduced, but measurement precision and reliability of force control deteriorate
Solution Approach 1:
The patent introduces an intermediary force estimation model that acts as a mediator between the catheter position and tissue interaction force. Instead of directly measuring force with sensors, the system uses a trained neural network model that estimates force based on catheter configuration and tissue mechanical properties, thereby avoiding sensor integration while maintaining acceptable force estimation accuracy
Solution Approach 2:
The patent replaces the mechanical sensor-based force measurement system with a computational model. The force estimation is achieved through software-based neural networks that process catheter position data and tissue mechanical models, substituting physical sensors with algorithmic calculations to reduce manufacturing complexity
2Device complexity
If shape sensing methods are used for force estimation, then sensor-free operation is achieved, but sensitivity to shape estimation errors increases
Solution Approach 1:
The patent implements a feedback mechanism where the force estimation model continuously refines its predictions based on the relationship between catheter configuration and estimated force. The system uses the estimated force information to adjust catheter positioning and maintain reliable force control, creating a closed-loop control system that compensates for estimation uncertainties
Solution Approach 2:
The patent changes the parameters used for force estimation from direct shape sensing measurements to a combination of catheter configuration parameters and tissue mechanical properties. By using multiple parameters and a trained neural network model, the system reduces sensitivity to individual measurement errors and improves overall reliability
3Measurement precision
If mechanistic models are used for force estimation, then measurement precision is improved, but computational cost and complexity increase
Solution Approach 1:
The patent performs preliminary action by training the neural network force estimation model offline before actual catheter procedures. The computationally intensive model training and parameter identification are done in advance using simulated or experimental data, allowing the deployed system to use the pre-trained model for fast, low-computation force estimation during real-time procedures
Data Source
AI summary
A method and system for controlling a force applied by a tip of a tendon-driven steerable catheter to a tissue of a body part through position control of the catheter. A forward force-contact model determines a desired indentation depth from a desired force and an inverse kinematic model determines a desired configuration of the catheter system based on the desired indentation depth of the tip. A feedback control loop determines an actual indentation depth based on an actual position of the tip within the tip and a position of the tip in free space corresponding to an actual configuration of the catheter and estimates an actual force applied on said tissue based on said actual indentation depth.