Single-Axis Sensor Catheter Tracking via Spherical Harmonics
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Solution Overview
Problem
Existing catheter navigation systems require tri-axial orthogonal magnetic sources for accurate position and orientation tracking, which is impractical and limits the accuracy and volume of magnetic field modeling, especially when using single-axis sensors.
Innovation Solution
A method using spherical harmonics to model magnetic fields within a predefined volume, coupled with a single-axis sensor and a processor to minimize a cost function through dipole terms, allowing for accurate position and orientation determination of a catheter within a living body without the need for tri-axial sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tri-axial orthogonal magnetic sources are used for accurate position and orientation tracking, then measurement precision is improved, but device complexity and hardware requirements increase
Solution Approach 1:
The patent extracts and removes the requirement for tri-axial orthogonal magnetic sources from the system. By using a single-axis sensor with spherical harmonics modeling, the invention eliminates the need for complex multi-axial magnetic source configurations while maintaining tracking accuracy through mathematical field representation.
Solution Approach 2:
The patent replaces the physical mechanical arrangement of tri-axial magnetic sources with a computational approach using spherical harmonics. Instead of requiring three perpendicular magnetic field generators, the system uses a single magnetic source with mathematically modeled field components that are processed through optimization algorithms to determine position and orientation.
2Measurement precision
If tri-axial orthogonal magnetic sources are used, then measurement precision is improved, but the volume of magnetic field modeling is limited
Solution Approach 1:
The patent transitions from a limited spatial configuration of tri-axial sources to a spherical coordinate system representation using spherical harmonics. This dimensional transformation allows the magnetic field to be modeled in a much larger volumetric space, as spherical harmonics naturally describe fields in three-dimensional spherical coordinates, extending the usable tracking volume beyond what linear orthogonal arrangements can provide.
3Device complexity
If single-axis sensors are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces spherical harmonics mathematical modeling as an intermediary between the single-axis sensor and the position/orientation determination. The spherical harmonics expansion acts as a mediator that translates the limited single-axis measurements into comprehensive three-dimensional position and orientation information by modeling the complete magnetic field structure and comparing measured values with theoretical predictions at different spatial locations.
Solution Approach 2:
The patent changes the parameters used for field representation from direct tri-axial magnetic field components to spherical harmonics coefficients. By transforming the problem into spherical coordinate parameters and using optimization to match measured field values with modeled values, the system extracts maximum information from the single-axis sensor, achieving accurate position and orientation tracking despite the simplified sensor configuration.
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 approach enhances computational efficiency and accuracy, enabling precise tracking of catheter position and orientation beyond the initial calibrated volume, with improved accuracy and reduced hardware requirements.
Implementation Method 1
generating a magnetic field in a predefined volume... measuring the magnetic field by a field detector
Data Source
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AI summary
A method includes generating a magnetic field in a predefined volume. A reference model is defined, which models the magnetic field at multiple points in the volume using spherical harmonics. The magnetic field is measured by a field detector, which is coupled to an intra-body probe inserted into an organ of a living body located in the volume. A cost function is defined by comparing the measured magnetic field with the reference magnetic field model within the volume. The cost function is minimized by a computation over dipole terms in a derivative over the cost function so as to find a position and orientation that matches the measured magnetic field. The found position and orientation is outputted as the position and orientation of the probe in the organ.