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Dear FSL experts, I noticed that the latest release of FSL comes with a new program for eddy current corrections (eddy) and another for susceptibility induced distortions (topup). I wanted to perform TBSS analysis on a 100 subjects dataset but since I'm just starting in the neuroimaging field, I'm running into some questions. Our acquisition protocol has 1 b=0, 30 b=1000 images (siemens) and 1 repetition, A>>P phase encoding direction, echo spacing=0.8 ms and acquisition matrix=128x128. Since all our acquisitions have the same polarity of the phase-encode blips, I can't use topup, can I? My second question concerns the usage of eddy or eddy_correct. Wich would be better to correct eddy current induced distortions? I tried both but the results seem a bit different. eddy_correct performs some kind of smoothing and the intensities are also quite different. Is this normal? In the subject I've been testing, both tools seem to have missed some major distortions/movements. How can I improve this? By the way, for eddy, my acqp file has 62 lines like this: 0 1 0 0.102 0 1 0 0.102 0 1 0 0.102 0 1 0 0.102 ... and the index file has one line with 62 1's. Thanks for your help. Best Regards, Paulo Marques.