Sinusoidal Gradient Waveforms for Low-Noise MRI
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Solution Overview
Problem
Current MRI systems generate substantial acoustic noise due to the driving of gradient coils, which limits the use of contrast types and increases scan duration, necessitating a low-noise approach that does not constrain proton-density contrast.
Innovation Solution
The method involves driving gradient coils using sinusoidal waveforms on multiple axes, generating RF pulses at crossover events, and acquiring readout signals to produce images, with sinusoidal waveforms producing a fundamental frequency below 60 Hz, reducing noise and allowing larger tip angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional gradient coil driving waveforms are used, then image acquisition can be performed, but substantial acoustic noise is generated
Solution Approach 1:
The patent changes the waveform parameter from conventional square or trapezoidal gradients to sinusoidal gradient waveforms. This parameter change transforms the acoustic noise characteristics while maintaining the gradient field generation capability for image acquisition, thereby reducing noise without sacrificing productivity
Solution Approach 2:
The patent employs periodic sinusoidal waveforms for gradient coil driving. The periodic nature of sinusoidal waves allows for controlled acoustic emissions at specific frequencies, enabling noise reduction through frequency selection while maintaining continuous image acquisition capability
2Object-affected harmful factors
If very low tip angle excitation pulses are used, then acoustic noise is reduced, but proton-density contrast is constrained
Solution Approach 1:
The patent introduces dynamic contrast preparation sequences that can adaptively adjust tip angles and timing parameters. This dynamic approach allows the system to optimize contrast types while maintaining low acoustic noise levels, resolving the contradiction between noise reduction and contrast versatility
Solution Approach 2:
The patent employs spin preparation sequences that perform contrast optimization before the main imaging sequence. By preparing spins in advance with controlled tip angles and phase encodings, the system achieves diverse contrast types without requiring high tip angles during the noisy gradient driving phases
3Adaptability or versatility
If spin-preparation sequences are employed to expand contrast range, then contrast versatility is improved, but sequence complexity and scan duration increase
Solution Approach 1:
The patent merges spin preparation operations with the main imaging sequence into a unified pulse sequence. By combining contrast preparation and image acquisition steps, the system expands contrast range without proportionally increasing sequence complexity or scan duration
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 results in a significantly quieter MRI environment, enabling larger tip angles and expanded contrast options without increasing complexity or scan duration, while maintaining image quality.
Implementation Method 1
driving at least a first gradient coil associated with a first gradient direction using a first sinusoidal gradient waveform and a second gradient coil associated with a second gradient direction using a second sinusoidal gradient waveform
Implementation Method 2
An RF coil is employed to produce an RF magnetic field. This RF magnetic field perturbs the spins of some of the gyromagnetic nuclei from their equilibrium directions, causing the spins to precess around the axis of their equilibrium magnetization. During this precession, RF fields are emitted by the spinning, precessing nuclei
Data Source
AI summary
Systems and method for magnetic resonance imaging are disclosed which utilize sinusoidal gradient waveforms to drive gradient coils in an MRI system. The sinusoidal gradient waveforms may be applied on all two or more (e.g. three) gradient axes to produce a relatively pure acoustic tone. In certain embodiments, gradient directions may be spiraled in three-dimensions to generate a radial pin-cushion k-space trajectory.