Traditional Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Non-Gaussian Diffusion

Monday May 9th
Exhibition Hall  14:00 - 16:00

1983.   Quantifying Non-Gaussian Diffusion in Brain Tissue at High b-Factors  
Farida Grinberg1, Ezequiel Farrher1, Joachim Kaffanke1, Ana-Maria Oros-Peusquens1, and N. Jon Shah1,2
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Juelich GmbH, 52425 Juelich, NRW, Germany, 2Department of Neurology, Faculty of Medicine, RWTH Aachen University, JARA, 52074 Aachen, Germany

Biexponential diffusion tensor analysis in the extended range of diffusion-encoding gradients permits one to overcome the limitations of conventional DTI based on the assumption of the Gaussian model with regard of displacements of water molecules in tissue. We illustrate the benefits of this approach with an in vivo diffusion study of the human brain performed on 14 healthy volunteers. Novel parameter maps are discussed in the context of their potential applications in brain diagnostics.

1984.   A novel approach to give more insides on anomalous diffusion processes: diffusion MR signal at varying of diffusion time versus signal at varying of gradient strength 
Silvia Capuani1,2, Marco Palombo1, Silvia De Santis1, and Andrea Gabrielli3
1Physics Department Sapienza University of Rome, Rome, Italy, 2CNR IPCF UOS Roma, Rome, Italy, 3CNR ISC, Rome, Italy

We developed and applied a new methodology based on CTRW to investigate the type of anomalous diffusion information obtenaible using methods based on PFG signal at varying of the time Ä and/or the gradient strenght g. using PFG experiments performed in controlled samples and human tissues with different (expected) diffusional characteristics we measured á by varying Ä and ì by varying g. Experimental data demonstrate that á and ì reflect some additional microstructural information which cannot be obtained using conventional diffusion procedures based on Gaussian diffusion models. Morover, our work allows a critical revision of previous anomalous diffusion literature.

1985.   Internal gradients affect the lower case Greek gamma value arising from Anomalous Diffusion stretched exponential model 
Marco Palombo1, Silvia De Santis1, and Silvia Capuani1,2
1Physics Department, Sapienza University of Rome, Rome, Italy, 2IPCF UOS Roma, CNR, Rome, Italy

lower case Greek gamma parameter arising from Anomalous diffusion stretched-exponential method has been used to investigate tissues, showing the ability of lower case Greek gamma maps to discriminate between different brain structures on the basis of their microstructural complexity. Here, we measure lower case Greek gamma in controlled phantoms comprised of monodispersed and polydispersed micro beads in water solution to tested the influence of the internal gradient (due to the magnetic susceptibility difference between diffusing water and obstacles) with respect to the capability of lower case Greek gamma to discriminate between structures characterized by different geometrical dimensions. Experimental data showed that the higher the internal gradient, the lower the lower case Greek gamma value.

1986.   A Simple Analytical Relationship between WM Tissue Characteristics and DWI Signal 
Sharon Peled1
1Brigham and Women's Hospital, Boston, MA, United States

This is a model-based representation of the DWI signal from white matter which will allow extraction of physiologically-relevant parameters.

1987.   Spectral lineshape reflects microscopic structure and ordering 
Alexander Ruh1, Philipp Emerich1, Dmitry S Novikov2, and Valerij G Kiselev1
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany, 2Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, NY, United States

NMR spectroscopy is commonly used to detect populations of nuclei in different chemical environments. We demonstrate for the first time that the lineshape of chemically homogeneous nuclei carries information about microscopic spatial variations of NMR parameters. In particular, the water lineshape is sensitive to the degree of structural ordering of magnetic susceptibility in microscopically heterogeneous samples, such as tissues with the susceptibility varying on a cellular scale. We explicitly focus on the lineshape features which distinguish an ordered (periodic) sample from a disordered one. Our results agree well with Monte Carlo simulations of transverse relaxation in synthetic three-dimensional media.

1988.   Time-dependent diffusion and kurtosis as a probe of tissue structure 
Dmitry S Novikov1, Els Fieremans1, Jens H. Jensen1, and Joseph A Helpern2
1Radiology, NYU School of Medicine, New York, NY, United States, 2Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, United States

Diffusion coefficient in tissues is known to depend on the diffusion time. The short-time limit, while useful in probing surface-to-volume ratio of restrictions, is challenging in the clinical DWI. Here we focus on the opposite, long-time limit, and argue that the way the diffusivity approaches its tortuosity asymptote reveals quantitative information about the long-range order in tissues. We show that both diffusivity and kurtosis decrease with time with the same power law exponent that distinguishes a periodic arrangement from a disordered one. Our results agree with numerical simulations and can be applied to characterize tissue composition over large diffusion lengths.

1989.   Stroke Analysis by Means of Kurtosis Diffusion Imaging in In Vivo Animal Studies 
Farida Grinberg1, Ezequiel Farrher1, Luisa Ciobanu2, Françoise Geffroy2, and N. Jon Shah1,3
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Juelich GmbH, 52425 Juelich, NRW, Germany, 2Neurospin, CEA, Gif sur Yvette, France, 3Department of Neurology, Faculty of Medicine, RWTH Aachen University, JARA, 52074 Aachen, Germany

DKI is a novel method that is considered as the simplest extension of DTI that enables one to quantify deviations from Gaussian diffusion of water molecules in brain tissue. Our results have shown that DKI has a potential to better characterize a pathological state of the brain in animals that have experienced stroke.

1990.   Q-Space Undersampled Diffusional Kurtosis Imaging 
Ali Tabesh1, Jens H. Jensen1, Els Fieremans1, and Joseph A. Helpern1,2
1Radiology, New York University School of Medicine, New York, NY, United States, 2Medical Physics, Nathan Kline Institute, Orangeburg, NY, United States

We assess the feasibility of reconstructing DKI parametric maps from q-space undersampled brain DKI scans. We present two constrained tensor estimation methods that extend our previous convex quadratic programming-based formulation, and enable estimation of DKI maps from undersampled DKI acquisitions. We compare the performance of these methods on highly undersampled scans. Our results indicate that mean and radial kurtosis maps can be estimated from undersampled DKI scans with acceptable fidelity. As a consequence, useful DKI maps are obtainable at 3T from scans as short as 90 seconds.

