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Hi, I don't think that tbss_1_preproc (at least the version with FSL4) can create new negative values, but it does multiply the original values to make them a lot larger, so maybe you started with VERY slightly negative values that are sufficiently small that you didn't notice them, and after the rescaling, they were more obvious? It's probably not a problem anyway if they are around the edge of the brain? Cheers, Steve. On 25 Jan 2008, at 10:36, Agnieszka Burzynska wrote: > Dear all, I resend this message, because I still do not know what is > wrong: > > > Hi, > I applied tbss_1_preproc to my S0 images. In origdata, none of them > had > values below 0, however, after the scaling in the FAi folder there > are 2 > cases, in which I see negative values around the brainstem. > > How did this happen and what should I do? I thought it is just a > simple > mulitiplication by a given number (here by 10). > > Thank you and best wishes, > Aga > --------------------------------------------------------------------------- Stephen M. Smith, Professor of Biomedical Engineering Associate Director, Oxford University FMRIB Centre FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) [log in to unmask] http://www.fmrib.ox.ac.uk/~steve ---------------------------------------------------------------------------