Modified Disc Implant Magnet Geometry for MRI Torque Reduction
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Solution Overview
Problem
Existing implantable hearing devices face issues during MRI due to torque and demagnetization of magnets, leading to displacement and potential damage, especially at high magnetic field strengths, limiting MRI use or requiring surgically removable magnets.
Innovation Solution
A modified disc-shaped implant magnet with a primary center rotation axis and secondary deflection axis, allowing controlled rotation and deflection to mitigate torque forces from external magnetic fields, housed in a magnet system with a damper oil and ferromagnetic domains for stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional disc-shaped implant magnet with perpendicular magnetic axis is used, then the magnet can effectively hold the external transmitter housing in place, but it experiences high torque and displacement during MRI at field strengths exceeding 1.5 Tesla
Solution Approach 1:
The implant magnet is designed with the ability to rotate about its central axis and deflect within a secondary deflection angle, transforming from a static to a dynamic structure. This allows the magnet to actively respond to external magnetic fields by realigning its magnetic dipole, thereby reducing torque and preventing displacement during MRI while maintaining holding force capability
Solution Approach 2:
The magnet's geometric parameters are optimized with a specific height-to-diameter ratio and a defined secondary deflection angle. These parameter changes enable the magnet to achieve both sufficient holding force and reduced MRI susceptibility by controlling its orientation response to external fields
2Force
If the implant magnet is made stronger to improve holding force, then the external transmitter housing is held more securely, but the torque and demagnetization risk during MRI increases
Solution Approach 1:
The patent converts the harmful effect of strong external magnetic fields during MRI into a beneficial realignment mechanism. The magnet's controlled rotation and deflection allow it to passively orient itself favorably relative to the MRI field, reducing torque while maintaining strong holding force capability in normal operation
Solution Approach 2:
The implant magnet system combines the magnet material with a housing structure that provides controlled rotational and deflecting capabilities. This composite structure enables the magnet to maintain strength while gaining mobility to respond to external fields, resolving the contradiction between holding force and MRI safety
3Adaptability or versatility
If MRI is permitted with conventional implant magnets, then patient diagnostic options are maintained, but the implant may be damaged or displaced
Solution Approach 1:
The dynamic rotation and deflection capabilities enable the implant magnet to survive MRI exposure by actively managing the interaction with external magnetic fields. This allows MRI compatibility while preserving implant structural integrity, unlike static magnets that would suffer damage or displacement
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
Enables safer MRI compatibility by reducing mechanical forces on the implant magnet, allowing for stronger magnet use without displacement, thus ensuring the external transmitter housing remains in place.
Implementation Method 1
the strong static magnetic field the MRI creates a torque T=m×B on the internal magnet 202
Implementation Method 2
Interactions occur between the implant magnet and the applied external magnetic field for the MRI
Implementation Method 3
Torque and forces acting on the implant magnet
Implementation Method 4
housed in a magnet system with a damper oil and ferromagnetic domains for stabilization
Implementation Method 5
housed in a magnet system with a damper oil and ferromagnetic domains for stabilization
Data Source
AI summary
A magnet arrangement for an implantable medical device is described. An implant magnet has a modified disc shape and is capable of responding to an external magnetic field by rotating about a primary center rotation axis. The implant magnet shape has at least one cross-sectional view, the cylindrical diameter corresponds to a horizontal coordinate axis, the center symmetry axis corresponds to a vertical coordinate axis, the height between the end surfaces is greatest at the center symmetry axis, and the height between the end surfaces progressively decreases from the center symmetry axis along the cylindrical diameter towards the outer circumference to define a secondary deflection angle with respect to the horizontal coordinate axis so that the implant magnet is capable of responding to the external magnetic field by deflecting within the secondary deflection angle about a secondary deflection axis defined by a cylinder diameter normal to the cross-sectional view.