Gradient Coil Wire Width Variation for Eddy Current Reduction
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Solution Overview
Problem
The challenge is to reduce eddy current magnetic fields in gradient magnetic field coil devices for MRI systems while minimizing heat generation, as current methods either increase eddy currents or heat, and existing solutions fail to adequately address both issues simultaneously.
Innovation Solution
A gradient magnetic field coil device is designed with forward and reverse coils where the wire width in the central region is smaller than in the outer region, allowing for a directional current flow that reduces eddy currents and heat generation by differentiating between regions generating even-order and odd-order eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the width of coil conductors is narrowed to reduce eddy currents, then eddy current magnetic field is reduced, but heat generation increases due to high current application
Solution Approach 1:
The patent applies different wire widths to different regions of the coil conductor. The central region (where even-order eddy currents are generated) uses narrower wire width to reduce eddy currents, while the outer region uses wider wire width to reduce heat generation. This local differentiation resolves the contradiction between reducing eddy current magnetic field and minimizing heat generation.
2Temperature
If the thickness of coil conductors is increased to reduce heat generation, then heat generation is reduced, but the coil device becomes thicker and the image capturing space must be widened
Solution Approach 1:
The patent uses different wire thicknesses in different regions. The central region uses thinner wire to reduce eddy currents, while the outer region uses thicker wire to reduce heat generation without significantly increasing the overall coil thickness. This allows heat generation to be reduced while maintaining a compact coil device structure.
3Power
If high intensity current is applied to achieve high gradient magnetic field intensity, then gradient magnetic field performance is improved, but eddy currents and heat generation become significant
Solution Approach 1:
The patent narrows the wire width specifically in the central region where the magnetic field is most intensive and eddy currents are generated. This local modification reduces eddy currents in the critical region while allowing high intensity current to be applied overall, maintaining gradient magnetic field performance while reducing harmful eddy current effects.
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 effectively reduces eddy current magnetic fields of even orders, improving MRI image quality by minimizing heat generation and maintaining a compact, open-space-compatible coil structure.
Implementation Method 1
a gradient magnetic field coil device generates a gradient magnetic field (with a primary gradient), which is temporally pulsed and spatially gradient
Implementation Method 2
when a pulsed gradient magnetic field is generated, eddy currents flowing in conductors such as a gradient magnetic field coil device also become high, and heat generation by the eddy currents and the magnetic field generated by the eddy currents (eddy current magnetic field) become significant
Data Source
AI summary
A gradient magnetic field coil device is provided in which an eddy current magnetic field of an even-ordered component can be reduced. The gradient magnetic field coil device includes a forward coil and a reverse coil which faces the forward coil so as to sandwich a middle surface and through which flows an electric current directed opposite to the forward coil. The forward coil and the reverse coil have a middle region approaching the middle surface and an outside-the-middle region where the distance from the middle surface is greater than the middle region. A line width of coil lines in the middle region is narrower than a line width of coil lines in the outside-the-middle region.