Diffusion Tensor Imaging of Scarring, Necrosis, and Cavitation Based on Histopathological Findings in Dogs with Chronic Spinal Cord Injury: Evaluation of Multiple Diffusion Parameters and Their Correlations with Histopathological Findings

The use of diffusion tensor imaging (DTI) for the characterization of various lesion types in dogs with spinal cord injury (SCI) has not been investigated. The aim of this study was to characterize scarring (loose immature scarring [LIMS], intermediate mature scarring [IMS], and dense mature scarring [DMS]), necrosis, cavitation, and acute hemorrhage using multiple DTI parameters and determine the correlations between the DTI parameters and histopathological finding in dogs with controlled SCI. All imaging data were obtained from the lumbar spinal cord (from L1 to L3) of normal and SCI dogs using a 3-Tesla magnetic resonance imaging scanner. Transverse multi-shot echo planar imaging (EPI) sequences (12 directions; b-value, 0 and 800s/mm(2)) were used for DTI. Regions of interest on DTI maps were selected according to the areas of normal white matter (NWM), normal gray matter (NGM), LIMS, IMS, DMS, necrosis, and cavitation on histopathological images and the area of acute hemorrhage with a hypointense signal on T2*-weighted images obtained 24h post-SCI. There were statistically significant differences in DTI parameters among NWM, NGM, multi-grade scarring, necrosis, and cavitation and between mature scarring and acute hemorrhage. The maturation grade of scarring demonstrated a positive linear correlation with fractional anisotropy and the planar index and a negative linear correlation with the spherical index and the radial, mean, and axial diffusivities. These results suggest the feasibility of using DTI for detailed noninvasive monitoring of SCI. DTI can provide critical information for guiding therapeutic strategies and determining the prognosis of SCI patients.