Ferromagnetic Frame MRI Magnet With Superconducting Coils
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) magnets with air core superconducting magnets face challenges such as claustrophobia for patients, inability to image obese patients, strong fringe fields, and mechanical vibrations from cryocoolers that degrade field uniformity and stability.
Innovation Solution
A ferromagnetic frame MRI magnet design incorporating superconducting coil units with toroidal vacuum vessels and elongated coil supports that minimize heat transfer and mechanical vibrations, allowing for a compact and efficient magnetic field generation with cryocoolers thermally connected but mechanically isolated, reducing the impact of cryocooler vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If air core superconducting magnets are used, then strong magnetic field is achieved, but patient accessibility deteriorates due to large bore size causing claustrophobia
Solution Approach 1:
The patent changes the magnetic circuit structure from air core to ferromagnetic core, fundamentally altering how the magnetic field is generated and contained. This allows achieving the same field strength with a more compact, open design that improves patient accessibility while maintaining the required magnetic field properties
Solution Approach 2:
The ferromagnetic core acts as an intermediary that concentrates and directs the magnetic flux generated by the superconducting coils. This mediator allows the magnetic field to be confined to the patient-receiving space, eliminating the need for a large bore while maintaining field strength
2Strength
If air core superconducting magnets are used, then strong magnetic field is achieved, but fringe field control deteriorates
Solution Approach 1:
The patent changes the magnetic circuit structure from air core to ferromagnetic core, fundamentally altering how the magnetic field is generated and contained. This allows achieving the same field strength with a more compact, open design that improves patient accessibility while maintaining the required magnetic field properties
Solution Approach 2:
The ferromagnetic core, which could be seen as adding complexity, actually benefits the system by confining the magnetic field and eliminating harmful fringe fields. The core material's high permeability naturally directs flux through desired paths, converting a potential complexity into a solution for field control
3Temperature
If cryocoolers are thermally connected to superconducting coils, then cooling efficiency is improved, but mechanical vibrations increase degrading field stability
Solution Approach 1:
The patent introduces a flexible thermal conductor as an intermediary between the cryocooler and the superconducting coils. This mediator provides thermal coupling for efficient cooling while mechanically isolating the coils from vibrations generated by the cryocooler, thus maintaining field stability
Solution Approach 2:
The patent separates the thermal function from the mechanical support function. The flexible thermal conductor extracts only the necessary thermal coupling function while leaving out the mechanical vibration transmission, allowing the coils to be thermally connected but mechanically isolated from the cryocooler
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
This design provides a strong, uniform magnetic field with improved patient accessibility and reduced fringe fields, enabling efficient imaging of diverse patient sizes while maintaining field stability and safety.
Implementation Method 1
the coils have no electrical resistance. The superconducting coils can conduct large currents and provide a strong magnetic field
Implementation Method 2
Iron core magnets use a ferromagnetic frame defining a flux path and usually include ferromagnetic poles projecting towards a patient-receiving space
Implementation Method 3
a generally toroidal vacuum vessel which is also coaxial with the axis. The vessel desirably has hollow support extensions extending into the recesses in the frame side walls
Data Source
AI summary
A magnetic resonance imaging magnet includes a ferromagnetic frame. A pair of generally toroidal superconducting coil units overlie interfaces of side walls incorporated in the frame. Each coil unit may include a vessel having hollow support extensions extending into recesses in the side walls. The coil units may further include elongated, low-thermal conductance supports disposed within the support extensions. The frame may include pole stems projecting inwardly from the side walls, and the coils may be disposed in close proximity to the pole stems. Cryocoolers may be mounted to the frame so that the cryocoolers are substantially mechanically isolated from the coils of the coil units, but are in thermal communication therewith. The cryocooler mountings may be arranged for convenient servicing and installation of the cryocoolers.