Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy

Diffusion Analysis

Thursday 15 May 2014
Space 2  10:30 - 12:30 Moderators: Flavio Dell'Acqua, Ph.D., Vesna Prchkovska, Ph.D.

10:30 0730.   Anisotropic Power Maps: A diffusion contrast to reveal low anisotropy tissues from HARDI data.
Flavio Dell'Acqua1,2, Luis Lacerda1, Marco Catani3, and Andrew Simmons1,2
1Dept of Neuroimaging, King's College London, Institute of Psychiatry, London, United Kingdom, 2NIHR Biomedical Research Centre for Mental Health and Biomedical Research Unit for Dementia, King's College London, Institute of Psychiatry, London, United Kingdom, 3Dept of Forensics and Neurodevelopmental Sciences, King's College London, Institute of Psychiatry, London, United Kingdom

All the anisotropy information in a HARDI signal is captured by the spherical harmonic coefficients of even order l ≥ 2. By measuring the total power of these coefficients it is possible to obtain an absolute measure of how much anisotropy information is available in each HARDI signal or a measure of the total anisotropic power (AP). This index can be use to better quantify and discriminate low anisotropy regions from CSF regions or noise. This measure is entirely model independent, robust to noise and can be easily applied on a large number of existing datasets.

10:42 0731.   
Fixel-Based Morphometry: Whole-Brain White Matter Morphometry in the Presence of Crossing Fibres
David Raffelt1, Robert E Smith1, Donald Tournier1,2, David Vaughan1,3, Graeme Jackson1,3, and Alan Connelly1,2
1Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia, 2Department of Medicine, University of Melbourne, Melbourne, VIC, Australia, 3Department of Neurology, Austin Health, Melbourne, VIC, Australia

When investigating morphometric white matter differences between populations, the direction of expansion or contraction relative to the underlying fibre tract is important. Expansion or contraction parallel to the fibre orientation implies a difference in axon length, while a change to the cross sectional area (CSA) in the perpendicular plane implies a difference in the number of axons and is therefore more relevant. We propose a method that uses Fibre Orientation Distributions to resolve multiple populations of fibres within each voxel (‘fixels’). We perform whole-brain statistical comparisons of the change in fixel CSA across groups in a method called fixel-based morphometry.

10:54 0732.   Normative Modeling of Early Brain Maturation from Longitudinal DTI Reveals Twin-Singleton Differences
Neda Sadeghi1, John H Gilmore2, Weili Lin3, and Guido Gerig1
1Scientific Computing and Imaging Institute, Salt Lake City, UT, United States, 2Department of Psychiatry, University of North Carolina, Chapel Hill, NC, United States, 3Department of Radiology, University of North Carolina, Chapel Hill, NC, United States

Early brain development is characterized by rapid organization and structuring of brain tissue. Magnetic Resonance diffusion tensor imaging (MR-DTI) can capture these changes non-invasively by following individuals longitudinally to better understand departures from normal brain development in neurological disorders or disease. We present analysis and modeling of neurodevelopmental growth trajectories from longitudinal infant DTI using recently developed image processing and statistical modeling tools. Comparing populations of healthy singleton and twin subjects, we find subtle group differences in axial diffusivity at birth, which disappear after 2-3 months. Color-coded 3D visualizations reveal large variability of these differences across white matter regions.

11:06 0733.   An optimized Tract-Based Spatial Statistics pipeline in longitudinally monitoring the dynamic of white matter reorganization in primate ischemic stroke model
Huaiqiang Sun1, Haoynag Xing1, Chunlin Wang1, Xianglong Li2, Jin Li2, and Qiyong Gong1
1Huaxi MR Research Center, West China Hospital of Sichuan University, Chengdu, Sichuan, China, 2Regenerative Medicine Research Center, West China Hospital of Sichuan University, Chengdu, Sichuan, China

An unbiased tensor-based image registration scheme was integrated into conventional Tract-Based Spatial Statistics to longitudinally monitor the dynamic of white matter reorganization in a primate permanent ischemic stroke model. Our findings suggest that white matter reorganization occurs in chronic phase of stroke and shows a dynamic pattern.

11:18 0734.   Direct native-space fiber bundle alignment for group comparisons
Eleftherios Garyfallidis1, Demian Wassermann2, and Maxime Descoteaux1
1University of Sherbrooke, Sherbrooke, Quebec, Canada, 2Harvard Medical School, MA, United States

We created a novel method that allows to investigate bundles for detailed group comparisons using streamline distances. This method opens the door to calculating group statistics beyond standard templates and average brains.

