Shielded Gradient Coil Asymmetric Winding MRI
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Solution Overview
Problem
Conventional gradient coils for magnetic resonance imaging (MRI) apparatuses face challenges in reducing unnecessary magnetic fields outside the imaging area, leading to eddy currents, electromagnetic interactions, and reduced magnetic field intensity, which hinder clear image acquisition.
Innovation Solution
The gradient coil design incorporates a primary gradient coil and a shielded gradient coil, where the shielded coil is positioned opposite to the imaging area to cancel the magnetic field generated by the primary coil, with a configuration that includes a central axis and an outer circumference area more inclined towards the imaging area, reducing magnetic field leakage and interactions with structural members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional gradient coil is used to generate gradient magnetic field, then the gradient magnetic field can be produced for MRI imaging, but unnecessary magnetic fields are generated outside the imaging area causing eddy currents and electromagnetic interactions with peripheral structures
Solution Approach 1:
A shield coil is introduced as an intermediary component between the gradient coil and the peripheral structures. The shield coil generates a magnetic field that opposes and cancels the unnecessary magnetic field from the gradient coil outside the imaging area, thereby preventing eddy currents and electromagnetic interactions with peripheral structures while maintaining the gradient field within the imaging area
Solution Approach 2:
The harmful magnetic field components outside the imaging area are extracted and separated from the useful gradient field within the imaging area. The shield coil specifically targets and removes the unnecessary magnetic field components that cause interference, allowing the gradient coil to maintain its primary function without the harmful side effects
2Object-generated harmful factors
If the shielded gradient coil is positioned closer to the imaging area, then magnetic field cancellation is improved, but the coil structure becomes more complex and larger
Solution Approach 1:
The shield coil is designed with non-uniform winding density and geometry that varies in different regions. The winding density is higher in areas where magnetic field cancellation is most needed and lower in areas where less cancellation is required, optimizing the shield coil's effectiveness while minimizing its size and complexity
Solution Approach 2:
The shield coil adopts an asymmetric configuration rather than a symmetric design, with varying distances and orientations relative to the gradient coil windings. This asymmetric arrangement allows for more efficient magnetic field cancellation in critical areas while reducing the overall coil structure complexity
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 unnecessary magnetic fields outside the imaging area, minimizing eddy currents and electromagnetic interference, thereby enhancing the accuracy and quality of MRI images by maintaining high magnetic field intensity and efficiency.
Implementation Method 1
The shielded gradient coil is adapted to cancel the magnetic field generated by the primary gradient coil
Implementation Method 2
The gradient magnetic field varies in pulse from the order of 0.1 milliseconds to the order of 1 second
Data Source
AI summary
The gradient coil for a magnetic resonance imaging apparatus is adapted to encode information on a spatial position of a subject to be inspected into a nuclear magnetic resonance signal. The gradient coil includes a primary gradient coil and a shielded gradient coil. The primary gradient coil generates a gradient magnetic field in the imaging area. The shielded gradient coil is located on the side opposite to the imaging area relative to the primary gradient coil and cancels the gradient magnetic field generated by the primary magnetic field. The shielded gradient coil has a first area including a central axis perpendicularly extending through the central portion of the imaging area and a second area located on the side of the outer circumference of the first area. The second area is more inclined toward the imaging area than the first area.