Cochlear Implant Magnet Assembly for MRI Torque Reduction
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Solution Overview
Problem
Conventional cochlear implants are not MRI-compatible due to misalignment of magnets, which can demagnetize or dislocate, and thick skin flaps create a large distance leading to weak magnetic attraction forces, preventing optimal alignment of headpiece and implant magnets.
Innovation Solution
A magnet assembly with a case, rotatable frame, and three elongate magnets - two diametrically magnetized and one mechanically biased - that facilitate alignment with MRI fields, reducing torque and improving magnetic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diametrically magnetized disk-shaped magnet is used in conventional cochlear implants, then the magnet can be positioned within the implant housing, but the magnet experiences demagnetization and excessive torque when misaligned with MRI magnetic fields by 30° or more, leading to potential dislocation and discomfort
Solution Approach 1:
The single disk-shaped magnet is segmented into three elongate diametrically magnetized magnets arranged in a specific configuration. This segmentation allows each magnet to experience reduced torque individually while collectively providing stable positioning during MRI procedures, resolving the contradiction between magnet stability and MRI compatibility.
Solution Approach 2:
The three elongate magnets are arranged asymmetrically with specific orientations relative to each other and to the implant housing. This asymmetric arrangement optimizes the magnetic field distribution to minimize torque effects during MRI while maintaining effective positioning force, addressing the contradiction between stability and MRI safety.
2Force
If axially magnetized magnets are used in cochlear implants, then the magnets provide strong retention force for headpiece positioning, but they are not compatible with MRI systems and require surgical removal and replacement
Solution Approach 1:
The axially magnetized magnet configuration is replaced with a mechanically arranged array of three diametrically magnetized magnets. This mechanical reconfiguration substitutes the problematic axial magnetization pattern with a diametric magnetization pattern that is inherently compatible with MRI fields while maintaining the necessary retention force through optimized spatial arrangement.
3Object-affected harmful factors
If the magnet assembly is designed to align with 3D MRI magnetic fields, then torque on magnets is minimized, but the complexity of the magnet apparatus increases with rotatable frames and multiple magnets
Solution Approach 1:
The three elongate magnets are configured to simultaneously perform multiple functions: providing retention force for headpiece positioning, aligning with MRI magnetic fields to minimize torque, and maintaining stable orientation during scanning. This multi-functionality reduces the need for additional complex alignment mechanisms while achieving MRI compatibility.
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
Enhances magnet retention and alignment, reducing friction and torque, and ensuring better alignment of headpiece and implant antennas, even with thick skin flaps, while being MRI-compatible.
Implementation Method 1
two or more elongate diametrically magnetized magnets that are located in the frame in close proximity to one another and that are rotatable about their respective longitudinal axis relative to the frame. This combination allows the magnets to align with three-dimensional (3D) MRI magnetic fields, regardless of field direction, which results in very low amounts of torque on the magnets
Implementation Method 2
The headpiece communicates with the cochlear implant by way of a transmitter (e.g., an antenna) on the headpiece and a receiver (e.g., an antenna) on the implant. Optimum communication is achieved when the transmitter and the receiver are aligned with one another. To that end, the headpiece and the cochlear implant may include respective positioning magnets that are attracted to one another
Data Source
AI summary
A magnet assembly including a case defining a central axis, a magnet frame within the case and rotatable about the central axis of the case, first and second elongate magnets, located within in the frame, that are diametrically magnetized, that each define a longitudinal axis and a N-S direction, that are rotatable about the longitudinal axis relative to the frame, that are separated from one another by a fixed non-zero distance that is perpendicular to at least one of the longitudinal axes, and that are not mechanically biased to respective N-S rotational orientations, and a third elongate magnet, located between the first and second elongate magnets, that defines a longitudinal axis and a N-S direction that is perpendicular to the longitudinal axis, and that is mechanically biased to a predetermined N-S rotational orientation.