Split Self-Shielded Gradient Coil Groups for Fast Switching
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Solution Overview
Problem
Existing gradient coil systems face challenges in generating strong magnetic fields with fast switching times while minimizing eddy currents and maintaining field symmetry, often due to high inductance and resistance from increased coil windings and shielding coil interference.
Innovation Solution
The gradient coil system is divided into N sub-coil groups, with each group comprising a main and shielding sub-coil connected in series, allowing individual current adjustment by a power supply system, which reduces inductance and resistance, enabling fast switching and optimized field generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the gradient coil system uses increased coil windings to generate strong magnetic fields, then the magnetic field strength is improved, but the inductance and resistance increase, reducing switching speed and increasing power consumption
Solution Approach 1:
The gradient coil system is divided into multiple independent coil windings (first, second, third, and fourth coil windings) that can be controlled separately. This segmentation allows the system to achieve strong magnetic fields through coordinated operation of multiple coils while managing inductance and resistance by distributing the total winding count across separate controllable units, thereby maintaining faster switching speeds.
2Strength
If the gradient coil system uses increased coil windings to generate strong magnetic fields, then the magnetic field strength is improved, but the power consumption increases
Solution Approach 1:
The coil system is segmented into multiple independently controllable windings with separate power supplies. This allows selective activation of only the necessary coil windings for each specific NMR experiment, reducing overall power consumption while still achieving the required magnetic field strength when all coils are operated together.
Solution Approach 2:
The system dynamically adjusts which coil windings are active based on experimental requirements. By controlling the switching of individual coil windings, the system optimizes power consumption by activating only the minimum necessary windings for each specific measurement task while maintaining the capability to generate strong fields when needed.
3Object-affected harmful factors
If the shielding coil is added to reduce eddy currents, then eddy current impact is reduced, but the gradient coil magnetic field in the target area is weakened
Solution Approach 1:
The shielding function is segmented into multiple independent coil windings that can be controlled separately from the main gradient coils. This allows the shielding coils to be activated specifically when eddy current reduction is needed, while the main gradient coils can be operated at full strength, thereby maintaining both eddy current protection and strong magnetic field generation.
Solution Approach 2:
The independently controllable coil windings act as intermediaries between the main gradient coils and the shielding function. By introducing these additional controllable coils, the system can mediate between the conflicting requirements of strong gradient fields and eddy current reduction, activating shielding only when and where needed without permanently compromising gradient field strength.
4Device complexity
If the main coil and shielding coil are arranged coaxially, then the structure is simplified, but the symmetry of the gradient coil magnetic field may be compromised
Solution Approach 1:
The magnetic field generation is segmented into multiple independently controllable coil windings arranged coaxially. This segmentation allows for fine-tuned control of the magnetic field distribution, enabling the system to maintain field symmetry through independent adjustment of each winding's current while preserving the simplified coaxial structure.
Solution Approach 2:
The system adjusts the current parameters of each independently controllable coil winding to optimize magnetic field symmetry. By varying the current magnitude and direction in each coaxially arranged winding, the system can compensate for any symmetry deviations while maintaining the compact coaxial configuration.
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 achieves fast switching times and strong gradient magnetic fields with reduced eddy current artifacts, maintaining high symmetry and measurement quality in NMR applications.
Implementation Method 1
a main coil (2) for generating a gradient coil magnetic field (Bz) in a target volume (10)
Implementation Method 2
a shielding coil (3) for shielding the main coil (2)
Data Source
AI summary
A gradient coil system for use in a magnetic resonance device comprises a main coil having at least two main sub-coils for generating a gradient coil magnetic field in a target volume, a shielding coil having at least two shielding sub-coils for shielding the main coil, and a power supply system configured to adjust a plurality of electric currents. The main coil and the shielding coil are arranged coaxially along a z-axis, wherein the gradient coil magnetic field is aligned with the z-axis and varies along a gradient direction. The gradient coil system comprises N sub-coil groups, with N≥2, with each of the N sub-coil groups comprising a main sub-coil and a shielding sub-coil (3a-3d) connected in series. The power supply system is configured to adjust the electric current of each of the N sub-coil groups individually. The system provides strong gradient coil magnetic fields with improved switching time.