Multi-shot Spiral MRE Pulse Sequence for Brain Tissue Characterization
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Solution Overview
Problem
Current magnetic resonance elastography (MRE) techniques face challenges in achieving high spatial resolution and Signal-to-Noise Ratio (SNR) for accurately measuring mechanical properties of tissues, particularly in the brain, due to limitations in image acquisition speed and sensitivity to field inhomogeneities, leading to incomplete characterization of viscoelastic properties.
Innovation Solution
The implementation of a multi-shot spiral MRE pulse sequence with k-space data correction, using variable-density spiral readout gradients and a Rayleigh damped model of brain tissue mechanics, enables high-resolution, three-dimensional displacement measurements and correction for phase errors, thereby enhancing spatial resolution and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-shot MRE sequence is used, then the image acquisition speed is fast, but the spatial resolution and SNR are insufficient for accurate mechanical property measurement
Solution Approach 1:
The patent divides the k-space acquisition into multiple shots (segments), where each shot collects a portion of the k-space data. This segmentation allows for longer total acquisition time to achieve higher spatial resolution and SNR through multiple averages, while managing the trade-off by distributing the acquisition across multiple shorter intervals rather than one extremely long scan.
2Measurement precision
If multi-shot MRE sequence is used to improve spatial resolution and SNR, then phase errors occur due to field inhomogeneities, but the measurement precision deteriorates
Solution Approach 1:
The patent performs preliminary phase correction by identifying the maximum signal intensity point in each shot before final image reconstruction. This preliminary action of locating and correcting phase offsets in each individual shot prevents cumulative phase errors from degrading the final image quality, ensuring reliable measurement precision.
Solution Approach 2:
The patent uses the maximum signal intensity point detected in each shot as feedback to correct phase errors. By continuously monitoring and adjusting based on the signal intensity distribution in each shot, the system maintains phase accuracy across multiple shots, resolving the contradiction between improved SNR and phase reliability.
3Measurement precision
If mechanical palpation is used to measure tissue mechanical properties, then the measurement is simple, but the accuracy is low and the procedure can be invasive
Solution Approach 1:
The patent replaces direct mechanical palpation with a non-invasive magnetic resonance-based measurement system. By using MRE to measure tissue displacement in response to applied vibrations and calculating mechanical properties from these measurements, the system achieves high measurement accuracy without the invasiveness of mechanical palpation, particularly for sensitive tissues like the brain.
Data Source
AI summary
Aspects of the subject disclosure include a system that applies magnetic resonance elastography to a sample to obtain uncorrected k-space data where the magnetic resonance elastography utilizes a multi-shot spin-echo sequence with variable density spiral readout gradients, and adjusts the uncorrected k-space data to corrected k-space data by adjusting a k-space trajectory by shifting a center point for each shot to a new center point according to signal intensity and by adjusting a phase for each shot based on a phase offset that is determined according to the signal intensity.