MRI-Compatible Cochlear Implant Magnet Assembly
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Solution Overview
Problem
Conventional cochlear implant magnet assemblies are not MRI-compatible, leading to potential demagnetization and dislocation issues, and plastic frames used in newer MRI-compatible assemblies are susceptible to damage from welding heat.
Innovation Solution
A magnet assembly with a disk-shaped case, a rotatable frame, and diametrically magnetized magnets, featuring a thermal insulation arrangement including air gaps to protect the frame and magnets from welding heat, ensuring compatibility with MRI fields and maintaining magnetic alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diametrically magnetized disk-shaped magnets are used in conventional cochlear implants, then magnetic alignment can be achieved, but the magnets are susceptible to demagnetization and dislocation when exposed to MRI magnetic fields misaligned by 30° or more
Solution Approach 1:
The magnet assembly incorporates a rotatable frame that can rotate about the central axis of the case, allowing the diametrically magnetized magnets to dynamically realign themselves with the direction of applied magnetic fields such as MRI fields, preventing demagnetization and dislocation
Solution Approach 2:
The magnets are pre-configured in a rotatable frame structure that enables them to automatically orient themselves in advance before exposure to MRI fields, ensuring they are properly aligned to resist demagnetization and dislocation forces
2Reliability
If plastic frames are used in MRI-compatible magnet assemblies, then MRI compatibility is achieved, but the plastic frames are susceptible to damage from welding heat during hermetic sealing
Solution Approach 1:
A metal ring is introduced as an intermediary component between the plastic frame and the welding process. The ring is positioned to create an air gap that thermally isolates the plastic frame from the welding heat, allowing hermetic sealing to proceed without damaging the plastic frame
Solution Approach 2:
The magnet assembly is segmented into distinct functional zones: the plastic frame containing the magnets, the metal ring providing thermal barrier, and the case structure. This segmentation allows each component to perform its specific function while protecting vulnerable parts from harmful effects
3Device complexity
If axially magnetized disk-shaped magnets are used, then simple magnet structure is achieved, but the magnets are not compatible with MRI systems and require surgical removal and replacement
Solution Approach 1:
The simple axially magnetized disk-shaped magnet structure is combined with a rotatable frame mechanism, allowing the magnet to dynamically change its magnetic orientation from fixed axial to adaptable diametric alignment with MRI fields, achieving both structural simplicity and MRI compatibility
Solution Approach 2:
The magnetic orientation parameter of the magnet is made changeable through the rotatable frame structure. The magnet can change its magnetic field direction from axial to diametric alignment, adapting to different operational conditions including MRI exposure without requiring structural redesign
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
The solution provides a magnet assembly that is MRI-compatible, reducing torque and discomfort, and protects the frame and magnets from heat damage during welding, enhancing the stability and safety of cochlear implants.
Implementation Method 1
three or more elongate diametrically magnetized magnets 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
a ring, defining an outer surface, between the frame and the case side wall and offset from the case side wall such that a first air gap is located between the inner surface of the case side wall and the outer surface of the ring
Data Source
AI summary
A magnet assembly in accordance with at least one of the present inventions may include a case defining a central axis and including first and second end walls and a side wall, with an inner surface, between the first and second end walls, a frame within the case and rotatable about the central axis of the case, a plurality of diametrically magnetized magnets that are located in the frame, that each define a longitudinal axis and a N-S direction, and that are rotatable about the longitudinal axis relative to the frame, and a ring, defining an outer surface, between the frame and the case side wall and offset from the case side wall such that a first air gap is located between the inner surface of the case side wall and the outer surface of the ring.