Implant Magnet Distance Estimation Using Magnetic Field Zero-Crossing
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Solution Overview
Problem
Implantable medical devices, such as cochlear implants, face challenges in maintaining the external part's position due to inadequate magnetic holding force, where the exact distance from the skin surface to the implant magnet is unknown post-surgery, making it difficult to determine if the issue is due to excessive distance or magnetization loss.
Innovation Solution
A method using a plane defined perpendicular to the skin with an array of magnetic sensors to measure the magnetic field strength, determining x-axis coordinates at y-axis zero positions, and calculating the y-axis coordinate to estimate skin thickness over the implanted magnet, which can be done with one-dimensional or two-dimensional sensor arrays and involves iterative or non-iterative calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If passive magnetic field measurement with magnetic sensors is used to determine implant magnet location, then distance estimation capability is provided, but computational complexity and energy consumption increase
Solution Approach 1:
The patent extracts only the essential measurement information needed for distance determination by identifying and measuring specific magnetic field components (y-axis component at y-axis zero positions) rather than performing full three-dimensional field mapping. This selective extraction reduces computational burden while maintaining measurement precision.
Solution Approach 2:
Instead of calculating distance directly from absolute magnetic field strength measurements (which requires knowing magnetization strength), the patent inverts the approach by using the spatial distribution pattern of magnetic field components and their zero-crossing positions to infer distance. This indirect method eliminates the need for absolute field strength calibration.
2Measurement precision
If complicated distance calculation algorithms are used to determine implant magnet location from magnetic field measurements, then measurement capability is provided, but device complexity increases
Solution Approach 1:
The patent segments the magnetic field measurement problem into distinct components: measuring the y-axis magnetic field component at specific y-axis zero positions along the x-axis. This segmentation transforms a complex three-dimensional field mapping problem into a series of simpler one-dimensional measurements that can be processed more efficiently.
Solution Approach 2:
The patent changes the measurement parameter from absolute magnetic field strength to the spatial position of zero-crossing points in the magnetic field component. This parameter transformation simplifies the calculation by using geometric relationships of field line intersections rather than requiring complex inversion of field strength equations.
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 allows for accurate estimation of skin thickness over the implanted magnet, providing a numerically stable and efficient computation of distance without requiring absolute magnetic field measurements or magnetization strength, suitable for battery-operated devices.
Implementation Method 1
The magnetic field strength of the implanted magnet is measured using an array of magnetic sensors on the skin of the patient
Data Source
AI summary
A method is described for estimating skin thickness over an implanted magnet. A plane is defined that is perpendicular to the skin of a patient over an implanted magnet and characterized by x- and y-axis coordinates. The magnetic field strength of the implanted magnet is measured using an array of magnetic sensors on the skin of the patient. From the measured magnetic field strength, at least one x-axis coordinate in the plane is determined for at least one y-axis zero position on the array where a y-axis component of the measured magnetic field strength is zero. From that, a y-axis coordinate of the at least one y-axis zero is calculated as a function of the at least one x-axis coordinate, such that the y-axis coordinate represents thickness of the skin over the implanted magnet.