MRI Eddy Current Asymmetry Correction via Inter-Coil Conductors
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Solution Overview
Problem
Magnetic resonance imaging (MRI) apparatuses face image quality degradation due to eddy currents induced in static coil units, which are not efficiently addressed by existing methods, especially when there are asymmetries in the distribution of these currents caused by setup errors or surface treatment issues between static and gradient coil units.
Innovation Solution
Installing conductors in the space between static and gradient coil units to achieve a symmetrical distribution of eddy currents, using materials like copper, aluminum, or stainless steel, and determining their size and number based on measured eddy current magnitudes to correct asymmetrical distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a pulse-type current is applied to the gradient coil unit to form a gradient field, then the gradient field can be generated for MRI imaging, but eddy current flows through the static coil unit causing image quality degradation
Solution Approach 1:
The patent installs conductors in the space between the static coil unit and gradient coil unit to convert the harmful eddy current effect into a beneficial one. These conductors generate eddy currents that create a magnetic field opposing the original eddy current's harmful magnetic field, thereby canceling out the image quality degradation while maintaining gradient field generation capability
2Stability of the object's composition
If the gradient coil unit is positioned in a reference state forming a concentric body with the static coil unit, then the structure is symmetrical, but setup errors or surface treatment issues cause asymmetry in eddy current distribution
Solution Approach 1:
The patent intentionally introduces asymmetry through strategically placed conductors to compensate for manufacturing-induced asymmetry. By positioning conductors in specific locations between the coil units, the system creates a controlled asymmetric configuration that counterbalances the unwanted asymmetric eddy current distribution caused by setup errors or surface treatment variations
Solution Approach 2:
The patent modifies the physical parameters of the system by adding conductors with specific materials, dimensions, and positions. These parameter changes alter the eddy current distribution characteristics, transforming the asymmetric harmful effect into a symmetric or controllable distribution that does not degrade image quality
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 approach effectively eliminates the asymmetry of eddy current distributions, enhancing the efficiency of existing pre-emphasis methods and preventing image quality degradation by ensuring a symmetrical eddy current distribution, thereby improving MRI image quality.
Implementation Method 1
In order to form a gradient field in a static field, it is necessary to supply a pulse-type current to a gradient coil unit
Implementation Method 2
the MRI apparatus supplies a specific frequency and energy to atomic nuclei in the state in which a constant magnetic field has been applied to the atomic nuclei
Implementation Method 3
If a pulse-type current is applied to the gradient coil unit, eddy current flows through a static coil unit for forming a static field in the subject, due to electromagnetic induction
Implementation Method 4
eddy current flows through a static coil unit for forming a static field in the subject, due to electromagnetic induction
Data Source
AI summary
A magnetic resonance imaging (MRI) method and apparatus in which conductors are installed in the space between a static coil unit and a gradient coil unit to eliminate asymmetry of eddy current induced in the static coil unit. The structure permits a symmetrical distribution of eddy current when the concentric arrangement of the static coil unit and gradient coil unit has deviated. The MRI apparatus includes: a static coil unit configured to form a static field in a subject; a gradient coil unit configured to form a gradient field in the static field; and one or more conductors installed in the space between the static coil unit and the gradient coil unit, and configured to symmetrically distribute eddy current induced in the static coil unit.