Objective To observe the characteristics of magnetic resonance diffusion tensor imaging (MR-DTI)for optic nerves and optic radiation in blind patients. Methods The optic nerves and optic radiation of 20 blind patients (blind group) and 20 controls (control group) were scanned by MR-DTI.Fractional anisotropy (FA) and directional encoded color (DEC) maps were acquired through postprocessing with the aid of volume-one 1. 72 software. The signal intensity of optic nerves and optic radiation were then observed. The FA, mean diffusivity (MD), λ∥ and λ⊥ value of bilateral optic nerves and optic radiation in two groups were measured in the DEC maps. Results While the high signal intensity was found in bilateral optic nerves in FA and DEC maps in control group, the signal decreased markedly in the blind group. The FA and λ∥ value of optic nerves in the blind group were declined obviously compared to that in the control group. The difference was statistically significant (t= 16. 294, 14. 660;P=0. 000). The MD and λ⊥ value of optic nerves in the blind group were increased obviously compared to that in the control group, the difference was also statistically significant (t=8. 096, 8. 538;P = 0. 000). The high signal intensity was found in bilateral optic radiation in FA and DEC maps in both the blind and control groups. There were no statistic differences in FA and MD value in bilateral optic radiation between the blind and control groups (Left:t=1.456,1.811;P = 0. 152,0.076. Right:t = 0. 779,0. 073;P = 0. 440,0. 942). Conclusion A low signal intensity of bilateral optic nerves and a high signal intensity of bilateral optic radiation were found in blind patients.

Objective To evaluate the possibility of diffusion tensor imaging(DTI)in detecting and quantifying the Wallerian degeneration of optic radiation in occipital lobe chronic infarction.Methods 20 patients with unilateral occipital chronic infarction were undergone DTI.Quantitative fractional anisotropy(FA)and mean diffusivity(MD)were obtained from the ipsilateral optic radiation of the occipital lobe infarction and compared with that of contralateral region using the independent samples t-test.Results On the three dimensional color-coding tensor fractional anisotropic map,the regions of occipital lobe chronic infarction were markedly low signal intensity,the FA value and MD value were 0.274?0.062 and(1.226?0.372)?10-3mm2/s,while in the contralateral region of optic radiation,FA and MD values were 0.495?0.035 and(0.775?0.070)?10-3mm2/s respectively,there was significant difference in FA and MD values in comparing both side(P〈0.01).Conclusion DTI can detect and quantify the Wallerian degeneration in optic radiation after occipital lobe chronic infarction.

Objective To study the MR diffusion tensor imaging(MR-DTI) feature of optic atrophy.Methods Diffusion tensor imaging data of optic nerve were acquired in twenty patients with optic atrophy and 20 healthy subjects.Results ①Atrophic optic nerves were thin obviously on MRI,and the signal of atrophic optic nerves decreased markedly on fractional anisotropy(FA) map and directionally encoded color(DEC) map.②The FA value(0.277?0.078) and ?∥ value(1.808?0.307) of atrophic optic nerves were declined obviously,and mean diffusivity(MD) value(1.442?0.264) and ?⊥ value(1.231?0.225) increased obviously in comparison to the normal optic nerves,there were statistically significant differences between the patients and the volunteers(P