YUXI PANG^1
1Department of Radiology, University of Michigan, Ann Arbor, MI, United States

An angle offset has been identified in proton magnetic resonance transverse relaxation orientation dependencies in the human brain WM in vivo when DTI primary diffusivity direction was used as an internal reference. This angle offset has not yet been accounted for in previous studies. The present work demonstrates that the observed angle offset can be removed using an angle derived from the perpendicular and parallel diffusivities of an axially symmetric diffusion tensor regardless of axon fiber orientations. The finding from this study clearly suggests that the diffusion tensor principal diffusivity direction deviates from an axon fiber orientation in WM.

Kellen Mulford¹, Sean Moen², Andrew W. Grande², David Darrow², Donald R. Nixdorf³, Pierre-Francois Van de Moortele¹, and Can Özütemiz^4
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Department of Neurosurgery, University of Minnesota, Minneapolis, MN, United States, ³Division of TMD & Orofacial Pain, University of Minnesota, Minneapolis, MN, United States, ⁴Department of Radiology, University of Minnesota, Minneapolis, MN, United States

Diffusion tensor imaging-based tractography of the peripheral nerves of the face is difficult owing to the complex tissue interfaces which degrade signal and introduce artifact. In this study, we used readout segmented EPI to attempt nerve fiber tracking of the inferior-alveolar, lingual, and infra-orbital branches of the trigeminal nerve. In 6 healthy participants we were able to visualize all three nerves on both sides of the face. This technique could be applies to nerve-injury and neuropathic pain populations to assess for alterations in nerve structure.

Sudhir Kumar Pathak¹, Yijen L Wu^2,3, Vijay Saradhi Gorantla⁴, Fatih Zor⁴, Yalcin Kulahci⁴, Alan Watson⁵, Yongxin Zhao⁶, and Walter Schneider^1,7
1Psychology, University of Pittsburgh, Pittsburgh, PA, United States, ²Rangos Research Center Animal Imaging Core, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA, United States, ³Developmental Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States, ⁴Regenerative Medicine, Wake Forest Institute for Regenerative Medicine, Winston-Salem, NC, United States, ⁵Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States, ⁶Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States, ⁷Neurosurgery, University of Pittsburgh, 15260, PA, United States

Accurate brain connectome mapping requires tracking fasciculus bundles of axons within tracts. In a porcine optic nerve harvested tissue, we optimized/tested MRI structural and diffusion imaging to demonstrate following fasciculi within the optic tract. On a 7T Bruker magnet, we can clearly identify fasciculus boarders and diffusion paths providing 29 micron precision MRI with clear tissue differentiation. We found that axons travel with no evidence of crossing fasciculi walls. This suggests Fasciculus Axonal Connective Tissue (FACT) imaging can provide full mapping of connectivity between cortical sources supporting comprehensive accurate mapping of connectivity in large mammal tract systems at viable cost.

Franziska Thiessen¹, Seyed-Ahmad Ahmadi², Virginia Flanagin², Joyce Bosmans³, Huseyin Ozenc Taskin⁴, Vincent Van Rompaey⁵, Geoffrey Karl Aguirre⁴, and Peter zu Eulenburg^6
1Institut for Neuroradiology, LMU Munich, Munich, Germany, ²Center for Vertigo and Balance Disorders, LMU Munich, Munich, Germany, ³Translational Neurosciences, University of Antwerp, Antwerpen, Belgium, ⁴Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States, ⁵Department of Otorhinolaryngology-Head & Neck Surgery, University of Antwerp, Antwerpen, Belgium, ⁶Institute for Neuroradiology, LMU Munich, Munich, Germany

We are on the road to further the role of high-resolution structural neuroimaging in the diagnostics of the most prevalent vestibular disorders. After creating an in-vivo template and atlas space for the inner ear, we have no investigated structural aging across all cochlear and vestibular anatomical regions in a representative cohort (n=87). We significant reduction along the aging process for cochlear width and length as well as some semicircular canal dimensions. Total intracranial volume was a highly relevant covariate in our analysis. Aging also seemed to affect most neuroimaging quality parameters as well and had to be controlled for.

Nilser J. Laines Medina ^1,2, Charley Gros^3,4, Julien Cohen-Adad^3,4, Arnaud Le Troter^1,2, and Virginie Callot^1,2,5
1CRMBM, Aix-Marseille Univ, CNRS, Marseille, France, ²CEMEREM, APHM, CHU Timone, Marseille, France, ³NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montreal, QC, Canada, ⁴MILA, Québec AI Institute, Montreal, QC, Canada, ⁵iLab-Spine, International Associated Laboratory, Marseille-Montreal, France

Automated methods for WM/GM segmentation in the spinal cord are now largely available. However, these techniques were mostly developed for conventional systems (≤3T) and do not necessarily perform well on 7T MRI data that feature finer details, contrasts, but also different artifacts or signal dropout.

The primary goal of this study was thus to propose a new deep-learning model allowing robust SC/GM multi-class segmentation based on high-resolution 7T T2*-w MR images. The second objective was to highlight the relevance of implementing a realistic hybrid data augmentation strategy to provide better model generalization.

