Quadrature Signal Analysis for Sheath Detection in Localization Systems
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Solution Overview
Problem
Impedance-based localization systems in medical procedures become unreliable when a localization element, such as an electrode, is withdrawn into an introducer sheath due to non-linear and erratic voltage gradients, making it difficult to accurately track the element's position.
Innovation Solution
The system detects state changes of a localization element relative to an introducer sheath by analyzing the quadrature component of localization signals, establishing a baseline component outside the sheath and detecting deviations to determine if the element is within or outside the sheath, allowing for alerts, data suspension, or data discard when the element is unreliable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance-based localization systems are used to track catheter position, then real-time positional information is obtained, but the measurements become unreliable when the catheter is withdrawn into the introducer sheath
Solution Approach 1:
The system performs preliminary calibration by establishing a baseline quadrature component value when the localization element is known to be outside the sheath. This baseline is stored and used for subsequent comparisons to detect sheath entry/exit events, enabling the system to anticipate and compensate for measurement reliability changes before they occur.
Solution Approach 2:
The system continuously monitors the quadrature component of the localization signal and compares it against the stored baseline. When deviations exceed a threshold, the system generates alerts or suspends data collection, creating a feedback loop that maintains measurement reliability by identifying and responding to sheath-related measurement degradation in real-time.
2Ease of operation
If the localization element is withdrawn into the introducer sheath for protection or repositioning, then the element is protected or repositioned, but the voltage gradient becomes non-linear and erratic causing localization errors
Solution Approach 1:
The quadrature component serves as an intermediary indicator that indirectly signals the localization element's position relative to the sheath. Instead of directly measuring position (which becomes unreliable inside the sheath), the system uses the quadrature component as a mediator to infer sheath entry/exit events, maintaining measurement precision without restricting catheter manipulation.
Solution Approach 2:
The system changes the state representation by using the quadrature component's deviation from baseline as an indicator signal. When the quadrature component deviates beyond a threshold, it signals a state change (sheath entry/exit), analogous to a color change indicator, allowing practitioners to recognize localization reliability changes without directly observing the voltage gradient distortions.
3Productivity
If continuous monitoring of localization signals is performed, then real-time position data is available, but data collected when the element is within the sheath becomes unreliable and potentially misleading
Solution Approach 1:
The system automatically discards localization data when the quadrature component indicates the element is within the sheath (by comparing against the baseline and threshold). This selective discarding prevents unreliable data from contaminating the dataset, while recovering data collection when the element exits the sheath, thereby maintaining both productivity and data quality.
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
This analytical method provides accurate detection of localization element/sheath state changes, reducing the burden on practitioners to visually recognize conditions and ensuring reliable measurements during electrophysiology studies by suspending or discarding data when the element is within the sheath.
Implementation Method 1
impedance-based localization systems determine the coordinates of the medical device by interpreting a voltage measured by the medical device (more particularly, the voltages measured by one or more electrodes carried on the medical device) as a location within an electrical field
Implementation Method 2
obtaining at least one localization signal from at least one catheter-borne localization element positioned within the localization field via an introducer sheath, the at least one localization signal including an in-phase component and a quadrature component
Data Source
AI summary
A method of detecting whether a localization element is within or outside of an introducer sheath generally includes obtaining a localization signal from the localization element and detecting the state of the localization element relative to the sheath based upon the quadrature component of the localization signal. A baseline quadrature component is typically established with the localization element outside of the sheath. When the quadrature component deviates from this baseline value, it is indicative of the localization element being within the sheath. Conversely, when the quadrature component remains relatively close to the baseline value, it is indicative of the localization element being outside of the sheath. In an electrophysiology study, the state information can be used to take corrective action with respect to the data being collected.