Rafael O'Halloran¹, Rebecca Feldman¹, Madeline Fields¹, Laura Marcuse¹, and Priti Balchandani^1
1Icahn School of Medicine at Mount Sinai, New York, NY, United States

A method for the quantification of cortical-to-cortical U-fiber fraction based on 7T MRI is presented and used to demonstrate group differences in the the U-fiber fractions in non-lesional and lesional epilepsy patients compared to healthy controls. Non-lesional epilepsy patients had the lowest u-fiber fractions followed by healthy control subjects, and then by lesional epilepsy subjects with the highest u-fiber fractions.

Chun-Hung Yeh¹, Robert Elton Smith¹, Thijs Dhollander¹, Fernando Calamante¹, and Alan Connelly^1
1The Florey Institute of Neuroscience and Mental Health, Melbourne, Australia

This study highlights the issue of using the common strategy for assigning individual streamlines to an atlas-based brain parcellation. This process is non-trivial and can introduce ambiguity into connectome quantification. In many fibre-tracking algorithms, track termination criteria can cause premature termination of streamlines within WM or CSF, which can result in up to ~50–80% of streamlines failing in identifying pairwise connections between nodes from streamline endpoints. Our results demonstrate that such issue can be largely ameliorated through the combination of biologically meaningful track terminations and an appropriate node assignment mechanism. This could therefore be advantageous to structural connectome construction.

Kayako Matsuo¹, Yung-Chin Hsu², Yasuo Takehara³, Wen-Yih Isaac Tseng², and Norio Mori^1
1Dept. Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan, ²Institute of Medical Devices and Imaging System, National Taiwan University College of Medicine, Taipei, Taiwan, ³Dept. Radiology, Hamamatsu University School of Medicine, Hamamatsu, Japan

DSI on a GE 3T was conducted for 22 normal controls to examine the neural basis of the response time (RT). RT was measured outside the scanner using button pressing by left or right hand in response to visual or auditory stimulation. Faster RT was associated with greater GFA of portions near the cortical hand area in the corticospinal tract (CST). Left and right hand specializations were found in the deeper CST. Greater GFA in portions near the cortex in the left auditory radiation was associated with faster RT by visual stimulations, suggesting an influence of language processing speed.

Daniel C. Alexander¹, Aurobrata Ghosh¹, Samuel A. Hurley², and Stamatios N. Sotiropoulos^2
1Computer Science, UCL, London, United Kingdom, ²FMRIB, Oxford University, Oxford, United Kingdom

We show benefits of image quality transfer to tractography. Diffusion MRI super-resolution through image quality transfer enables recovery of thin tracts in a dataset with low spatial resolution (2.5mm isotropic). Specifically, we reconstruct four pathways arising from the motor area that have been distinguished before when using high (1.25mm) resolution HCP data. Quantitative results confirm that image quality transfer enhances tractography more than standard interpolation. The results highlight the major potential of image quality transfer in learning information from bespoke high quality data sets to enhance the specificity of information derived from more modest but readily available data.

Eleftherios Garyfallidis¹, Marc-Alexandre Côté¹, François Rheault¹, and Maxime Descoteaux^1
1Computer Science, Université de Sherbrooke, Sherbrooke, QC, Canada

QuickBundlesX shows a remarkable 20+X speedup over it’s predecessor who was until today the fastest clustering algorithm for streamlines. In addition, it returns a useful tree of clusters at different resolutions which allows to query streamlines and easily process millions of streamlines by comparing only with their neighbours.

Greg D Parker¹, George J.A. Evans², and Derek K Jones^1,3
1CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom, ²School of Medicine, Newcastle University, Newcastle, United Kingdom, ³Neuroscience and Mental Health Research Institute (NMHRI), School of Medicine, Cardiff University, Cardiff, United Kingdom

Even amongst healthy subjects, brain function and structure is known to be highly variable across individuals^1,2. Recently³ it was shown that inter-subject variation in functional connectivity is sufficient to allow robust and reliable identification of individuals across different sessions and tasks. Here we demonstrate for the first time that the same is true of white matter structure; using the shape of an individual's white matter tracts we generate fingerprints that uniquely identify individuals across different scan sessions.

