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Probing the myelin water compartment with a saturation-recovery, multi-echo gradient-recalled echo sequence
Elena Kleban1,2, Penny Gowland1, Richard Bowtell1
1Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK.
Magnetic Resonance in Medicine
|February 12, 2021
Summary
Varying T1-weighting in MRI can adjust white matter signal contrast, but effects are less pronounced than expected due to counteracting factors like magnetization transfer and exchange. This impacts myelin water imaging.
Area of Science:
- Neuroimaging
- Biophysics
- Magnetic Resonance Imaging
Background:
- Multi-echo gradient-recalled echo (mGRE) sequences analyze complex signal evolution in white matter.
- Signal analysis separates short- and long-T2 components, reflecting myelin water and intra-/extra-axonal compartments.
Purpose of the Study:
- To investigate the impact of varying T1-weighting on white matter signal evolution in saturation-recovery mGRE sequences.
- To assess how T1-weighting affects the relative signal contributions from different white matter compartments.
Main Methods:
- Complex saturation-recovery mGRE data acquired from the splenium of the corpus callosum in healthy volunteers.
- Frequency difference mapping (FDM) preprocessing followed by analysis using a 3-pool model of signal evolution.
Main Results:
- An increase in apparent T1 with echo time was observed, but significantly smaller than predicted by known myelin water T1 values.
- This suggests counteracting effects from magnetization transfer and exchange phenomena.
Conclusions:
- T1-weighting amplitude variation in mGRE can modulate white matter compartment signal strengths.
- Observed modulation is less than predicted, indicating the influence of confounding biophysical processes.
