Shielded MRI Gradient Coil Assembly for Eddy-Current Reduction
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Solution Overview
Problem
Existing MRI systems face issues with dissipated fields generated by gradient coils affecting primary magnets, leading to eddy currents, heat, and reduced image quality, while shimming structures face challenges in maintaining magnetic field homogeneity due to vibration and heat effects.
Innovation Solution
The gradient coil assembly includes a primary gradient coil and a shielding gradient coil arranged coaxially, with multiple coil paths to distribute current and reduce dissipated fields, and a shimming structure with a support unit and accommodating cavity to stabilize the shimming unit, ensuring magnetic field homogeneity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gradient coils are wound by multiple conductors along a single coil path with concentrated current distribution, then the gradient magnetic field can be generated effectively, but a large dissipated field is formed in the periphery which generates eddy currents in the primary magnet and affects image quality
Solution Approach 1:
The patent divides the gradient coil assembly into multiple independent gradient coil units (first gradient coil unit, second gradient coil unit, third gradient coil unit, fourth gradient coil unit) arranged along the longitudinal axis. Each unit has its own coil path and current distribution, segmenting the concentrated current into distributed currents that reduce the dissipated field intensity in the periphery while maintaining the required gradient magnetic field generation capability.
2Manufacturing precision
If shimming structures are added to improve main magnetic field homogeneity, then image quality can be improved, but the shimming structures are affected by vibration and heat effects which compromise their ability to maintain field homogeneity
Solution Approach 1:
The patent introduces a support structure as an intermediary between the gradient coil units and the shimming structures. This support structure isolates the shimming structures from the vibration and heat effects generated by the gradient coils, allowing the shimming structures to maintain their position and function effectively in improving main magnetic field homogeneity without being compromised by the operational conditions of the gradient coils.
3Object-generated harmful factors
If multiple gradient coil units are arranged along the longitudinal axis with different coil paths, then current distribution is improved and dissipated field is reduced, but the device complexity increases
Solution Approach 1:
The patent combines multiple gradient coil units into a single integrated gradient coil assembly that works cooperatively to generate the required gradient magnetic fields. The first, second, third, and fourth gradient coil units are arranged and connected to function as a unified system, reducing the overall device complexity compared to having separate independent gradient coil systems while still achieving the benefit of distributed current paths and reduced dissipated field.
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
The design reduces dissipated fields, maintains primary magnet stability, and improves image quality by minimizing eddy currents and heat effects, while enhancing the homogeneity and stability of the main magnetic field.
Implementation Method 1
the gradient coils are wound by multiple conductors along a single coil path, in which the gradient coils are distributed sparsely and the current distribution of the gradient coils is concentrated, resulting in a large dissipated field formed in the periphery of the gradient coil assembly
Implementation Method 2
using hydrogen atoms in Larmor precession in a homogenous main magnetic field (B0 field) to generate magnetic resonance phenomena under excitation of a radio frequency field
Implementation Method 3
The dissipated field can generate an eddy current in the primary magnet that affects the use of the MRI system
Data Source
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AI summary
MRI systems(100) and compositions thereof are provided. The MRI systems(100) may include a main magnet(1,201) configured to generate a primary magnetic field, the main magnet(1,201) forming a bore. The MRI system(100) may include a gradient coil assembly(5, 202, 300, 500, 1100, 1200) arranged in the bore and configured to generate a gradient magnetic field that provides a magnetic field environment with the main magnetic field. The gradient coil assembly(5, 202, 300, 500, 1100, 1200) may include a shielding gradient coil(320, 520-1, 520-2, 1102-1, 1102-2, 1210-1, 1210-2) including two or more coil units(521, 522, 523, 524, 810, 820, 1221, 1222, 1223, 1224, 1225, 1226, 1227, 1228, 1221', 1222', 1223' 1224', 1125',1126', 1127', 1128'). One of the two or more coil units(521, 522, 523, 524, 810, 820, 1221, 1222, 1223, 1224, 1225, 1226, 1227, 1228, 1221', 1222', 1223' 1224', 1125',1126', 1127', 1128') may be wound along a first coil path(400). Another one of the two or more coil units(521, 522, 523, 524, 810, 820, 1221, 1222, 1223, 1224, 1225, 1226, 1227, 1228, 1221', 1222', 1223' 1224', 1125',1126', 1127', 1128') may be wound along a second coil path. The MRI system(100) may also include a shimming unit(3) arranged between the gradient coil assembly(5, 202, 300, 500, 1100, 1200) and the main magnet(1, 201) and configured to homogenize the main magnetic field.