Merged Gradient and Main Field Coil System for MRT Homogeneity
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Solution Overview
Problem
Current magnetic resonance tomography (MRT) systems face challenges in achieving optimal homogeneity and reducing noise terms in the main magnetic field, particularly due to eddy currents and dimensional tolerances in gradient coils, which affect image quality and require additional shielding measures.
Innovation Solution
The use of a gradient field coil system that generates both gradient and main magnetic fields, with independently controllable coil parts and additional correction coils, allows for precise optimization of field homogeneity and noise reduction through superposition of currents and external shielding measures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a separate main field magnet is used to generate the main magnetic field B0, then the main field homogeneity is improved, but the device complexity and cost increase
Solution Approach 1:
The patent combines the main field generation function with the gradient coil system by using the same coil windings to generate both the main magnetic field B0 and the gradient field BG through superposition of currents. This eliminates the need for a separate main field magnet, reducing device complexity while maintaining field homogeneity through precise current control and correction coils.
Solution Approach 2:
The gradient coil system is designed to perform multiple functions: generating the main magnetic field B0, generating the gradient field BG, and providing field correction. The coil windings can be controlled to produce different field configurations, making the system universal and eliminating the need for dedicated separate components.
2Device complexity
If gradient coils are used to generate both main field and gradient field, then the device complexity is reduced, but the main field homogeneity deteriorates due to eddy currents and dimensional tolerances
Solution Approach 1:
The gradient coil system is divided into multiple independently controllable coil parts or windings. Each coil part can be controlled separately to generate specific field components, allowing precise manipulation of the superposition to achieve both main field and gradient field while correcting for eddy currents and dimensional tolerances.
Solution Approach 2:
The system employs correction coils that can be controlled to compensate for field inhomogeneities, eddy currents, and dimensional tolerance variations. By measuring the actual field characteristics and adjusting the correction coil currents accordingly, the system maintains main field homogeneity despite using the gradient coil system for dual purposes.
3Manufacturing precision
If additional shielding measures are implemented to reduce noise terms, then the main field homogeneity is improved, but the device complexity and cost increase
Solution Approach 1:
The shielding function is merged with the gradient coil system itself. The gradient coil windings are designed and controlled to simultaneously provide gradient field generation, main field generation, and noise reduction through appropriate current superposition, eliminating the need for separate shielding components.
Solution Approach 2:
The system converts the potentially harmful eddy currents and noise terms into beneficial effects by using the same coil system to generate compensating fields. The gradient coil windings produce not only the desired gradient field but also compensating fields that reduce noise and improve homogeneity, turning potential problems into solutions.
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 improved homogeneity and reduced noise terms, enhancing image quality and allowing for MRT imaging without an additional main field magnet, while minimizing shim drift and eddy current effects.
Implementation Method 1
generating a main field B0 using a gradient field coil system that may also be used to generate a gradient field BG
Data Source
AI summary
In one embodiment, a magnetic resonance tomography system that has a gradient field coil system for generating a gradient field is provided. The gradient field coil system is also a main magnetic field generation system for generating a main field.