Reference Catheter Dislodgement Detection in Medical Localization
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Solution Overview
Problem
The navigational reference in medical localization systems can become dislodged due to mechanical or perceived movements, leading to invalid position measurements, and existing methods struggle to distinguish between actual and false dislodgements.
Innovation Solution
A method that computes slow- and fast-moving average locations of reference localization elements, compares distances to a dislodgement threshold, and analyzes angles to determine if the reference catheter has dislodged, providing guidance for repositioning or adjusting measurements accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a catheter-mounted reference localization element is inserted into the heart to establish the origin of the coordinate system, then the navigational reference is positioned proximate to the mapping catheter for improved measurement accuracy, but the reference catheter becomes vulnerable to dislodgement due to collision, entanglement, or patient movement
Solution Approach 1:
The system continuously monitors the position of the reference localization element by comparing fast-moving average location with slow-moving average location. When the distance between these averages exceeds a threshold, the system generates a dislodgement alert, providing real-time feedback to maintain reference stability while preserving measurement accuracy
Solution Approach 2:
The patent implements dynamic threshold adjustment based on the operational state of the catheter. The dislodgement detection threshold varies depending on whether the catheter is in navigation mode or mapping mode, allowing the system to adapt to different operational requirements and reduce false alarms while maintaining sensitivity to actual dislodgement
2Ease of operation
If the navigational reference is allowed to move freely within the heart chamber, then the reference catheter can be easily positioned and repositioned, but the coordinate system origin becomes unstable leading to invalid position measurements
Solution Approach 1:
The system pre-establishes a slow-moving average location of the reference element before the dislodgement detection process begins. This preliminary reference point allows the system to detect deviations from the intended position while permitting normal operational movements during catheter positioning
Solution Approach 2:
The detection threshold is dynamically adjusted based on the operational mode. During navigation when positioning is frequent, the threshold is higher to allow movement. During mapping when precision is critical, the threshold is lower to detect even minor dislodgements, thus balancing ease of operation with measurement validity
3Reliability
If a dislodgement detection system is implemented using location averaging and threshold comparison, then actual dislodgements can be detected, but false dislodgements may occur due to patient movement, hydration, and respiration
Solution Approach 1:
The system dynamically adjusts the dislodgement detection threshold based on the operational state. In navigation mode where some movement is expected, a higher threshold is used. In mapping mode where precision is critical, a lower threshold is applied. This dynamic adjustment reduces false dislodgement detection while maintaining sensitivity to actual dislodgements
Solution Approach 2:
The slow-moving average location acts as an intermediary between the raw fast-moving average position data and the dislodgement detection decision. This intermediate reference smooths out transient movements caused by respiration and patient motion, allowing the system to distinguish between normal physiological movements and actual catheter dislodgement
Data Source
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AI summary
A method of detecting dislodgement of a navigational reference for a localization system (8) includes securing a reference catheter (29), including at least one reference localization element, at an initial reference location within a localization field. The positions of one or more of the reference localization elements are monitored for a perceived displacement that suggests that the reference catheter (29) has become dislodged from the initial reference location (e.g., a displacement above a certain threshold, such as about 4 mm). The direction of this perceived displacement may then be further analyzed (e.g., compared to a predicted or most likely direction of displacement) to determine whether there has been an actual dislodgement of the reference catheter (29), and, if so, an appropriate signal (e.g., an audible or visual warning) may be generated. Upon dislodgement, guidance may be provided to aid the practitioner in restoring the reference catheter (29) to its initial location.