Diffusion tensor MR imaging of the neurologically intact human spinal cord

BACKGROUND AND PURPOSE: The aim of this study was to characterize the diffusion properties of the entire human spinal cord in vivo. These data are essential for comparisons to pathologic conditions as well as for comparisons of different pulse sequence design parameters aimed to reduce scan time and more accurately determine diffusion coefficients. MATERIALS AND METHODS: A total of 13 neurologically intact subjects were enrolled in this study, A single-shot, twice-refocused, spin-echo, diffusion-weighted, echo-planar imaging (EPI) pulse sequence was used to obtain axial images throughout the entire spinal cord (C1-L1) in 45 minutes. RESULTS: Diffusion images indicated slight geometric distortions; however, gray and white matter contrast was observed. All measurements varied across the length of the cord. Whole cord diffusion coefficients averaged 0.5-1.3 X 10(-3) mm(2)/s depending on orientation, mean diffusivity (MD) averaged 0.83 +/- 0.06 X 10(-3) mm(2)/s, fractional anisotropy (FA) averaged 0.49 +/- 0.05, and volume ratio (VR) averaged 0.73 +/- 0.05. CONCLUSION: This study provided normative diffusion values for the entire spinal cord for use in comparisons with pathologic conditions as well as improvements in pulse sequence design.