Joint Longitudinal Modeling of Brain Appearance in Multimodal MRI for the Characterization of Early Brain Developmental Processes - Longitudinal Registration and Shape Modeling - page 59

NLME. The usage of multivariate NLME for contrast modeling enables joint esti-
mation of appearance change parameters in T1W and T2W modalities, hence
accounting for correlations between multimodal scans. The timing parameters
extracted from this model and statistical inferences from the same quantify lag
in appearance of white-gray matter contrast observed in T2W scans compared
with T1W, confirming the utility of the method in early brain developmental
studies. Modeling of SIR enables the inclusion of information about the direc-
tion of white-gray intensity gradient. CONTDIR assigns a directional value to
contrast and captures contrast reversals by finding the relative direction of the
white-gray intensity gradients compared to the adult-like image. Future studies
would involve multimodal estimation of time of contrast reversal using neonate
scans, extending the current analysis to several other modalities, and exploring
applications of this work in detecting developmental abnormalities. The effect
that switching from univariate to multivariate modeling has on prediction of
abnormal trajectories of appearance change also holds interest.
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