Feasibility of brain intra-axonal microstructure imaging with ultrahigh B-encoding using MAGNUS...

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• High-performance MRI gradient platforms are crucial for advanced diffusion MRI (dMRI) techniques.
• Exploring the intra-axonal space requires advanced dMRI protocols with high b-values and gradient strengths.
• Current methods face limitations in resolving microstructural details of white matter.

Purpose of the Study:

• To assess the feasibility and reproducibility of mapping the effective intra-axonal radius (r_eff) in vivo using the MAGNUS MRI gradient platform.
• To evaluate r_eff as a potential neuroimaging biomarker for white matter integrity and neuroplasticity.

Main Methods:

• Utilized the MAGNUS high-performance MRI gradient platform (300 mT/m, 750 T/m/s).
• Employed multi-shell dMRI protocols with high b-values (b~7-≥30 ms/μm²) and a test-retest paradigm (short and long-term).
• Integrated a post-processing framework including real-valued diffusion data and gradient non-linearity correction.

Main Results:

• Demonstrated feasibility of mapping whole-brain r_eff in healthy volunteers (mean r_eff = 2.75 ± 0.15 μm).
• Observed good short- and long-term test-retest repeatability for voxel-wise and parcel-based estimates (mean CV = 3.2%).
• Noted good agreement with prior literature regarding white matter asymmetry and tract segmentation.

Conclusions:

• The MAGNUS platform facilitates feasible and reproducible in vivo mapping of the effective intra-axonal radius (r_eff).
• r_eff shows promise as a sensitive neuroimaging biomarker for white matter integrity and neuroplastic changes.
• This technique advances the non-invasive investigation of brain microstructure.