1991.   The effects of cross-sectional asymmetry and anisotropy of the pore space on double-PFG MR signal 
Evren Ozarslan1,2, and Peter Joel Basser1
1STBB / PPITS / NICHD, National Institutes of Health, Bethesda, MD, United States, 2Center for Neuroscience and Regenerative Medicine, USUHS, Bethesda, MD, United States

Previous theoretical studies performed to relate the pore morphology to the double pulsed field gradient (double-PFG) signal have assumed that the compartments are symmetric about their center of gravity. For example, axons have been envisioned to be cylinders with perfectly circular cross sections. To understand the effects of any asymmetry, we modeled an ensemble of infinitely long tubes with wedge-shaped cross sections. The findings indicate that the signal behavior resembles that for symmetric pore shapes, and for reasonable levels of asymmetry, employing a model with an isotropic cross section would lead to only a slight overestimation of the compartment size.

1992.   Hindered or restricted predominance of the diffusion weighted signal function of the diffusion time at ultra-high magnetic field. 
Yohan van de Looij1,2, Nicolas Kunz1,2, Petra S Hüppi1, Rolf Gruetter2,3, and Stéphane V Sizonenko1
1Division of Child Growth & Development, University of Geneva, Geneva, Switzerland, 2Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3Department of Radiology, Universities of Lausanne and Geneva, Lausanne and Geneva, Switzerland

The exact origin of water diffusion anisotropy in brain white matter is not fully understood. It is still not clear whether the observed diffusion anisotropy arises from the intra-axonal compartment (restricted) or the extra-axonal compartment (hindered) or some combination thereof. Through the increased sensitivity, the use of ultra-high magnetic field could give new information about the exact origin of this signal. Here we propose to assess the effect of the diffusion times on DTI derived parameters at 9.4T and 14.1T. This study gives a new insight into the understanding of the diffusion signal origin.

1993.   How White Matter Tracts Cross Determines the DWI SIgnal 
Sharon Peled1, and Carl-Fredrik Westin1
1Brigham and Women's Hospital, Boston, MA, United States

The DWI signal from crossing tracts in white matter voxels depends on whether fibers interleave finely or remain in relatively large bundles. The difference has implications for DWI analysis.

1994.   In Vivo Neuroanatomical Segmentation of Human Corpus Callosum Based on Axonal Diameter and Density Using Q-planar MRI 
Jun-Cheng Weng1,2, and Wen-Yih Isaac Tseng3,4
1School of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan, 2Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung, Taiwan, 3Center for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan, 4Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan

The corpus callosum (CC) is the main fiber tract connecting bilateral cerebral hemispheres, serving information transfer and processing in various cognitive functions. Different CC regions might be affected differently in the development of disease, and their structural parameters such as size and shape might associate with cognitive or functional tests involved in different modes of interhemispheric interactions. Previously we proposed a novel magnetic resonance imaging method called q-planar imaging (QPI), which could in vivo map the relative axonal diameters and density of CC in human brain. We also studied the optimum parameters, cutoff values of diffusion sensitivity b and sampling number, to apply this technique to clinical study. In the study, to further visualize the difference in the computed axonal diameter and density distribution for each voxel, we used cluster analysis to segment the CC based on the QPI parameters, displacement and probability. Correlation analysis was also performed between diffusion spectrum imaging (DSI) and QPI derived parameters. Our cluster results demonstrated that QPI produced reasonable segmentation of relative axonal diameters and density of CC in normal human brain. Poor to moderate correlations between the DSI indices and the parameters derived from QPI implied the incompatibility of the two methods.

1995.   The displacement correlation tensor from double wave vector diffusion experiments encodes information about pore microstructure and ensemble properties 
Sune Nørhøj Jespersen1, and Niels Buhl1,2
1CFIN/MINDLab, Aarhus University, Aarhus, Denmark, 2Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark

Pulsed field gradient diffusion sequences with multiple diffusion encoding blocks have recently gained renewed interest in the magnetic resonance community. Some of the properties that appear most promising are the ability to measure pore sizes, detect anisotropic pores in macroscopically isotropic media, and the enhancement of diffraction peaks. Here we introduce the displacement correlation tensor Q, and discuss some of its properties. In particular, we derive a new result revealing the nature of the interplay between ensemble and microscopic anisotropy. We also note that Q is sensitive to pore surface-to-volume ratio, and can be used to measure curvature of fibers.

1996.   A Monte Carlo study of the effects of cell membrane permeability on DWI-MRI contrast with oscillating diffusion gradients 
Blake Walters1, Greg Duane2, and Jae Kim2
1Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada, 2Thunder Bay Regional Research Institute

This study describes the effects of nuclear and cell membrane permeability on contrast between healthy and malignant cells in diffusion-weighted MRI with oscillating diffusion gradients. The study uses a Monte Carlo simulation of diffusion in a model cell geometry, a powerful method for determining the effects of cell characteristics on the diffusion-weighted signal given the lack of available analytical models. Results show that nuclear membrane permeability plays an important role in contrast, while cell wall permeability has minimal effect. The results have important implications for the ability of DWI-MRI to detect cancer based on intracellular characteristics.

1997.   Double-PFG MR reveals insights into compartment shape, organization and morphology in heterogeneous specimens 
Noam Shemesh1, and Yoram Cohen1
1School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel

The angular d-PFG methodology recently gained interest owing to its ability to characterize underlying microstructure even when compartments are randomly oriented. Here, we applied the angular bipolar-d-PFG (bp-d-PFG) methodology to study yeast cells, a synthetic porous medium, and an emulsion. The angular bp-d-PFG accurately reported on compartment morphology, yielding unique signatures for underlying microstructure. Furthermore, the emulsion can be regarded as a model for intra/extracellular spaces. While the single-PFG MR only showed isotropic diffusion, the bp-d-PFG showed that toluene is confined in spherical compartments while water molecules undergo restricted diffusion in randomly oriented anisotropic compartments between the toluene droplets.

