TRADITIONAL POSTER - ismrm

Poster Sessions
correlation. Positive correlations of FA with task performance were also seen in white matter adjoining prefrontal and occipital areas for some tasks.
Results support a dual-stream (dorsal and ventral) model of auditory comprehension.
1559. The Effects of HIV and Hepatitis C Infection on Diffusion Tensor Imaging Measures
Huiling Peng 1 , Jewell Thomas 1 , Joseph Mettenburg 2 , Avi Snyder 1 , Tammie Benzinger 2 , David Clifford 1 ,
Robert Paul 3 , Beau Ances 4
1 Neurology, Washington University in St. Louis, St. Louis, MO, United States; 2 Radiology, Washington University in St. Louis, St.
Louis, MO, United States; 3 Psychology, University of Missouri St. Louis, St. Louis, MO, United States; 4 Neurology, Washington
University in St. Louis, St. Louis, MO , United States
Hepatitis C virus (HCV) is a frequent co-infection with HIV. Both affect brain function raising the possibility of synergistic interactions. We investigate the
relationship between neurological function and white matter integrity using DTI in mono (HIV+) (n=15) vs. co-infected (HIV+/HCV+) (n=13) participants.
Regions-of-interest corresponding to the cingulum and genu of the corpus callosum were selected. Co-infected participants were more impaired than monoinfected
HIV+ subjects on neuropsychological testing but no significant differences were seen for DTI values. The combination of HIV and HCV coinfection
affected measures within the brief neurocognitive screening but not structural neuroimaging measures.
1560. Fractional Anisotropy in Various White and Gray Matter Regions in Adulthood. Dependence on Age
and Comparison of Two DTI Sequences
Jiøí Keller 1,2 , Aaron Michael Rulseh 1 , Michael Syka 1 , Josef Vymazal 1
1 Nemocnice Na Homolce, Prague, Czech Republic; 2 3rd Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
We measured FA in white and gray matter regions using two different DTI sequences (12 and 30 directions) in 23 healthy adult volunteers A number of
white and gray matter regions were selected including basal ganglia and corpus callosum. The gray matter results were correlated with expected iron
concentration. We detected a significant correlation between age and FA for both DTI sequences in the rostrum of the corpus callosum, anterior internal
capsule and the pyramidal tract. A significant difference in FA between DTI sequences was detected in the basal ganglia where correlation between iron
amount and FA was found.
Diffusion: White Matter Modeling
Hall B Tuesday 13:30-15:30
1561. Optimized Diffusion MRI Protocols for Estimating Axon Diameter with Known Fibre Orientation
Torben Schneider 1 , Henrik Lundell 2,3 , Tim B. Dyrby 2 , Daniel C. Alexander 4 , Claudia Angela Michela
Wheeler-Kingshott 1
1 NMR Unit, Department of Neuroinflammation, UCL Institute of Neurology, London, United Kingdom; 2 Danish Research Centre for
Magnetic Resonance, Copenhagen University Hospital Hvidovre, Copenhagen, Denmark; 3 Department of Excercise and Sport
Sciences, University of Copenhagen, Copenhagen, Denmark; 4 Centre for Medical Image Computing, Department of Computer
Science, UCL, London, United Kingdom
We present a method that optimizes diffusion MRI protocols to be sensitive to axon diameter and axonal density in white matter structures with known
single fibre direction. Computer simulations clearly show that our method improves accuracy of measurements compared to protocols independent of fibre
orientation, especially when signal-to-noise-ratio is low. Furthemore, we generate indices of axon diameter and density from a fixated monkey spinal cord
and are able to discriminate anatomically different white matter regions.
1562. In Vivo Mapping of Relative Axonal Diameter of Human Corpus Callosum Using Q-Planar Magnetic
Resonance Imaging
Jun-Cheng Weng 1,2 , Wen-Yih Iascc Tseng 1,3
1 Center for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan; 2 Department of Medical
Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan; 3 Department 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. In view of the topographically-specific relation between callosal regions and the connected cortical regions, several partitioning approaches have
been proposed to allow separate analysis of different callosal sectors. Vertical partitions are commonly used which subdivide the CC into five regions based
on fractions of its maximal anterior-posterior length as proposed by Wiltelson. These 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. This study proposed a novel technique, q-planar imaging (QPI) to map the relative axonal diameters of CC in normal human brain. It was based
on the Fourier relationship between probability density function (PDF) of the water molecular diffusion and sampled diffusion attenuated images in the
space of spatial modulation, dubbed q-space. It provided MR images in which physical parameters of water diffusion such as the mean displacement and the
probability at zero displacement of water molecules were used as image contrast. Our results demonstrated that QPI produced reasonable distribution of
relative axonal diameters of CC in normal human brain.
1563. The Extracellular Diffusion Weighted Signal Predicts Axon Diameter Distribution Parameters
Hubert Martinus Fonteijn 1 , Matt G. Hall 1 , Daniel C. Alexander 1
1 Computer Science, Centre for Medical Image Computing, London, United Kingdom
The estimation of axon diameter distribution parameters remains a big challenge for diffusion-weighted imaging. Generally, only intracellular diffusion is
considered to be influenced by axon diameter. Extracellular diffusion on the other hand is considered to be approximately Gaussian in the long diffusion
time limit and to be independent of axon diameter. In this abstract, we perform Monte Carlo simulations of diffusion in the extracellular compartment for a