Magnetic Resonance Fingerprinting Pulse Sequences for Acoustic Noise Reduction
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Solution Overview
Problem
Magnetic resonance fingerprinting (MRF) scans generate excessive acoustic noise, which is uncomfortable for patients and personnel and louder than conventional MRI scans, affecting scan efficiency and repeatability.
Innovation Solution
Implementing a magnetic resonance fingerprinting system that uses arbitrary gradient waveforms and random repetition times in the pulse sequence to control and reduce acoustic noise, while maintaining the ability to quantify tissue properties like T1 and T2 values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast switching gradients are used in MRF pulse sequences, then scan efficiency and quantification capability are improved, but acoustic noise levels increase significantly
Solution Approach 1:
The patent applies dynamics by making the gradient waveforms non-static and non-repetitive. Each TR cycle uses different gradient waveforms (e.g., different spiral readout trajectories, varying slice encoding gradients) rather than repeating the same fast switching pattern. This temporal variation in gradient dynamics reduces acoustic noise through incoherent noise accumulation while preserving the fast switching capability needed for efficient scanning and quantitative measurement.
Solution Approach 2:
The patent changes multiple pulse sequence parameters including gradient waveforms, repetition times (TR), echo times (TE), and flip angles in a varied manner across TR cycles. Specifically, it uses arbitrary gradient waveforms for each gradient axis and random or varied repetition times. These parameter variations prevent consistent acoustic noise generation while maintaining the necessary gradient switching speed for efficient MRF scanning and accurate tissue characterization.
2Object-generated harmful factors
If conventional MRI pulse sequences are used, then acoustic noise is reduced, but quantitative measurement capability and scan efficiency are compromised
Solution Approach 1:
The patent segments the MRF scan into multiple TR cycles, each with varied pulse sequence parameters. Within each TR cycle, different gradient waveforms and timing parameters are applied to generate unique signal evolutions. This segmentation allows the system to accumulate quantitative information across multiple varied measurements while using softer gradient switching in each individual cycle, thereby reducing overall acoustic noise while preserving quantification capability.
Solution Approach 2:
The patent uses periodic repetition of TR cycles with varied parameters. Instead of a single repetitive pulse sequence, it employs periodic action where each period (TR cycle) contains different gradient waveforms and timing parameters. This periodic variation in parameters reduces acoustic noise through incoherent accumulation while the repeated measurements across periods enable robust quantitative measurement through pattern recognition and signal evolution analysis.
3Measurement precision
If varied pulse sequence parameters are used in MRF, then tissue characterization accuracy is improved, but acoustic noise becomes more variable and potentially louder
Solution Approach 1:
The patent introduces asymmetry in the pulse sequence parameters, using non-symmetric gradient waveforms (e.g., asymmetric spiral readouts, varying slice encoding gradient amplitudes and durations). It employs asymmetric TR timing and varied flip angles. This asymmetry prevents predictable acoustic noise patterns and reduces peak noise levels while the varied asymmetric parameters create unique signal evolutions that improve tissue characterization accuracy through better discrimination of tissue properties.
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
The system effectively reduces acoustic noise levels during MRF scans to levels comparable to conventional quiet MRI scans, enhancing patient and operator comfort and scan efficiency without compromising quantitative imaging capabilities.
Implementation Method 1
Characterizing tissue species using nuclear magnetic resonance ('NMR') can include identifying different properties of a resonant species (e.g., T1 spin-lattice relaxation, T2 spin-spin relaxation, proton density)
Implementation Method 2
acoustic noise is produced during an MRF scan. The acoustic noise may be, for example, loud banging noises... an MRF scan has an average sound pressure level (aSPL) of 88.4 dB and maximum sound pressure level (mSPL) of 90.3 dB
Data Source
AI summary
A method for magnetic resonance fingerprinting (MRF) with reduced acoustic noise includes accessing a MRF dictionary using a magnetic resonance imaging (MRI) system, acquiring MRF data using the MRI system and a pulse sequence comprising a plurality of arbitrary gradient waveforms for each gradient axis and random repetition times to control acoustic noise, comparing the MRF data to the MRF dictionary to identify at least one parameter of the MRF data and generating a report indicating the at least one parameter of the MRF data.