1998.   Influence of Boundary Condition on Multiple Exponential Diffusion Phase Transition 
Lingchih Lin1, and Jianhui Zhong1,2
1Department of Physics and Astronomy, University of Rochester, Rochester, NY, United States, 2Department of Imaging Sciences, University of Rochester, Rochester, NY, United States

The correlation between water molecule and tissue interface can induce various diffusion diffraction patterns and lead to phase transition from mono-exponential to multi-exponential signal decay. We compared the diffusion propagator with mixed boundary conditions, (1) absorbing-permeable, (2) reflecting-permeable, to pure (3) reflecting, (4) absorbing, and (5) permeable interfaces. The local magnetization evolving from the position close to a typical boundary condition to a mixed interface can be quantified from slow, medium and fast diffusion coefficients according to the relaxation rate and diffusion time. A shift of diffraction minimum to larger q is observed between the absorbing and permeable interfaces compared to the reflecting boundary conditions.

Traditional Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Application of Diffusion Sensitive MR

Tuesday May 10th
Exhibition Hall  13:30 - 15:30

1999.   The appearance of the apparent diffusion coefficient in complex fiber architecture 
Sjoerd B Vos1, Derek K Jones2, Max A Viergever1, and Alexander Leemans1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2CUBRIC, Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff, United Kingdom

Although many investigations focus on the ‘crossing fibers’ issue in DTI, so far, no research has described the effect of complex fiber architecture on the apparent diffusion coefficient. In this work, we demonstrate that the mean diffusivity is decreased in regions of fiber crossings compared to regions with predominantly one fiber population. We further show that the extent of this decrease depends on the angle of intersection between the multiple fiber populations and on the relative contribution of these fiber populations.

2000.   Asymmetry in Multi-Modal White Matter Microstructural Indices 
Sonya Bells1, Sean Deoni2,3, Mara Cercignani4, Ofer Pasternak5, and Derek K Jones1
1CUBRIC, School of Psychology, Cardiff, United Kingdom, 2School of Engineering, Brown University, Providence, Rhode Island, United States, 3Centre of Neuroimaging Sciences-Institute of Psychiatry, King's College, London, United Kingdom, 4Santa Lucia Foundation, Neuroimaging Laboratory, Rome, Italy, 5Brigham and Women's Hospital, Harvard Medical School, Bostan, MA, United States

Asymmetry in structure and function has been reported in humans. Structural connectivity and the microstructural organization of the pathways connecting these hemispheres are important in our understanding of this specialization. Diffusion weighted imaging is often used to study white matter, and measures such as FA and radial diffusivity incorrectly used as an indicator of myelination. We propose that other quantitative microstructural imaging methods, such as magnetization transfer imaging and multicomponent T2 species from relaxometry might be more sensitive indicators of asymmetries in microstructure

2001.   Sexual dimorphism in white matter development in pre-adolescence: a tract based spatial statistics study 
Kiran Kumar Seunarine1, Jon Clayden1, Sebastian Jentschke1, Monica Muñoz1,2, Janine Cooper1, Martin J Chadwick1,3, Tina Banks4, Faraneh Vargha-Khadem1, and Chris A Clark1
1Institute of Child Health, University College London, London, United Kingdom, 2School of Medicine, University of Castilla-La Mancha, Albacete, Spain, 3Institute of Neurology, University College London, London, United Kingdom, 4Radiology Department, Great Ormund Street Hospital, London, United Kingdom

There are widespread structural changes in the brain as it matures throughout childhood and into early adulthood. Several studies have investigated the effect of age and gender on white-matter development using diffusion MRI but they typically use a large age range. This work focusses on investigating sexual dimorphism in pre-adolescence (children aged 8-13 years) using tract-based spatial statistics (TBSS). Results show significant (p<0.05) correlations between diffusion tensor measures and age in males in this age range but not females. This suggests a different course of white-matter development in males and females in the 8-13 year age range.

2002.   Independent Component Analysis of DTI Reveals Multivariate Microstructural Correlations of Human Brain White Matter 
Yi-Ou Li1, Fan-Pei Yang1, Christopher Nguyen2, Shelly Cooper1, Sara LaHue1, Sandya Venugopal1, and Pratik Mukherjee1
1University of California San Francisco, San Francisco, CA, United States, 2University of California Los Angeles

We perform a whole-brain multivariate analysis of microstructural white matter correlations at the voxel scale using independent component analysis (ICA). The resulting independent components show distinct spatial localization patterns indicating high fractional anisotropy co-variation across subjects. These component maps localize the strongest microstructural correlations to well-known anatomic white matter pathways, or homologous pairs of pathways, as well as segmenting certain large tracts into functionally distinct subdomains that have different patterns of connectivity. Thus, ICA of DTI maps might provide an interesting alternative to tractography for studying white matter microstructure in the normal human brain and in neurological and psychiatric disorders.

2003.   Testing the variability of Diffusion Spectrum Imaging (DSI): Inter- and intra-site comparison on “identical” 3T scanners 
Alia Lemkaddem1, Alessandro Daducci1, Serge Vulliémoz2, Margitta Seeck2, Francois Lazeyras3, Reto Meuli4, Gunnar Krueger5, and Jean-Philippe Thiran1
1Signal Processing Laboratories (LTS5), Ecole Polythechnique Fédéral de Lausanne (EPFL), Lausanne, Switzerland, 2Presurgical epilepsy evaluation unit, Hôpitaux Universitaires et faculté de médecine de Genève (HUG), Switzerland, 3Department of radiology, Hôpitaux Universitaires et faculté de médecine de Genève (HUG), Switzerland, 4Department of radiology, University Hospital Center and University of Lausanne (CHUV), Switzerland, 5Advanced clinical imaging technology, Siemens medical solutions-CIBM, Switzerland

The purpose of this study was to evaluate if it was possible to merge DSI data from two different sites. Therefore, we assessed inter- and intra-site reproducibility of two identical 3T scanners at two different hospitals in six healthy subjects. For investigating the reproducibility we used FA, ADC and GFA as measurements of the diffusivity. To validate our results we decided to use three different methodologies: A Tract-based, Regional based and whole brain voxel-based analysis. Our findings support the feasibility of cross-site pooling of DSI data from identical scanners.

