Integrated Gradient Coil for MRI Homogeneity Compensation
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Solution Overview
Problem
Conventional shim coils in magnetic resonance scanners are limited in generating dynamic magnetic fields of higher order, leading to reduced homogeneity of magnetic fields and the formation of magnetic vortex fields, which compromise image quality and require additional space and complex positioning.
Innovation Solution
A compact gradient coil with two independent conductors that can generate both a magnetic field gradient and a magnetic field of higher order, allowing for simultaneous and dynamic compensation of magnetic vortex fields without the need for a dedicated shim coil, thereby enhancing homogeneity and reducing spatial requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional shim coils are used to compensate for magnetic field homogeneity, then magnetic field homogeneity can be improved, but the device complexity increases and additional space is required
Solution Approach 1:
The patent combines the gradient coil and shim coil into a single integrated structure. The gradient coil is designed with an inner conductor and an outer conductor that work together to generate both the magnetic field gradient and the compensation field, eliminating the need for a separate shim coil and reducing overall system complexity
Solution Approach 2:
The gradient coil is designed to perform multiple functions simultaneously: generating the magnetic field gradient for spatial encoding and generating the magnetic field of higher order for homogeneity compensation. This multi-functionality is achieved through the specific configuration of the inner and outer conductors that can produce both gradient and compensation fields
2Manufacturing precision
If shielded shim coils are used to reduce eddy currents, then magnetic field homogeneity improves, but the examination region is restricted due to additional space requirements
Solution Approach 1:
By merging the gradient coil and shim coil into a single structure, the patent eliminates the need for additional shielding space. The outer conductor of the gradient coil serves dual purposes: generating the gradient field and providing shielding against eddy currents, thereby preserving the examination region
3Area of stationary object
If unshielded shim coils are used to save space, then the examination region is maximized, but eddy currents and magnetic vortex fields compromise the shim effect
Solution Approach 1:
The outer conductor acts as an intermediary element that provides shielding against eddy currents while allowing the examination region to remain maximized. This conductor mediates between the gradient field generation and the need for electromagnetic shielding, enabling both functions to coexist without compromising performance
4Adaptability or versatility
If three separate gradient coils are used to generate gradients in three directions, then spatial encoding capability is achieved, but the device complexity and space requirements increase
Solution Approach 1:
The patent segments the gradient coil into two independent conductors (inner and outer) that can be controlled separately. This segmentation allows each conductor to be optimized for its specific function while working together to achieve the overall gradient field, providing flexibility in spatial encoding
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 solution effectively compensates for dynamic modifications in magnetic field homogeneity, improves image quality, and reduces the cost and complexity of the gradient system by eliminating the need for a separate shim coil, while allowing for flexible and precise control of magnetic fields.
Implementation Method 1
A gradient coil of this type has at least one conductor, with which a magnetic field gradient is generated in precisely one direction by applying a current to the at least one conductor
Implementation Method 2
the at least two independent conductors are designed to operate in combination with one another so as to jointly generate a magnetic field gradient in an examination region of a magnetic resonance scanner and to jointly generate a magnetic field of a higher order in that examination region
Implementation Method 3
The magnetic field gradients are switched on and off as gradient pulses within milliseconds, which causes eddy currents to form on the conductive structures surrounding the gradient coils due to the induction
Implementation Method 4
The eddy currents in turn generate magnetic vortex fields which may reduce the homogeneity of the magnetic field gradient
Data Source
AI summary
A gradient coil for magnetic resonance imaging has at least two conductors that are independent of one another, designed to jointly generate a magnetic field gradient and a magnetic field of a higher order in the examination region of a magnetic resonance scanner.