MRI Diffusion-Relaxation Mapping With Multi-Echo EPI Acquisition
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Solution Overview
Problem
Existing MRI techniques for studying the coupling between diffusion and relaxation times are inefficient, leading to prolonged scan times and increased vulnerability to subject motion, with limited spatial resolution and signal-to-noise ratio.
Innovation Solution
A magnetic resonance imaging method and system that utilizes a stimulated multi-echo-train EPI sequence and multi-readout DWI technique with reduced field-of-view excitation, allowing simultaneous acquisition of diffusion-weighted images at different echo times and spin-spin relaxation times in a single shot, using gradient echoes and RF refocusing pulses to achieve efficient mapping of parameters like ADC, T1, T2*, and T2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple diffusion-weighted images with different TEs are acquired successively using hybrid multidimensional imaging, then coupling between diffusion and spin-spin relaxation can be studied, but scan time is substantially lengthened
Solution Approach 1:
The patent combines multiple diffusion-weighted imaging acquisitions at different echo times into a single hybrid multidimensional imaging sequence. By integrating TE variation within one scan protocol rather than performing separate acquisitions, the method studies diffusion-relaxation coupling while minimizing scan time extension to only what is necessary for the additional contrast information.
2Productivity
If multi-readout echo-planar imaging is used to accelerate data acquisition, then scan time is reduced, but echo-train length becomes substantially lengthy reducing signal-to-noise ratio
Solution Approach 1:
The patent segments the k-space acquisition into multiple parallel readout echo-trains, each acquiring data at a different echo time. This segmentation allows the total k-space to be covered efficiently without requiring an excessively long single echo-train, thereby maintaining signal-to-noise ratio while achieving accelerated acquisition through parallel processing of multiple TEs.
3Measurement precision
If spatial resolution is improved in diffusion-weighted imaging, then tissue microstructure characterization is enhanced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent employs continuous background gradient application during the diffusion encoding periods to maintain signal coherence and minimize dephasing effects. This continuous gradient action preserves signal intensity even when high spatial resolution encoding gradients are applied, allowing improved spatial resolution without the usual penalty of signal-to-noise ratio deterioration.
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 method enables rapid, reliable mapping of tissue microstructures with improved spatial resolution and reduced scan time, facilitating clinical applications such as cancer diagnosis and characterization.
Implementation Method 1
relaxation time is inherently related to the tissue biochemical composition. Joint analysis of diffusion MRI data acquired at different echo times (TEs) allows for characterization of the coupling between diffusion and spin-spin relaxation
Implementation Method 2
acquiring the plurality of image contrasts, wherein the plurality of image contrasts correspond to diffusion-weighted images, each diffusion-weighted image being acquired with a train of gradient echoes consistent with echo-planar imaging and at a specific effective echo time (TEeff)
Implementation Method 3
a plurality of TE or TEeff are generated by a train of radiofrequency (RF) refocusing pulses, each RF refocusing pulse producing a spin echo from which the train of gradient echoes are acquired
Implementation Method 4
Diffusion magnetic resonance imaging (MRI) is sensitive to tissue microstructures
Implementation Method 5
Diffusion magnetic resonance imaging (MRI) is sensitive to tissue microstructures
Implementation Method 6
Reduced field-of-view (rFOV) imaging provides an alternative strategy to reduce the echo-train length for EPI sequences, while maintaining high spatial resolution
Data Source
AI summary
Magnetic resonance imaging systems and methods are provided for time-efficiently producing a plurality of image contrasts, the plurality of image contrasts including a first contrast being coupled with a second contrast and acquired over a plurality of key parameters that govern the second contrast to which the first contrast is coupled. In addition, the plurality of image contrasts is used to simultaneously map the first contrast, the second contrast, and additional contrasts.