Diffusion properties of cortical and pericortical tissue: regional variations, reliability and methodological issues

Area of Science:

• Neuroimaging
• Biophysics
• Human Anatomy

Background:

• Cortical tissue diffusion analysis is challenging due to anatomical variability.
• Standardized methods are needed to compare diffusion properties across individuals.
• Understanding diffusion aids in characterizing brain structure and function.

Purpose of the Study:

• To develop and apply methods for measuring diffusion properties in aligned cortical gyri and sulci.
• To analyze fractional anisotropy (FA), mean diffusivity (MD), and cortical primary diffusion direction (cPDD) across cortical depth.
• To investigate relationships between diffusion metrics and local cortical features.

Main Methods:

• Diffusion tensor imaging (DTI) data from 82 young subjects were analyzed.
• High-resolution T1 images were co-registered and mapped to a standardized cortical surface template.
• Diffusion metrics (FA, MD, cPDD) were measured at surfaces parallel to the white/gray matter junction.

Main Results:

• Fractional anisotropy (FA) increased with depth from the pial surface.
• Mean diffusivity (MD) and cortical primary diffusion direction (cPDD) decreased with depth.
• Significant regional and hemispheric differences in FA, MD, and cPDD were observed.
• FA correlated with cortical curvature and sulcal depth; MD was influenced by nearby cerebrospinal fluid (CSF).

Conclusions:

• Diffusion properties vary systematically with cortical depth and local anatomy.
• These findings provide insights into the microstructural organization of cortical fiber projections.
• The developed methods enhance the characterization of diffusion in the human cortex.