Gradient Coil Assembly with Aluminum Outer Coils
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Solution Overview
Problem
Current gradient coil assemblies for magnetic resonance imaging systems are expensive, heavy, and difficult to handle due to their copper composition, leading to high manufacturing costs and challenges in installation, while also experiencing issues with heat dissipation and hot spots.
Innovation Solution
Replacing at least part of the outer gradient coils with aluminum, while maintaining copper for the inner coils, reduces weight and cost without compromising image quality, and incorporating cooling mechanisms to manage dissipation and hot spots, with parallel conductive loops and hollow conductors for efficient heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If copper is used for gradient coils to minimize dissipation and ensure excellent conductive properties, then electrical conductivity and heat dissipation are improved, but weight and manufacturing cost increase significantly
Solution Approach 1:
The patent applies local quality by differentiating material selection between inner and outer coils based on their functional requirements. Inner coils use copper for low dissipation where high current density is required, while outer coils use aluminum for weight reduction where shielding function predominates. This localized material optimization resolves the contradiction between minimizing overall dissipation and reducing total weight.
Solution Approach 2:
The gradient coil assembly employs a composite material structure combining copper and aluminum in different coil positions. This composite approach allows the system to benefit from copper's superior electrical conductivity in critical inner coils while utilizing aluminum's lightweight properties in outer shielding coils, thereby achieving a balance between energy loss minimization and weight reduction.
2Reliability
If copper is used for gradient coils to ensure excellent conductive properties, then electrical conductivity is improved, but manufacturing cost and handling difficulty increase
Solution Approach 1:
The invention applies local quality by restricting copper usage to only the inner coils where high reliability and excellent conductive properties are critical for gradient field generation. Outer shielding coils use aluminum, which is cheaper and easier to manufacture, thereby reducing overall manufacturing cost while maintaining necessary reliability in critical components.
Solution Approach 2:
The patent utilizes aluminum for outer coils as a cost-effective alternative to copper. Although aluminum has higher dissipation, the outer coils serve primarily as shielding structures where absolute minimum dissipation is less critical than cost and ease of manufacture. This approach applies the principle of using cheaper materials for components where performance requirements are less stringent.
3Weight of moving object
If outer gradient coils are replaced with aluminum to reduce weight and cost, then weight and manufacturing cost are reduced, but dissipation increases
Solution Approach 1:
The patent resolves this contradiction by applying local quality - inner coils maintain copper construction to handle high current density and minimize dissipation where it matters most, while outer coils use aluminum for weight reduction where the primary function is shielding. The system accepts higher dissipation in outer coils because their shielding function is more weight-sensitive than their conductive performance.
4Loss of energy
If copper is used throughout the gradient coil assembly, then dissipation is minimized, but the assembly becomes difficult to handle and install
Solution Approach 1:
The gradient coil assembly uses composite materials with copper inner coils for minimal dissipation and aluminum outer coils for reduced weight. This composite construction maintains energy efficiency in critical components while improving overall ease of handling and installation through the lightweight aluminum outer structure.
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 configuration results in a cost-effective, lightweight gradient coil assembly that maintains high-performance MR imaging capabilities, with reduced hot spots and increased rms current values, enabling reliable generation of magnetic resonance information.
Implementation Method 1
gradient coil assemblies are used to generate gradient magnetic fields... These gradient magnetic fields are generated in three axial directions, i.e. in the x, y, and z-direction of the gradient coil assemblies
Implementation Method 2
the set of outer gradient coils and the set of inner gradient coils are provided in concentric cylinders, which are spaced apart. The set of outer gradient coils generally provides a shielding of the set of inner gradient coils to avoid the generation of eddy currents due to the changing magnetic fields
Implementation Method 3
incorporating cooling mechanisms to manage dissipation and hot spots, with parallel conductive loops and hollow conductors for efficient heat management
Data Source
Figure 1
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Figure 3~4
AI summary
The present invention provides a gradient coil assembly (122) for use in a magnetic resonance imaging system (110) comprising a set of inner coils (142) and a set of outer coils (144), which are concentrically arranged in respect to a common rotational axis of the set of inner and outer coils (142, 144), wherein the set of inner coils (142) and a set of outer coils (144) can be controlled to generate gradient magnetic fields within an inner space of the gradient coil assembly (122), and at least one coil (152, 154, 156) of the set of outer coils (144) is at least partially made of aluminum. The present invention further provides a magnetic resonance (MR) imaging system (110) comprising the above magnetic gradient coil assembly (122). By replacing at least a part of one coil of the outer coils by aluminum, the gradient coil assembly (122) can be significantly improved in respect to cost and weight without reducing the accuracy in respect to the generation of diagnostic images based on magnetic resonance information. Accordingly, the outcome of an MR scan is not reduced. The outer coils usually contain about half the weight of the copper used for state of the art gradient coil assemblies.