Correlation between diffusion tensor indices and fascicular morphometric parameters of peripheral nerve.

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Radiology

Background:

• Diffusion Tensor Imaging (DTI) is a Magnetic Resonance Imaging (MRI) technique measuring water diffusion anisotropy.
• Clinical MRI resolution is limited for depicting peripheral nerve fascicular morphology.
• High-field strength MRI is required for detailed fascicular pattern visualization.

Purpose of the Study:

• To quantify diffusion tensor indices within median nerve anatomical compartments using high-field strength MRI.
• To determine correlations between diffusion tensor indices and fascicular-level nerve structure.

Main Methods:

• Utilized a 9.4T MRI scanner with a 3D pulsed gradient spin-echo sequence.
• Acquired data from five fresh cadaver median nerve samples (9mm segments, 0.625mm slices).
• Segmented fascicles, perineurium, and interfascicular epineurium; calculated diffusion tensor indices and assessed correlations with structural parameters.

Main Results:

• Nerve fascicles exhibited the highest anisotropy (Fractional Anisotropy [FA] = 0.44 ± 0.05).
• Interfascicular epineurium showed diffusion prominent in orthogonal directions (FA = 0.13 ± 0.02).
• Significant differences in diffusion tensor indices were found within fascicles and perineurium between subjects (p < 0.0001), but not in the interfascicular epineurium (p ≥ 0.37). No correlations were found between diffusion tensor indices and fascicular nerve structure (p ≥ 0.29).

Conclusions:

• High-field strength MRI successfully depicted anisotropic diffusion within median nerve fascicles and perineurium.
• Diffusion tensor indices at the fascicular level did not correlate with nerve structural parameters.
• Future research should explore relationships between diffusion tensor indices and axon/myelin parameters.