Dynamic Gradient Pulse Thresholding for MRI Acoustic Noise Reduction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in reducing acoustic noise, which affects patient and operator safety and can impact MRI performance, particularly due to the limitations of existing derating methods that use static thresholds, leading to increased gradient rise time and reduced phase-encoding bandwidth.
Innovation Solution
The implementation of a pulse sequence threshold function that dynamically adjusts the amplitude and slew rate of gradient pulses based on individual pulse characteristics, allowing for tailored derating to achieve desired acoustic noise reduction levels without compromising MRI performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If static threshold derating methods are used to reduce acoustic noise, then acoustic noise levels are reduced, but gradient rise time increases and phase-encoding bandwidth is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from static threshold derating to dynamic threshold adjustment. The system continuously monitors acoustic noise levels and adjusts gradient pulse parameters (amplitude, duration, timing) in real-time based on current operating conditions. This allows the thresholds to adapt dynamically throughout the MRI sequence execution, optimizing noise reduction at each moment without permanently compromising gradient performance.
Solution Approach 2:
The patent implements parameter changes by modifying multiple gradient pulse parameters simultaneously (amplitude, duration, timing, slew rate) rather than relying on fixed thresholds. The system changes these parameters dynamically based on acoustic feedback, allowing optimization of the noise-performance tradeoff for each specific gradient pulse in the sequence rather than applying uniform static limits.
2Object-affected harmful factors
If static threshold derating methods are used to reduce acoustic noise, then acoustic noise levels are reduced, but phase-encoding bandwidth is reduced
Solution Approach 1:
The system dynamically adjusts gradient parameters during sequence execution to maintain phase-encoding bandwidth while reducing noise. By monitoring acoustic levels in real-time and adapting gradient amplitudes and timings dynamically, the system preserves bandwidth where acoustic conditions permit while applying noise reduction only where necessary.
Solution Approach 2:
The patent changes multiple parameters including gradient amplitude, pulse duration, and timing to optimize the tradeoff between noise reduction and bandwidth preservation. Rather than fixed threshold reduction, the system adjusts parameters individually for each gradient pulse based on sequence requirements and acoustic feedback.
3Object-affected harmful factors
If gradient pulse parameters are reduced to lower acoustic noise, then acoustic noise levels are reduced, but MRI performance is compromised
Solution Approach 1:
The patent implements feedback by continuously monitoring acoustic noise levels during MRI sequence execution and using this information to adjust subsequent gradient pulses. The system measures actual acoustic output and feeds this information back to the pulse sequence controller, which then optimizes remaining gradient parameters to maintain performance while staying within acoustic limits.
Solution Approach 2:
The system transitions from static parameter reduction to dynamic parameter optimization. Gradient pulse parameters are adjusted in real-time based on actual acoustic measurements and sequence requirements, allowing the system to maintain optimal MRI performance while dynamically adapting to acoustic constraints rather than applying fixed conservative limits.
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 effectively reduces acoustic noise levels while maintaining or improving MRI performance, allowing for efficient operation across various clinical applications without the need for specialized pulse sequences, and also alleviates eddy current effects and peripheral nerve stimulation.
Implementation Method 1
Acoustic noise results from Lorenz forces between the main magnetic field and conductors carrying time-varying electric current in the gradient system. The interaction causes vibrations that generate sound pressure waves
Data Source
AI summary
A pulse sequence generation computing device for a magnetic resonance imaging (MRI) system includes a processor in communication with a memory device. The processor is programmed to receive a pulse sequence including a plurality of gradient pulses and provide a pulse sequence threshold function corresponding to an acoustic noise reduction level. For each gradient pulse in the pulse sequence, the processor is programmed to determine an amplitude and a slew rate of the gradient pulse, determine a threshold amplitude and slew rate of the gradient pulse, and compare the determined amplitude and slew rate to the threshold amplitude and slew rate. If either the determined amplitude or slew rate exceeds the threshold amplitude or slew rate, the processor adjusts at least one of the amplitude and the slew rate of the gradient pulse to an amplitude and a slew rate as defined by the pulse sequence threshold function.