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Myelin water imaging at 0.55 T using a multigradient-echo sequence
Jessica Schäper1,2, Oliver Bieri1,2
1Department of Biomedical Engineering, University of Basel, Basel, Switzerland.
Purpose:
To investigate the prospects of a multigradient-echo (mGRE) acquisition for in vivo myelin water imaging at 0.55 T.
Methods:
Scans were performed on the brain of four healthy volunteers at 0.55 and 3 T, using a 3D mGRE sequence. The myelin water fraction (MWF) was calculated for both field strengths using a nonnegative least squares (NNLS) algorithm, implemented in the qMRLab suite. The quality of these maps as well as single-voxel fits were compared visually for 0.55 and 3 T.
Results:
The obtained MWF values at 0.55 T are consistent with previously reported ones at higher field strengths. The MWF maps are a considerable improvement over the ones at 3 T. Example fits show that 0.55 T data is better described by an exponential model than 3 T data, making the assumed multi-exponential model of the NNLS algorithm more accurate.
Conclusion:
This first assessment shows that mGRE myelin water imaging at 0.55 T is feasible and has the potential to yield better results than at higher fields.
Insights
Multigradient-echo (mGRE) myelin water imaging at 0.55 T shows promise for better results than higher field strengths. This technique is feasible and yields improved myelin water fraction maps.
Area of Science:
- Neuroimaging
- Biophysics
Background:
- Myelin water imaging (MWI) is crucial for assessing white matter integrity.
- Higher magnetic field strengths (e.g., 3 T) are commonly used for MWI.
- Challenges exist in MWI at higher field strengths, including signal-to-noise ratio and susceptibility artifacts.
Purpose of the Study:
- To evaluate the feasibility and potential of a 3D multigradient-echo (mGRE) sequence for in vivo myelin water imaging at 0.55 T.
- To compare the quality of myelin water fraction (MWF) maps generated at 0.55 T with those acquired at 3 T.
Main Methods:
- A 3D mGRE sequence was employed to scan the brains of four healthy volunteers at both 0.55 T and 3 T.
- Myelin water fraction (MWF) was calculated using a nonnegative least squares (NNLS) algorithm within the qMRLab software.
- Visual comparison of MWF map quality and single-voxel fitting accuracy was performed between the two field strengths.
Main Results:
- Myelin water fraction values obtained at 0.55 T align with previously reported findings at higher field strengths.
- The MWF maps generated at 0.55 T demonstrated a significant improvement in quality compared to those from 3 T.
- Data acquired at 0.55 T were better represented by an exponential model, enhancing the accuracy of the NNLS algorithm's multi-exponential assumption.
Conclusions:
- Myelin water imaging using mGRE at 0.55 T is feasible.
- This lower field strength shows potential for yielding superior results compared to higher field strengths.
- The findings suggest 0.55 T mGRE is a viable and potentially advantageous approach for in vivo myelin water imaging.
