The neuroradiology journal
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Radial diffusivity is a diffusion tensor imaging (DTI) metric that has received increased attention in recent studies as a parameter that may better reflect myelination than the more commonly-used fractional anisotropy (FA). This study compared rates of radial diffusivity decrease against FA increase and axial diffusivity decrease on DTI maps in the corpus callosum of normal infants during the first postnatal year. Fifty-three normal infants (range: 0-52 weeks adjusted for gestational age) underwent six-direction DTI on a 1.5 Tesla scanner (b= 1,000 s/mm(2), one excitation). ⋯ The high rate of radial diffusivity decrease compared to axial diffusivity decrease is consistent with myelination. Decreases in radial diffusivity were greater than increases in FA values. This finding is further support of the concept that radial diffusivity and FA values represent two different types of microstructural change during development of white matter.