Experimental Research Of DTI Quantitative Evaluation Of Functional Changes After Acute Traumatic Spinal Cord Injury In Rats

Objective:To explore the value of diffusion weighted imaging(DTI)quantitativeparameters in evaluating neurological function changes of acute traumatic spinal cord injury(TSCI)model in rats.Materials and Methods: The NYU impactor were used to establish rat TSCI models,the rats were divided into mild injury(n=10),moderate injury(n=10)and severe injury groups(n=10).Magnetic resonance imaging(MRI),DTI examination and Basso-Beattie-Bresnahan(BBB)score were performed on pre-TSCI and 0 h,6 h,24 h,3 day,7 day and 14 day post-TSCI,respectively.The BBB scores and DTI parameters,including fractional anisotropy(FA),mean apparent diffusivity(MD),radial diffusivity(RD)and axial diffusivity(AD),were measured and compared among different time points and injury degrees using.Diffusion tensor tractography(DTT)were constructed by fiber tracts crossing the region of interest(ROI).Multi-factor analysis of variance with the Bonferroni post hoc test was adopted to statistically analyze the variation of each parameter at all timepoints.Pearson's correlation analysis was conducted to compare the correlation between BBB scores and DTI parameters.Results: MRI among varying injury degrees demonstrate as hemorrhage type(n=12),edema type(n=7)and contusion type(n=11).The site of edema in spinal cord almost disappeared after 7d post-TSCI,the contusion areas gradually diminished during the follow-up process,and malacia could be found within 7 to 10 days with varying degrees ofspinal atrophy.DTT illustrated disruption of spinal cord among groups at all timepoints,and the extent increased as the time prolongs.The difference of FA,MD and RD value were significant among varying injury degrees and different time points after TSCI(all P<0.05).The AD value had significant difference among different time points (F=12.720,P<0.001),whereas no difference among varying injury degrees(F=0.469,P=0.630).The FA and MD value decreased while RD increased on 0h post-TSCI.Then,RD and MD increased continuously whereas FA decreased continuously until 24 h post-TSCI(all P<0.05),and parameters kept stable after 24 h post-TSCI(all P>0.05).AD decreased at 0h post-TSCI,but no statistic difference among all time points.The BBB scores were lowest on 0 h post-TSCI,then maintained increasing(all P<0.05).In addition,the BBB scores and MD values reached a good correlation(r=0.958,P<0.01).Conclusions: DTI plays an important role in quantitative evaluating function changes of TSCI.DTI parameters have correlation with injury degrees,and MD value could accurately reflect the function changes of cord injury.Moreover,treatment within 24 h post-TSCI might be the recommended time for TSCI therapy.