Diffusion Tensor Imaging to Assess Injury Severity in Rabbits With Acute Spinal Cord Injury

The function of diffusion tensor imaging (DTI) metrics for assessing spinal cord injury (SCI) in different phases is controversial. The aim of this study was to evaluate the sensitivity of DTI metrics for the assessment of damage severity and functional recovery following acute SCI. A total of 36 rabbits received a graded contusion injury via different inflated volume balloon catheters (40 μL, 50 μL, or no inflation). Serial multisequence MRI scans were implemented to obtain the intramedullary lesion length (IMLL), DTI metrics of fractional anisotropy (FA) and average dispersion coefficient (DCavg). Additionally, damage severity was evaluated through behavioral and histological methods. Conventional MRI revealed a significant difference in the IMLL between the moderate and severe injury groups at 1 and 7 days (p < 0.01), whereas there was no difference at 3 days. The DCavg and FA in the epicenter were significantly reduced after SCI (p < 0.01). The DCavg in the severe injury group was lower than that in the moderate injury group at 1, 3, and 7 days (p < 0.01). However, there were no differences in the FA metrics at those times. Correlation analysis revealed that the DCavg value at 3 days was negatively correlated with the Reuters score and cavity area, and positively correlated with the Rivlin test and white matter residue. However, FA was only positively correlated with white matter residue and was not correlated with the behavioral score or cavity area. After acute SCI, DCavg metrics of DTI be used to quantitatively evaluate damage severity and indicate functional recovery, whereas FA may not be a sensitive indicator during this acute phase.