Abstract #4210

A Constrained Estimator of Myelin Water Fraction from Steady-State Data

John M. Ollinger¹, Samuel A. Hurley², Andrew L. Alexander³, Gerard Riedy¹

¹NICoE, Walter Reed National Military Medical Center, Bethesda, MD, United States; ²Medical Physics, University of Wisconsin-Madison, Madison, WI, United States; ³Medical Physics, University of Wisconsin, Madison, WI, United States

The parameters of the two-compartment mcDESPOT model for myelin water fraction are estimated with a non-linear least-squares algorithm constrained by a uniform prior. Combined with improved flip angle calibration, flip angle selection, and phase-cycling angles, the method yields estimates of myelin water fraction of visually high quality. However, estimates of myelin T1 and myelin residence time were strongly dependent on the choice of constraint and starting values. Quantitative values of myelin water fraction depended on these values as well as the parameterization of the model. This suggests that myelin water fraction images may represent a combination of physiological parameters.