Sinusoidal Gradient Waveforms for MRI Acoustic Noise Reduction
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Solution Overview
Problem
Conventional arterial spin labeling (ASL) methods in MRI systems generate significant acoustic emissions due to mechanical vibrations, leading to discomfort, compromised image quality, and potential premature failure of components, which increases operating costs and downtime.
Innovation Solution
The use of a pCASL sequence with a sinusoidal gradient signal and a half-wave rectified sinusoidal RF signal, avoiding frequencies corresponding to mechanical resonance frequencies, reduces acoustic noise and vibrations, thereby enhancing image quality and extending component durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If square or trapezoidal gradient waveforms are used for sufficient labeling of flowing blood spins, then labeling efficiency is improved, but acoustic noise and mechanical vibrations increase
Solution Approach 1:
The patent changes the waveform parameter from square or trapezoidal to sinusoidal, and specifically uses a half-wave rectified sinusoidal waveform. This parameter change maintains the necessary gradient strength for effective blood spin labeling while eliminating the high-frequency mechanical vibrations and acoustic noise associated with abrupt waveform transitions.
2Manufacturing precision
If high gradient strengths and slew rates are used for sufficient labeling, then labeling efficiency is improved, but mechanical strain on components increases
Solution Approach 1:
The patent modifies the gradient waveform shape to sinusoidal while maintaining appropriate gradient strengths. The smooth transitions of the sinusoidal waveform reduce mechanical strain on gradient coils and other components, preventing premature failure while still achieving sufficient blood spin labeling efficiency.
Solution Approach 2:
The patent applies curvature to the gradient waveform by using sinusoidal shapes instead of linear square or trapezoidal waveforms. This curvature eliminates abrupt transitions, reducing mechanical stress and vibrations on system components while maintaining the necessary gradient area for effective labeling.
3Manufacturing precision
If gradient switching is performed at frequencies close to mechanical resonance frequency, then labeling efficiency is improved, but vibrations and acoustic emissions increase
Solution Approach 1:
The patent changes the gradient waveform from square or trapezoidal to sinusoidal, which fundamentally alters the frequency spectrum. The sinusoidal waveform concentrates energy at the fundamental frequency rather than spreading it across harmonics, allowing operation away from mechanical resonance frequencies while maintaining labeling 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 acoustic noise emissions and mechanical strain, improving image quality and reducing the risk of component failure, thus lowering operating costs and downtime.
Implementation Method 1
these vibrations may compromise image quality and may adversely affect component durability (e.g., due to mechanical strain) especially when a repetition time (Tr) of the field gradient waveform is close to a mechanical resonance frequency (f MR ) of an MRI system
Implementation Method 2
selectively label blood (e.g., using a labeling pulse sequence which may magnetize or invert the blood water spins)
Implementation Method 3
labeled spins and nearby static tissue (e.g., cranial tissue). After labeling, at least part of the labeled blood water spins travel from the labeling region to the imaging region where magnetically labeled spins exchange with tissue water molecules, thereby, reducing overall tissue magnetization
Data Source
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AI summary
A magnetic resonance imaging (MRI) system (100, 600) that generates information indicative of a fluid flow in accordance with a pseudo-continuous arterial spin labeling (pCASL) method. The MRI system may include at least one controller (104, 610) configured to generate a pseudo-continuous arterial spin labeling (pCASL) pulse sequence (200) including at least a first gradient (GR) pulse sequence (207) having a sinusoidal waveform including a plurality of cycles, and a second radio frequency (RF) pulse sequence (205) including a half-wave rectified sinusoidal waveform having a plurality of cycles and which is synchronous with the first GR pulse sequence; label at least part of the fluid flow in a labeling region during a labeling mode using the pCASL pulse sequence; acquire label and control image information of the fluid flow at an imaging region proximal to downstream of the labeling region; and/or generate image information in accordance with a difference of the acquired label and control image information. The sinusoidal gradient waveform results in less acoustic noise during execution of the pulse sequence.