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Some studies have used diffusion tensor imaging (DTI) to investigate white matter development of the visual pathway in humans and animals after visual deprivation. However, the alterations in the bilateral optic tract after the transection of unilateral optic nerve have not been well explored. In this study, we attempted to investigate the structural integrity of and pathological changes to the bilateral optic tract after transection of the unilateral optic nerve in rats using DTI. Eight healthy male Sprague-Dawley (SD) rats were randomly divided into 2 groups, with 4 in each group. Group A served as a control group. Transection of the unilateral (right) optic nerve was performed in the four rats in group B at seven days after birth to establish the early monocular blind model. Four months after the operation, MnCl 2 was injected into the left eyes of all rats, and MRI examinations were performed 24 h after injection. We detect the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values of the bilateral optic tract in all rats. In a comparison of the ipsilateral optic tract of group B with group A, a significant decrease in FA (P < 0.001) and an increase in RD (P < 0.01) of the left optic tract were found in group B, while no significant difference was found in the right optic tract. In group B, the FA and RD values of the left optic tract were significantly lower (P < 0.01) and significantly higher (P < 0.05), respectively, than those of the right optic tract. Consequently, transection of the right optic nerve can lead to structural integrity damage of and pathological changes to the left optic tract in rats. Some DTI-derived parameters (such as FA and RD) may serve as biomarkers of optic tract degeneration. [ABSTRACT FROM AUTHOR]

Aims We investigated the usefulness of diffusion tensor tractography ( DTT) for differentiating between histological pathologies and evaluating white matter ( WM) damage resulting from brain tumors. We also sought to categorize the appearance of brain tumor-related WM tract changes. Methods A total of 18 inpatients with intracranial neoplasms were enrolled. MRI examinations were performed at 3 T using an 8-channel phased array coil. DTT was reconstruction from the raw data of diffusion tensor imaging. WM tract-based analysis of the mean diffusivity ( MD), eigenvalues (λ1, λ2, λ3), and fractional anisotropy ( FA) was performed by the manual placement of regions of interest ( ROIs) on the color-coded FA maps using DTIStudio software. The axial diffusivity ( DA, namely λ1) and the tensor shape (Cl, namely (λ1 − λ2)/3 (λ)) were also compared between groups. P values <0.05 were considered statistically significant. Results In cases of low-grade glioma ( LGG), the tracts adjacent to the tumors displayed the highest levels of invasion. Tract disruption was mainly observed in cases of high-grade glioma ( HGG). We found significant differences regarding the FA, MD, DA, and radial diffusivity between ROIs in patients with LGG or HGG. There were also significant differences in DA and tensor shape ( Cl) between patients with LGG and HGG. Conclusion Axial diffusivity and Cl may be useful early markers for differentiating between LGG and HGG. [ABSTRACT FROM AUTHOR]