• Jing Zhang, Shannon H Kolind, Cornelia Laule, and Alex L MacKay.
• UBC MRI Research Centre, Department of Radiology, University of British Columbia, Vancouver, BC, Canada.
• Magn Reson Med. 2015 Jan 1; 73 (1): 223-32.

PurposeMyelin water fraction is conventionally measured from the T2 decay curve. Recently, a steady-state approach entitled multicomponent-driven equilibrium single pulse observation of T1 /T2 (mcDESPOT) was employed for myelin water fraction mapping. However, no direct comparison between the established multiecho T2 relaxation method and mcDESPOT has been performed.MethodsGradient and spin echo (GRASE) acquired T2 decay curve and mcDESPOT measurements were acquired from 10 healthy volunteers using a 3T MRI. We compared myelin water fraction, transmit radio frequency field (B1 ), and T2 's of intra- and extracellular water obtained from both methods.ResultsFor all brain regions examined, myelin water fractions from mcDESPOT were significantly higher than those from multiecho GRASE. B1 maps were qualitatively similar between GRASE and mcDESPOT, but multicomponent T2 times were significantly different. To investigate the effect of exchange, mcDESPOT data were analyzed with and without exchange. When exchange was turned off, intra- and extracellular T2 times from mcDESPOT were roughly consistent with GRASE results; however, myelin water fractions derived from mcDESPOT were still significantly higher than those derived from GRASE.ConclusionMyelin water fraction values derived from mcDESPOT cannot be considered to be equivalent to those derived from T2 decay curve approaches.© 2014 Wiley Periodicals, Inc.

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