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Abstract #0358

How Many Diffusion Gradient Directions Are Required for HARDI?

J-Donald Tournier1,2, Fernando Calamante1,2, Alan Connelly1,2

1Brain Research Institute, Florey Neuroscience Institutes (Austin), Melbourne, Victoria, Australia; 2Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia

While the number of DW directions required for DTI has been extensively studied, the equivalent studies have not been performed for HARDI. However, due to the large number of directions inherent in HARDI acquisitions, this information is crucial to keep scan times practical. In this study, we use sampling theory to determine the minimum number of DW directions required for HARDI experiments, independent of the particular algorithm used to estimate fibre orientations. Results obtained at b = 3000s/mm2 indicate that 45 directions are required to adequately characterize the angular frequency information contained in the DW signal.