High-Frequency Shielding Unit for MRI with Segmented Conductive Layers
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Solution Overview
Problem
Conventional high-frequency shielding units for magnetic resonance devices with low main magnetic field strengths (B0) suffer from increased losses and reduced damping effects on external disturbances, limiting their effectiveness.
Innovation Solution
A high-frequency shielding unit comprising four layers: a carrier layer, a first conductive layer, an insulation layer, and a second conductive layer, where the insulation layer is thin (≤50 μm) and applied via spraying or printing, with the conductive layers having interruptions to minimize eddy currents and enhance capacitance for improved shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional three-layer high-frequency shielding unit is used, then the structure is simple and easy to manufacture, but the shielding efficiency is significantly lower and losses are significantly higher for magnetic resonance devices with low main magnetic field strengths (B0 < 1 T)
Solution Approach 1:
The shielding unit is segmented into four distinct layers: carrier layer, first conductive layer, insulation layer, and second conductive layer. This segmentation allows each layer to perform its specific function optimally, with the two conductive layers working together to enhance shielding efficiency while the thin insulation layer minimizes losses for low B0 field strengths.
Solution Approach 2:
The shielding unit employs a composite structure combining different materials with complementary properties: the carrier layer provides mechanical support, while the conductive layers (made of conductive materials) provide electromagnetic shielding. This composite approach enables simultaneous optimization of structural integrity and shielding performance for low B0 applications.
2Reliability
If the insulation layer thickness is increased, then the mechanical stability and insulation performance improve, but the capacitance between conductive layers decreases and shielding efficiency is reduced
Solution Approach 1:
The insulation layer thickness is optimized to a specific range (5-50 μm) to achieve the desired balance between mechanical stability and electrical capacitance. This parameter optimization ensures sufficient capacitance for effective shielding while maintaining adequate mechanical integrity and insulation performance.
Solution Approach 2:
The insulation layer is applied with locally varying properties: it is thinnest (5-50 μm) where maximum capacitance is needed between conductive layers, while the carrier layer provides overall structural support. This local quality differentiation optimizes both electrical and mechanical performance.
3Object-affected harmful factors
If continuous conductive layers are used, then the shielding effect is maximized, but eddy currents are induced by gradient coil fields causing heating and image artifacts
Solution Approach 1:
The conductive layers are segmented with intentional interruptions rather than being continuous. This segmentation breaks the eddy current paths, preventing large circulating currents from forming in response to gradient coil fields, thereby reducing heating and image artifacts while maintaining high-frequency shielding effectiveness.
Solution Approach 2:
The interruptions in the conductive layers, which might seem to reduce shielding effectiveness, actually convert the harmful eddy currents into beneficial localized currents that maintain shielding while minimizing heating. The interruptions prevent the formation of large eddy current loops that would cause excessive heating and artifacts.
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 efficiency for the high-frequency antenna and improved interference attenuation, specifically optimized for magnetic resonance devices with low main magnetic field strengths, reducing heating and image artifacts.
Implementation Method 1
an insulation layer (130), arranged between the first conductive layer (120) and the second conductive layer (140), wherein the insulation layer has a layer thickness of at most 50 μm
Implementation Method 2
the high-frequency shielding unit should conduct high-frequency currents as well as possible in order to ensure optimal efficiency of the high-frequency antenna unit
Implementation Method 3
the magnetic resonance device also includes a gradient coil unit, with which magnetic field gradients are generated. The magnetic field gradients are superimposed on a static main magnetic field B 0
Implementation Method 4
Another problem can be interfering couplings, e.g. in the form of field peaks (spikes), which can be caused by switching clocks of gradient amplifiers, for example. Interference associated with this should also be attenuated by the high-frequency shielding unit
Data Source
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AI summary
The invention relates to a high-frequency shielding unit for shielding a high-frequency antenna unit of a magnetic resonance device, as well as a magnetic resonance device itself. The high-frequency shielding unit comprises a carrier layer, a first conductive layer, an insulating layer, and a second conductive layer. The first conductive layer is arranged between the carrier layer and the insulating layer, and the insulating layer is arranged between the first conductive layer and the second conductive layer.