Pierre-Louis Bazin¹, Christine Lucas Tardif¹, Arno Villringer¹, and Nicholas Bock^2
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ²McMaster University, Ontario, Canada

This work studies a newly proposed morphometric measurement in the cerebral cortex, the myelinated thickness and myelinated thickness ratio, in the context of high resolution 7 Tesla imaging. A new algorithm for myelinated thickness estimation is proposed, and the measures extracted from T1-weighted and quantitative T1 contrasts are compared at multiple resolutions.

Alessio Fracasso¹, Susanne J van Veluw², Fredy Visser^3,4, Jaco JM Zwanenburg⁴, Serge O Dumoulin¹, and Natalia Petridou^4
1Experimental Psychology, Helmholtz institute, Utrecht University, Utrecht, Netherlands, ²Neurology, Brain Center Rudolf Magnus, University Medical Center, Utrecht, Netherlands, ³Philips Medical Systems, Best, Netherlands, ⁴Radiology, Imaging Division, University Medical Center, Utrecht, Netherlands

Myelin content can be estimated in vivo to identify a large number of cortical areas, however extra-striate, within-area myelination at sub-mm scale is harder to visualize. Using a modified T1-w MPRAGE we visualize striate and extra-striate laminar intensity variations in in-vivo and ex-vivo data, comparing ex-vivo results with histological sections. In-vivo, ex-vivo and histology striate areas as well extra-striate cortex showed a reliable, high-contrast structure around the middle of cortical thickness in T1-w laminar profiles. This structure likely represents the two separated lines of Baillarger. This T1-w sequence provides the basis for studying laminar structure in humans, in vivo.

Christine Lucas Tardif¹, Nicholas A Bock², Arno Villringer¹, and Pierre-Louis Bazin^1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, ²McMaster University, Hamilton, Ontario, Canada

We present a novel intra-cortical boundary estimated from high-resolution T1 images where cortical layer structure is visible. The boundary between deeper myelinated cortical layers and more superficial ones can be used to derive two morphometric measures of local myeloarchitecture: myelinated cortical thickness and myelinated thickness ratio. We compare group averages of these two contrasts to T1 and total cortical thickness, and discuss their relevance to brain mapping and plasticity studies.

Eric R. Muir¹, Damon P. Cardenas¹, and Timothy Q. Duong^1
1Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States

High-altitude, where air pressure and thus oxygen content are reduced, could lead to a broad spectrum of disorders in the brain, such as white matter hyperintensity and brain swelling. Previous studies investigated high altitude sickness post exposure. Studies of the brain during hypobaric conditions could lead to a better understanding of its effects. In this work, we constructed an MRI-compatible hypobaric chamber for animal MRI scanner and performed B0 and relaxation time measurements during acute hypobaric exposure. B0 was slightly shifted under hypobaric pressure, and T2 and T2* were decreased under hypobaric air.

Anna Varentsova¹, Shengwei Zhang², Ekaterina Shanina¹, and Konstantinos Arfanakis^2,3
1Physics Department, Illinois Institute of Technology, Chicago, IL, United States, ²Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States, ³Rush Alzheimer's Disease Center, Rush University, Chicago, IL, United States

Digital human brain atlases consisting of MRI-based templates and semantic labels delineating different brain regions serve a critical role in neuroimaging, mainly facilitating spatial normalization and automated segmentation, for the purposes of voxel-wise, region-of-interest, and network analyses. As part of the IIT Human Brain Atlas project (www.nitrc.org/projects/iit2), we have recently developed, anatomical as well as state-of-the-art diffusion tensor and high angular resolution diffusion imaging (HARDI) templates, as well as probabilistic gray matter (GM) labels in ICBM-152 space. The purpose of this project was to construct the first probabilistic connectivity-based atlas of human brain white matter (WM) in ICBM-152 space.

Xavier Tomas-Fernandez¹, Benoit Scherrer¹, Catherine Wan¹, and Simon K. Warfield^1
1Boston Children's Hospital, Boston, MA, United States

In this work, we evaluated the ability of tractography based in diffusion compartment imaging to recover the complete length of the arcuate fasciculus and compare it with that achieved by difussion tensor based tractography.

Sonya Bells¹, C John Evans¹, and Derek K Jones^1
1School of Psychology, CUBRIC, Cardiff, Wales, United Kingdom

To be able to evaluate the differences in white matter across time plays an important role in brain research. We aim to estimate the sample size necessary to detect changes within white matter tracts in a repeated measures design. Three white matter sequences were acquired (diffusion weighted, multi-component relaxometry and non-Gaussian diffusion) to assess the variance within 18 different white matter tracts, which was then used in power calculations. Power calculations varied between the different white matter sequences and tracts. For example, detecting a 15% change within FA for the uncinate 18 subjects are needed while in cingulum-hippocampus it is 45.

Jan Scholz¹, Matthijs van Eede¹, Jason P Lerch^1,2, and Mark Henkelman^1,3
1Mouse Imaging Centre, Hospital for Sick Children, Toronto, ON, Canada, ²Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Medical Biophysics, University of Toronto, ON, Canada

Investigating variability of brain anatomy using three common mouse strains.

Jérémie Pierre Fouquet¹, Réjean Lebel¹, Luc Tremblay¹, and Martin Lepage^1
1CIMS, Université de Sherbrooke, Sherbrooke, QC, Canada

A method allowing in vivo magnetic resonance imaging of the mouse neurovasculature at high resolution (<100 µm) is presented. It uses the Resovist contrast agent and a dedicated head coil. Images and extracted vessel sizes obtained in vivo are compared against ex vivo results obtained at the same resolution. A study of the vessels size distributions in three main regions of the brain is presented and used as a basis for the comparison.

John Huston III¹, Shengzhen Tao¹, Joshua D. Trzasko¹, Paul T. Weavers¹, Yunhong Shu¹, Erin Gray¹, Seung-Kyun Lee², Jean-Baptiste Mathieu², Christopher J. Hardy², John Schenck², Ek Tsoon Tan², Thomas K.F. Foo², and Matt A. Bernstein^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²GE Global Research, Niskayuna, NY, United States

A second generation head-only gradient system with asymmetric transverse coils and all hollow-conductor coils was constructed and human volunteers imaged. Testing occurred inside a conventional whole-body 3T magnet to assess image quality and peripheral nerve stimulation (PNS). The gradient was integrated with a custom-built birdcage transmit/receive coil and a Nova 32-channel receiver array. Initial experience demonstrated high quality brain images with gradients performing at 80 mT/m and 500 T/m/s simultaneously while minimizing peripheral nerve stimulation. In addition, a novel integrated gradient nonlinearity correction strategy was found to improve in vivo images acquired on this system.