2004.   A Framework for Analysis of Living Phantom Data in a Multicenter DTI study 
Lindsay Walker1, Nicholas Lange2, Lin-Ching Chang3, Carlo Pierpaoli1, and . the Brain Development Cooperative Group4
1STBB, NICHD, National Institutes of Health, Bethesda, MD, United States, 2Departments of Psychiatry and Biostatistics, Harvard Schools of Medicine and Public Health, Boston, MA, United States,3Department of Electronic Engineering adn Computer Science, The Catholic University of America, Washington, DC, United States,

In Multicenter DTI studies it is important to assess the impact of site related variability to meaningfully pool quantitative imaging data across sites. We propose two tools for the assessment of living phantom data. 1) Outlier identification using the median of tensor derived metrics, and 2) analysis of inter-site and intra-site variability for assessment of sources of variance. High variability is seen at tissue interfaces, suggesting inconsistent morphology is a significant issue, even in a single subject. Thus, a single subject should be used as living phantom in multicenter studies in order to avoid the confound of inter-subject anatomical variability.

2005.   Diffusion Tensor Image Registration Using Uncertainty Information 
Mustafa Okan Irfanoglu1,2, Cheng Guan Koay3, Sinisa Pajevic3, Raghu Machiraju4, and Peter J Basser3
1Computer Sciences and Engineering, The Ohio State University, Columbus, OH, United States, 2NICHD, NIH, Bethesda, MD, United States, 3NIH, 4The Ohio State University

We propose a novel method for deformable tensor–to–tensor registration of Diffusion Tensor Imaging (DTI) data. Our registration method considers estimated diffusion tensors as normally distributed random variables whose covariance matrices describe uncertainties in the mean estimated tensor due to factors such as noise in diffusion weighted images (DWIs), tissue diffusion properties, and experimental design. The dissimilarity between distributions of tensors in two different voxels is computed using the Kullback-Leibler divergence to drive a deformable registration process, which is not only affected by principal diffusivities and principal directions, but also the underlying DWI properties.

2006.   Inter-Subject Correlations between DTI Indices and Tissue Fractions in Human Brain 
Wang Zhan1, Wanyong Shin2,3, Xiujuan Geng3, Hong Gu3, and Yihong Yang3
1Radiology and Medical Imaging, University of California, San Francisco, San Francisco, California, United States, 2Imaging Institute, Cleveland Clinic, Cleveland, Ohio, United States,3Neuroimaging Branch, National Institute on Drug Abuse, Baltimore, Maryland, United States

The histological mechanism for DTI index (FA/MD) changes is still poorly understood. It remains unclear to what extent the variations of FA measurements should be explained by the intra-voxel white matter (WM) tissue fraction rather than the underlying WM integrity. This study aims to identify the correlations between DTI indices and tissue fractions across subjects. Our data indicated that significant correlations between DTI indices and tissue fractions do exist in selective regions, including thalamus and superior frontal lobes. This result suggests the need to consider the effects of tissue fraction variations for a group DTI analysis in those correlation-sensitive regions.

2007.   Reproducibility of automated measurements of Diffusion Tensor Imaging at 3T Using Histogram Analysis 
Ryan Hutten1, Shawn Sidharthan1, Christopher Glielmi1,2, Hongyan Du3, Fiona Malone1, Ann Ragin1,4, Robert Edelman1,4, and Ying Wu1,4
1Radiology, Northshore University HealthSystem, Evanston, IL, United States, 2Siemens Healthcare, Chicago, IL, United States, 3Center for Clinical Research Informatics, Northshore University Health Systems, Evanston, IL, United States, 4Radiology, Feinberg School of Medicine, Chicago, IL, United States

Quantitative analysis of Diffusion Tensor Imaging (DTI) can be used to monitor and detect the onset of neurodegenerative diseases such as Alzheimer's and Parkinson's. This reliability study was conducted in order to show the reproducibility of an automated segmentation procedure incorporated with Fractional Anisotropy (FA) maps using several histogram metrics. When compared to the mean FA approach, the histogram median, mean, and peak location showed a higher reproducibility. These findings suggest that histogram metrics may be potentially more useful than the mean approach in the longitudinal studies of various chronic neurodegenerative diseases.

2008.   Diffusion imaging in vivo with whole-body gradient amplitude of 65 mT/m 
Ek Tsoon Tan1, Wesley M Skeffington1, Juan Sabate1, Bruce D Collick2, Song Chi1, Rixin Lai1, Christopher J Hardy1, Luca Marinelli1, and Thomas K Foo1
1GE Global Research, Niskayuna, NY, United States, 2GE Healthcare, Waukesha, WI, United States

A higher performance gradient driver system was developed, capable of delivering gradient amplitude of 65 mT/m in a conventional whole-body MRI system. Imaging at 65 mT/m was compared against the standard 50 mT/m in diffusion MRI. Diffusion images were acquired in two human subjects at b-values of 1000-10000 sec/mm2. As compared to 50 mT/m, imaging with 65 mT/m provided SNR improvements of 7-20% in white matter.

