This work was supported in part by awards from the National Science Foundation. The authors would like to thank Andrew L. Alexander, Assistant Research Professor in the Department of Radiology, University of Utah School of Medicine, for involving them in his research on diffusion tensor imaging and for providing them with datasets. The authors are also grateful for the work of Eric Lundberg in processing the raw data, and for the helpful detailed comments from Chris Johnson, Peter Shirley, Sean Heffernan, Matthew Bane, and the anonymous reviewers.