MRI Gradient Coil Noise Reduction via Constant Slice Selection
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Solution Overview
Problem
Conventional MRI scanners produce excessive acoustic noise during scanning, causing discomfort to patients, especially in pediatric and elderly populations, due to vibrations in gradient coil structures, and existing noise reduction techniques are inadequate for T2-weighted imaging sequences like Spin Echo (SE) and Fast Spin Echo (FSE).
Innovation Solution
The solution involves reducing acoustic noise by maintaining a constant slice selection gradient during data acquisition in SE and FSE sequences, combined with techniques such as longer gradient ramps and reshaped waveforms, to minimize the number and amplitude of gradient transitions, thereby reducing noise levels significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional gradient transitions are used in SE and FSE sequences, then scanning speed and image acquisition efficiency are maintained, but excessive acoustic noise is generated causing patient discomfort
Solution Approach 1:
The patent applies parameter changes by modifying gradient waveform parameters including using longer gradient ramps, reshaping gradient waveforms, and maintaining constant slice selection gradient during data acquisition. These parameter modifications reduce the slew rate and amplitude of gradient transitions, thereby reducing acoustic noise while preserving scanning efficiency
Solution Approach 2:
The patent employs dynamic gradient waveform design where the slice selection gradient is maintained constant during data acquisition rather than being pulsed. This dynamic approach optimizes the balance between noise reduction and scanning speed by adapting gradient behavior to the specific phase of the sequence
2Object-affected harmful factors
If gradient transition amplitude and frequency are reduced to lower noise, then acoustic noise is reduced, but image quality and motion correction capabilities may deteriorate
Solution Approach 1:
The patent carefully adjusts gradient parameters including ramp duration, waveform shape, and amplitude to achieve noise reduction while maintaining sufficient gradient strength for adequate spatial encoding and image quality
Solution Approach 2:
The patent incorporates feedback mechanisms where gradient parameters are optimized based on their effect on both noise levels and image quality metrics, ensuring that noise reduction does not compromise diagnostic image quality
3Object-affected harmful factors
If existing noise reduction techniques are applied, then some noise reduction is achieved, but they are inadequate for T2-weighted imaging sequences like SE and FSE
Solution Approach 1:
The patent develops a universal noise reduction approach that can be applied to multiple T2-weighted sequences including both SE and FSE. The technique of maintaining constant slice selection gradient during data acquisition is sequence-agnostic and can be adapted to various echo train lengths and timing parameters
Solution Approach 2:
The patent modifies gradient parameters specifically optimized for T2-weighted sequences, adjusting ramp durations and waveform shapes to accommodate the longer echo times and multiple echo acquisitions characteristic of SE and FSE sequences
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 approach achieves a substantial reduction in acoustic noise, typically lowering it to 8 dB above background in a 3T scanner, while maintaining image quality and motion correction capabilities, without increasing scan time or signal-to-noise ratio.
Implementation Method 1
this 'scanner noise' is produced by vibrations in the gradient coil related structures due to induced Lorentz forces which are proportional to the product of magnetic field strength and the gradient of amplitude changes
Implementation Method 2
spatial encoding and readout during MRI data acquisition sequences
Data Source
AI summary
Magnetic resonance imaging (MRI) systems and methods to effect MRI data acquisition with reduced noise in fast spin echo (FSE) and spin echo (SE) implementations are described. The improved MRI data acquisition is performed by acquiring k-space data while maintaining a constant or near constant slice select gradient amplitude throughout a sequence kernel. The acquired k-space data can then be used to generate an MR image.