盲人视神经的MRI和MR-DTI研究

MRI and MR Diffusion Tensor Imaging of Optic Nerve in Blindman

目的探讨盲人视神经的MRI和磁共振扩散张量成像(MR-DTI)特点。资料与方法对20例盲人进行视神经常规MRI和DTI扫描,并与20名正常健康者作对照。分别测量盲人和正常人双侧视神经的直径、各向异性(FA)值、平均扩散率(MD)值和水分子平行于纤维走行方向的扩散程度(λ∥)值、水分子垂直于纤维走行方向的扩散程度(λ⊥)值。统计分析采用独立样本t检验,检验水准α=0.05。结果(1)盲人视神经均明显变细、萎缩,在FA图和方向编码彩色(DEC)图上盲人视神经的信号强度较对照组明显降低;(2)盲人视神经的FA值(0.277±0.078)和λ∥值(1.808±0.307)较正常对照组明显降低,盲人视神经的MD值(1.442±0.264)和λ⊥值(1.231±0.225)较正常对照组明显升高,比较均有统计学意义(P均<0.001)。结论常规MRI仅能反映盲人视神经的形态学变化,而MR-DTI对视神经的信号变化非常敏感,并且可以定量反映盲人视神经萎缩后轴索和髓鞘的病理变化。

Objective To study the MRI and MR diffusion tensor imaging （MR-DTI） features of optic nerve atrophy. Materials and Methods Twenty blindman and 20 healthy subjects underwent MRI and MR-DTI scan. The diameter,fractional anisotropy value,mean diffusivity value,λ∥ value and λ⊥ value of optic nerves were measured in two groups. The data were analyzed by simple t test with the test level of 0.05. Results （1）Optic nerves of blindman showed thin and atrophic obviously on MRI,and markedly signal intensity decreased on FA map and DEC map.（2）The FA value（0.277±0.078） and λ∥ value（1.808±0.307） were declined obviously,MD value（1.442±0.264） and λ⊥ value（1.231±0.225） increased markedly compared to normal subjects. Statistically significant differences were found between healthy volunteers and blindman in The FA,λ∥,MD andλ⊥ value（P0.001）. Conclusion Conventional MRI demonstrate only the morphological changes of optic nerves of blindman,combined with DTI is sensitive to quantitatively analyze the pathological changes of axonal disruption and demyelination.