MRI Gradient Waveform Optimization for Acoustic Noise Reduction
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Solution Overview
Problem
Existing MR imaging techniques generate uncomfortably loud acoustic noise due to vibrations in gradient coils, limiting the acquisition of T2 and FLAIR contrast while compromising image quality.
Innovation Solution
The implementation of a system and method that uses optimized gradient waveforms and a 180-degree prep pulse in conjunction with the PROPELLER acquisition technique to minimize acoustic noise levels during MR imaging, allowing for reduced noise without significant impact on image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional gradient pulses are used in MR imaging, then image quality and contrast (T2 and FLAIR) can be acquired, but acoustic noise levels become uncomfortably loud
Solution Approach 1:
The patent modifies gradient waveform parameters including amplitude, duration, and timing to reduce acoustic noise while preserving image quality. Specifically, gradient pulses are optimized to minimize Lorentz force vibrations that generate noise, while maintaining the necessary gradient strength for T2 and FLAIR contrast acquisition
Solution Approach 2:
The patent employs periodic gradient pulse sequences with optimized repetition and timing patterns. By structuring gradients as periodic sequences with controlled echo trains and repetition times, the system reduces noise while maintaining the periodic signal acquisition needed for image reconstruction
2Object-affected harmful factors
If gradient slew rate is derated to reduce acoustic noise, then noise level decreases, but echo spacing increases causing image blurriness and SNR loss
Solution Approach 1:
The patent optimizes gradient slew rate parameters to find the optimal balance between noise reduction and image quality. By carefully selecting slew rate values and compensating with adjusted gradient amplitudes and timing, the system achieves noise reduction without the detrimental effects of excessive echo spacing
Solution Approach 2:
The patent employs dynamic gradient waveform design where gradient parameters are continuously optimized based on the specific imaging sequence and noise requirements. The system dynamically adjusts gradient timing and amplitude profiles to maintain optimal performance across different imaging conditions
3Object-affected harmful factors
If SWIFT technique is used to reduce acoustic noise, then noise level becomes close to inaudible, but T1/PD contrast capability is limited
Solution Approach 1:
The patent creates a gradient optimization framework that works across multiple MR imaging sequences and contrast types. By developing universal gradient waveform optimization principles that can be applied to different pulse sequences (spin echo, gradient echo, echo planar), the system achieves noise reduction while maintaining versatility for T1, T2, and FLAIR contrast acquisition
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 by 10 dBA or more, enabling the acquisition of T2 and FLAIR contrast while maintaining image quality, and is applicable to various MR pulse sequences.
Implementation Method 1
The noise/vibration from the gradient coils is due to Lorentz forces applied thereto that result from an interaction of a static magnetic field and electrical current, with the Lorentz forces thereby creating vibrations in the gradient coil.
Implementation Method 2
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency.
Implementation Method 3
When utilizing these signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used.
Data Source
AI summary
A system and method for reducing MRI-generated acoustic noise is disclosed. A system control of an MRI apparatus causes a plurality of gradient coils and an RF coil assembly in the MRI apparatus to generate pulse sequences that each cause an echo train to form and acquire blades of k-space data of the subject of interest from the pulse sequences, with the blades being rotated about a section of k-space compared to every other blade. The system control also causes the plurality of gradient coils to generate gradient pulses in each pulse sequence having an optimized gradient waveform that reduces an acoustic noise level generated thereby and causes the RF coil assembly to generate a 180 degree prep pulse subsequent to generation of an RF excitation pulse and prior to generation of a first RF refocusing pulse, the 180 degree prep pulse minimizing echo spacing in the echo train.