BUDA SAGE MRI for Distortion-Free Diffusion Imaging
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Solution Overview
Problem
Existing MRI systems face challenges in rapid scanning and robustness against patient motion, particularly for vulnerable populations, leading to geometric distortions and resolution loss in diffusion-weighted imaging.
Innovation Solution
A multi-shot echo planar imaging (msEPI) pulse sequence with blip up-down acquisition (BUDA) encoding is used to acquire multi-contrast data, incorporating field inhomogeneity information for distortion-free imaging, combined with a SAGE pulse sequence to reduce geometric distortions and enhance resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid scanning is performed to reduce scan time, then productivity is improved, but measurement precision deteriorates due to geometric distortions and resolution loss
Solution Approach 1:
The imaging process is divided into multiple shots where k-space is segmented and acquired in separate segments. Each shot acquires a portion of k-space data, allowing for longer readout times per segment while maintaining overall fast scanning. This segmentation enables distortion correction to be applied to each segment individually, preserving image resolution while maintaining high productivity.
Solution Approach 2:
The patent applies reverse phase-encoding in alternating shots (blip-up in odd shots, blip-down in even shots). This inversion strategy allows distortion correction by combining data from opposite encoding directions, eliminating geometric distortions while maintaining rapid scanning capability through efficient k-space coverage.
2Loss of information
If multi-contrast data are acquired with multiple echoes, then information completeness is improved, but scan time increases
Solution Approach 1:
Multiple contrasts (gradient echo, spin echo, and mixed echoes) are merged into a single multi-shot EPI sequence. By acquiring all contrast types within the same shot framework and using parallel imaging acceleration, the patent obtains comprehensive contrast information without proportionally increasing scan time, as all contrasts are acquired simultaneously rather than sequentially.
Solution Approach 2:
The patent acquires more echo data than traditionally necessary by including both gradient and spin echoes within the same shot. This excessive action provides redundant information that can be used for both contrast generation and distortion correction, improving information completeness while the parallel imaging and compressed sensing techniques prevent proportional time increases.
3Manufacturing precision
If distortion correction is applied using field inhomogeneity data, then image quality is improved, but processing complexity increases
Solution Approach 1:
Field inhomogeneity mapping is performed as a preliminary step before main image acquisition. By pre-characterizing the field distortions, the correction process during image reconstruction becomes simpler and more efficient, as the distortion parameters are already known and can be directly applied to correct the multi-shot data without complex iterative optimization.
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
Enables distortion-free, high-resolution multi-contrast MRI in a short time, improving image interpretation and registration, especially for pediatric and elderly patients, and facilitating quantitative parameter mapping.
Implementation Method 1
magnetic resonance imaging ('MRI')
Implementation Method 2
a first echo time associated with a gradient echo
Implementation Method 3
a third echo time associated with a spin echo
Data Source
AI summary
Magnetic resonance imaging (“MRI”) using a spin- and gradient-echo (“SAGE”) pulse sequence with blip up-down acquisition (“BUDA”) encoding enables distortion-free, high-resolution diffusion-weighted imaging and/or quantitative parameter mapping. Phase-encoding polarities are alternated across shots during a multi-shot acquisition. In each shot, multi-contrast data are acquired at echo times associated with a gradient echo, a mixed gradient-and-spin echo, and a spin echo. High in-plane resolution and distortion-free quantitative parameter maps can be generated, such as T2 maps. T2* maps, paramagnetic susceptibility maps, and diamagnetic susceptibility maps. Diffusion-weighted data can be acquired using diffusion encoding gradients and BUDA encoding, where multi-contrast data are acquired in the b=0 acquisition. Diffusion parameter maps can be generated from the b=0 and diffusion-weighted data.