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Abstract #2637

The effect of diffusion in the extracellular space on double-PFG measurements of axon size: Insights from Monte-Carlo simulations

Gregory T Baxter 1 , Vitaly Galinsky 1 , Evren Ozarslan 2 , Peter J Basser 3 , and Lawrence R Frank 1,4

1 Center for Scientific Computation in Imaging, Dept. of Radiology, University of California, San Diego, CA, United States, 2 Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, 3 Section on Tissue Biophysics and Biomimetics, PPITS, NICHD, National Institutes of Health, Bethesda, MD, United States, 4 Center for Functional MRI, Dept of Radiology, University of California, San Diego, CA, United States

We present Monte-Carlo simulations of diffusion within hexagonally packed arrays of cylinders mimicking the white-matter, and report the signal behavior for double-PFG experiments with zero mixing times. We investigate the accuracy of the axonal diameter estimates when a bi-compartmental model that assumes Gaussian diffusion outside the cells is employed. Despite the substantially underestimated bulk diffusivity values, cell diameter and volume fraction estimates are both adequately captured by such a bi-compartmental model. Some underestimation of cell diameters is expected only for tightly packed configurations.

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