Actively Shielded MRI Gradient Coil Reducing Magnetic Coupling
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Solution Overview
Problem
Conventional magnetic gradient coils in MRI systems cause unwanted magnetic coupling with the main superconducting magnet, leading to induced currents, heating, and potential loss of the main magnetic field, due to their design that fails to efficiently manage the external magnetic field.
Innovation Solution
The design of actively shielded magnetic gradient coils with multiple layers of windings that tailor the magnetic field to reduce external field interference, creating discrete reduced field regions aligned with the main magnet's coils, allowing the magnetic field to expand between them, thereby minimizing coupling and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional gradient coil design is used, then gradient field generation is achieved, but unwanted magnetic coupling with main superconducting magnet occurs causing induced currents and heating
Solution Approach 1:
The gradient coil is divided into multiple discrete windings arranged in specific patterns (e.g., split-ring configurations, layered structures). These segmented windings are independently controlled to create localized reduced field regions that align with superconducting magnet coils, thereby minimizing overall magnetic coupling while maintaining gradient functionality.
Solution Approach 2:
The coil design creates non-uniform magnetic field distribution with specific regions of reduced field strength positioned at strategic locations. These local field modifications are achieved through varied winding densities and patterns in different spatial zones, allowing the coil to minimize coupling at critical interfaces while maintaining gradient performance in the imaging region.
2Object-affected harmful factors
If active shielding is added to reduce eddy currents, then magnetic coupling is reduced, but device complexity increases
Solution Approach 1:
The active shielding function is merged with the gradient coil windings themselves. The same coil structure that generates the gradient field also provides shielding through its multi-layer winding configuration and split-ring patterns, eliminating the need for separate shielding components and reducing overall device complexity.
Solution Approach 2:
The gradient coil windings serve multiple functions simultaneously: generating the gradient magnetic field, providing active shielding against eddy currents, and creating reduced field regions to minimize coupling. This multi-functionality is achieved through carefully designed winding patterns that fulfill all three requirements within a single coil assembly.
3Stability of the object's composition
If magnetic field is constrained to reduce coupling, then main magnet stability is improved, but gradient coil efficiency decreases
Solution Approach 1:
The magnetic field management is segmented into different spatial zones. Reduced field regions are created at specific locations where coupling with superconducting magnet coils occurs, while other regions maintain full gradient field strength for efficient imaging. This selective field management preserves main magnet stability without compromising overall gradient coil efficiency.
Solution Approach 2:
The design converts the potential harmful effect of magnetic field interaction into a beneficial pattern. By strategically positioning reduced field regions to align with superconducting coil locations, the interaction that would normally cause coupling and heating is transformed into a controlled configuration that minimizes energy loss while maintaining gradient performance.
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 enhances the efficiency of the magnetic gradient coil by reducing unwanted magnetic coupling, allowing the magnetic field to expand between main magnet coils, leading to lower power consumption and improved imaging capabilities while maintaining the stability of the main magnetic field.
Implementation Method 1
gradient coils, which are used to superimpose a magnetic field gradient upon the B0 magnetic field
Implementation Method 2
actively shielded magnetic gradient coil... creating discrete reduced field regions aligned with the main magnet's coils
Implementation Method 3
The magnetic field generated by the gradient coils can cause eddy currents within the superconductive coils. These eddy currents can be avoided or reduced by using gradient coils with active shielding
Data Source
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AI summary
The invention provides for a magnetic gradient coil (110) for a magnetic resonance imaging system (100, 200). The magnetic gradient coil is actively shielded, wherein the magnetic gradient coil is operable for generating a magnetic field (504). The magnetic field has a cylindrical axis of symmetry (130). The gradient coil has a length (132) parallel with the cylindrical axis of symmetry. The magnetic gradient coil has an outer surface (134). The magnetic field comprises an external magnetic field outside of the outer surface. The external magnetic field has at least four reduced field regions (136, 138, 140, 142) along the length where the modulus of the magnetic field is less than the average of the modulus of the magnetic field along the length.