11:30 0735.   Reproducibility of the structural connectome and other open challenges
Paulo Rodrigues1, Alberto Prats-Galino2, David Gallardo-Pujol3, Pablo Villoslada4, Carles Falcon5, and Vesna Prčkovska4
1Mint Labs S.L., Barcelona, Spain, 2LSNA, Facultat de Medicina, University of Barcelona, Barcelona, Spain, 3Dept. of Personality, Faculty of Psychology, University of Barcelona, Barcelona, Spain, 4Center for Neuroimmunology, Department of Neurosciences, IDIBAPS, Hospital Clinic, Barcelona, Spain, 5GIB-UB, CIBER-BBN, Barcelona, Spain

Connectomics', studies have gained significant importance over the last years. Especially they are becoming popular in clinical studies where the connectivity matrices are used to classify among patients and healthy controls or predict the course of the diseases (neurodegenerative diseases). In functional connectomics, from RS-fMRI, the variability and reproducibility has been researched. In structural connectomics however, there are many different approaches for acquisition, modeling and choice for tractography algorithms and the variability of the structural connectome has not yet been properly investigated. These types of studies are very important pre-requisite for using these techniques when working with clinical data.

11:42 0736.   Consensus between pipelines in whole-brain structural connectivity networks
Christopher S Parker1,2, Fani Deligianni2, M. Jorge Cardoso1, Pankaj Daga1, Marc Modat1, Chris A Clark2, Sebastien Ourselin1,3, and Jonathan D Clayden2
1Centre for Medical Image Computing, UCL, London, United Kingdom, 2Imaging and Biophysics Unit, UCL, London, United Kingdom, 3Dementia Research Centre, UCL, London, United Kingdom

A variety of image processing pipelines have been used to reconstruct whole-brain structural connectivity networks from diffusion MRI data. The choice of reconstruction method can impact network topology measures. We assessed similarity in networks obtained using two alternative and independent state-of-the-art reconstruction pipelines in order to identify core connections emerging robustly in both. We found high convergence between group-averaged networks across a range of network densities and identified a ‘consensus network’, which had high convergence and anatomical plausibility. Future work will investigate convergence using finer node scale parcellations, allowing a more detailed analysis of the convergence structure.

11:54 0737.   Comprehensive Geometric Distortion Correction for Diffusion Tensor Imaging at Ultra-High Field
Myung-Ho In1, Oleg Posnansky1, and Oliver Speck1,2
1Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany, Magdeburg, Germany, 2Leibniz Institute for Neurobiology, Magdeburg, Germany, Magdeburg, Germany

A well-known problem in echo-planar imaging (EPI) is geometric distortion due to field inhomogeneities induced by susceptibility effects. In diffusion weighted EPI (DW-EPI), in addition, the distortions vary due to eddy-currents from diffusion gradients. To correct both susceptibility and eddy-current induced distortions, a comprehensive approach using the point spread function (PSF) mapping based methods is presented. An extended PSF method with a reversed gradient approach suggested recently was adapted for susceptibility-induced distortion correction, and a fast PSF-based eddy-current calibration method is newly suggested in this study. The combination of the methods thus allows distortion-free DW-EPIs without loss of spatial resolution.

12:06 0738.   
Cardiac Diffusion Tensor Imaging: Adaptive Anisotropic Gaussian Filtering to Reduce Acquisition Time
Ria Mazumder1,2, Bradley D. Clymer1, Richard D. White2,3, and Arunark Kolipaka2,3
1Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, United States, 2Department of Radiology, The Ohio State University, Columbus, OH, United States, 3Department of Internal Medicine-Division of Cardiology, The Ohio State University, Columbus, OH, United States

The counter-directional helical structure of the heart plays an important role in regulating cardiac mechanics and can be quantified on the basis of the angle it subtends known as helical angle (HA). Non-invasive measurement of HA is possible using diffusion tensor imaging, the accuracy of which is dependent on increased diffusion encoding directions (DED) and high signal to noise ratio (i.e. increase in averages). The purpose this study is to robustly estimate HA using fewer averages and DED (thereby, reducing the acquisition time) by implementing a 3D adaptive anisotropic Gaussian post-processing filter.

12:18 0739.   
High-resolution diffusion weighted MRI enabled by multiplexed sensitivity-encoding using projection on convex set (POCSMUSE)
Mei-Lan Chu1,2, Hing-Chiu Chang2, and Nan-Kuei Chen2,3
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, Taiwan, 2Brain Imaging and Analysis Center, Duke University, Durham, North Carolina, United States, 3Department of Radiology, Duke University, Durham, North Carolina, United States

Diffusion-weighted imaging (DWI) data acquired with interleaved EPI sequence are highly susceptible to inter-segment phase variations and aliasing artifacts induced by motion in the presence of strong diffusion weighting gradients. Here we report a novel and efficient approach to remove aliasing artifacts in interleaved EPI based high-resolution DWI data through developing a MUSE algorithm based on projection onto convex set (POCS) 2. The new technique, termed POCSMUSE, can provide high-quality image without navigator echo, and can be generally applied to DWI data acquired with arbitrary k-space trajectory.