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Mapping an index of the myelin g-ratio in infants using magnetic resonance imaging

Research output: Contribution to journalArticlepeer-review

Douglas C. Dean III, Jonathan O'Muircheartaigh, Holly Dirks, Brittany G. Travers, Nagesh Adluru, Andrew L. Alexander, Sean Deoni

Original languageEnglish
Pages (from-to)225-237
Issue number0
Early online date22 Feb 2016
Accepted/In press12 Feb 2015
E-pub ahead of print22 Feb 2016
Published15 May 2016


King's Authors


Optimal myelination of neuronal axons is essential for effective brain and cognitive function. The ratio of the axon diameter to the outer fiber diameter, known as the g-ratio, is a reliable measure to assess axonal myelination and is an important index reflecting the efficiency and maximal conduction velocity of white matter pathways. Although advanced neuroimaging techniques including multicomponent relaxometry (MCR) and diffusion tensor imaging afford insight into the microstructural characteristics of brain tissue, by themselves they do not allow direct analysis of the myelin g-ratio. Here, we show that by combining myelin content information (obtained with mcDESPOT MCR) with neurite density information (obtained through NODDI diffusion imaging) an index of the myelin g-ratio may be estimated. Using this framework, we present the first quantitative study of myelin g-ratio index changes across childhood, examining 18 typically-developing children 3 months to 7.5 years of age. We report a spatio-temporal pattern of maturation that is consistent with histological and developmental MRI studies, as well as theoretical studies of the myelin g-ratio. This work represents the first ever in vivo visualization of the evolution of white matter g-ratio indices throughout early childhood.

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