An Age-Specific Atlas for Delineation of White Matter Pathways in Children Aged 6-8 Years

Abstract Diffusion MRI allows non-invasive assessment of white matter maturation in typical development and of white matter damage due to brain injury or pathology. Probabilistic white matter atlases provide delineation of white matter tracts, allowing diffusion metrics to be measured in specific white matter pathways. However, given the known age-dependency of developmental change in white matter it may not be optimal to use an adult template when assessing data acquired from children. This study develops an age-specific probabilistic white matter atlas for delineation of 12 major white matter tracts in children aged 6-8 years. By comparing to subject-specific tract tracing in two validation cohorts, we demonstrate that this age-specific atlas gives better overall performance than simply registering to the Johns Hopkins University adult white matter template. Specifically, when normalising diffusion data acquired from children to an adult template, estimates of fractional anisotropy (FA) values for corticospinal tract, uncinate fasciculus, forceps minor, cingulate gyrus part of the cingulum and anterior thalamic radiation were all less accurate than those obtained when using an age-specific atlas, potentially leading to false negatives when performing group comparisons. We then applied the newly developed atlas to compare FA between children treated with therapeutic hypothermia for neonatal encephalopathy and age-matched controls, which revealed significant reductions in the fornix, the left superior longitudinal fasciculus, and both the hippocampal and cingulum parts of the left cingulate gyrus. To our knowledge, this is the first publicly available probabilistic atlas of white matter tracts for this age group.