Thermal Bus Structure for MRI Shield Temperature Control
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Solution Overview
Problem
Conventional electromagnetic shields in magnetic resonance imaging devices suffer from temperature variations due to varying eddy currents, leading to imaging artifacts and reduced efficiency of the main magnetic field.
Innovation Solution
A magnetic resonance imaging device with a thermal bus structure and spaced shield elements, connected to a cryocooler, that dynamically adjusts heat transfer properties to equalize eddy currents and maintain consistent temperatures across the shield elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional electromagnetic shields are used to block magnetic stray fields, then electromagnetic shielding is improved, but temperature variations occur due to varying eddy currents causing imaging artifacts
Solution Approach 1:
The electromagnetic shield is divided into multiple discrete shield elements spaced apart from each other. This segmentation allows each element to independently respond to magnetic stray fields, reducing the propagation of temperature variations through the shield structure while maintaining effective electromagnetic shielding.
Solution Approach 2:
Different regions of the shield are designed with varying properties - the shield elements are positioned at specific locations and orientations to locally counteract magnetic stray field effects. This local optimization reduces eddy current variations in critical areas while maintaining overall shielding effectiveness.
2Area of stationary object
If the electromagnetic shield is separated into disjoint structures to reduce footprint, then device compactness is improved, but temperature variations increase causing imaging artifacts
Solution Approach 1:
The shield is segmented into multiple discrete elements distributed in space rather than a single continuous structure. This segmentation reduces the overall footprint while maintaining temperature consistency through strategic placement of thermal management components and careful design of thermal pathways between elements.
Solution Approach 2:
Thermal bus structures act as intermediaries connecting the shield elements to the cryocooler system. These thermal pathways ensure uniform temperature distribution across the dispersed shield elements, preventing temperature variations that would otherwise arise from the disjointed structure.
3Object-affected harmful factors
If active electromagnetic shields are used to decrease magnetic stray field impact, then electromagnetic shielding is improved, but additional space and cooling requirements increase distance from main magnet
Solution Approach 1:
The shield elements are designed to passively respond to magnetic stray fields through their inherent electromagnetic properties. The spacing and configuration of elements allow them to automatically counteract stray field effects without requiring active control systems or additional cooling infrastructure, thereby minimizing the distance from the main magnet.
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
Reduces imaging artifacts and maintains efficient main magnetic field generation by minimizing temperature variations and superimposed eddy fields, enhancing image quality.
Implementation Method 1
a thermal bus structure (31) thermally connecting the shield elements (12i) to a cold head (32a) of the cryocooler (32)
Implementation Method 2
a cryocooler (32) with a cold head (32a), wherein the thermal bus structure (31) thermally connecting the shield elements (12i) to the cold head (32a) of the cryocooler (32)
Implementation Method 3
an electromagnetic shield (12) arranged between the gradient system (19) and the main magnet (17), wherein the electromagnetic shield (12) comprises a plurality of spaced shield elements (12i)
Data Source
Figure 1
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Figure 3~4
AI summary
The invention relates to a magnetic resonance imaging device (11) comprising a main magnet (17), a gradient system (19) with at least one gradient coil, a cryocooler (32), a thermal bus structure (31) and an electromagnetic shield (12) arranged between the gradient system (19) and the main magnet (17), wherein the electromagnetic shield (12) comprises a plurality of spaced shield elements and wherein the electromagnetic shield (12) is configured to provide an electromagnetic shielding of the main magnet (17) from a magnetic field generated by the at least one gradient coil, wherein the thermal bus structure (31) comprises a plurality of thermal bus elements configured to provide a thermal connection between the plurality of spaced shield elements and a cold head of the cryocooler (32) and wherein at least two thermal bus elements of the plurality of thermal bus elements comprise different heat transfer properties for providing an individualized temperature control of the plurality of spaced shield elements.