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Hi, Here's what I'm trying to do: I resampled fMRI-based ROIs from a group omnibus contrast onto dti scans to investigate the tracts underlying my functional networks. The DTI scans are 60 directions, b=700. I ran BEDPOSTX and PROBTRACKX without errors, but it seems that between equivalent pairs of ROIs (a seed and a target, registered onto all individual DTI space), my waytotal varies between 18.00 and 30,000 depending on subjects. What could cause such a discrepancy, given that the seed and target ROIs seem to have registered fine and are approximately the same size in all subjects? The probtrack command I used for each subject looks like: probtrackx --mode=seedmask -x $subject/dti/DTI_ROIs/lh.TPJ.label.nii -l -c 0.2 -S 2000 --steplength=0.5 -P 5000 --stop=$subject/dti/DTI_ROIs/lh_supPrecentralS.label.nii --forcedir --opd -s $subject/dti/dti.bedpostX/merged -m $subject/dti/dti.bedpostX/nodif_brain_mask --dir=$subject/dti/dti.bedpostX/probtrackx_lhTPJ2lhsupPrecentral --waypoints=$subject/dti/DTI_ROIs/lh_supPrecentralS.label.nii Any help in troubleshooting or ideas welcome! Thanks, Cherif