How does magnetization transfer influence mcDESPOT results?

PurposeA steady-state approach that was termed multicomponent driven equilibrium single pulse observation of T-1 and T-2 (mcDESPOT) has recently been proposed for myelin water fraction (f(M)) mapping in brain development and demyelinating diseases. However, f(M)s estimated by mcDESPOT are significantly higher than myelin water fraction derived from multiecho spin echo T-2-decay curve approaches. Magnetization transfer (MT), enhanced by the use of short, relatively high amplitude radiofrequency (RF) pulses in mcDESPOT, may artifactually influence f(M) maps. Our goal was to investigate the role of MT in mcDESPOT. MethodsmcDESPOT data was collected twice from three healthy volunteers using short RF pulses with higher MT effect and long RF pulses with lower MT effect. MR parameters from 11 white and gray regions were compared using a paired student t-test. Whole slice difference images were also compared. ResultsMT effects had a substantial influence on the signal generated by the balanced steady-state free procession sequences used in mcDESPOT. However, these MT effects were not clearly evident in the f(M) values determined by the conventional two-pool mcDESPOT analysis. ConclusionThe signal generated from mcDESPOT is sensitive to MT, but the extracted myelin water fractions are relatively insensitive to changes of MT. Magn Reson Med 74:1327-1335, 2015. (c) 2014 Wiley Periodicals, Inc.