Applied Research, Diffusion Tensor Imaging In Cervical Spondylotic Myelopathy

PART ONE PRELIMINARY STUDY OF MR DIFFUSION TENSOR IMAGING ON NORMAL CERVICALSPINAL CORDObjectives: To study the optimal technology of MR diffusion tensor imaging and the signal intensity and anisotropy of the nomal cervical cord by comparing the influence of different b values and different directions of gradients on normal cervical cord in diffusion tensor imaging(DTI).Materials and Methods: Twenty-two healthy volunteers were performed respectively by diffusion tensor imaging(DTI) of cervical cord with MRI scanning(GE Signa Exciteâ…¡1.5T unit),on the base of using echo planar imaging(EPI) sequence,with 6 directions and 25 directions of gradients and different b value(s0,100 s/mm²,200 s/mm²,400s/mm²,600 s/mm²,800 s/mm²,1000s/mm² ), the images characteristics of cervical spinal cord were compared and analyzed respectively, ADCav values,FA values,λ₁,λ₂ andλ₃ were calculated respectively at the relatively wide cervical cord of C₂-C₃ level and the more narrow cervical cord of C₄-C₇ level of Region of interest(ROI) on the sagittal-orientated images. Results: (1)Without changing of other scan parameters, ADCav values,FA values,λ₁,λ₂ andλ₃ with 6 directions and 25 directions had no significant difference from corresponding position (P>0.05). (2)With b value increased,average quality index decreased (P<0.01),but the distinction of average quality index among DTI with b=100 s/mm²,200 s/mm²,400s/mm²,600 s/mm² had no significant difference (P>0.05), b=1000s/mm² had no satisfied average quality index and SNR, the SNR of b=100 s/mm²,200s/mm²,600s/mm²,800 s/mm² and b=1000s/mm² had significant difference among them (P<0.01), but the SNR of b=600 s/mm² had no significant difference compared with the SNR of b=400 s/mm² (P>0.05).(3)With the same scan parameters, the ADC_av values and FA values measured of the normal spinal cord at the more narrow C₄-C₇ level were slightly lower than those measured at the relatively wide C₂-C₃ level (P<0.05),λ₁>λ₂>λ₃(P<0.05).Conclusions: Diffusion tensor imaging of the spinal cord can be performed with MRI scanning(GE Signa Exciteâ…¡1.5T unit),using Single shot-SE Echo planar imaging, adoptting b=600 s/mm² and using 6 directions were reasonable for the spinal cord of DTI,the spinal cord has distinct diffused anisotropy, ADCav values with the diffusion gradients parallel to the white matter tract were markedly high. PART TWO THE STUDY OF CERVICAL SPONDYLOTIC MYELOPATHY USING DIFFUSION TENSOR IMAGINGObjectives: To evaluate the value of ADCav values and FA values in the diagnosis of cervical spondylotic myelopathy(CSM).materials and methods: Thirty-five cases with CSM and twenty healthy volunteers matched with age were undergone conventional MRI scan and spinal cord of DTI by using SE-EPI. The average apparent diffusion coefficient(ADC_av) and fraction anisotropy(FA) values were measured respectively at the compression site of CSM and the normal spinal away from the compression site of CSM and the corresponding site of healthy volunteers,then statistical analysis made. Sensitivity and specificity of both T₂-weighted imaging and diffusion tensor imaging(ADC maps and FA maps) to display pathological changes were calculated and compared.Results : FA values measured at the compression site of CSM were distinctly lower than control group (P<0.05), ADCav values were distinctly higher than control group (P<0.05). ADCav values and FA values of the normal spinal away from the compression site of CSM showed no significant difference compared with the control group (P>0.05).ADC maps and FA maps and T₂-weighted imaging of Sensitivity and specificity each was 57.1% (20/35),72.7% (8/11);77.1% (27/35),100% (11/11);31.4% (11/35),100% (11/11).Conclusions: The cervical spinal cord of DTI was a reliable tool in demonstrating the lesions of CSM,in which isotropy diffusion increased evidently and anisotropy diffusion decreased distinctly,could reflect the quantitive pathologic changes of CSM in the early stage,DTI improved the diagnostic sensitivity and provided a feasible examine technique with CSM who were uncertain of damnification grade, also provided credibility help to the early diagnoses.