Clinical Application of Diffusion Tensor Imaging
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Tuesday May 10th
Room 710B  16:00 - 18:00 Moderators: Marco Essig and Majda Thurnher

16:00 344.   Investigating the role of ICBM-space human brain diffusion tensor templates in inter-subject spatial normalization 
Shengwei Zhang1, and Konstantinos Arfanakis1
1Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States

The purpose of this study was to compare the role of the ICBM81 and IIT2 diffusion tensor (DT) templates in inter-subject spatial normalization of DT data with a) minimal and b) visible artifacts, using three different DT registration approaches. First, the registration techniques that result in more accurate DT spatial normalization when registering data with different levels of artifacts to the two templates were determined. It was then shown that, regardless of the artifact content of the DT data, the accuracy of inter-subject spatial normalization increases when using the IIT2 template as a reference instead of the ICBM81 template.

16:12 345.   Cerebral viscoelasticity in normal pressure hydrocephalus: Disorder and softening of the mechanical matrix of the brain and its reorganization after shunt treatment. 
Ingolf Sack1, Sebastian Hirsch1, Dieter Klatt2, Kaspar Josche Streitberger3, Florian Freimann4, Christian Sprung4, and Jürgen Braun5
1Department of Radiology, Charité University Medicine, Berlin, Germany, 2Charité University Medicine, 3Department of Radiology, Charité University Medicine, 4Department of Neurosurgery, Charité University Medicine, 5Institute of Medical Informatics, Charité University Medicine, Berlin, Germany

The alteration of the viscoelastic properties of brain is a key point in current theories of the pathogenesis of normal pressure hydrocephalus (NPH). MR elastography (MRE) is capable of measuring the mechanical connectivity and micromechanical order of brain tissue in vivo. This paper reports data of 19 NPH-patients studied prior and after shunt operation by cerebral multifrequency MRE and compared to 25 age-matched controls. Conclusion: NPH is associated with disorder and softening of brain tissue. Rehabilitation is seen in re-increasing micromechanical order whereas shear elasticity remains lower than in age-matched controls.

16:24 346.   A longitudinal study of microstructural white matter changes after mild traumatic brain injury 
Fan-pei Gloria Yang1, Charvi Shetty1, Hana Lee1, Sara Lahue1, Shelly Cooper1, Chirstopher Nguyen1, Mehul Sampat1, Jamshid Ghajar2, Geoffrey Manley3,4, Sandya Venugopal1, and Pratik Mukherjee1,4
1Radiology and Bioengineering, University of California San Francisco, San Francisco, CA, United States, 2Brain Trauma Foundation, New York, New York, United States,3Department of Neurological Surgery, University of California San Francisco, San Francisco, CA, United States, 4Brain and Spinal Injury Center, University of California San Francisco, United States

Diffusion tensor imaging (DTI) shows promise in mild TBI patients as a biomarker for neurocognitive outcome. However, using diffusion tensor imaging for prognosis remains controversial because recent studies of the early phase of mild traumatic brain injury have shown conflicting results. Furthermore, there is a lack of prior longitudinal DTI studies of mild head trauma. We used tract-based spatial statistics (TBSS), a whole-brain data-driven diffusion tensor analysis method, to examine microstructural white matter changes measured within 2 weeks, at 1 month, and at 1 year after mild head trauma with loss of consciousness and post-traumatic amnesia, with correlation to performance on tests of verbal memory and visuospatial attention. Thirty adult patients were compared with 29 controls matched for age, gender, and level of education. Following brain extraction, motion correction, and generation of DTI parametric maps using the tools provided in FSL, the voxel-wise statistical analysis of DTI parameter maps was conducted with TBSS.Multiple comparison correction was conducted with Threshold-Free Cluster Enhancement (TFCE) in Randomise. Widespread decreases of FA and increases of mean diffusivity and radial diffusivity were found in patients versus controls at the early time point. The loss of white matter FA was progressive over time, worsening both in magnitude and spatial extent across the three time points. The left and right anterior corona radiata showed the greatest early reduction in FA, with values in the right anterior corona radiata strongly correlating with verbal memory performance. We also demonstrate that early FA measurements in the right superior longitudinal fasciculus predict long-term outcome on visuospatial attention testing. Finally, those patients whose verbal memory did not improve during the first year after injury showed greater and more widespread decreases compared to controls in white matter FA, measured at the early time point, than did those patients whose verbal memory did improve over the three time points.

