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Hiya - There are no constraints in dtifit to ensure positive eigenvalues in the diffusion tensor hence you can get FA >1 . The number of voxels in which you see this, will depend on the noise in your data.. Cheers T ------------------------------------------------------------------------------- Tim Behrens Centre for Functional MRI of the Brain The John Radcliffe Hospital Headley Way Oxford OX3 9DU Oxford University Work 01865 222782 Mobile 07980 884537 ------------------------------------------------------------------------------- On Sun, 31 Oct 2004, Ruiwang Huang wrote: > Dear Tim > > Re-checking the bvecs, I found one gradient direction was not > normalized. After correcting the bvecs, the DTIFIt is ok now. > > But FA values for some pixels seems larger than one? > > Thanks again for your help > > rhuang > > On Sunday 31 October 2004 18:17, you wrote: > > Hi there - > > We are aware of this problem. These "errors" are not really errors - they > > are the standard output of eddy_correct. They are just being reported as > > errors by the GUI - we will fix this for the next release. For now, just > > ignore them - The output files of eddy_correct will be fine. > > > > Cheers > > > > T > > > > --------------------------------------------------------------------------- > >---- Tim Behrens > > Centre for Functional MRI of the Brain > > The John Radcliffe Hospital > > Headley Way Oxford OX3 9DU > > Oxford University > > Work 01865 222782 > > Mobile 07980 884537 > > --------------------------------------------------------------------------- > >---- > > > > On Sun, 31 Oct 2004, R Huang wrote: > > > Hello > > > > > > I have got error message when I running eddy current corrections. > > > > > > The diffusion-weighted data were converted > > > into 4D analsyse format using mricro, 1+12 volumes > > > with one b=0 and 12b=1000. I tried 3 times > > > running 'eddy-current correction'. Every time, > > > a popup window reported the following error message: > > > > > > Errors: Writing vol0000 > > > Writing vol0001 > > > Writing vol0002 > > > Writing vol0003 > > > > > > ... > > > Writing vol0012 > > > > > > Two files, (data.nii.gz) and (gata.ecclog) > > > were created. > > > > > > > > > Any suggestions for using 'eddy current correction'? > > > > > > Thanks in advance > > > > > > rhuang >