Diffusion tensor imaging for understanding brain development in early life

Abstract

The human brain rapidly develops during the final weeks of gestation and in the first two years following birth. Diffusion tensor imaging (DTI) is a unique in vivo imaging technique that allows three-dimensional visualization of the white matter anatomy in the brain. It has been considered to be a valuable tool for studying brain development in early life. In this review, we first introduce the DTI technique. We then review DTI findings on white matter development at the fetal stage and in infancy as well as DTI applications for understanding neurocognitive development and brain abnormalities in preterm infants. Finally, we discuss limitations of DTI and potential valuable imaging techniques for studying white matter myelination.

Keywords: brain development; diffusion tensor imaging; infancy; magnetic resonance imaging; myelination; white matter.

Figure 1

The hypothesized relationship between maturational processes and diffusion indices in white matter. Abbreviations: FA, fractional anisotropy; >D<, mean diffusivity; λ_//, axial diffusivity; λ_⊥, radial diffusivity. Adapted with permission from Dubois et al. (2008).

Figure 2

Panels a and b, respectively, show axial images of 19-gestational-week fetal (left), 0-year (center), and 5-year (right) brains at the levels of the brain stem and midbrain. Panels c and d, respectively, show axial images of 20-gestational-week fetal (left), 0-year (center), and 5-year (right) brains at the levels of the corpus callosum and the superior corona radiata. Abbreviations: ac, anterior commissure; acr, anterior corona radiate; alic, anterior limb of internal capsule; cc, corpus callosum; cg, cingulum; cr, corona radiata; cst, cortical spinal tract; dscp, decussation of superior cerebellar peduncle; ec, external capsule; Fmajor, forceps major; Fminor, forceps minor; fx, fornix; gcc, genu of corpus callosum; GE, ganglionic eminence; icp, inferior cerebellar peduncle; ifo, inferior fronto-occipital peduncle; ilf, inferior longitudinal fasciculus; mcp, middle cerebellar peduncle; ml, medial lemniscus; oc, optical chiasm; on, optical nerve; or, optical radiation; ot, optical tract; plic, posterior limb of internal capsule; scc, splenium of corpus callosum; scp, superior cerebellar peduncle; scr, superior region of corona radiata; sfo, superior fronto-occipital fasciculus; ss, sagittal stratum; st, stria terminalis; unc, uncinate fasciculus. Adapted with permission from Huang et al. (2006).

Figure 3

Axial images of children at age of 0, 3, 6, 9, 12, 24, 36, and 48 months. Rows show (top to bottom) color maps, fractional anisotropy, mean diffusivity, and T₂-weighted images. Figure adapted with permission from Hermoye et al. (2006).

Figure 4

The major processes involved in structural network analysis using diffusion tensor imaging (DTI). (a) Diffusion-weighted (DW) images of each subject are aligned to those of the brain atlas. (b) The parcellation of cortical and subcortical regions using the brain atlas. (c) The whole-brain tractography using DTI deterministic tractography. (d ) Nodes (red spheres) representing cortical and subcortical regions. (e) Weighted edges (black lines) obtained using the tract information. Figure adapted with permission from Ratnarajah et al. (2013).

Figure 5

The mean myelin water fraction (MWF), T₁, and T₂ maps from seven age groups are respectively shown from the top to bottom rows. Note that T₂ was only calculated in voxels with a corresponding T₁ less than 3,500 ms for ages 9 months and above. Figure adapted with permission from Deoni et al. (2012).

Figure 6

Scatter plots of the mean myelin water fraction (MWF) at ages 0 days to 2,400 days. Figure adapted with permission from Deoni et al. (2012).