Dynamic MRI Scan Time Reduction via Undersampled EPI
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Solution Overview
Problem
Current Magnetic Resonance Imaging (MRI) techniques, particularly 4D flow imaging, face challenges in reducing scan time while maintaining high spatial resolution, especially in dynamic imaging applications like cardiac MRI, where motion artifacts and long acquisition times are prevalent, leading to increased costs and patient discomfort.
Innovation Solution
The method combines Echo Planar Imaging (EPI) with randomly undersampled k-space reconstruction techniques, using compressed sensing and radial ordering to reduce scan time and minimize eddy currents, allowing for faster acquisition of dynamic MRI images with improved spatial and temporal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional MRI sequences are used for dynamic imaging, then spatial resolution can be maintained, but scan time becomes excessively long (30+ minutes)
Solution Approach 1:
The patent applies partial sampling of k-space by acquiring only a subset of phase-encoding lines (e.g., every other line or using radial undersampling patterns) rather than complete sampling. This partial action reduces scan time significantly while reconstruction algorithms fill in the missing information, achieving acceptable spatial resolution with much faster acquisition.
Solution Approach 2:
The patent changes the sampling parameters in k-space by using non-Cartesian radial trajectories or compressed sensing sampling patterns instead of conventional Cartesian grid sampling. This parameter change allows fewer samples to be acquired while still enabling accurate image reconstruction through advanced algorithms.
2Productivity
If EPI is used to reduce scan time, then acquisition speed increases, but spatial resolution becomes limited and eddy currents increase
Solution Approach 1:
The patent segments the k-space acquisition into multiple radial trajectories or shots, where each trajectory samples a different angular range. This segmentation allows the acquisition to be distributed over time while maintaining high temporal resolution and reducing the impact of eddy currents within each individual trajectory.
Solution Approach 2:
The patent uses curved radial trajectories in k-space instead of straight Cartesian lines. These circular or spiral trajectories naturally sample k-space more efficiently, improving spatial resolution while maintaining fast acquisition speed and reducing susceptibility to eddy current artifacts compared to conventional EPI.
3Measurement precision
If flow encoding gradients are applied after each RF excitation for Phase Contrast imaging, then flow quantification accuracy is maintained, but scan time increases significantly
Solution Approach 1:
The patent maintains continuous flow encoding throughout the rapid acquisition sequence by applying gradients during each radial trajectory without interruption. This continuous application of flow encoding ensures accurate flow measurement is maintained throughout the entire fast scan, unlike intermittent encoding that would lose flow information between acquisitions.
Data Source
AI summary
A method and apparatus for reducing scan time, eddy currents and image factors in dynamic magnetic resonance (MR) imaging associated with at least a portion a k-space. The method includes scanning at least a portion of the k-space with an Echo-Planar Imaging (EPI) pulse sequence technique, acquiring a randomly under-sampled k-space; and reconstructing the under-sampled k-space utilizing a constrained reconstruction technique. A dynamic image is constructed of the at least a portion of the k-space based on EPI and the randomly undersampled k-space techniques to each segment of the EPI pulse sequence technique.