Microstructural development of human brain assessed in utero by diffusion tensor imaging

Background: Diffusion-weighted MR imaging (DWI) has been shown to be a great tool to assess white matter development in normal infants. Comparison of cerebral diffusion properties between preterm infants and fetuses of corresponding ages should assist in determining the impact of premature ex utero life on brain maturation. Objective: To assess in utero maturation-dependent microstructural changes of fetal cerebral white matter using diffusion tensor MR imaging. Materials and methods: An echoplanar sequence with diffusion gradient (b=700 s/mm2) applied in six non-colinear directions was performed between 31 and 37(+3) weeks of gestation in 24 fetuses without cerebral abnormality on T1- and T2-weighted images. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured in the white matter. Results: Mean ADC values were 1.8 mu m(2)/ms in the centrum semiovale, 1.2 mu m(2)/ms in the splenium of the corpus callosum and 1.1 mu m(2)/ms in the pyramidal tract. The paired Wilcoxon rank test showed significant differences in ADC between these three white matter regions. Mean FA values were 1.1%, 3.8% and 4.7%, respectively, in the centrum semiovale, corpus callosum and pyramidal tract. A significant age-related decrease in ADC and an increase in FA towards term were demonstrated in the pyramidal tract and corpus callosum. Conclusion: Diffusion tensor imaging in utero can provide a quantitative assessment of the microstructural development of fetal white matter. Anisotropic parameters of the diffusion tensor should improve with technical advances.