Shim Coil Switching Matrix for MRT Field Homogeneity
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Solution Overview
Problem
Current magnetic resonance tomography (MRT) systems face challenges in maintaining homogeneous magnetic fields, particularly at patient borders where tissue inhomogeneities cause significant distortions, leading to suboptimal fat saturation and image quality.
Innovation Solution
The MRT system employs a controller-driven shim coil arrangement with a controllable switching matrix to dynamically generate and distribute coil currents for shim coils, allowing for localized compensation of field inhomogeneities near the patient, enabling flexible and cost-effective adjustment of the magnetic balancing field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If shim coils are fastened to superconducting magnets with fixed current sources, then the magnetic field homogeneity can be improved at specific locations, but the system lacks flexibility to adapt to different patient geometries and tissue inhomogeneities
Solution Approach 1:
The patent implements dynamic control of shim coil currents through a switching matrix that can rapidly reconfigure current distribution among multiple shim coils based on detected field inhomogeneities. This allows the system to adapt to different patient geometries and tissue distributions while maintaining field homogeneity, resolving the contradiction between fixed hardware configuration and adaptive performance.
Solution Approach 2:
The system changes the operational parameters (current magnitudes and directions) of shim coils dynamically based on measured field inhomogeneities. By adjusting these electrical parameters rather than physical hardware configuration, the system achieves adaptability to various patient scenarios while maintaining manufacturing precision in field homogeneity.
2Manufacturing precision
If multiple independent shim current sources are provided for each shim coil connection, then localized field compensation can be achieved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent makes a single shim current source universal by enabling it to supply current to multiple different shim coil connections through a switching matrix. This multi-functional approach allows one current source to perform the work of multiple independent sources, achieving localized field compensation while reducing device complexity and cost.
Solution Approach 2:
The switching matrix creates virtual copies of the current source output to multiple shim coil connections. Instead of requiring physically separate current sources for each connection, the system uses electronic switching to replicate the current supply function, achieving the same effect with fewer physical components.
3Manufacturing precision
If the volume with homogeneous magnetic field is enlarged using shim coils, then fat saturation quality improves, but the system cannot dynamically adapt to tissue inhomogeneities at patient borders
Solution Approach 1:
The patent implements a feedback mechanism where field inhomogeneities are detected and measured, then this information is used to dynamically adjust shim coil currents through the switching matrix. This closed-loop control allows the system to compensate for tissue inhomogeneities at patient borders in real-time, maintaining field homogeneity and fat saturation quality despite varying patient geometries.
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 image quality by effectively compensating for non-structurally specific field inhomogeneities caused by patient tissue, improving the homogeneity of the magnetic field and reducing the need for extensive hardware, thereby optimizing MR image quality.
Implementation Method 1
this base field may be overlaid with a balancing field using balancing or shim coils. The inhomogeneities may be compensated for at the borders of the volume using the balancing or shim coils.
Implementation Method 2
The shim coils are supplied with an electrical current by a shim current source in each instance, the current strength of which is set within the scope of adjusting the MRT system
Data Source
AI summary
In order to balance out a field inhomogeneity, a value for a coil current is determined by a controller as a function of an item of information relating to the field inhomogeneity and an item of information relating to a position of at least one balancing or shim coil arranged in the magnetic field. The value is to be supplied to the at least one shim coil in order to generate a magnetic balancing field to balance out the field inhomogeneity. A control signal for at least one shim current source and for at least one switching matrix coupling the at least one shim current source to the at least one shim coil is generated as a function of the at least one value.