Catheter Force Sensor Zero-Force Calibration via Phase Shift Detection
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Solution Overview
Problem
Existing methods for verifying electrode contact with body tissue during ablation procedures are often unreliable, particularly due to impedance-based binary contact indications that are sensitive to changes in skin impedance, and lack accurate detection of zero-force conditions for force sensors.
Innovation Solution
A catheter system equipped with a force sensor and a processor that injects a current between the electrode and tissue, measures phase shifts, and calibrates the zero-force point by detecting a consistent increase in phase shifts below a threshold over a predetermined time period, allowing for accurate detection of non-contact conditions with high probability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If impedance-based binary contact indication is used, then contact verification is simple, but reliability is poor due to sensitivity to skin impedance changes
Solution Approach 1:
The patent replaces electrical impedance measurement with mechanical force sensing using a force sensor at the catheter tip. The force sensor directly measures contact force between the electrode and tissue, eliminating sensitivity to skin impedance changes while maintaining simple operation through direct force measurement
Solution Approach 2:
The patent introduces a force sensor as an intermediary element between the electrode and tissue to indirectly measure contact conditions. This intermediary device provides reliable contact verification by measuring mechanical force rather than relying on electrical impedance properties of the tissue
2Measurement precision
If force sensor is used for contact detection, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines the force sensor with the electrode assembly at the catheter tip, merging two functions (force sensing and electrical contact) into a single integrated component. This reduces overall device complexity while maintaining high measurement precision through the force sensor
3Device complexity
If traditional contact verification methods are used, then device complexity is low, but measurement precision is insufficient for accurate zero-force detection
Solution Approach 1:
The patent implements a self-calibrating force sensor that automatically determines its zero-force reference point during the ablation procedure. The sensor monitors force measurements and autonomously identifies when contact force is zero, eliminating the need for complex external calibration equipment while achieving high measurement precision
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 method provides a quick and accurate means to determine if the catheter tip is not in contact with tissue, ensuring reliable calibration of the force sensor and minimizing waiting time for detection, with a high probability of correctness (>99%) and short detection time.
Implementation Method 1
A processor measures a succession of phase shifts of a current injected between an electrode on the catheter and the tissue
Data Source
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AI summary
A method, including injecting a current between an electrode of a catheter and tissue in proximity to the catheter, the catheter having a force sensor configured to measure a force between the catheter and the tissue. The method further includes measuring a succession of phase shifts of the current relative to a fixed reference and verifying that a cardinality of the measured phase shifts falling below a predetermined threshold increases over a predetermined time period. A zero-force point for the force sensor is calibrated according to the force measured by the force sensor during the predetermined time period.