Single-shot Pseudo-centric EPI for MRI Echo Time Reduction
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Solution Overview
Problem
Current single-shot echo plane imaging (EPI) techniques have limitations in reducing echo time, leading to low signal-to-noise ratio (SNR) in magnetization-prepared imaging, and existing methods to reduce echo time either prolong scan time or are not suitable for magnetization-prepared imaging.
Innovation Solution
The introduction of phase encoding grouping in single-shot centric-reordered EPI (1sh-CenEPI) allows for centric reordering in Cartesian coordinates, encoding the whole K-space from center to edge with grouped oscillating readout gradients and large phase encoding jumps, reducing echo time while maintaining high SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If single-shot linear phase encoding EPI is used, then the imaging can be completed in a single shot, but the echo time is relatively long (>30 ms) leading to low SNR
Solution Approach 1:
The K-space is divided into multiple phase encoding line groups that are acquired in a pseudo-centric order (from center to edge), allowing the echo time to be reduced while maintaining single-shot acquisition. This segmentation of the phase encoding process enables optimal signal capture at the K-space center.
Solution Approach 2:
Instead of the conventional linear phase encoding order that starts from the K-space edge, the patent inverts the approach by using a pseudo-centric order that starts from the K-space center and moves outward. This inversion allows the most important signal information to be captured at the earliest possible time, reducing echo time while maintaining SNR.
2Reliability
If multi-shot centric EPI is used, then the SNR is improved by reducing echo time, but the scan time is prolonged proportional to the number of shots
Solution Approach 1:
The patent performs preliminary organization of phase encoding lines into groups that follow a pseudo-centric order within a single shot. This preliminary structuring of the acquisition sequence allows the system to achieve multi-shot-like SNR performance without actually requiring multiple shots, thereby avoiding the prolonged scan time.
Solution Approach 2:
The patent employs periodic oscillating readout gradients combined with phase encoding blips to systematically traverse the K-space in a pseudo-centric manner. This periodic action pattern enables efficient single-shot acquisition while maintaining the signal quality benefits of centric ordering.
3Loss of time
If phase encoding grouping is introduced, then centric reordering is achieved in single-shot EPI, but the sequence complexity increases
Solution Approach 1:
The patent changes the parameter of phase encoding order from linear to pseudo-centric, and introduces grouping of phase encoding lines. By systematically varying the phase encoding parameters within groups and using oscillating readout gradients, the patent achieves centric reordering with manageable sequence complexity that balances performance improvement with implementation feasibility.
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 significantly reduces echo time, improving SNR in magnetization-prepared imaging, achieving results comparable to multi-shot centric EPI while maintaining a similar readout duration, and is applicable to pseudo-continuous arterial spin labeling (pCASL) imaging.
Implementation Method 1
applying a radio-frequency (RF) excitation pulse
Implementation Method 2
completing a K-space by acquiring a plurality of phase encoding line groups
Data Source
AI summary
Provided is a method for generating MRI data including applying, by an MRI computing device, an RF excitation pulse, and completing, by the MRI computing device, a K-space by acquiring a plurality of phase encoding line groups, in a state in which any other RF excitation pulse is not applied after applying the RF excitation pulse, in which each of the plurality of phase encoding line groups includes a plurality of phase encoding lines, and an absolute value of an average phase encoding size of a phase encoding line group acquired earlier is not greater than an absolute value of an average phase encoding size of a phase encoding line group acquired later, among the plurality of phase encoding line groups.