In Vivo Myelin Water Quantification Using Diffusion-Relaxation Correlation MRI: A Comparison of 1D and 2D Methods

Area of Science:

• Biomedical Engineering
• Neuroimaging
• Magnetic Resonance Imaging

Background:

• Multidimensional Magnetic Resonance Imaging (MRI) is essential for detailed tissue microstructure mapping.
• Understanding myelin water is critical for diagnosing neurological conditions.
• Existing MRI techniques have limitations in myelin water quantification.

Purpose of the Study:

• To investigate the potential of various multidimensional MRI methods for quantifying tissue microstructure.
• To specifically assess the ability of these techniques to measure the myelin water fraction (MWF).
• To compare the quality and speed of myelin mapping using different MRI approaches.

Main Methods:

• Utilized a diffusion weighted inversion recovery spin echo (DW-IR-SE) sequence with spiral readouts.
• Acquired a comprehensive diffusion-relaxation dataset using ultra-strong gradients.
• Reconstructed 1D and 2D spectra using a two-step convex optimization approach.
• Investigated 1D multi-component relaxometry, 1D multi-component diffusometry, 2D relaxation correlation imaging, and 2D diffusion-relaxation correlation spectroscopic imaging (DR-CSI).

Main Results:

• Observed a distinct spectral peak attributed to myelin water across multiple imaging techniques (T1 relaxometry, T1-T2, T1-D, T2-D correlation).
• Relaxometry-based MWF maps demonstrated higher quality due to shorter achievable echo times compared to diffusometry.
• 1D multi-component T1 data enabled significantly faster myelin mapping.

Conclusions:

• Multidimensional MRI, particularly relaxometry, offers high-quality myelin water fraction mapping.
• While 1D methods provide faster myelin mapping, 2D approaches offer deeper insights into microstructure and myelin diffusion.
• These advanced MRI techniques hold promise for improved diagnostics and understanding of neurological disorders.