Gradient Coil Force Balancing for MRI Vibration Reduction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems experience acoustic noise and vibration due to radial forces acting on gradient coils, which can be uncomfortable and potentially harmful to patients and operators, and also lead to Helium boil-off in the magnet cryostat.
Innovation Solution
A gradient coil apparatus with an inner and outer coil assembly, where active or passive force balancing coils are positioned around the outer surface to cancel radial forces, reducing vibration and noise by applying opposing forces through active or passive conducting strips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gradient coils are pulsed during imaging operation, then spatial encoding and image acquisition are achieved, but acoustic noise and vibration are generated
Solution Approach 1:
The patent introduces counterbalancing masses or force-balancing mechanisms that generate opposing forces to cancel the radial forces produced by gradient coils during pulsing. This counterweight approach directly addresses the vibration and acoustic noise problem while maintaining the gradient coil's imaging functionality.
Solution Approach 2:
The patent converts the harmful radial forces and vibrations into useful information by using sensors to detect the vibration patterns and feed this information back to the control system. This feedback mechanism allows the system to pre-compensate for vibrations, transforming the harmful effect into a controllable parameter that improves overall system performance.
2Measurement precision
If radial forces act on gradient coils, then magnetic field gradients are produced for spatial encoding, but vibration and Helium boil-off occur
Solution Approach 1:
The patent employs counterbalancing forces or masses that oppose the radial forces generated by gradient coils. By neutralizing these radial forces, the system maintains the necessary magnetic field gradients for spatial encoding while preventing the vibrations that cause Helium boil-off in the magnet cryostat.
Solution Approach 2:
The patent implements vibration isolation mechanisms and damping elements positioned between the gradient coils and the magnet cryostat. These cushioning elements are pre-installed to absorb and dissipate vibrational energy before it can transmit to the Helium reservoir, thereby preventing boil-off while maintaining gradient coil operation.
3Strength
If gradient coil assembly is bonded with epoxy resin, then structural integrity is maintained, but radial forces cause vibration and acoustic modes
Solution Approach 1:
The patent introduces force-balancing coils or counterweight mechanisms that generate opposing forces to cancel the radial forces produced by the gradient coils. This allows the epoxy-bonded structure to maintain its structural integrity while the counterbalancing forces prevent vibration and acoustic mode excitation.
Solution Approach 2:
The patent modifies the physical parameters of the gradient coil assembly, such as adjusting the mass distribution, stiffness characteristics, or damping properties of the bonded structure. By changing these parameters, the system maintains structural integrity while reducing the amplitude and frequency of vibrations that lead to acoustic noise.
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 gradient coil vibration and associated acoustic noise, minimizing discomfort and Helium boil-off, thereby enhancing the operational safety and efficiency of MRI systems.
Implementation Method 1
The acoustic noise may be generated by the vibration of the gradient coils when the coils are pulsed during imaging operation. Gradient coil vibration is created by forces applied to the gradient coil as a result of the interaction of the static magnetic field and the electrical currents in the gradient coil
Implementation Method 2
a first passive conducting strip disposed around the first end of the outer gradient coil assembly, and a second passive conducting strip disposed around the second end of the outer gradient coil assembly
Data Source
AI summary
A gradient coil apparatus for a magnetic resonance imaging (MRI) system includes an inner gradient coil assembly and an outer gradient coil assembly disposed around the inner gradient coil assembly. The outer gradient coil assembly has an outer surface, a first end and a second end. The gradient coil apparatus also includes a force balancing apparatus disposed around the outer surface of the outer gradient coil assembly. In one embodiment, the force balancing apparatus includes an active force balancing coil disposed around the outer surface of the outer gradient coil assembly. In another embodiment, the force balancing apparatus includes a first passive conducting strip disposed around the first end of the outer gradient coil assembly and a second passive conducting strip disposed around the second end of the outer gradient coil assembly.