16:36 347.   Disrupted Anatomical Brain Connectivity in Retired Professional Football Players 
Feng Shi1,2, Pew-Thian Yap1,2, J. Keith Smith1, Kelly S. Giovanello2,3, Candice Goerger4,5, Weili Lin1,2, Kevin M. Guskiewicz4,5, and Dinggang Shen1,2
1Department of Radiology, University of North Carolina, Chapel Hill, NC, United States, 2Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, United States, 3Department of Psychology, University of North Carolina, Chapel Hill, NC, United States, 4Department of Exercise and Sport Science, Orthopedics, University of North Carolina, Chapel Hill, NC, United States, 5Center for the Study of Retired Athletes, University of North Carolina, Chapel Hill, NC, United States

Recurrent concussions in contact sports may cause delayed brain damages that affect retired athletes. In this study, we recruited 34 retired NFL players and 20 matched controls to investigate the brain circuitry changes in relation to their functional deficits. White matter fibers were tracked and connections between brain regions were taken as a graph of brain network. Results show that although the brain network of players has small-world topology, they have significantly lower network efficiency and longer path length. Meanwhile, fiber connections involved in the frontal regions are severely affected, which may be related with their impaired brain function.

16:48 348.   Propagation of Probabilistic Tractography of the Optic Radiation for Neuronavigation in Epilepsy Surgery 
Gavin P Winston1, Pankaj Daga2, Jason Stretton1, Marc Modat2, Mark R Symms1, Andrew W McEvoy3, Sebastien Ourselin2, and John S Duncan1,3
1UCL Institute of Neurology, London, United Kingdom, 2UCL Centre for Medical Image Computing, London, United Kingdom, 3National Hospital for Neurology and Neurosurgery, London, United Kingdom

Anterior temporal lobe resection (ATLR) is an effective treatment for temporal lobe epilepsy refractory to medication, but leads to a visual field deficit in between 52% and 100% of patients. Probabilistic tractography is required to accurately depict Meyer's loop of the optic radiation, but cannot be performed in real-time. Propagation of preoperative probabilistic tractography to intraoperative images using non-linear registration techniques accounting for brain shift and deformation and subsequent integration into the neuronavagional suite should improve the outcome from epilepsy surgery. Such a technique is described and validated with outcome in patients undergoing ATLR using pre- and postoperative images.

17:00 349.   Patterns of CNS Injury in HIV Infection: a DTI Tract-Based Spatial Statistics Study 
Tong Zhu1, Jianhui Zhong1, Rui Hu2, Wei Tian1, Sven Ekholm1, Constantin Yiannoutsos3, Ron Cohen4, Bradford Navia5, Michael Taylor6, Eric Daar7, Elyse Singer8, Thomas Campbell9, Deborah McMahon10, Yuen So11, and Giovanni Schifitto1,12
1Dept. Imaging Sciences, University of Rochester, Rochester, NY, United States, 2Dept. Biostatistics, University of Rochester, Rochester, NY, United States, 3Division of Biostatistics, Indiana University School of Medicine, Indianapolis, Indiana, United States, 4The Miriam Hospital, Brown University, Providence, Rhode Island, United States,5Tufts University School of Medicine, Boston, Massachusetts, United States, 6University of California at San Diego, La Jolla, CA, United States, 7UCLA/Harbor, Torrance, CA, United States, 8UCLA, Los Angeles, CA, United States, 9University of Colorado, Denver, CO, United States, 10University of Pittsburgh, Pittsburgh, PA, United States,11Stanford University, Palo Alto, CA, United States, 12Dept. Neurology, University of Rochester, Rochester, NY, United States

It is well established that HIV infection is associated with injury to the central nervous system (CNS) that can lead to cognitive impairment, including dementia. In this study, we used diffusion tensor imaging (DTI) and specifically Tract-Based Spatial Statistics to further investigate changes in white matter structures across the entire brain in HIV-infected subjects. The correlation between longitudinal changes in DTI and neuropsychological test scores were also evaluated to further investigate the structural-functional connection during the progression of CNS injury due to HIV infection. Results from this study show significantly decreased FA and increased MD values in multiple white matter structures as the disease progresses from neuroasymptomatic (HIV+NA) to cognitive impairment (HIV+CI). Compared to controls, in the early stages of HIV-associated CNS injury, significantly increased MD values were observed only within fiber bundles that are mainly associated with the posterior areas of the frontal and the parietal lobes. As CNS injury progresses, DTI changes were also seen in fiber bundles connecting to the prefrontal lobe, including the genu of the corpus callosum and the anterior corona radiata. Our results suggest that the combinations of DTI parameters such as FA and MD can differentiate control subjects from HIV+ infected subjects with and without cognitive impairment. The results also suggest a transition with more involvement of the frontal lobes in those subjects that develop cognitive impairment. The correlation with disease duration is consistent with this possibility. Among the different cognitive domains tested, verbal fluency had the highest correlation with DTI parameters. It is of interest that this cognitive domain is sub-served by neuronal circuitry that involves both the temporal and frontal lobes. As part of an ongoing project, we expect further validations of these results in future longitudinal analyses.

