Catherine Lebel1, Thomas Benner2, Christian Beaulieu3
1Biomedical Engineering, University of Alberta, Edmonton, AB, Canada; 2Athinoula Martinos Center for Functional & Structural Biomedical Imaging, Harvard University, Boston, MA, United States; 3Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
Simulations suggest that using more than the minimum 6 diffusion-encoding gradient directions provides more robust DTI parameter estimates. Deterministic tractography is often criticized for using only 6 directions despite the lack of experimental evaluation. Diffusion measurements were compared between 6 versus 30 directions in healthy volunteers for 12 major white matter tracts. FA, MD and volume differences were very minimal (1/12 tracts had FA or MD differences, 2/12 had different volumes). These results suggest that 6-direction DTI data with adequate SNR is sufficient for FA, MD, and volume measurements and thus should not be considered inferior for population DTI studies.