Traditional Posters: Diffusion & Perfusion - ismrm

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1631. On the Accuracy of Diffusion Models for Fast Low-Angle Short-TR SSFP-Echo (FLASH-DW SSFP) Oliver Bieri 1 , Carl Ganter 2 , Klaus Scheffler 1 1 Radiological Physics, University of Basel Hospital, Basel, Switzerland; 2 Department of Diagnostic Radiology, Technical University Munich, Munich, Germany Several models have been developed for the description of diffusion in steady-state free precession (SSFP) sequences. For clinical practice, high SNR and short acquisition times are desirable with DW-SSFP. In this work, a new approach for quantitative diffusion imaging is proposed using a fast low-angle short-TR (FLASH) diffusion-weighted (DW) SSFP sequence. The accuracy of diffusion models is assed in-vitro and the feasibility of high resolution quantitative diffusion mapping is demonstrated in-vivo for human articular cartilage. 1632. Simultaneously Measuring Axonal Diameter Distribution and Direction of Rat Brain Using Q-Space Diffusion Tensor Magnetic Resonance Imaging Jun-Cheng Weng 1 1 Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan Fundamental relationships between diffusion tensor imaging (DTI) and q-space imaging can be derived which establish conditions when these two complementary MR methods are equivalent. When the 3D displacement distribution is measured by q-space imaging with large displacement and small q vector, the result is similar to 3D Gaussian assumed in DTI. Combing displacement information from q-space imaging and fiber direction from DTI, distribution of axonal diameters and directions could be derived at the same time. The study proposed a novel technique, q-space diffusion tensor imaging (qDTI), combined with two image reconstruction methods based on the assumption to simultaneously map axonal diameter distribution and direction of rat brain. One was tensor-based method. The 3D Gaussian displacement distribution could be obtained directly by the displacement tensor. The other was displacement projection method. The effective axonal diameter was defined as the average of several displacements projected to the direction of the fiber section. They provided MR images in which physical parameters of water diffusion such as the mean displacement and maximum diffusivity of water molecules were used as image contrast. Our results demonstrated that two qDTI methods both produced reasonable distribution of effective axonal diameters and directions in rat brain. 1633. Measuring Isotropic Diffusion with Rotating Diffusion Gradients Irvin Teh 1,2 , Xavier Golay 1,3 , David Larkman 2 1 Lab of Molecular Imaging, Singapore Bioimaging Consortium, Singapore, Singapore; 2 Imaging Sciences Department, Imperial College London, London, United Kingdom; 3 Institute of Neurology, University College London, London, United Kingdom A diffusion-weighted fast spin echo periodically rotated overlapping parallel lines with enhanced reconstruction (DW-FSE- PROPELLER) sequence was combined with a multiple axis Stejskal-Tanner diffusion weighting scheme that rotated and alternated across blades. This reduced the number of DW acquisitions needed to acquire the mean apparent diffusion coefficient from three to one, halving the total acquisition time. This motion and distortion robust method was tested in the in-vivo mouse brain and compared to previously proposed rotating DW strategies. 1634. Novel Diffusion-Diffraction Patterns in Double-PFG NMR Afford Accurate Microstructural Information in Size Distribution Phantoms Noam Shemesh 1 , Evren Özarslan 2 , Peter J. Basser 2 , Yoram Cohen 1 1 School of Chemistry, Tel Aviv University, Tel Aviv, Israel; 2 Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States Diffusion-diffraction minima, which convey important microstructural information, vanish from the signal decay in single-pulsedfield-gradient (s-PFG) experiments conducted on specimens characterized by size distributions. The double-PFG (d-PFG) methodology, an extension of s-PFG, was recently predicted to exhibit zero-crossings (analogous to s-PFG diffusion-diffraction minima) that would persist even when the specimen is characterized by a broad size-distribution. We therefore studied the signal decay in both s- and d-PFG in size-distribution phantoms consisting of water-filled microcapillaries of various sizes. We find that the diffusion-diffraction minima in s-PFG indeed vanish, while the zero-crossings in d-PFG indeed persist, allowing to extract important microstructural information. 1635. Metrics for Distinguishing Axon Disorder from Demyelination in Regions of Decreased Fractional Anisotropy Christine Marie Zwart 1 , David H. Frakes 1,2 , Josef P. Debbins 3 1 School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States; 2 School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ, United States; 3 Keller Center for Imaging Innovation, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States Many diseases of the white matter are accompanied by an observable decrease in fractional anisotropy as measured with Diffusion Tensor Imaging. This decrease can be attributable to a general increase in extracellular space or an absence of collinearity with respect to axon orientations. For studying the progression of diseases such as multiple sclerosis (demyelination) and epilepsy (disorder) we have developed a correlation based metric that distinguishes between these processes.
