Background: The purpose of this study was to investigate the anisotropic features of fetal pig cerebral white matter\n(WM) development by magnetic resonance diffusion tensor imaging, and to evaluate the developmental status of\ncerebral WM in different anatomical sites at different times.\nMethods: Fetal pigs were divided into three groups according to gestational age: E69 (n = 8), E85 (n = 11), and E114\n(n = 6). All pigs were subjected to conventional magnetic resonance imaging (MRI) and diffusion tensor imaging using\na GE Signa 3.0 T MRI system (GE Healthcare, Sunnyvale, CA, USA). Fractional anisotropy (FA) was measured in deep WM\nstructures and peripheral WM regions. After the MRI scans,the animals were sacrificed and pathology sections\nwere prepared for hematoxylin & eosin (HE) staining and luxol fast blue (LFB) staining. Data were statistically\nanalyzed with SPSS version 16.0 (SPSS, Chicago, IL, USA). A P-value < 0.05 was considered statistically significant. Mean FA\nvalues for each subject region of interest (ROI), and deep and peripheral WM at different gestational ages were calculated,\nrespectively, and were plotted against gestational age with linear correlation statistical analyses. The differences of data\nwere analyzed with univariate ANOVA analyses.\nResults: There were no significant differences in FAs between the right and left hemispheres. Differences were observed\nbetween peripheral WM and deep WM in fetal brains. A significant FA growth with increased gestational age was found\nwhen comparing E85 group and E114 group. There was no difference in the FA value of deep WM between the E69\ngroup and E85 group. The HE staining and LFB staining of fetal cerebral WM showed that the development from the E69\ngroup to the E85 group, and the E85 group to the E114 group corresponded with myelin gliosis and myelination,\nrespectively.\nConclusions: FA values can be used to quantify anisotropy of the different cerebral WM areas. FA values did not change\nsignificantly between 1/2 way and 3/4 of the way through gestation but was then increased dramatically at term, which\ncould be explained by myelin gliosis and myelination ,respectively.
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