Adaptive Electromagnet Grid for MRI Field Uniformity
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in achieving uniform magnetic fields due to non-linearities in gradient coil fields, leading to image warping and field inhomogeneities, which require extensive post-processing and increased power consumption.
Innovation Solution
A method and system for transforming a smooth wire pattern into a discretized pattern for application on a conducting grid, allowing adaptive control of current distribution in an electromagnet to actively manage magnetic field profiles, reducing the need for multiple power amplifiers and improving field uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional gradient coils are used to produce magnetic fields, then spatial information can be encoded, but non-linearities in the gradient coil fields cause image warping and field inhomogeneities
Solution Approach 1:
The patent divides the gradient coil system into multiple independent electromagnets, each capable of producing specific field patterns. This segmentation allows individual optimization of each electromagnet to reduce non-linearities while maintaining the overall gradient functionality needed for spatial encoding.
Solution Approach 2:
The patent implements active shim coils that can locally adjust magnetic field uniformity in specific regions. By placing shim coils strategically and controlling their currents independently, the system compensates for local field inhomogeneities and non-linearities without affecting the entire field uniformly.
2Measurement precision
If multiple shim coils are used to correct field inhomogeneities, then field uniformity improves, but device complexity and power consumption increase
Solution Approach 1:
The patent designs electromagnets that can serve multiple functions: producing gradient fields for spatial encoding and acting as shim coils for field uniformity correction. By making the gradient coils themselves adjustable and capable of producing higher-order field patterns, the system eliminates the need for separate shim coil sets, reducing device complexity while maintaining field uniformity.
3Power
If gradient coil strength is increased to improve imaging performance, then spatial encoding capability improves, but peripheral nerve stimulation occurs
Solution Approach 1:
The patent employs multiple electromagnets with independently controllable currents, allowing dynamic adjustment of field parameters. By optimizing the current distribution across multiple coils, the system can achieve the required gradient strength for spatial encoding while shaping the field to minimize harmful effects like peripheral nerve stimulation.
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 enables efficient and adaptive control of magnetic fields, reducing power consumption, minimizing image distortion, and allowing for faster switching without peripheral nerve stimulation, while maintaining field uniformity and reducing eddy currents.
Implementation Method 1
The gradient coils produce magnetic fields on the order of mT by passing hundreds of amperes of current through their windings
Implementation Method 2
allowing adaptive control of current distribution in an electromagnet to actively manage magnetic field profiles
Data Source
AI summary
A method of configuring a conducting grid of elements interconnected at intersecting nodes by switches is described. The method includes: constructing a background grid by connection of centroids of the cell shape of the conducting grid; identifying a subset of elements in the background grid that intersect the smooth pattern of loops; identifying a subset of elements in the conducting grid that intersect the subset of elements in the background grid; the subset of elements in the conducting grid forming a discretized pattern of loops representing the smooth pattern of loops; for each of the discretized pattern of loops identifying current-in and current-out nodes; altering the on-off state of individual switches in accordance with the discretized pattern of loops; opening the switch between each respective pair of current-in and current out nodes; and applying power to the conducting grid via at least one pair of the input and output current nodes such that the current flow through the elements generates the magnetic field profile.