Intra and inter-site reproducibility of myelin water volume fraction values derived using McDESPOT.

INTRODUCTION: Investigation of neuronal tissue microstructure, integrity and biochemical composition has wide neuroscience application. Multicomponent relaxometry, which aims to decompose the measured MR signal into contributions from discrete micro-anatomical water components, provides specific information related to tissue micro-structure and has demonstrated utility in white matter disorders, such as multiple sclerosis, and psychiatric disorders, such as schizophrenia. Recently introduced, mcDESPOT (multi-component Driven Equilibrium Single Pulse Observation of T1 and T2) , offers a promising alternative to conventional T2-based multi-component relaxometry techniques. To be of broad applicability, however, the method should provide consistent estimates or have high intra-site reproducibility, of relaxation time and volume fraction parameters. Further, values should agree across imaging centres (high inter-site reproducibility) in order to permit meaningful comparisons across data from different groups, and to allow application of the technique to increasingly common multi-centre investigations. The aim of this work, therefore, was to establish the intraand inter-site reproducibility of mcDESPOT-derived myelin water volume fraction (fMW) estimates.