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Hi, Yes, a scaling of about 5,000,000 is about right - as long as you apply the same scaling to all MD images (which is what the script will do) then that's fine - and what you want to interpret any final results you can just divide by 5,000,000 to get back to the original MD units that your data had. Cheers, Steve. On 13 May 2008, at 21:04, Dana Perantie wrote: > Dear FSL list, > I have a region of interest from TBSS analyses of FA images and > would like > to find the mean diffusivity (MD) values for the same region. To > get the > MD in the same space, I am running tbss_1_preproc (after re-naming > them > the same as the FA), and then tbss_non_FA. tbss_1_preproc requires a > scaling argument -- my understanding is that the goal is to get the > range > on the order of 0 to 10,000. Here are a few examples ranges of our MD > images: > .00046336 to .0021267 > .00063775 to .0022076 > .00058721 to .0018281 > So, should I be using something like 5,000,000 for scaling? Is it a > little arbitrary -- what's the effect of 5,000,000 versus 4,800,000 in > this situation? What will be the meaning of the values after this re- > scaling? Will the values relate in any way to the usual units for > diffusivity (something like x10^3 mm2/s)? > > Thank you, > Dana > --------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------