title: Age-related variations in white matter anisotropy in school-age children.
abstract: BACKGROUND
  Determination of diffusion tensor metrics in typically developing school-age children shows that maturational increases in fractional anisotropy (FA) vary across the brain and that age effects on FA are to increases in axial diffusivity in some regions, to decreases in radial diffusivity in some, and to both increases in axial and decreases in radial diffusivity in others.
  
  
  OBJECTIVE
  When studying developing white matter (WM) using diffusion tensor imaging (DTI), knowledge of age-related normative tensor metrics is important, as normal variations can mask or mimic disease effects.
  
  
  METHODS
  Right-handed English-speaking children (n = 32) 6-18 years old (mean 11.0) were studied over 31 months, 7 longitudinally. Anisotropy data were analyzed using tract-based spatial statistics; 43 regions showing significant (P < 0.05) age effects on fractional anisotropy (FA) were analyzed for age effects (r), coefficient of variability (CV), and FA, axial and radial diffusivity. This study was IRB-approved.
  
  
  RESULTS
  The callosal genu and splenium showed the highest FA values, smallest age effects, and lowest between-subject variability. Mean FA was lower and age effects were greatest in the dorsal callosal body. The highest age effects on FA were in the cingulum, centrum semiovale, right corticospinal tract, and right temporal WM. The dorsal callosal body, calcarine WM, superior frontal and temporal gyri, and right corticospinal tract showed the highest CV. Radial diffusivity decreased while axial diffusivity increased in the cingulum, decreased in the optic tracts, and showed minimal or no age effects in most other regions.
  
  
  CONCLUSIONS
  Age effects on FA and variability in FA are location-dependant in developing WM.
authors.affiliation: Department of Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA. nancy.rollins@childrens.com
authors.forename: Nancy K
authors.initials: NK
authors.lastname: Rollins
authors.forename: Paul
authors.initials: P
authors.lastname: Glasier
authors.forename: Youngseob
authors.initials: Y
authors.lastname: Seo
authors.forename: Michael C
authors.initials: MC
authors.lastname: Morriss
authors.forename: Jonathan
authors.initials: J
authors.lastname: Chia
authors.forename: Zhiyue
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000375:Aging / Q000473:pathology*; D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology*; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013334:Students