3 T Magnetic Resonance Diffusion Tensor Imaging And Fiber Tracking In Detecting Acute Spinal Cord Injury

Objectives: To investigate the feasibility and clinical application of MR diffusion tensor imaging (MR-DTI) and diffusion tensor tractography (DTT) in acute spinal cord injury(ASCI), we also hypothese that fractional anisotropy (FA) values in spinal cord injury may be abnormal not only in the lesion but also in the surrounding normal-appearing spinal cord.Materials and Methods: Diffusion tensor imaging (DTI) was performed in 23 patients with ASCI(cervical cord injury, n=8; thoracic cord injury, n=1; lumbar and sacral cord injury, n=14;17 men,6 women; mean age,49.54±13.56) and 30 normal volunteers (cervical cord, n=10; thoracic cord, n=10; lumbar and sacral cord, n=10, 20 men,10 women; mean age, 42.73±10.28). GE Signa HDxt 3.0T Echo speed superconducting magnetic resonance machine and an MR phase-arrayed total spine coil were used. Single-shot echo-planar pulse image sequence (EPI) was chosen as scanning technology. Axial images of the spinal cord were obtained by using the 15 gradient sensitive direction as well as diffusion coefficient b=0,400 s/mm. After scanning, Functool software were used for DTI parameters at ADC and FA values were calculated at T2WI sagittal image for the different level of spinal cord of normal volunteers and three level of the spinal cord: lesion, proximal normal-appearing spinal cord and distal normal-appearing spinal cord in patients with ASCI. Finally, DTT was performed. All patients'clinical motor and sensory functions were examined according to the criteria of ASIA made by NASCIS (National Acute Spinal Cord Injury Study).Results: FA values are clearly increase in cervical 1 level and cervical 4 level compare with other segment of spinal cord. But the FA value at cervical 7 level is more higher than thoracic 4 level of spinal cord only(0.65±0.054 versus 0.58± 0.015,p<0.05). The ADC value of different segment of spinal cord has no statistical difference. FA values of spinal cord injury lesions and in distal normal-appearing spinal cord were significantly lower than those in control group (0.50±0.017, 0.592±0.0224 versus 0.69±0.017,p<0.01). But there was no significance in proximal normal-appearing spinal cord compared with the cervical control groups(0.67±0.0277 versus 0.69±0.017,p>0.05). The ADC values of lesions in cervical cord injury were decreased compared with the normal group (p<0.05). FA values of lumbar and sacral cord injury lesions and in proximal normal-appearing spinal cord were also significantly lower than in normal volunteers(0.443±0.02,0.527±0.017 versus 0.62±0.01,p<0.01); The ADC values of lesion were decreased compared with that in the normal group(p<0.05), but the surrounding part of lesion was not changed. The fiber bundles directly showed deformity, displacement and interruption at level of the injury area in the spinal cord. According to criteria of ASIA made by NASCIS (National Acute Spinal Cord Injury Study), 4 grades of injury in patients were classified, comprising B, C, D, E respectively, the ASCI grade correlated to the decreased FA value and show negative correlation.Conclusions:1. The FA and ADC value of patients with ASCI were both decreased in the lesion . The decrease of FA value was related to the severity of neurologic deficit.2. Normal surrounding areas also show abnormal in FA value. MR-DTI is more sensitivity than conventional MRI when evaluating the ASCI.3. MR-DTI can directly show the spinal cord fiber damage and deformation.