Multimodal FLAIR/MPRAGE segmentation of cerebral cortex and cortical myelin.

The MR signal from gray matter has been long known to present small differences in intensity that have been attributed to variations in cortical myelin content. Previous studies have shown that the T1-, T2-weighted signal and their ratio are sensitive to these variations. Here, we investigated different combinations of signal from MPRAGE and FLAIR images in multimodal segmentation with parametric models of signal intensity to identify a procedure for the identification of contrast in cortical gray matter and the segmentation of different cortical components at 3T. We show that a three-modal combination of these signals delivers a stable segmentation of the cortical mantle in which two distinct components are reliably identified. The resulting intensity maps correspond well to known regional myeloarchitectural differences between cortical regions. These results confirm that widely available MR sequences contain signal that may be used to reliably detect subtle differences in the composition of gray matter with a segmentation approach.