 |
 |
Hi everybody, On 5 Mar 2007, at 13:52, Tim Behrens wrote: >> I am working with your wonderful diffusion software package and I >> have one >> question concerning the sample data for the Fdt tutorial, >> especially about >> the direction scheme. Looking at the given bvecs file I noticed >> that the >> gradient vectors are not unit vectors; they all sum up to >> approximately >> 1.019. Could you explain me why? > > No reason - In early versions of FDT this would matter, and would > give you an underestimate of the diffusivity (leaving all other > parameters unchanged). In the current version, I believe they are > normalised internally in FDT code, so it should make no difference > at all. Just to clarify, does this mean that I do not need to normalise the bvecs for my data, that I can instead just plug in the values I got from my scanner manufacturer and FDT will perform the normalisation itself? Thanks in advance, -- Dr Colm G. Connolly School of Psychology and Institute of Neuroscience The Lloyd Building University of Dublin Trinity College, Dublin 2, Éire Tel: +353-1-896-8475 Fax: +353-1-671-3183