2009.   Effects of sustained high-altitude hypoxia on cerebral hydration and diffusion 
John S Hunt, Jr.1, Rebecca J Theilmann1, Bill C Hsu1, Ethan Li1, Zachary Myles Smith1, Miriam Scadeng1, and David J Dubowitz1
1Radiology, University of California San Diego, La Jolla, CA, United States

Cerebral edema and acute mountain sickness (AMS) share many symptoms suggesting a common etiology. However, the effects of uncomplicated AMS on brain water remain controversial. To investigate the impact of high-altitude hypobaric hypoxia on cerebral water content, we measured T2 signal and ADC during normoxia, and two and seven days hypoxia. In contrast to previous hypoxic studies in a chamber at sealevel, we found a significant reduction in T2 signal and a small (non-significant) increase in ADC in the corpus callosum and caudate nuclei at altitude. This suggests barometric pressure and hydration may be important in the cerebral response to hypoxia.

2010.   Preparation of Diffusion–Weighted MR Image Data for Cortical Parcellation 
Zoltan Nagy1, David Lee Thomas2, Nikolaus Weiskopf1, and Martin Sereno3,4
1Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom, 2Institute of Neurology, Department of Brain Repair and Rehabilitation, University College London, London, United Kingdom, 3Department of Psychology, University College London, London, United Kingdom, 4Department of Psychology, Birkbeck College, London, United Kingdom

Both cognitive and anatomical neuroscience relies on commonly held reference systems such as the Brodmann map. Unfortunately, these maps are relatively coarse and ignore inter–individual individual variability. Both these limitations can be overcome by MRI, although the exact contrast is unclear. We propose diffusion–weighted images, present a image processing pipe–line and demonstrate reproducible signal which is specific to the given cortical region the voxel resides in. Such data should allow computer intensive pattern recognition methods to parcellate the human cortex in–vivo.

2011.   Dual tensor for tract-based analysis: towards application to routine clinical diffusion images 
Virendra Mishra1, and Hao Huang1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States

Tract-based analysis, in contrast to voxelwise analysis, has the advantage of delineating the integrity of white matter at the tract level rather than voxel. However, in tract-based analysis, underestimation of the FA of target tracts still exists when they go through the crossing fiber area. In this abstract, we proposed an improved tract-based approach, DTTA (Dual Tensor for Tract based Analysis) to restore the FA values of the targeted tract along its path while removing the influence of crossed fibers. It integrates spherical harmonics (SH) to identify the crossing fiber location and Levenberg-Marquardt estimation algorithm to fit dual tensors.

2012.   Aging-related changes in apparent diffusion coefficient values of the cerebral metabolites using diffusion weighted MR spectroscopy 
Dandan Zheng1, Zhenghua Liu2, Jing Fang1,3, Xiaoying Wang1,2, and Jue Zhang1,3
1Academy for Advanced Interdisciplinary Studies, Peking University, BEIJING, BEIJING, China, People's Republic of, 2Dept. of Radiology, Peking University First Hospital, BEIJING, BEIJING, China, People's Republic of, 3College of Engineering, Peking University, BEIJING, BEIJING, China, People's Republic of

Diffusion weighted magnetic resonance spectroscopy (DW-MRS) is more releted for the understanding of pathphysiological process. The aging process is characterized by physiological changes which impair numerous organs and systems, especially their functions. It has been reported that changes of diffusion of metabolite can be observed in rat brain due to aging effect. The purpose of this study was using DW-MRS to reveal the aging-related changes in apparent diffusion coefficient (ADC) values of metabolites in human brain in vivo. The results suggested that the ADC value of the cerebral metabolites of the health people have a significantly change in elderly people.

2013.   Functional Muscle MRI in Human Calf Muscle using IVIM 
Patrick Hiepe1, and Jürgen Reichenbach1
1Medical Physics Group, Department of Diagnostic and Interventional Radiology I, Jena University Hospital, Jena, Germany

In biologic tissues, ADC is determined by the microscopic motion of water including not only molecular diffusion, but also microcirculation of blood in the capillary network, as described by the IVIM model. This theory, which predicts an additional component in the signal equation due to perfusion effects, has recently been applied to MR studies of skeletal muscles. Previous studies in human skeletal muscles were analysed by calculating separately linear signal decays within predefined different intervals of b-values. This approach is limited, however, due to the missing estimation of the perfusion fraction within the signal decay. We present an approach to determine diffusion and perfusion changes in exercised human calf muscles by employing bi-exponential fitting.

2014.   A Novel Method for Automatic Extraction of Apparent Diffusion Coefficients in Breast MRI 
Darryl McClymont1, Andrew Mehnert1, Adnan Trakic1, Dominic Kennedy2, and Stuart Crozier1
1University of Queensland, Brisbane, QLD, Australia, 2Queensland X-Ray, Brisbane, QLD, Australia

This paper provides a method for extracting representative Apparent Diffusion Coefficients from Diffusion-weighted MRI for the purpose of improved classification of benign and malignant breast lesions. This is achieved without the need for manual segmentation of the diffusion weighted images, which reduces the variability between individuals. 26 breast lesions were analysed, with results indicating that the use of automatically selected apparent diffusion coefficients can provide valuable classification.

2015.   Diffusion weighted imaging (DWI) of Non-Hodgkin Lymphoma (NHL) patients refractory to previous treatment(s): preliminary results 
Hamed Mojahed1, Thorsten Persigehl2, Owen A. O'Connor3, Ahmed Sawas3, Truman R. Brown4, and Fernando Arias-Mendoza2
1Department of Biomedical Engineering, Columbia University, New York, NY, United States, 2Department of Radiology, Columbia University, New York, NY, United States, 3NYU Cancer Institute, NYU Langone Medical Center, New York University, New York, NY, United States, 4Center for Advanced Imaging Research (CAIR), Medical University of South Carolina, United States

Apparent diffusion coefficient (ADC) of Non-Hodgkin Lymphoma (NHL) refractory to the previous treatments and a newly diagnosed NHL were assessed by diffusion weighted imaging at a 1.5T Philips MR scanner. In our study ADC of refractory NHL did not show significant difference compared to normal lymph nodes in healthy volunteers. This is different than an earlier report where newly diagnosed NHL had significantly lower ADC than normal lymph nodes. However, ADC of our newly diagnosed NHL was similar to the literature. Thus, a differentiation between malignant and normal lymph nodes was not achievable by quantitative ADC evaluations for refractory NHL.

