MRI Vibration Suppression via Segmented Conductive Rings
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Solution Overview
Problem
Vibrations between the gradient magnetic field generating device and the static magnetic field generating device in MRI devices cause deterioration of tomographic images and sound noise, leading to reduced diagnosis accuracy and patient discomfort.
Innovation Solution
The implementation of conductive rings arranged in pairs on both sides of the homogeneous magnetic field direction to reduce vibrations by shielding residual magnetic fields and inducing eddy currents that counteract Lorentz forces, thereby suppressing vibrations and eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a pulse current is caused to flow through the gradient magnetic field generating source to generate a linear gradient magnetic field, then the gradient magnetic field is generated successfully, but Lorentz force is generated due to coupling between the static magnetic field and the pulse current, causing vibrations in the gradient magnetic field generating device and transmitted to the static magnetic field generating device
Solution Approach 1:
Conductive rings are introduced as intermediary elements disposed between the gradient magnetic field generating device and the static magnetic field generating device. These rings shield the static magnetic field generating device from the full impact of Lorentz forces by providing a controlled path for eddy currents, thereby reducing vibration transmission while maintaining gradient magnetic field generation functionality.
Solution Approach 2:
The invention converts the harmful Lorentz forces and eddy currents into a beneficial damping mechanism. By strategically placing conductive rings, the eddy currents induced in these rings create magnetic fields that oppose the original Lorentz forces, thereby reducing vibrations. The harmful electromagnetic interactions are transformed into a vibration suppression mechanism through controlled eddy current damping.
2Object-generated harmful factors
If an electric conductor plate is installed to enclose the gradient magnetic field generating device to shield magnetic field leakage, then eddy currents and Lorentz forces in the static magnetic field generating device are reduced, but the device complexity and structural burden increase
Solution Approach 1:
Instead of using a single enclosing electric conductor plate, the invention segments the shielding function into multiple discrete conductive rings positioned at specific locations. This segmentation reduces the overall structural burden and complexity compared to a complete enclosure, while still achieving effective vibration suppression through localized eddy current generation.
Solution Approach 2:
The conductive rings are strategically positioned at specific locations where vibration transmission is most problematic, rather than providing uniform shielding throughout. This local quality approach concentrates the vibration suppression function where it is most needed, reducing overall device complexity while maintaining effectiveness.
3Object-generated harmful factors
If high frequency components in the gradient magnetic field are completely shielded by hard connecting an electric conductor surrounding the gradient magnetic field, then vibrations of the static magnetic field generating device are reduced, but the device complexity and potential impact on magnetic field homogeneity increase
Solution Approach 1:
Conductive rings serve as intermediary elements that selectively dampen high-frequency vibration components without completely shielding the magnetic field. Their discrete positioning and electrical properties allow them to act as frequency-selective dampers, reducing vibrations while preserving the homogeneity of the static magnetic field in the imaging region.
Solution Approach 2:
Instead of completely shielding all frequency components, the conductive rings provide partial damping action targeted at the problematic high-frequency vibrations. This partial action is sufficient to reduce vibrations to acceptable levels without the excessive shielding that would compromise magnetic field homogeneity.
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 solution effectively reduces vibrations and eddy currents, enhancing the quality of tomographic images and reducing sound noise, leading to improved diagnosis accuracy and patient comfort.
Implementation Method 1
a magnetic field leaked from a gradient magnetic field generating source to a side of the static magnetic field generating device is shielded by installing an electric conductor plate
Implementation Method 2
This reduces eddy currents and Lorentz forces generated in the static magnetic field generating device
Implementation Method 3
This reduces eddy currents and Lorentz forces generated in the static magnetic field generating device
Implementation Method 4
high frequency components in the gradient magnetic field are completely shielded by hard connecting an electric conductor, having a cylindrical shape, surrounding the gradient magnetic field to the gradient magnetic field generating device
Implementation Method 5
reduce the vibrations of the static magnetic field of the static magnetic field generating device
Data Source
AI summary
A device includes: a static magnetic field generating device including static magnetic field generating sources generating a homogeneous magnetic field in a space; gradient magnetic field generating sources superimposing a gradient magnetic field on the homogeneous magnetic field, and conductor rings arranged between the static magnetic field generating sources and the gradient magnetic field generating sources in a pair of arranging regions on both sides in a direction of the homogeneous magnetic field in a region where the homogeneous magnetic field is generated (imaging region), respectively, the conductor rings being separated from each other and making a pair. The conductor rings are mechanically connected to the gradient magnetic field generating device or the static magnetic field generating device. This provides an MRI device 1 capable of reduction in vibration with suppression of the image quality deterioration of the tomographic images.