Characterization and limitations of diffusion tensor imaging metrics in the cervical spinal cord in neurologically intact subjects

Abstract

To characterize diffusion tensor imaging (DTI) metrics across all levels of the cervical spinal cord (CSC) and to study the impact of age and signal quality on these metrics. DTI metrics were calculated for gray matter (GM) and white matter (WM) funiculi throughout the CSC (C1-T1) in 25 healthy subjects (22-85 years old). Signal-to-noise ratios (SNRs) and mean DTI metrics were measured for the upper (C1-3), middle (C4-6) and lower (C7-T1) cervical segments. Age-related changes in DTI metrics were analyzed for the individual segment groups. Fractional anisotropy (FA), mean diffusivity (MD) and transverse apparent diffusion coefficient (tADC) showed significant differences between GM and WM funiculi. Significant age-related changes were observed in FA in upper and middle CSC segments but not in the lower CSC. The median SNR was significantly lower in the middle and lower segment groups as compared to the upper levels, contributing to poor spatial resolution in these regions. This study provides DTI data for GM and WM funiculi throughout the CSC. While DTI metrics may be used to define cord pathology, variations in metrics due to age and signal quality need to be accounted for before making definitive conclusions.