Yajun Ma¹, Hyungseok Jang¹, Alecio F Lombardi ¹, Annie Hiniker ², Roland R Lee ¹, Eric Y Chang^1,3, Amy J Jak^3,4, Dawn Schiehser ^3,4, Alan N Simmons ^3,4, Brian P Head^3,5, Graeme M Bydder¹, and Jiang Du^1
1Radiology, University of California, San Diego, San Diego, CA, United States, ²Pathology, University of California, San Diego, San Diego, CA, United States, ³Veterans Affairs San Diego Healthcare System, San Diego, CA, United States, ⁴Psychiatry, University of California, San Diego, San Diego, CA, United States, ⁵Anesthesiology, University of California, San Diego, San Diego, CA, United States

Myelin water imaging (MWI) has been proposed as a myelin-specific technique to quantify water trapped within or tightly bound to myelin bilayers and thus provides an indirect assessment of myelin content and integrity. In this study, we developed and evaluated a novel 3D short TR adiabatic inversion recovery prepared short echo time (STAIR-STE) Cones sequence for robust MWI on a clinical 3T scanner. Our results show that the 3D STAIR-STE Cones sequence robustly suppresses long-T2 intra/extracellular water signals and provides selective volumetric imaging and quantification of myelin water fraction in the whole brain.

Laurel A Dieckhaus¹, Courtney J Comrie¹, Kelsey E McDermott², Daniel T Gray², Carol A Barnes^2,3,4, and Elizabeth B Hutchinson^1
1Biomedical Engineering, University of Arizona, Tucson, AZ, United States, ²Evelyn F. McKnight Brain Institute, University of Arizona, Tucson, AZ, United States, ³Psychology, Neurology and Neuroscience, University of Arizona, Tucson, AZ, United States, ⁴Psychology and Neurology, University of Arizona, Tucson, AZ, United States

White matter (WM) is commonly studied using the Diffusion Tensor Imaging (DTI) metric Fractional Anisotropy (FA), which has limitations especially in regions where more than one fiber population exists. We compared FA to diffusion techniques (Mean Apparent Propagator (MAP-MRI)) and relaxometry techniques (Myelin Water Fraction (MWF) and Bound Pool Fraction (BPF)) mapping in the normal bonnet macaque brain. The combination of histograms and correlation analysis revealed that MAP-MRI metric, Propagator Anisotropy (PA) and MWF may offer more information about WM than FA alone, while remaining relatively correlated with FA; while BPF did not have strong association with FA or MWF. 

Marta Lancione^1,2, Matteo Cencini^1,2, Elena Scaffei^1,3, Emilio Cipriano^1,4, Guido Buonincontri¹, Chiara Ticci¹, Rosa Pasquariello¹, Roberta Battini^1,5, Raffaello Canapicchi¹, Laura Biagi^1,2, Michela Tosetti^1,2, and Italian DEvelopmental Age Health Network (IDEA)^6
1IRCCS Stella Maris, Pisa, Italy, ²Imago7 Research Foundation, Pisa, Italy, ³Department of Neuroscience, Psychology, Drug Research and Child Health, Neurofarba, University of Florence, Florence, Italy, ⁴Department of Physics, University of Pisa, Pisa, Italy, ⁵Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy, ⁶Italian DEvelopmental Age Health Network (RETE IDEA Ministry of Health), Rome, Italy

New biomarkers for myelination could improve the understanding of neurodevelopmental diseases and their diagnosis and treatment. We quantified Myelin Water Fraction (MWF) using MRF in a cohort of children with leukoencephalopathies and age-matched controls and we compared it to DTI-based FA. We obtained normative curves of white matter development with both techniques. MWF discriminated between controls and patients with higher sensitivity than FA, it was more myelin-specific and independent of the degree of axonal packing. Thanks to short scan time and simultaneous acquisition of other quantitative maps, MRF-based MWF may represent a valuable tool to study developmental disorders.

Ana Han¹, Jordan A. Chad^1,2, Thijs Dhollander³, and J. Jean Chen^1,2
1Rotman Research Institute, Baycrest Health Sciences, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Developmental Imaging, Murdoch Children's Research Institute, Melbourne, Australia

White matter (WM) microstructural aging is often studied with diffusion MRI via voxelwise metrics such as fractional anisotropy (FA). Decreasing FA with advancing age is frequently interpreted as WM microstructural degeneration, but relying on FA for this purpose only makes sense if a voxel contains a single fiber tract. In this work we use fixel-based analysis (FBA) to investigate the association of fiber-specific measures with age among each individual "fixel" within a voxel. We find intra-voxel differences in age associations of crossing fixels, demonstrating that traditional voxel-based analyses are inappropriate for probing age-related fiber degeneration in scenarios of multi-fiber crossings.

Alexandros Popov¹, Ivy Uszynski¹, Bastien Herlin¹, Maelig Chauvel¹, Igor Maldonado², Christophe Destrieux², and Cyril Poupon^1
1BAOBAB, NeuroSpin, CEA, Université Paris-Saclay, CNRS, Gif-sur-Yvette, France, France, ²iBrain U1253, Université de Tours, CHU Bretonneau, INSERM, Tours, France

Mesoscopic diffusion datasets allow to study the superficial tracts of the human brain. We exploit the new Chenonceau Dataset, an ultra-high resolution diffusion-weighted dataset, to investigate the organization of short fibers ( between 10 and 60 mm ) in the whole brain.

To achieve this goal, we process the dense Chenonceau connectogram with a hierarchical clustering algorithm to obtain coherent fiber bundles, sorted over a centimetric range. It leads to the first density mapping of short fibers across the whole human brain. This mapping displays important inter-hemispheric variations, supporting the functional lateralization of various functional networks.