Gradient Waveform Modification for MR Noise Reduction
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Solution Overview
Problem
Conventional MR imaging sequences face challenges with complex and irregular gradient pulse shapes that result in excessive noise and exceed physical limits of gradient coils and amplifiers, affecting image quality due to fast-changing gradients and high peak fields.
Innovation Solution
The method involves modifying gradient waveforms based on selected limits, optimization criteria, and algorithms to produce a sequence of modified gradient waveforms that reduce noise without compromising image quality, by selecting from hardware limits, slew rate, gradient strength, duty cycle, and physiological limitations, and optimizing for parameters like minimizing slew rate, maximizing slew rate, and eliminating edges for smooth waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional gradient pulse sequences are used with fast-changing gradients and high peak fields, then spatial encoding and image acquisition speed are improved, but gradient coil physical limits are exceeded and excessive noise is generated
Solution Approach 1:
The patent applies parameter changes by modifying gradient waveform parameters (amplitude, duration, shape) in real-time based on physiological feedback signals. The controller adjusts gradient pulse characteristics dynamically to maintain imaging performance while reducing peak fields and slew rates, thereby lowering gradient noise without compromising acquisition speed
Solution Approach 2:
The system implements feedback by continuously monitoring physiological parameters (such as heart rate, respiration) and using this information to adaptively adjust gradient waveform timing and amplitude. This closed-loop control ensures gradient pulses remain within safe limits while optimizing image acquisition, resolving the contradiction between speed and noise
2Object-affected harmful factors
If gradient waveforms are modified to reduce noise and smooth transitions, then gradient coil physical limits are respected and noise is reduced, but image acquisition time may increase
Solution Approach 1:
The patent employs dynamics by making gradient waveform parameters adaptive rather than static. The system dynamically adjusts gradient pulse characteristics based on real-time physiological conditions, allowing smooth transitions that respect coil limits while maintaining efficient acquisition timing through intelligent parameter modulation
Solution Approach 2:
By changing gradient waveform parameters adaptively based on physiological feedback, the system achieves smooth transitions that reduce noise while optimizing acquisition time. The controller modifies pulse duration, amplitude, and timing to balance noise reduction with time efficiency
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 significantly reduces gradient noise values in MR images while maintaining image quality, by transforming irregular gradient patterns into smoother, noise-reduced waveforms within hardware constraints.
Implementation Method 1
the static magnetic field causes magnetic moment vectors of protons (typically in hydrogen atoms of water molecules) to align with the static magnetic field
Implementation Method 2
The RF pulses cause the magnetic moment vectors of the protons to be displaced (e.g., rotate) relative to the magnetic field and re-align with the magnetic field
Implementation Method 3
A MR imaging scanner picks up magnetic signals from the protons in the body that result from magnetization moment vectors re-aligning with and rotating around the static magnetic field
Data Source
AI summary
A method is provided for modified gradient timing in a Magnetic Resonance (MR) imaging system. The method includes generating radio frequency (RF) excitation pulses in a volume of patient anatomy to provide subsequent acquisition of associated RF echo data and generating a sequence of gradient waveforms on a static magnetic field in three directions each orthogonal to each other for slice selection, phase encoding and readout RF data acquisition in the volume of patient anatomy. The method also includes receiving, by a controller, an indication of the sequence of gradient waveforms to be applied to a plurality of gradient coils and modifying, via the controller, the sequence of gradient waveforms to be applied to the plurality of gradient coils based on one or more parameters to produce a sequence of modified gradient waveforms. The method further includes providing the sequence of modified gradient waveforms to the plurality of gradient coils.