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Updated: Jun 21, 2026
Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
Myelin water imaging from accelerated 3D-GRASE acquisitions using subspace constrained reconstruction
Riwaj Byanju1, Stefan Klein1, Alexandra Cristobal-Huerta1
1Department of Radiology and Nuclear Medicine, Erasmus MC, Rotterdam, The Netherlands.
Purpose:
Quantitative MRI markers, such as myelin water fraction (MWF) and geometric mean (IET2) (the intra-/extra-cellular water compartment), can be biomarkers for various brain disorders. However, these markers require acquiring multi-echo spin-echo images which requires long scan times. Undersampled 3D-GRAdient Echo and Spin Echo (3D-GRASE) scans with parallel imaging have been used for faster scans. Still, further acceleration is desirable. Reconstruction techniques that utilize redundancy along the echoes could be employed to achieve artifact-free maps at higher acceleration. This work examines the possibility of using one such technique, subspace constrained reconstruction (SCR), for further accelerating the 3D-GRASE scan.
Methods:
We propose two techniques to undersample the 3D-GRASE acquisition and exploit the redundancy across echoes. We retrospectively undersample fully sampled data from phantom and in-vivo acquisition to test these techniques. We compared our results for mapping MWF and IET2 to a reference multi-spin-echo technique. Additionally, we compare the proposed, state-of-the-art, and reference techniques with prospectively undersampled in-vivo acquisitions.
Results:
The RMSD of the MWF in retrospectively undersampled data was worse for the proposed techniques than the state-of-the-art. However, for IET2, RMSD was similar or slightly improved. In prospectively undersampled scans, undersampling artifacts deteriorated MWF maps, but not IET2 maps, which were within 10 ms of the reference map.
Conclusion:
Our findings suggest that exploiting redundancy across echoes does not result in additional acceleration beyond the current state-of-the-art for MWF mapping, while it is possible to accelerate beyond state-of-the-art for IET2 mapping.
Insights
This study explored subspace constrained reconstruction for faster brain MRI scans. While it improved myelin water fraction (MWF) and intra-/extra-cellular water (IET2) mapping, it did not surpass current methods for MWF but offered acceleration for IET2.
Area of Science:
- Neuroimaging
- Quantitative MRI
- Biomarker Development
Background:
- Quantitative MRI markers like myelin water fraction (MWF) and intra-/extra-cellular water T2 (IET2) are crucial for diagnosing brain disorders.
- Current methods for acquiring these markers involve lengthy scan times due to multi-echo spin-echo sequences.
- Accelerated imaging techniques, such as undersampled 3D-GRASE with parallel imaging, are needed to reduce scan duration.
Purpose of the Study:
- To investigate the potential of subspace constrained reconstruction (SCR) for further accelerating 3D-GRAdient Echo and Spin Echo (3D-GRASE) MRI scans.
- To assess the feasibility of using SCR to generate artifact-free myelin water fraction (MWF) and intra-/extra-cellular water T2 (IET2) maps at higher acceleration factors.
- To evaluate the performance of SCR compared to state-of-the-art and reference multi-spin-echo techniques for quantitative MRI marker mapping.
Main Methods:
- Two novel undersampling techniques for 3D-GRASE acquisition were developed, exploiting redundancy across echoes.
- Retrospective undersampling of fully sampled phantom and in-vivo data was performed to test the proposed techniques.
- Comparisons included MWF and IET2 mapping against a reference multi-spin-echo technique and prospective undersampled in-vivo acquisitions.
Main Results:
- Retrospective analysis showed worse Root Mean Square Deviation (RMSD) for MWF with proposed techniques compared to state-of-the-art.
- For IET2, retrospective RMSD was similar or slightly improved using the proposed techniques.
- Prospective scans revealed that undersampling artifacts degraded MWF maps, but IET2 maps remained accurate within 10 ms of the reference.
Conclusions:
- Exploiting echo redundancy with SCR does not yield additional acceleration benefits beyond the current state-of-the-art for myelin water fraction (MWF) mapping.
- However, SCR enables acceleration beyond the state-of-the-art for intra-/extra-cellular water T2 (IET2) mapping.
- These findings highlight the potential of SCR for specific quantitative MRI biomarkers, improving scan efficiency.
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