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Water/fat separation for self-navigated diffusion-weighted multishot echo-planar imaging
Yiming Dong1, Malte Riedel2, Kirsten Koolstra3
1C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
NMR in Biomedicine
|August 28, 2022
Summary
A new self-navigation strategy enhances water/fat-separated diffusion-weighted imaging. This method improves scan efficiency and image quality for multishot echo-planar imaging (ms-EPI) by reducing artifacts and improving fat suppression.
Area of Science:
- Magnetic Resonance Imaging
- Medical Imaging Physics
- Biomedical Engineering
Background:
- Multishot echo-planar imaging (ms-EPI) offers improved geometric distortion and signal-to-noise ratio for diffusion-weighted imaging compared to single-shot methods.
- Physiological motion necessitates shot-to-shot phase error correction in ms-EPI, typically via external navigators or self-navigation.
- Effective fat suppression is crucial, particularly in areas with magnetic field (B0) inhomogeneity, making chemical shift encoding valuable.
Purpose of the Study:
- To develop a self-navigation strategy for optimizing scan efficiency and image quality in water/fat-separated, diffusion-weighted ms-EPI.
- To enable direct k-space data reconstruction using a chemical shift-encoded diffusion-weighted signal model.
- To address challenges in ms-EPI phase navigation caused by fat signal displacement.
Main Methods:
- A novel model-based, self-navigated water/fat separation reconstruction algorithm was developed.
- Chemical shift-encoded diffusion-weighted data were acquired.
- The algorithm was validated through experiments on 10 subjects in leg and head-neck regions, comparing it against 2D navigated and conventional fat saturation methods.
Main Results:
- The self-navigation approach reduced ms-EPI shot duration by 30%-35% compared to 2D navigated methods.
- Improved diffusion-weighted water images were achieved in both leg and head-neck regions versus the 2D navigator-based approach.
- Superior fat suppression was observed in B0 inhomogeneous regions compared to conventional fat saturation techniques.
Conclusions:
- The proposed self-navigated reconstruction algorithm yields superior water-only diffusion-weighted EPI images.
- The method effectively reduces artifacts and enhances fat suppression in ms-EPI.
- This technique offers a significant improvement over existing water/fat separation methods for diffusion-weighted imaging.