Diffusion Artifacts & Reproducibility Hall B Thursday 13:30-15:30 1636. Enhanced ICBM Diffusion Tensor Template of the Human Brain Shengwei Zhang 1 , Huiling Peng 1 , Robert Dawe 1 , Konstantinos Arfanakis 1 1 Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States The purpose of this study was to develop a diffusion tensor (DT) template that is more representative of the microstructure of the human brain, and more accurately matches ICBM space than existing templates. This was achieved by normalizing 67 DT datasets with minimal artifacts using high-dimensional non-linear registration. The normalization accuracy achieved for the 67 datasets was evaluated. The properties of the resulting template were compared to those of the current state of the art. The new template was shown to be more representative of single-subject human brain diffusion characteristics, and more accurately matches ICBM space than previously published templates. 1637. Variability of Diffusion Tensor Characteristics in Human Brain Templates: Effect of the Number of Subjects Used for the Development of the Templates Shengwei Zhang 1 , John D. Carew 2 , Konstantinos Arfanakis 1 1 Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States; 2 Dickson Institute for Health Studies, Carolinas Healthcare System, Charlotte, NC, United States Development of a diffusion tensor (DT) brain template that is not biased by the properties of a single subject requires averaging of the DT information from multiple subjects. The purpose of this study was to investigate the variability of DT characteristics in templates developed using different numbers of subjects. The variability of template DT properties decreased as the number of subjects increased. Furthermore, DT templates constructed from 30 subjects demonstrated high stability in tensor properties of voxels with FA=(0.6,1]. When considering voxels with FA=(0.2-1], more than 60 subjects were necessary in order to achieve sufficiently high stability in tensor properties. 1638. Assessing the Accuracy of Spatial Normalization of Diffusion Tensor Imaging Data in the Presence of Image Artifacts Anton Orlichenko 1 , Robert J. Dawe 2 , Huiling Peng 2 , Konstantinos Arfanakis 2 1 Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, IL, United States; 2 Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States Use of diffusion tensor imaging (DTI) data with minimal image artifacts may enhance the accuracy of inter-subject spatial normalization. This effect was investigated by comparing the coherence of primary eigenvectors after normalizing separately a) data with minimal artifacts, and b) data with typical field inhomogeneity-related artifacts, acquired on the same subjects. Tensors derived from data with minimal artifacts were found to have higher primary eigenvector coherence in white matter, compared to tensors derived from data contaminated with image artifacts. These results demonstrate that achieving the most accurate spatial normalization of DTI data requires minimization of image artifacts. 1639. The Effect of Template Selection on Diffusion Tensor Imaging Voxel Based Analysis Results Wim Van Hecke 1,2 , Caroline Sage 2 , Jan Sijbers 3 , Stefan Sunaert 2 , Paul M. Parizel 1 1 Department of Radiology, Antwerp University Hospital, Antwerp, Belgium; 2 Department of Radiology, Leuven University Hospital, Leuven, Belgium; 3 VisionLab, University of Antwerp, Antwerp, Belgium In this work, we examined the effect of the template or atlas selection on the voxel based analysis results of diffusion tensor images. To this end, simulated data sets were used. 1640. Artificial Phantoms for Studies of Anisotropic Diffusion in the Brain Ezequiel Alejandro Farrher 1 , Erasmo Batta 1 , Yuliya Kupriyanova 1 , Oleg Posnansky 1 , Farida Grinberg 1 , N Jon Shah 1,2 1 Medical Imaging Physics, Institute of Neuroscience and Medicine 4 , Forschungszentrum Juelich GmbH, Juelich, Germany; 2 Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany Diffusion Tensor Imaging (DTI) provides access to fibre pathways and structural integrity in the white matter and finds important applications in the clinical practice. Many advanced techniques have been recently suggested for the reconstruction of the diffusion orientation distribution function with an enhanced angular resolution (HARDI). Examination of the sensitivity of the proposed diffusion indices to the underlying microstructure requires a development of the model systems with deliberately tailored properties. The aim of this work was to construct artificial phantoms that are characteristic of sufficiently strong diffusion anisotropy and are suitable for the validation of the analytical models. 1641. Evaluating the Uncertainty of DTI Parameters at 1.5, 3.0 and 7.0 Tesla Daniel Louis Polders 1 , Alexander Leemans 2 , Johannes M. Hoogduin 1,3 , Jeroen Hendrikse 1 , Manus Donahue 4 , Peter R. Luijten 1 1 Radiology, University Medical Center Utrecht, Utrecht, Netherlands; 2 Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands; 3 Rudolf Magnus Institute of Neuroscience, University Medical
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Traditional Posters: Diffusion & Perfusion - ismrm

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