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