Diffusion tensor imaging of forearm nerves in humans

Purpose: To implement a diffusion tensor imaging (DTI) protocol for visualization of peripheral nerves in human forearm. Materials and Methods: This Health Insurance Portability and Accountability Act (HIPAA)-compliant study was approved by our Institutional Review Board and written informed consent was obtained from 10 healthy participants. T₁- and T₂-weighted turbo spin echo with fat saturation, short tau inversion recovery (STIR), and DTI sequences with 21 diffusion-encoding directions were implemented to acquire images of the forearm nerves with an 8 channel knee coil on a 3T MRI scanner. Identification of the nerves was based on T₁-weighted, T ₂-weighted, STIR, and DTI-derived fractional anisotropy (FA) images. Maps of the DTI-derived indices, FA, mean diffusivity (MD), longitudinal diffusivity (λ_//), and radial diffusivity (λ; _⊥) along the length of the nerves were generated. Results: DTI-derived maps delineated the forearm nerves more clearly than images acquired with other sequences. Only ulnar and median nerves were clearly visualized on the DTI-derived FA maps. No significant differences were observed between the left and right forearms in any of the DTI-derived measures. Significant variation in the DTI measures was observed along the length of the nerve. Significant differences in the DTI measures were also observed between the median and ulnar nerves. Conclusion: DTI is superior in visualizing the median and ulnar nerves in the human forearm. The normative data could potentially help distinguish normal from diseased nerves.