2016.   4-Tesla High Angular Resolution Diffusion Tractography Analysis of the Human Connectome in 234 Subjects: Sex Differences and EPI Distortion Effects 
Neda Jahanshad1, Iman Aganj2, Christophe Lenglet2,3, Guillermo Sapiro2, Arthur W Toga1, Katie L McMahon4, Greig I de Zubicaray5, Nicholas G Martin6, Margaret J Wright6, and Paul M Thompson1
1Laboratory of Neuro Imaging, Department of Neurology, UCLA, Los Angeles, CA, United States, 2Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, United States, 3Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN, United States, 4Centre for Advanced Imaging, University of Queensland, Brisbane, Australia, 5School of Psychology, University of Queensland, Brisbane, Australia, 6Queensland Institute of Medical Research, Brisbane, Australia

Cortical fiber connectivity, assessed with diffusion-based tractography, has great potential for investigating how the normal and diseased brains are organized. Connectivity patterns may differ between men and women, contributing to sex differences in normal developmental and cognitive traits. In one of the largest-ever HARDI tractography studies, we analyzed cortical connectivity in 234 young adults. We use a novel Hough transform based full brain tractography method to trace the connections within and between 35 cortical surface regions in each hemisphere. We discovered sex differences in regional connection densities. We also find that EPI distortion correction affected the results.

2017.   Evaluation of fiber radius mapping using diffusion MRI under clinical system constraints 
Chun-Hung Yeh1,2, Irina Kezele1, Daniel Alexander3, Benoit Schmitt1, Jing-Rebecca Li1, Denis Le Bihan1, Ching-Po Lin2, and Cyril Poupon1
1NeuroSpin, I2BM, CEA, Gif-sur-Yvette, France, 2National Yang-Ming University, Taipei, Taiwan, 3University College London, London, United Kingdom

We assessed the feasibility in mapping white matter fiber radius using diffusion MRI on clinical scanners. We performed Monte Carlo simulations on water diffusion in various fiber radii, and evaluated a list of conventional pulsed-gradient spin-echo imaging protocols with the constraints on the gradient system capability. Within a clinical acceptable acquisition time of 30 minutes, we observed that using three q-space sampling shells with moderate to high b-values is potentially feasible to accurately estimate fiber radii ranging from 2-6 um. Meanwhile we provided a guideline to setup clinical protocols for the purpose of fiber radius estimation.

Traditional Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.

Wednesday May 11th
Exhibition Hall  13:30 - 15:30

2018.   Accurate tractography propagation mask using T1-weighted data rather than FA 
Pamela Guevara1,2, Delphine Duclap1,2, Linda Marrakchi-Kacem1,2, Denis Rivière1,2, Yann Cointepas1,2, Cyril Poupon1,2, and Jean-François Mangin1,2
1Neurospin, CEA Saclay, Gif-sur-Yvette, France, 2Institut Fédératif de Recherche 49, Gif-sur-Yvette, France

We present an improved propagation mask built from T1 data and dedicated to dMRI tractography. This mask allows a better tracking of fibers until the GM/WM interface, including the short association U-fibers. Contrary to usual FA-based masks failing at including low FA regions such as AC/PC, the fornix or crossings, this novel technique provides an accurate mask of the brain WM+GM independent of the DW data quality. Consequently, its use in conjunction with tractography techniques improves the accuracy of the anatomical connectivity of the brain by reducing false positives and increasing the detection of the subcortical connectivity.

2019.   Effect of step size on probabilistic streamlines: implications for the interpretation of connectivity analyses. 
J-Donald Tournier1,2, Fernando Calamante1,2, and Alan Connelly1,2
1Brain Research Institute, Florey Neuroscience Institutes, Melbourne, Victoria, Australia, 2Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia

Probabilistic streamlines algorithms aim to provide an estimate of the uncertainty of the path of fibre tracks. In this study we investigate the effect of step size using theory, simulations, and in vivo data. Our results show that the estimate of tracking uncertainty provided by many implementations is strongly dependent on the step size specified by the user (in contrast to the equivalent deterministic streamlines case). This has strong implications for the interpretation of such results, since a small step size will give a grossly misleading representation of the probability of a connection.

2020.   Potential Importance of Secondary Connections in Tractography 
Kyle Taljan1,2, Cameron C McIntyre1, and Ken E Sakaie3
1Lerner Research Institute, Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States, 2Biomedical Engineering, Cleveland State University, Cleveland, OH, United States, 3Imaging Institute, Cleveland Clinic

Pioneering work by Behrens et al demonstrated the potential of high angular resolution diffusion imaging (HARDI) for segmenting brain structures based on their anatomical connectivity. The methodology uses a “winner-takes-all” approach in which classification does not distinguish between slight or large differences in connectivity. However, secondary connections may be important but are masked by the winner-takes-all approach. We demonstrate this point by examining connectivity of the internal capsule (IC), a potentially significant target for deep brain stimulation (DBS) treatment of refractory depression.

2021.   GPGPU-Computing for the cluster analysis of fiber tracts: Replacing a $15000 high end PC with a $500 graphics card 
Christia Ros1, Ralph Tandetzky1, Daniel Güllmar1, and Jürgen R Reichenbach1
1Medical Physics Group, Department of Diagnostic and Interventional Radiology I, Jena University Hospital, Jena, Thuringia, Germany

Whole brain tractography reconstruct a multitude of fiber tracts and the number of tracts in typical data sets easily exceed several thousand up to more than a million fiber tracts. Due to huge amount of raw data that needs to be processed as well as the high computational complexity of cluster analysis (CA) techniques, the application of CA methods is restricted to relatively small data sets. Even though the processing time can be dramatically reduced by employing advanced CA methods, the computational most demanding part of the CA – the calculation of the fiber tracts similarities – remains and limits the application of CA severely. To facilitate the use of cluster analysis for exploratory data analysis and the applicability of cluster analysis for large tractography data sets, we focused on the parallel computation of fiber tract similarities during this study. The potential of Symmetric-Multi-Processing systems (SMPs) and General Purpose Graphics Processing Units (GP-GPU) to speed up the computation of fiber tract similarities was investigated and analyzed. One SMP systems as well as three GPU Systems were employed for the calculation of the Hausdorff similarity metric and the minimum Euclidean Tract distance metric.

