Angularly Magnetized Implant Magnet MRI Torque Reduction
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Solution Overview
Problem
Existing implantable medical devices with conventional magnetic arrangements face issues during Magnetic Resonance Imaging (MRI) due to interactions between implant magnets and external MRI fields, leading to potential tissue damage, displacement of implant components, and imaging artifacts, particularly at high field strengths like 1.5 Tesla, necessitating limitations on MRI use or surgically removing magnets.
Innovation Solution
A cylindrical implant magnet with a central axis of symmetry and magnetization direction angled away from the axis of symmetry at a non-zero angle (e.g., between 10° and 30°) allows for self-alignment with external magnetic fields, reducing torque and maintaining magnetic strength, even at high MRI field strengths, and is compatible with conventional axially-magnetized external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional axially-magnetized implant magnet is used, then strong magnetic attraction is achieved for holding external devices, but torque is generated during MRI that can displace the implant and cause tissue damage
Solution Approach 1:
The implant magnet uses angular magnetization where the magnetic axis is angled at 10-30 degrees relative to the central axis of the cylindrical magnet, rather than being aligned with it. This asymmetric magnetization configuration reduces the torque generated during MRI while maintaining sufficient magnetic attraction force for device attachment.
2Force
If the implant magnet size is increased to maintain magnetic strength, then magnetic attraction is improved, but the implant volume increases requiring bone recess preparation
Solution Approach 1:
The invention changes the magnetization parameter from axial (0 degrees) to angular (10-30 degrees) orientation. This parameter change allows the magnet to maintain sufficient attraction force with a smaller volume, eliminating the need for bone recess preparation while still providing adequate magnetic coupling for external device attachment.
3Device complexity
If conventional implant magnets are used, then simple design is maintained, but MRI compatibility is poor requiring surgical magnet removal
Solution Approach 1:
The angular magnetization configuration (10-30 degrees from central axis) fundamentally changes how the magnet interacts with MRI fields. This asymmetric design maintains structural simplicity while dramatically improving MRI compatibility by reducing torque and preventing the need for surgical magnet removal during or after imaging procedures.
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 angularly magnetized implant magnet maintains magnetic field strength and compatibility with conventional external devices, reducing the need for larger magnet sizes and minimizing tissue displacement during MRI, while allowing for safe use at high field strengths without the need for surgical magnet removal.
Implementation Method 1
transcutaneous magnetic interaction with a corresponding external attachment magnet
Implementation Method 2
magnetization direction along a magnetic axis angled away from the axis of symmetry at a non-zero angle less than 45 degrees... reducing torque and maintaining magnetic strength
Data Source
AI summary
A magnetic arrangement is described for an implantable system for a recipient patient. An implantable coil housing contains a signal coil for transcutaneous communication of an implant communication signal. Freely rotatable within the coil housing is a cylindrical implant magnet for transcutaneous magnetic interaction with a corresponding external attachment magnet. The implant magnet has a central cylinder axis of symmetry, and a magnetization direction along a magnetic axis angled away from the axis of symmetry at a non-zero angle less than 45 degrees.