Preliminary clinical applications of DTI in human cervical spinal cord

Objective: To condcut preliminary study of the value of DTI(diffusion tensor imaging) in human cervical spinal cord. Methods: Twenty-one patients suffering from cervical spondylotic myelopathy and twenty volunteers without any clinical symptoms underwent routine MRI and DTI examination. DTI was performed in six non-collinear directions with single-shot fast spin echo echo, planar imaging sequence(b value = 400 s·mm-2). ADC(apparent diffusion coefficient) and FA(fractional anisotropy)values were measured by ROIs(regions of interest) in 4 different level segment spinal cord (C2/3, C3/4, C4/5, C5/6) in normal volunteers, in lesions and normal segmental spinal cord in clinical cases respectively. DTI original images were automatically processed by using IDL (Version 5.6) soft- ware to produce color tensor images. SPSS11.0 software for windows was used for t-test and one-way ANOVA analysis. The difference was considered statistically significant if P < 0.05. Results: (1) For volunteers, cervical spinal cord exhibited intermediated signal intensity on ADC map, high signal intensity on FA map, and blue color on the colorized FA map. Four different level segment spinal cord, C2/3, C3/4, C4/5, C5/6, were analyzed and it was found that FA value between them had a significant difference by ANOVA, F=159.24, P<0.001, with the highest FA value (0.85±0.03) of spinal cord segment of C2/3 level. However, ADC value between 4 segments had no significant difference(F=2.191, P>0.05). (2)In patients of cervical spondylotic myelopathy, routine MRI T2WI showed abnormal signal in 9 cases, and showed no abnormal signal in 12 dases. In sixteen cases it was found that abnormal patchy green signal on colorized tensor maps appeared on the normal blue spinal cord. Also, in patients of cervical spondylotic myelopathy, there was significant difference in ADC and FA value between lesions and normal spinal cord (paired t test, for ADC, t=2.88, P<0.05, for FA, t=2.62, P<0.05). Conclusion: FA value of C2/3 level segment spinal cord in normal volunteers (0.85 ± 0.03) is the highest among other segments. FA value decreases gradually along cervical spinal cord towards the caudal direction. However, the difference of ADC values amongst 4 segments is not significant. DTI colorized tensor maps can show more lesions than routine MRI. With the technique of single-shot fast spin echo echo-planar imaging sequence and diffusion in six non-collinear directions and a b value of 400 s·mm-2, DTI can clearly display the anatomic structure and lesions in the cervical spinal cord. (authors)