2022.   Validation of DTI-tractography-based measures of primary motor area cortical connectivity 
Yurui Gao1,2, Ann S Choe1,2, Xia (Lisa) Li2, Iwona Stepniewska3, and Adam W Anderson1,2
1Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 3Department of Psychology, Vanderbilt University, Nashville, TN, United States

DTI tractography offers the potential to examine cortical-cortical connectivity in the human brain noninvasively, but on what scale can it reflect true anatomical connectivity? Using the neuroanatomic tracer BDA and DTI measurements in the squirrel monkey, we reconstruct, on the surface of the gray-white matter interface, 3D distribution density maps of BDA stained fibers, BDA stained cell bodies, DTI tracotography derived fibers and DTI fiber terminals. We compared these maps of connectivity between the primary motor cortex (M1) and five other frontal cortex regions. The variation of agreement across different projection regions indicates that the FACT algorithm may not reveal cortical-cortical connectivity with uniform sensitivity across the whole brain.

2023.   Gender effect on the asymmetries of brain pathways in the human living brain 
Michel Thiebaut de Schotten1,2, Flavio Dell'Acqua1,3, Stephanie Forkel1,4, and Marco Catani1,3
1Natbrainlab, Institute of Psychiatry, London, United Kingdom, 2Hôpital de la Salpêtrière, CRICM-INSERM UMRS 975, Paris, France, 3Department of Neuroimaging Sciences, Institute of Psychiatry, London, United Kingdom, 4Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, London, United Kingdom

Until the advent of DTI, our knowledge of white matter anatomy was based on a small number of influential 19th and early 20th century post-mortem dissection atlases. These atlases emphasize the average anatomy of representative subjects and a symmetrical anatomical organization of both brain hemispheres is generally taken for granted. Here, we used diffusion tensor imaging (DTI) tractography to address the question of the white matter interhemispheric differences and its interaction with the gender for the major lateralized tracts.

2024.   Along-tract statistics allow for enhanced tractography analysis 
John B Colby1,2, Lindsay Soderberg1, Catherine Lebel1, Ivo D Dinov1,3, Paul M Thompson1,2, and Elizabeth R Sowell1
1Department of Neurology, UCLA, Los Angeles, CA, United States, 2Interdepartmental Program for Biomedical Engineering, UCLA, 3Department of Statistics, UCLA

Despite the large amount of within-tract variability in diffusion imaging indices like FA, the vast majority of neuroscience applications still utilize a traditional tract-averaged approach for their deterministic tractography analyses. Here, we lay out a straightforward workflow for conducting one type of within-tract analysis that attains an economical balance between accessibility and improved modeling ability. We then demonstrate the advantages of this approach over traditional tract-averaged methods by looking at both within-subject and between-group examples.

2025.   Reproducibility of Fiber Bundles from Different Subsampled q-space DSI Data Set 
Getaneh Bayu Tefera1, Yuxiang Zhou1, and Ponnada A Narayana1
1Diagnostic and Interventional Imaging, University of Texas at Houston, Houston, Texas, United States

Acquisition of diffusion spectral imaging data involves long scan times. One way of reducing the scan time is by minimizing the number of q-space points based on its symmetry. In this study we have adapted a tracking procedure and compared the fiber pathways generated from three subsample data sets to the fully sampled q-space data set. For both fornix and cingulum fiber bundles, qualitatively and quantitatively the 198 subsample data set with angles of threshold between 41 and 45 degrees have shown a result that are close to the full data set. This reduces the scan time by 11 minute.

2026.   Assessment of cortico-cortical connectivity in the presence of image artifact 
Kerstin Pannek1,2, Jane Mathias3, Greg Brown4, Jamie Taylor5, and Stephen Rose2
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia, 2Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia,3School of Psychology, University of Adelaide, Adelaide, South Australia, Australia, 4MRI Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia, 5Radiology, Royal Adelaide Hospital, Adelaide, South Australia, Australia

Motion artifacts are often seen in diffusion weighted data of patient participants, but less frequently in data of control participants. We investigated the influence of the presence of motion artifact on cortico-cortical tractography streamline number by artificially introducing corrupted slices into the diffusion datasets. We found that as few as 10 slices affected by motion artifact significantly bias streamline number with no pathology present. This study highlights the importance of removing data affected by motion artifact from analysis.

2027.   Estimation of anatomical connection strength in diffusion MRI tractography by a global message-passing algorithm 
Milos Ivkovic1, and Ashish Raj1
1Radiology, Weill Cornell Medical School, New York, NY, United States

This paper addresses an important problem in difussion weighted MRI tractography -anatomical strength of reconstructed fiber tracts. The developed method incorporates information on the amount of white matter in voxels (small regions of brain) with diffusion data and estimates structural strength of fibers globally, by considering all the fibers and all the voxels simultaneously. We achieve this by using a message-passing optimization procedure, specially tailored for this problem, that operates on a bipartite graph with nodes corresponding to fibers and voxels.

