NODDI-PLOS-ONE-Chang et al 2015

Diffusion tensor imaging (DTI) studies of human brain development have
consistently shown widespread, but nonlinearly increasing white matter
anisotropy through childhood, adolescence, and into adulthood. However,
despite its sensitivity to changes in tissue microstructure, DTI lacks the
specificity to disentangle distinct microstructural features of white and
gray matter. Neurite orientation dispersion and density imaging (NODDI) is
a recently proposed multi-compartment biophysical model of brain
microstructure that can estimate non-collinear properties of white matter,
such as neurite orientation dispersion (OD) and neurite density (ND). In
this study, we apply NODDI to 67 healthy controls aged 7-63 years to
investigate changes of OD and ND with brain maturation, with comparison to
standard DTI metrics. Using both region-of-interest and voxel-wise
analyses, we find that ND exhibits striking increases over the studied age
range following a logarithmic growth pattern, while OD rises following an
exponential growth pattern. This novel finding is consistent with
well-established age-related changes of FA over the lifespan that show
growth during childhood and adolescence, plateau during early adulthood,
and accelerating decay after the fourth decade of life. Our results
suggest that the rise of FA during the first two decades of life is
dominated by increasing ND, while the fall in FA after the fourth decade
is driven by the exponential rise of OD that overcomes the slower
increases of ND. Using partial least squares regression, we further
demonstrate that NODDI better predicts chronological age than DTI.
Finally, we show excellent test-retest reliability of NODDI metrics, with
coefficients of variation below 5% in all measured regions of interest.
Our results support the conclusion that NODDI reveals biologically
specific characteristics of brain development that are more closely linked
to the microstructural features of white matter than are the empirical
metrics provided by DTI.