Portal de Periódicos da CAPES

T2* mapping and B0 orientation-dependence at 7T reveal cyto- and myeloarchitecture organization of the human cortex

2012; Elsevier BV; Volume: 60; Issue: 2 Linguagem: Inglês

10.1016/j.neuroimage.2012.01.053

1095-9572

Julien Cohen‐Adad, Jon̈athan R. Polimeni, Karl G. Helmer, Thomas Benner, Jennifer A. McNab, Lawrence L. Wald, Bruce R. Rosen, Caterina Mainero,

Functional Brain Connectivity Studies

Ultra-high field MRI (≥ 7 T) has recently shown great sensitivity to depict patterns of tissue microarchitecture. Moreover, recent studies have demonstrated a dependency between T2* and orientation of white matter fibers with respect to the main magnetic field B0. In this study we probed the potential of T2* mapping at 7 T to provide new markers of cortical architecture. We acquired multi-echo measurements at 7 T and mapped T2* over the entire cortex of eight healthy individuals using surface-based analysis. B0 dependence was tested by computing the angle θz between the normal of the surface and the direction of B0, then fitting T2*(θz) using model from the literature. Average T2* in the cortex was 32.20 +/− 1.35 ms. Patterns of lower T2* were detected in the sensorimotor, visual and auditory cortices, likely reflecting higher myelin content. Significantly lower T2* was detected in the left hemisphere of the auditory region (p < 0.005), suggesting higher myelin content, in accordance with previous investigations. B0 orientation dependence was detected in some areas of the cortex, the strongest being in the primary motor cortex (∆R2* = 4.10 Hz). This study demonstrates that quantitative T2* measures at 7 T MRI can reveal patterns of cytoarchitectural organization of the human cortex in vivo and that B0 orientation dependence can probe the coherency and orientation of gray matter fibers in the cortex, shedding light into the potential use of this type of contrast to characterize cyto-/myeloarchitecture and to understand the pathophysiology of diseases associated with changes in iron and/or myelin concentration.