Rotating Cylindrical Implant Magnet for MRI Torque Elimination
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) interactions with implant magnets in hearing devices cause torque, displacement, and demagnetization, limiting MRI usage to lower field strengths or requiring surgical modifications, due to the existing magnet arrangements not effectively managing the strong external magnetic fields.
Innovation Solution
A single cylindrical implant magnet with a central axis of symmetry perpendicular to the magnet case axis, allowing free rotation within the case, and optionally paired with gravity masses to maintain vertical orientation, effectively eliminating torque and demagnetization issues by aligning magnetization parallel to the external MRI field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cylindrical implant magnet with magnetic dipole axis perpendicular to the skin is used, then the external transmitter device can be magnetically held in place, but torque and demagnetization occur during MRI exposing to strong external magnetic fields
Solution Approach 1:
The patent applies the dynamics principle by making the implant magnet freely rotatable within the magnet case about its central axis. This dynamic configuration allows the magnet to rotate and realign its magnetic dipole axis with the external MRI magnetic field, thereby eliminating torque and preventing demagnetization while maintaining the magnetic holding capability for the external transmitter device
Solution Approach 2:
The patent changes the orientation parameter of the magnetic dipole from fixed perpendicular to the skin to variable orientation that can adapt to external magnetic fields. By allowing the magnet to rotate freely, the magnetic dipole axis can change its orientation relative to the external field, transforming the system from a static to an adaptive configuration that prevents harmful torque and demagnetization effects
2Object-affected harmful factors
If the implant magnet is made surgically removable or spherical, then torque issues during MRI are reduced, but device complexity or surgical requirements increase
Solution Approach 1:
Instead of removing the magnet surgically or using a complex spherical design, the patent employs a simple dynamic solution where the cylindrical magnet is allowed to rotate freely within its case. This dynamic realignment capability eliminates torque issues without requiring surgical removal or complex geometry, maintaining device simplicity while addressing the MRI compatibility problem
3Object-affected harmful factors
If MRI field strength is limited to lower fields, then torque and demagnetization are reduced, but imaging quality and diagnostic capability are compromised
Solution Approach 1:
The patent enables the use of high field strength MRI scanners by making the implant magnet freely rotatable. The magnet can dynamically realign with the strong external magnetic field, eliminating torque and demagnetization effects that would otherwise limit MRI field strength. This allows high-quality diagnostic imaging without compromising patient safety or device integrity
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 ensures the implant magnet remains torque-free and demagnetization-free, even at high MRI field strengths, maintaining proper device positioning and reducing imaging artifacts, thus enabling safe and effective MRI procedures without the need for surgical modifications or limiting field strength.
Implementation Method 1
the strong static magnetic field from the MRI creates a torque on the internal magnet, which may displace the internal magnet or the whole implant device out of proper position
Implementation Method 2
the direction magnetization of the implant magnet is essentially perpendicular to the skin of the patient. In this example, the strong static magnetic field from the MRI creates a torque on the internal magnet
Implementation Method 3
an implantable device contains signal processing circuitry configured for receiving an implant communications signal transmitted by an external transmitting coil through overlying skin of an implanted patient
Implementation Method 4
The external attachment magnet has a conventional cylindrical disc-shape and a north-south magnetic dipole having an axis that is perpendicular to the skin of the patient to produce external magnetic field lines
Implementation Method 5
There also may be a pair of gravity masses configured to lie on opposing sides of the implant magnet offset from the case axis of symmetry so as to shift a center of gravity of the magnet case and its contents away from the case axis of symmetry
Data Source
AI summary
A magnet arrangement for a hearing implant device is described. A magnet case is contained within an implantable device and has a central case axis of symmetry that is perpendicular to the outermost surface of the implantable device. The magnet case is configured to be freely rotatable within the implantable device about the case axis of symmetry. An implant magnet is contained within the magnet case and consists of a single cylindrical magnet having a central magnet axis of symmetry perpendicular to the case axis of symmetry. The implant magnet is configured to be freely rotatable within the magnet case about the magnet axis of symmetry.