2 mm thickness, matrix: 128 × 128; FOV: 256 × 256 mm2. Diffusion gradients were encoded in 12 directions with a b values of 1000 s/mm2 and an additional image with no diffusion gradient (b = 0 s/mm2). Three sets of DTI data were acquired for average and the total DTI acquisition time was 5 min 47 sec. To improve the signal-to-noise ratio (SNR) for the Inhibitors,research,lifescience,medical DTI images, the three separate sets of images were averaged automatically by the “Neuro3D task card” (Siemens Syngo). We determined the SNR according to Kasprian et al. (2008). The SNR is defined as the mean

value of the signal of a circumscribed WM region of the fetal brain on diffusion unweighted (b = 0 s/mm2) images divided by the standard deviation determined Inhibitors,research,lifescience,medical in the same region. A b value of 1000 s/mm2 was used in fetal DTI as Huang et al. (2009). This value was adapted to high ADC values expected at the fetal WM in order to the formula 1.1 per ADC that have been thought to provide the best contrast-to-noise ratio (Dudink et al. 2008). Data postprocessing Diffusion tensor parameters DTI calculation and postprocessing were performed after transferring diffusion-weighted images to a Siemens off-line workstation, using the “DTI task

Card” Inhibitors,research,lifescience,medical software, and the four classical parameters were computed: the longitudinal diffusivity (λ// or λ1), the radial diffusivity λ = (λ2+λ3)/2, the ADC, and the FA. Definition of seed Inhibitors,research,lifescience,medical regions and tractography Seed regions for DTI tractography were determined based on anatomical landmarks observed on the ADC and FA color-coded directionality maps (Figs. 2 and ​and3).3). Using the “Neuro3D task card” (Siemens Syngo), each axes of the MPR (multi-planar reconstruction) was rotated (double oblique) to get axial, coronal, and sagittal planes in the anatomical referential for each fetus. ADC maps provided a good contrast, and the overlay of color-coded FA helped to depict coherent Inhibitors,research,lifescience,medical fiber

pathways nearby the ROIs by indicating fiber direction and degree of anisotropy. However, because the fetus head in utero is randomly positioned relative to the scanner referential, the color code used in this study did not correspond to the regular color code obtained in see more adults with standard positioning (red: right–left, green: antero–posterior, blue: supero–inferior) (Pajevic and Pierpaoli 1999). The “Neuro3D DTI task card” did not allow to apply tensor however rotation to keep this conventional color code. Figure 2 Diffusion tensor tractography method used to depict cortico-spinal tract (CST), optic radiations (OR), and CC bundles. Regions-of-interest (ROIs) were delineated based on anatomical landmarks observed on ADC and FA color-coded directionality maps. (A) … Figure 3 Example of DTI tractography of CST and OR obtained in utero and in vivo for fetal brain.