Farida Grinberg¹, Ezequiel Farrher¹, Joachim Kaffanke¹, Ana-Maria Oros-Peusquens¹, and N. Jon Shah^1,2
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.

Silvia Capuani^1,2, Marco Palombo¹, Silvia De Santis¹, and Andrea Gabrielli^3
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.

Marco Palombo¹, Silvia De Santis¹, and Silvia Capuani^1,2
1Physics Department, Sapienza University of Rome, Rome, Italy, ²IPCF UOS Roma, CNR, Rome, Italy

 parameter arising from Anomalous diffusion stretched-exponential method has been used to investigate tissues, showing the ability of  maps to discriminate between different brain structures on the basis of their microstructural complexity. Here, we measure  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  to discriminate between structures characterized by different geometrical dimensions. Experimental data showed that the higher the internal gradient, the lower the  value.

Sharon Peled^1
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.

Alexander Ruh¹, Philipp Emerich¹, Dmitry S Novikov², and Valerij G Kiselev^1
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.

Dmitry S Novikov¹, Els Fieremans¹, Jens H. Jensen¹, and Joseph A Helpern^2
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.

Farida Grinberg¹, Ezequiel Farrher¹, Luisa Ciobanu², Françoise Geffroy², and N. Jon Shah^1,3
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.

Ali Tabesh¹, Jens H. Jensen¹, Els Fieremans¹, and Joseph A. Helpern^1,2
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.

Evren Ozarslan^1,2, and Peter Joel Basser^1
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.

Yohan van de Looij^1,2, Nicolas Kunz^1,2, Petra S Hüppi¹, Rolf Gruetter^2,3, and Stéphane V Sizonenko^1
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.

Sharon Peled¹, and Carl-Fredrik Westin^1
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.

Jun-Cheng Weng^1,2, and Wen-Yih Isaac Tseng^3,4
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.

Sune Nørhøj Jespersen¹, and Niels Buhl^1,2
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.

Blake Walters¹, Greg Duane², and Jae Kim^2
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.

Noam Shemesh¹, and Yoram Cohen^1
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.

Lingchih Lin¹, and Jianhui Zhong^1,2
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.

Pamela Guevara^1,2, Delphine Duclap^1,2, Linda Marrakchi-Kacem^1,2, Denis Rivière^1,2, Yann Cointepas^1,2, Cyril Poupon^1,2, and Jean-François Mangin^1,2
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.

J-Donald Tournier^1,2, Fernando Calamante^1,2, and Alan Connelly^1,2
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.

Kyle Taljan^1,2, Cameron C McIntyre¹, and Ken E Sakaie^3
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.

Christia Ros¹, Ralph Tandetzky¹, Daniel Güllmar¹, and Jürgen R Reichenbach^1
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.

Yurui Gao^1,2, Ann S Choe^1,2, Xia (Lisa) Li², Iwona Stepniewska³, and Adam W Anderson^1,2
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.

Michel Thiebaut de Schotten^1,2, Flavio Dell'Acqua^1,3, Stephanie Forkel^1,4, and Marco Catani^1,3
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.

John B Colby^1,2, Lindsay Soderberg¹, Catherine Lebel¹, Ivo D Dinov^1,3, Paul M Thompson^1,2, and Elizabeth R Sowell^1
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.

Getaneh Bayu Tefera¹, Yuxiang Zhou¹, and Ponnada A Narayana^1
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.

Kerstin Pannek^1,2, Jane Mathias³, Greg Brown⁴, Jamie Taylor⁵, and Stephen Rose^2
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.

Milos Ivkovic¹, and Ashish Raj^1
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.

Monica Bucci¹, Kelly Westlake², Bagrat Amirbekian^2,3, Srikantan Nagarajan², and Roland G Henry^2,3
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.

Luis Manuel Colon-Perez¹, Remington Horesh², William Triplett³, Mansi Parekh⁴, Sachin Talathi⁵, Paul Carney⁵, and Thomas Mareci^3
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.

Ken E Sakaie¹, Lael Stone², Robert Bermel², Micheal D Phillips¹, and Mark J Lowe^1
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.

Pim Pullens^1,2, Alard Roebroeck¹, Matteo Bastiani¹, Rainer Goebel^1,2, and Kamil Uludag^1
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.

Yong Wang¹, Qing Wang², Peng Sun¹, Fang-Cheng Yeh³, Wen-Yih Isaac Tseng^4,5, and Sheng-Kwei Song^6
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.

Ezequiel Farrher¹, Joachim Kaffanke¹, Tony Stoecker¹, Farida Grinberg¹, and N Jon Shah^1,2
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.

Michal E Komlosh¹, Evren Ozarslan¹, Martin J Lizak², Ferenc Horkay¹, Raisa Z Freidlin³, and Peter J Basser^1
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.