Mapping apparent eccentricity and residual ensemble anisotropy in the gray matter using angular...

Area of Science:

• Neuroimaging
• Biophysics
• Magnetic Resonance Imaging

Background:

• Conventional diffusion MRI (dMRI) primarily visualizes white matter microarchitecture via diffusion anisotropy.
• Double-pulsed-field-gradient (dPFG) MRI offers microstructural insights, including compartment shape and microscopic anisotropies, even in randomly oriented tissues.

Purpose of the Study:

• To introduce and apply angular double-pulsed-gradient-spin-echo (aDPGSE) MRI in the rat brain, both ex vivo and in vivo.
• To investigate the potential of aDPGSE MRI for characterizing gray matter microstructural features.

Main Methods:

• Application of angular double-pulsed-gradient-spin-echo MRI on rat brains (ex vivo and in vivo).
• Analysis of angular dependencies at long mixing times (t(m)).
• Development of an analysis scheme to map structural indices like apparent eccentricity (aE) and residual phase (φ).

Main Results:

• Robust angular dependencies were detected in the rat brain at long t(m).
• Observed oscillations suggest origins from residual directors in randomly oriented media (residual ensemble anisotropy).
• The developed analysis scheme successfully mapped structural indices (aE, φ) for brain characterization.

Conclusions:

• Angular double-pulsed-gradient-spin-echo MRI is demonstrated for the first time in the rat brain.
• The technique shows promise for characterizing gray matter morphological features.
• This method may become valuable for identifying gray matter pathologies in neuroscience research.