Ex vivo diffusion tensor imaging and quantitative tractography of the rat spinal cord during long-term recovery from moderate spinal contusion.
OBJECTIVE
To characterize DTI metric changes throughout the length of the entire spinal cord from the acute through chronic stages of spinal cord injury (SCI).


METHODS
Ex vivo DTI was performed at 9.4 Tesla to examine changes in water diffusion throughout the entire spinal cord (7-cm) up to 25 weeks after injury in a rat model of contusive SCI. Animals were grouped according to recovery times after injury (2, 5, 15, 20, or 25 weeks), and various DTI metrics were evaluated including transverse and longitudinal apparent diffusion coefficient (tADC and lADC), mean diffusivity (MD), and fractional anisotropy (FA).


RESULTS
An overall decrease in lADC throughout the cord and decreases in MD remote from the lesion site were observed, along with an increase in tADC within fiber tracts throughout the recovery period. These trends were statistically significant at P<0.05 and were found in both white and gray matter regions. tADC and lADC distributions in fiber bundles extracted using DTI tractography were well fit by an exponential model (R=0.998) with time constants of 4.6 and 3.3 days, respectively.


CONCLUSIONS
Results from the current study support the hypothesis that the spinal cord undergoes continual changes during recovery from SCI.
Ellingson
Benjamin M
BM
Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin 53201-1881, USA.
Kurpad
Shekar N
SN
Schmit
Brian D
BD
D019412:Anatomy, Cross-Sectional / Q000379:methods; D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function; D013116:Spinal Cord / Q000473:pathology*; D013119:Spinal Cord Injuries / Q000473:pathology*