MRI and DTI acquisition and analysis protocols were described previously (Pfefferbaum et al. 2007; Pfefferbaum et al. 2009). Imaging was performed on a 1.5 T GE clinical whole body system. A dual-echo fast spin-echo (FSE) coronal structural sequence was acquired (47 contiguous, 4-mm thick slices; TR/TE1/TE2 = 7,500/14/98 ms; \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\hbox{matrix}} = {256} \times {192} $$\end{document}). DTI was performed with the same slice location parameters as the dual-echo FSE, using a single shot spin-echo echo-planar imaging technique (47 contiguous, 4-mm thick slices, TR/TE = 10,000/103 ms, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\hbox{matrix}} = {128} \times {128} $$\end{document}, in-plane resolution = 1.875 mm2, b value = 860 s/mm2). Diffusion was measured along six non-collinear directions (six NEX) with alternating signs to minimize the need to account for cross-terms between imaging and diffusion gradients (Neeman et al. 1991). For each slice, six images with no diffusion weighting (b = 0 s/mm2) were also acquired.