Michiel Cottaar¹, Matteo Bastiani¹, Charles Chen², Krikor Dikranian², David C. Van Essen², Timothy E. Behrens¹, Stamatios N. Sotiropoulos¹, and Saad Jbabdi^1
1FMRIB, Oxford University, Oxford, United Kingdom, ²Washington University School of Medicine, Saint Louis, MO, United States

Close to the cortical white/gray matter boundary surface fiber orientations sharply transition from being nearly tangential to the surface in the white matter to mostly radial in the gray matter. We propose a geometric model that describes this transition at sub-voxel resolution based on high-resolution histology data and fit this model to lower resolution diffusion MRI data. We assess its performance using qualitative comparisons with histology and test the reproducibility of the estimated parameters across multiple diffusion MRI resolutions. This model allows the in-vivo estimation of fiber orientations across the white/gray matter boundary, which may improve tracking to the cortex.

Ulysse Gimenez¹, Franck Mauconduit¹, Benoit Boulan², Eric Denarier², Jacques Brocard², Sylvie Gory-Fauré², Annie Andrieux², Jean Christophe Deloulme², and Hana Lahrech^1
1Clinatec Lab U1205, INSERM, Grenoble, France, ²Grenoble Institute of Neurosciences, INSERM, La Tronche, France

High spatial resolution 3D DTI was developed and used for white matter tractography to quantify neuronal tract alterations on the MAP6-KO mouse. In this model, the microtubule-associated protein 6 (MAP6) which is involved in the neuromorphogenesis is deleted leading to a model characterized by severe behavior impairments, similar to the clinical features of schizophrenia. As 3D DTI tractography and fluorescent microscopy on cleared brains both show a deficiency of the post-commissural fornix, in accordance with our previous 2D DTI results, the 3D DTI tractography imaging is validated. Using 3D DTI tractography, new major alterations in different neuronal tracts are detected. 

Fulvia Palesi^1,2, Andrea De Rinaldis^2,3, Letizia Casiraghi^2,4, Gloria Castellazzi^2,3, Paolo Vitali⁵, Nicoletta Anzalone⁶, Federica Denaro⁷, Elena Sinforiani⁸, Giuseppe Micieli⁷, Egidio D'Angelo^2,4, and Claudia Angela Michela Gandini Wheeler-Kingshott^2,9
1Department of Physics, University of Pavia, Pavia, Italy, ²Brain Connectivity Center, C. Mondino National Neurological Institute, Pavia, Italy, ³Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Pavia, Italy, ⁴Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy, ⁵Brain MRI 3T Mondino Research Center, C. Mondino National Neurological Institute, Pavia, Italy,⁶Scientific Institute H. S. Raffaele, Milan, Italy, ⁷Department of Emergency Neurology, C. Mondino National Neurological Institute, Pavia, Italy, ⁸Alzheimer's Disease Assessment Unit, Laboratory of Neuropsychology, C. Mondino National Neurological Institute, Pavia, Italy, ⁹NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, University College London, London, United Kingdom

Dementia is the most common disorder in elderly people and comprises Alzheimer’s disease (AD) and vascular disease (VaD). In this work graph theoretical approach was applied to a cohort of AD, VaD and healthy controls (HC) aimed at investigating the presence of a disease-specific pattern of alterations. Brain structural networks were built using the Cohen functional atlas (nodes) and advanced probabilistic tractography (edges). Our main finding was that VaD patients showed severe impairment in the large-scale brain networks while AD patients mainly showed inefficiency of short-range connections emphasizing the fact that alterations are restricted to specific brain regions.

Luis Manuel Colon-Perez¹, Michelle Couret², William Triplett³, Catherine Price³, and Thomas H Mareci^3
1Psychiatry, University of Florida, Gainesville, FL, United States, ²Medicine, Columbia University, New York, NY, United States, ³University of Florida, Gainesville, FL, United States

Brain networks are organized in a heterogeneous range of white-matter tract sizes suggesting that the brain is organized in broad range of white matter connection strengths. Studies of brain structure with a binary connection model have shown a small-world network topological organization of the brain. We developed a generalized framework to estimate the topological properties of brain networks using weighted connections, which offers a more realistic model of the brain compared to the binary connection model. In addition, this model reduces the need for thresholding to obtain topological properties in dense and weighted connectomes.