Diffusion-Weighted MRI Noise Reduction via Gradient Timing
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Solution Overview
Problem
Diffusion-weighted magnetic resonance (DWI) measurements are typically very loud due to the high demands on the gradient system, making them unpleasant for patients and sometimes causing refusal.
Innovation Solution
The method involves activating a diffusion module with diffusion gradients and an acquisition module that reads out measurement data by repetitions of RF excitation pulses, where the RF excitation pulse is applied only after the phase-encoding gradients have reached their required strength, significantly reducing noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diffusion gradients are activated for diffusion encoding in DWI measurements, then diffusion weighting and diagnostic information are improved, but noise level increases making measurements unpleasant for patients
Solution Approach 1:
The phase-encoding gradients are activated in advance before the RF excitation pulse is applied. This preliminary action ensures that the gradients reach their required strength before the measurement sequence begins, thereby reducing the noise generated during the actual diffusion-weighted imaging acquisition.
2Measurement precision
If high strength diffusion gradients are used for diffusion encoding, then diffusion weighting capability is improved, but load on the gradient system increases
Solution Approach 1:
The phase-encoding gradients are activated in advance before the RF excitation pulse, allowing the gradient system to reach the required strength beforehand. This distributes the load more efficiently and reduces peak demands on the gradient system during the actual measurement.
3Manufacturing precision
If diffusion gradients are activated for spatial encoding, then image quality and diagnostic information are improved, but noise level increases causing patient discomfort
Solution Approach 1:
The phase-encoding gradients are activated in advance before the RF excitation pulse is applied. This ensures that the gradients reach their required strength before the measurement sequence begins, thereby reducing the noise generated during the actual diffusion-weighted imaging acquisition while maintaining image quality.
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 facilitates quiet DWI measurements by minimizing noise, allowing for the acquisition of diffusion data such as parameter maps, while reducing the load on the gradient unit and maintaining image quality.
Implementation Method 1
placing the subject under examination in a magnetic resonance scanner in a strong static, homogeneous basic magnetic field, also called the B0 field
Implementation Method 2
Radio frequency excitation pulses (RF pulses, also known as the B1 field) are applied to the subject under examination in order to induce nuclear spin resonances
Implementation Method 3
diffusion of water molecules along the applied diffusion gradients attenuates the measured magnetic resonance signal
Implementation Method 4
Rapidly switched magnetic gradient fields are superimposed on the basic magnetic field for spatially encoding the measurement data
Data Source
AI summary
The method and magnetic resonance apparatus for acquiring diffusion-weighted measurement data from a subject, (a) a diffusion module is activated that contains at least one diffusion gradient, and (b) an acquisition module is activated, which reads out measurement data by repetitions of RF excitation pulses, which are applied to the subject under examination, and phase-encoding gradients that are activated to spatially encode signals induced by the RF pulses. For at least one repetition, the RF excitation pulse are applied to the subject only if the phase-encoding gradients, activated for the spatially encoding signals, which are generated after the RF excitation pulse, have already reached their required strength. Steps (a) and (b) are repeated until all the required measurement data are acquired. The acquired measurement data are stored. A significant reduction in the noise level of DWI measurements is thereby achieved.