Elongate Medical Device Image Smoothing via Curvature Estimation
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Solution Overview
Problem
Conventional systems for monitoring the position and orientation of elongate medical devices, such as catheters, within the body are prone to systematic errors due to sensor impedance variations and amplifier channel differences, leading to distorted images, especially for curved devices where existing smoothing algorithms are inadequate.
Innovation Solution
A computer-based model construction system that estimates true parameters including curvature and torsion terms, calculates measurement errors based on stiffness parameters, and computes smoothed data points to generate accurate images of elongate medical devices by describing sensor positions as deviations from a curved parametric form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional smoothing algorithms are used on curved catheters, then processing speed is maintained, but image accuracy deteriorates due to induced errors such as reduced catheter diameter
Solution Approach 1:
The patent applies curvature-based basis functions instead of straight-line basis functions to model catheter positions. This allows the smoothing algorithm to properly handle curved catheters by describing measured electrode positions as deviations from a curved parametric form, thereby maintaining both image accuracy and computational efficiency without inducing artificial diameter reduction
Solution Approach 2:
The patent introduces curvature and torsion parameters to describe the three-dimensional shape of the catheter. By changing the mathematical parameters from simple linear deviations to curved parametric descriptions involving curvature and torsion terms, the algorithm can accurately represent curved catheter geometries while maintaining computational tractability
2Reliability
If position sensors are used to monitor catheter location, then real-time tracking is achieved, but systematic errors occur due to sensor impedance variations and amplifier channel differences
Solution Approach 1:
The patent employs an iterative optimization process that uses feedback from the measured electrode positions to refine the estimated catheter shape parameters. By repeatedly adjusting the curvature and torsion parameters to minimize the difference between measured and predicted electrode positions, the system compensates for systematic errors in sensor measurements
Solution Approach 2:
The patent introduces a parametric curve model as an intermediary between the raw sensor measurements and the final catheter position representation. This intermediate model acts as a filter that separates true catheter shape information from measurement noise and systematic errors, thereby improving position accuracy while maintaining reliable real-time tracking
3Ease of manufacture
If basis functions modeling deviations from a straight line are used, then computational simplicity is maintained, but accuracy deteriorates for catheters with substantial curvature
Solution Approach 1:
The patent replaces straight-line basis functions with curvature-based basis functions that inherently account for catheter bending. By using parametric curves with curvature and torsion terms, the algorithm maintains mathematical tractability and ease of implementation while accurately representing curved catheter geometries that straight-line models cannot capture
Data Source
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AI summary
The present disclosure provides systems and methods for generating smoothed images of an elongate medical device including a plurality of position sensors. The system includes a model construction system configured to be coupled to the medical device and acquire data points corresponding to positions of the position sensors. The computer-based model construction system is further configured to establish a coordinate system, calculate a coordinate for each position sensor, estimate a set of true parameters describing the medical device including a curvature term and a torsion term, calculate a measurement error for each position sensor based on a stiffness parameter, compute smoothed data points for the position sensors based on (i) a function of the estimated set of true parameters and the coordinates of the position sensors, and (ii) a weighting of the measurement error, generate an image of the medical device using the smoothed data points, and display the image.