Probing the myelin water compartment with a saturation-recovery, multi-echo gradient-recalled echo sequence

Kleban, Elena; Gowland, Penny; Bowtell, Richard

Abstract

Purpose: To investigate the effect of varying levels of (Formula presented.) -weighting on the evolution of the complex signal from white matter in a multi-echo gradient-recalled echo (mGRE) saturation-recovery sequence. Theory and Methods: Analysis of the complex signal evolution in an mGRE sequence allows the contributions from short- and long- (Formula presented.) components to be separated, thus providing a measure of the relative strength of signals from the myelin water, and the external and intra-axonal compartments. Here we evaluated the effect of different levels of (Formula presented.) -weighting on these signals, expecting that the previously reported, short (Formula presented.) of the myelin water would lead to a relative enhancement of the myelin water signal in the presence of signal saturation. Complex, saturation-recovery mGRE data from the splenium of the corpus callosum from 5 healthy volunteers were preprocessed using a frequency difference mapping (FDM) approach and analyzed using the 3-pool model of complex signal evolution in white matter. Results: An increase in the apparent (Formula presented.) as a function of echo time was demonstrated, but this increase was an order of magnitude smaller than that expected from previously reported myelin water (Formula presented.) -values. This suggests the presence of magnetization transfer and exchange effects which counteract the (Formula presented.) -weighting. Conclusion: Variation of the (Formula presented.) amplitude in a saturation-recovery mGRE sequence can be used to modulate the relative strength of signals from the different compartments in white matter, but the modulation is less than predicted from previously reported (Formula presented.) -values.

• Journal Article Type: Article
• Acceptance Date: Jan 4, 2021
• Online Publication Date: Feb 12, 2021
• Publication Date: Jul 1, 2021
• Deposit Date: Feb 24, 2021
• Publicly Available Date: Feb 24, 2021
• Journal: Magnetic Resonance in Medicine
• Print ISSN: 0740-3194
• Electronic ISSN: 1522-2594
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 86
• Issue: 1
• Pages: 167-181
• DOI: https://doi.org/10.1002/mrm.28695
• Keywords: Radiology Nuclear Medicine and imaging
• Public URL: https://nottingham-repository.worktribe.com/output/5348447
• Publisher URL: https://onlinelibrary.wiley.com/doi/10.1002/mrm.28695