MRI Gradient Coil Elastic Joint Dampens Acoustic Noise
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Solution Overview
Problem
Magnetic resonance imaging (MRI) gradient coils experience significant acoustic noise due to mechanical resonance modes, which are not effectively dampened by existing designs optimized for withstanding Lorentz forces, leading to enhanced vibration amplitudes and noise.
Innovation Solution
A cylindrical gradient coil is split mechanically at the z=0 mid-plane and joined using an elastic material, with each half being force and torque-balanced to incorporate mechanical damping, reducing mechanical quality factor and acoustic noise emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the gradient coil is designed with a rigid carrier to withstand Lorentz forces, then the structural strength is improved, but the acoustic noise increases due to mechanical resonance modes
Solution Approach 1:
The gradient coil is divided into two separate gradient coil sections that are coupled together. This segmentation allows each section to be independently optimized for force balance while the coupling mechanism provides mechanical damping, thereby reducing acoustic noise without compromising the overall structural strength.
Solution Approach 2:
The coupling between the two gradient coil sections employs a composite approach combining rigid elements for structural support with elastic or viscoelastic elements for damping. This composite structure maintains the necessary mechanical strength to withstand Lorentz forces while introducing mechanical damping to reduce acoustic noise from resonance modes.
2Measurement precision
If the B0 field strength is increased to improve image resolution and contrast, then the diagnostic quality is improved, but the Lorentz forces and acoustic noise increase
Solution Approach 1:
By segmenting the gradient coil into two force-balanced sections, the patent enables the system to operate at higher B0 fields with improved resolution while the segmentation-induced damping reduces the acoustic noise that would otherwise increase with higher field strength.
Solution Approach 2:
The patent converts the harmful acoustic noise generated at higher B0 fields into a beneficial damping effect. The coupling mechanism between the two sections is designed to exploit the mechanical resonance characteristics, transforming the noise-generating vibrations into controlled damping that reduces overall acoustic noise even as field strength increases.
3Force
If the gradient coil is made rigid to transfer Lorentz forces effectively, then the force transfer efficiency is improved, but the mechanical damping is reduced leading to enhanced vibration amplitudes
Solution Approach 1:
The gradient coil is segmented into two sections where each section maintains rigidity for effective force transfer, while the coupling between sections introduces the necessary mechanical damping. This segmentation allows simultaneous optimization of both force transfer efficiency and vibration suppression.
Solution Approach 2:
Different parts of the gradient coil structure have different mechanical properties: the gradient coil sections themselves are rigid for effective force transfer, while the coupling mechanism between sections has elastic or viscoelastic properties for mechanical damping. This local differentiation of material properties resolves the contradiction between force transfer and vibration suppression.
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 effectively reduces acoustic noise by dampening mechanical resonance modes, making MRI operations quieter and more comfortable for patients.
Implementation Method 1
joined using an elastic material, with each half being force and torque-balanced to incorporate mechanical damping, reducing mechanical quality factor and acoustic noise emission
Implementation Method 2
The connecting element comprises an elastic material. The elastic material is in contact with both the first and second elements
Implementation Method 3
Magnetic field gradient coils are used to generate spatially and temporally variying magnetic fields which are used to spatially encode the nuclear spins being imaged
Implementation Method 4
As current flows through a magnetic field gradient coil the Lorentz force on the coil may be enormous
Data Source
Figure 1
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Figure 3a~3c
AI summary
A magnetic resonance imaging magnet assembly (100) comprising: -a magnet (102) adapted for generating a main magnetic field for aligning the magnetic spins of nuclei of a subject (502) located within an imaging volume (504); and -a gradient coil (103) for generating a gradient magnetic field for spatial encoding of the magnetic resonance signal of spins of nuclei within the imaging volume, wherein the gradient coil is adapted to be mounted into the magnet, wherein the gradient coil comprises: - a first gradient coil section (112), wherein the first gradient coil section comprises a first rigid element (113), - a second gradient coil section (114), wherein the second gradient coil section also comprises a second rigid element (115), - a connecting element (116, 300, 302, 304, 400) for joining the two half gradient coils, wherein the connecting element comprises an elastic material (116), wherein the elastic material is in contact with the first rigid element and the second rigid element.