Insulated Shim Tray Layout for MRI Field Homogeneity
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Solution Overview
Problem
Existing shim trays in magnetic resonance devices are bulky and can cause deviations in the homogeneity of the main magnetic field, leading to reduced quality of magnetic resonance images due to environmental interference, and they often require complex and costly adjustments for optimal field homogeneity.
Innovation Solution
A space-saving shim tray design with insulating coatings and optimized dimensions, allowing for efficient integration into the gradient coil unit, which accommodates multiple shim plates without intermediate layers, reducing height and minimizing electrical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional shim trays are used to correct magnetic field inhomogeneity, then field homogeneity is improved, but the device diameter increases and patient comfort is reduced
Solution Approach 1:
The shim tray is integrated into the gradient coil unit by nesting the shim tray receptacle within the gradient coil structure. The shim tray receptacle is positioned inside the gradient coil unit's cylindrical structure, allowing the shim correction function to be embedded within the existing device geometry without increasing the overall diameter.
Solution Approach 2:
The shim tray receptacle extends in the longitudinal direction rather than radially outward, utilizing the longitudinal dimension of the gradient coil unit. This allows multiple shim trays to be arranged along the length of the gradient coil unit, providing comprehensive shim correction without increasing the device's radial footprint.
2Volume of moving object
If multiple shim plates are stacked without intermediate layers to reduce height, then spatial requirements are minimized, but electrical interference may increase
Solution Approach 1:
An intermediate layer is positioned between stacked shim plates to provide electrical insulation. This intermediate layer acts as a mediator that prevents direct electrical contact between adjacent shim plates, reducing electrical interference while allowing the shim plates to be stacked in a space-efficient manner.
Solution Approach 2:
The shim tray structure incorporates multiple materials with different properties: conductive shim plates for magnetic field correction, insulating intermediate layers to prevent electrical interference, and non-magnetic structural materials for the tray body. This composite approach allows simultaneous optimization of magnetic performance and electrical isolation.
3Device complexity
If shim trays are integrated into the gradient coil unit, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The shim tray receptacle is pre-formed with precise geometric features during gradient coil unit manufacturing. Reference surfaces, positioning features, and mounting interfaces are created in advance with high precision, ensuring that subsequent shim tray installation achieves the required positioning accuracy without requiring complex adjustment procedures.
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 provides enhanced magnetic field homogeneity with improved image quality by minimizing spatial requirements and reducing errors in shim plate placement, thus optimizing the main magnetic field without increasing the device's diameter, thereby enhancing patient comfort and operational efficiency.
Implementation Method 1
The surfaces of the at least two shim plates have an insulating coating
Implementation Method 2
The shim plates are typically arranged outside the gradient coil unit at the corresponding position of the shim tray and together with the shim tray are placed within the shim tray receptacle, in particular pushed into the shim tray receptacle. Shim plates are conventionally made of iron.
Data Source
AI summary
A shim tray designed to be pushed into a shim tray receptacle of a gradient coil unit may elongated and have a length in a longitudinal direction, a height in a radial direction and a width in a circumferential direction. The shim tray may include at least two shim pockets each configured to accommodate at least two shim plates, and at least two shim plates arranged one above the other in a radial direction in one of the shim pockets. The surfaces of the at least two shim plates may have an insulating coating.