2028.   Human Structural Hand Motor Network Inferred by Probabilistic q-ball Tractography & MEG 
Monica Bucci1, Kelly Westlake2, Bagrat Amirbekian2,3, Srikantan Nagarajan2, and Roland G Henry2,3
1Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, 2Department of Radiology and Biomedical Imaging, UCSF, San Francisco, United States, 3Graduate Group in Bioengineering, UCSF, United States

We performed a neuroimaging assessment with active task-based spatiotemporal data (using MEGI) and structural connectivity of the white matter sensorimotor pathways (using dMRI) in 10 normal controls. We used high angular resolution diffusion imaging in conjunction with probabilistic tractography methods and MEGI to estimate the structural connectivity of white matter tracts within the established sensorimotor network. We mapped the expected human structural hand motor network, including connections previously not characterized in vivo. Our preliminary data indicate that functional MEGI of motor cortex increases our ability to confidently delineate the structural connectivity involved in the motor network through HARDI fiber tracking.

2029.   Normalized edge weight connectivity measure derived from diffusion weighted images: Application to the limbic system. 
Luis Manuel Colon-Perez1, Remington Horesh2, William Triplett3, Mansi Parekh4, Sachin Talathi5, Paul Carney5, and Thomas Mareci3
1Physics, University of Florida, Gainesville, FL, United States, 2Biology, University of Florida, 3Biochemistry and Molecular Biology, University of Florida, 4Neuroscience, University of Florida,5Pediatrics, University of Florida

High angular resolution diffusion weighted imaging (DWI) may provide sufficient information for the creation of brain structural connectivity graphs from fiber track estimation. Our objective in this work was to develop network connectivity measures that are independent of the method used to calculate fiber tracts. We introduce a new normalized edge weight, derived from DWI estimated fiber tracks, which can be used to calculate node connection strengths. To test these measures, we defined a low-resolution network of the limbic system in excised rat brains and calculated these network structural connectivity parameters.

2030.   Comparison of Anatomical Connectivity Metrics 
Ken E Sakaie1, Lael Stone2, Robert Bermel2, Micheal D Phillips1, and Mark J Lowe1
1Imaging Institute, The Cleveland Clinic, Cleveland, OH, United States, 2Mellen Center, The Cleveland Clinic, Cleveland, OH, United States

Tractography-based anatomical connectivity (tAC) can complement the information provided by resting state functional connectivity (rsFC). However, the best way to define anatomical connectivity is unclear. We assess two metrics for tAC by comparison with rsFC in a multiple sclerosis (MS) model for disconnection: tract counts and transverse diffusivity along a pathway. The results suggest that the latter may be a more appropriate metric for comparison with rsFC.

Traditional Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Diffusion Phantoms

Thursday May 12th
Exhibition Hall  13:30 - 15:30

2031.   Physical orientation in the magnetic field affects diffusion measures: a hardware phantom study 
Pim Pullens1,2, Alard Roebroeck1, Matteo Bastiani1, Rainer Goebel1,2, and Kamil Uludag1
1Maastricht Brain Imaging Center, Maastricht University, Maastricht, Netherlands, 2Brain Innovation BV, Maastricht, Netherlands

We investigated the effect of orientation of an anisotropic diffusion phantom on the diffusion MRI signal and derived measures: b0 signal, FA and the first eigen value. Our results show considerable variations in b0, FA and the first eigenvalue in the anisotropic phantom at different orientations of the phantom in the magnetic field. These findings have important implications for diffusion MRI in tissue with varying anisotropic structures such as white matter.

2032.   Noninvasively Diffusion Basis Spectrum Imaging (DBSI): A Phantom Study 
Yong Wang1, Qing Wang2, Peng Sun1, Fang-Cheng Yeh3, Wen-Yih Isaac Tseng4,5, and Sheng-Kwei Song6
1Radiology, Washington University, Saint Louis, MO, United States, 2Mechanical Engineering and Material Sciences, Washington University, Saint Louis, MO, United States, 3Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States, 4Nuclear Engineering, National Taiwan University Medical College, 5Center for Optoelectronic Biomedicine, 6Radiology, Washington University in St. Louis, Saint Louis, MO, United States

Diffusion tensor imaging (DTI) fails dealing with crossing fiber and partial volume effect from surrounding environments (CSF, infiltrating cell, edema). To address the limitation of DTI, a multi-tensor based approach, diffusion basis spectrum imaging (DBSI), was proposed to accurately quantify multiple diffusion components in this study. Mouse trigeminal nerves were fixed and examined with and without gel embedding as the realistic phantom for the evaluation of DBSI. The preliminary findings suggest that DBSI has the potential to correctly determine the angle of crossing fibers as well as the diffusion properties of individual crossing fiber with gel mimicking vasogenic edema.

2033.   Novel Artificial Phantom for Studies of Anisotropic Diffusion in the Model Brain Tissue 
Ezequiel Farrher1, Joachim Kaffanke1, Tony Stoecker1, Farida Grinberg1, and N Jon Shah1,2
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany, 2Department of Neurology, Faculty of Medicine, JARA, RWTH Aachen University, 52074 Aachen, Germany

Diffusion-weighted MRI provides access to fibre pathways and structural characteristics in fibrous tissues such as white matter in the brain. Various factors such as restrictions, anisotropy, and compartmentalization imposed by the cellular microstructure cause a complexity of diffusion behaviour of water in the brain tissue. Therefore, it is important to develop artificial model systems with a reduced complexity in order to enable a better understanding of the relation between the experiments and the microstructure. In this work, we present a novel design for diffusion phantoms made of polyethylene fibres that exhibit sufficiently high anisotropy and a variation of fibre density within the same sample.

2034.   Novel Anisotropic Diffusion MRI Phantom 
Michal E Komlosh1, Evren Ozarslan1, Martin J Lizak2, Ferenc Horkay1, Raisa Z Freidlin3, and Peter J Basser1
1STBB,PPITS,NICHD,NIH, Bethesda, MD, United States, 2NMRF,NINDS,NIH, Bethesda, MD, United States, 3CIT,NIH, Bethesda, MD, United States

A novel anisotropic diffusion MRI phantom was developed, which consists of stacked wafers of glass capillary arrays having different pore diameters. This phantom is intended to provide a “gold standard” to test diffusion MRI methods. We have demonstrated its applicability using DTI and D-PFG MRI experiments.