17:12 350.   Atypical Gray and White Matter Microstructure in Autism Spectrum Disorders 
Mariana Lazar1, Laura Miles1, Jeffrey Donaldson1, Jens H Jensen1, and Joy Carol Ming2
1Department of Radiology, New York University School of Medicine, New York, New York, United States, 2Livingston High School, Livingston, New Jersey, United States

Autistic Spectrum Disorders are developmental disorders characterized by deficits in social interaction, language, and repetitive behaviors. In this abstract we present evidence that both gray and white matter microstructure is affected in extended brain regions in ASD.

17:24 351.   Can Structural Connectivity Analyses Measure Brain Plasticity in Amyotrophic Lateral Sclerosis? 
Stephen Rose1, Kerstin Pannek1, Fusun Baumann2, and Robert Henderson2
1Centre for Clinical Research, University of Queensland, Brisbane, Queensland, Australia, 2Neurology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia

Structural connectivity analyses, using diffusion tractography in conjunction with cortical parcellation of structural MRI, are useful techniques for studying neurological disease processes associated with multiple white matter (WM) networks. In this study, we introduce a new quantitative connectivity measure based on the amplitude of the Fibre Orientation Density (FOD) function and apply this strategy to measure the integrity of corticomotor WM pathways in patients with Amyotrophic Lateral Sclerosis (ALS). Compared to measures of fractional anisotropy, the FOD amplitude is less sensitive to contamination from crossing fibre tracts. This approach was found to provide new insight into brain plasticity in ALS.

17:36 352.   Using surface connectivity atlases to measure striato-cortical "disconnection rate" in Huntington disease 
Linda Marrakchi-Kacem1,2, Christine Delmaire3, Alan Tucholka4,5, Pauline Roca1,2, Pamela Guevara1,2, Sophie Lecomte1,2, Fabrice Poupon1,2, Jerome Yelnik6, Alexandra Durr6, Jean-François Mangin1,2, Stephane Lehericy2,3, and Cyril Poupon1,2
1NeuroSpin, CEA, Gif-Sur-Yvette, France, 2IFR49, Gif-Sur-Yvette, France, 3CENIR, Pitié Salpêtrière Hospital, Paris, France, 4Centre de Recherche Hôpital Ste-Justine, Montreal, Canada, 5Université de Montréal, Montreal, Canada, 6CRICM, Inserm/UPMC, Paris, France

In this study, we use average surface striato-cortical connectivity atlases to compare the connectivity of subjects suffering from the Huntington's disease and healthy subjects. We define a disconnection rate measure for Huntington patients, for each nucleus and each cortical region of interest, using healthy subjects as a reference. These measures computed for each nucleus of the striatum and each gyrus allowed the quantification of the decrease in striato-cortical connections for Huntington subjects compared to healthy subjects. These disconnection rates constitue novel connectivity Biomarkers of Huntington's disease.

17:48 353.   Prediction of genetic risks in schizophrenia: A DTI based pattern classification study 
Madhura Ingalhalikar1, Stathis Kanterakis1, Drew Parker1, Raquel E Gur2, Ruben C Gur2, and Ragini Verma1
1Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Brain Behavior Laboratory, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, United States

This study investigates the presence of endophenotypic brain patterns in first-degree family members of patients with schizophrenia via a diffusion tensor based classification study. High dimensional gender specific classifiers were constructed for patients diagnosed with schizophrenia or schizoaffective disorder and healthy controls. Superior cross-validated classification was obtained between patients with schizophrenia and healthy controls with 88.25% accuracy in males and 75.04% accuracy in females. The classifier associated a genetic pattern score to each of the asymptomatic FM. The female FM displayed scores that were closer to the patient spectrum than the male FM, indicating possibly enhanced genetic susceptibility of schizophrenia in females.