Mapping the myelin bilayer with short-T₂ MRI: Methods validation and reference data for healthy human brain

Area of Science:

• Neuroimaging
• Biophysics
• Magnetic Resonance Imaging

Background:

• Short T2 signals in human brain tissue are complex and influenced by experimental conditions.
• Understanding these signals is crucial for accurate tissue characterization.
• Existing models may not fully capture the properties of these short T2 signals.

Purpose of the Study:

• To explore the properties of short T2 signals in human brain.
• To investigate the impact of experimental procedures (D2O exchange, frozen storage) on these signals.
• To evaluate the performance of a three-component analysis for signal characterization.

Main Methods:

• Acquisition of multi-echo (33-2067 μs) short T2 data from human brain tissue samples.
• Application of a two-step, three-component complex model to recover signal properties.
• Validation of component amplitude maps using immunohistochemical myelin staining.

Main Results:

• A myelin bilayer signal component with super-exponential decay (T2,min = 5.48 μs) was identified and successfully mapped in white and gray matter.
• Myelin maps correlated well with immunohistochemical staining.
• Frozen storage affected component amplitudes but not signal components; D2O exchange was essential for non-aqueous components.

Conclusions:

• The developed myelin mapping approach yields stable and reliable results for human brain tissue.
• The findings provide a foundation for interpreting short T2 signals in both ex vivo and in vivo studies.
• The three-component model effectively characterizes complex signals in brain tissue.