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Abstract #1562

In Vivo Mapping of Relative Axonal Diameter of Human Corpus Callosum Using Q-Planar Magnetic Resonance Imaging

Jun-Cheng Weng1,2, Wen-Yih Iascc Tseng1,3

1Center for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan; 2Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan; 3Department 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.