Dynamic Metal Immunity in Electromagnetic Position Sensing
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Solution Overview
Problem
Electromagnetic locating and tracking systems face inaccuracies due to the introduction of moving metallic or magnetically-responsive articles, which cause distortions in magnetic fields, leading to errors in determining the position of objects being tracked, especially in surgical environments with conductive and permeable materials.
Innovation Solution
The system employs a control unit that uses a spatial interpolation algorithm to calculate corrected magnetic field values for a probe by incorporating measured magnetic field values from both the probe and reference elements, accounting for errors induced by interfering objects, allowing for accurate tracking without extensive initial calibration or cumbersome means to reduce eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic fields are used for non-contact tracking of medical probes, then real-time location information can be obtained without X-ray imaging, but the presence of moving metallic or magnetically-responsive articles distorts the magnetic fields and causes tracking inaccuracies
Solution Approach 1:
The patent introduces reference elements as intermediary objects that mediate between the magnetic field and the metal article. These reference elements experience the same field distortion as the probe but can be mathematically accounted for, allowing the system to compensate for the distortion and recover accurate probe position information despite the presence of metallic articles
Solution Approach 2:
The system implements feedback by continuously monitoring the positions of reference elements and using this information to dynamically adjust and compensate for magnetic field distortions. The control unit calculates corrected probe positions based on real-time reference element data, creating a closed-loop system that maintains tracking accuracy despite changing field conditions
2Measurement precision
If traditional calibration procedures are used to account for magnetic field distortions, then some accuracy can be achieved, but extensive initial calibration is required and cannot account for moving metal objects
Solution Approach 1:
The patent transitions from static calibration to dynamic compensation by using reference elements that continuously track field distortions during the procedure. Instead of performing extensive initial calibration that assumes fixed field conditions, the system adapts in real-time to changing magnetic field environments caused by moving metal objects, eliminating the need for prolonged calibration procedures
Solution Approach 2:
The system performs preliminary placement of reference elements at known positions before the procedure begins. These reference elements are positioned in advance to establish a baseline reference framework that enables real-time compensation without requiring extensive calibration during the procedure itself
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 enables accurate tracking of objects regardless of the number, conductive characteristics, velocities, orientations, and durations of metal objects, improving positional accuracy and reducing the need for extensive calibration procedures.
Implementation Method 1
a set of radiators (34), which are adapted to be placed at respective positions in a vicinity of a body of a subject and to generate electromagnetic energy fields
Implementation Method 2
a position sensor, which is adapted to placed in the body of the subject and to generate sensor signals responsive to the energy fields
Data Source
AI summary
The disclosure concerns position-sensing apparatus, having radiators which generate electromagnetic energy fields and a position sensor which generates sensor signals responsive to the energy fields. Reference elements are placed at respective positions near the sensor to generate reference signals responsive to the energy fields. And, a control unit is used to calculate a position of the sensor based on sensor signals and reference element errors in order to account for the effects of interfering metal objects.