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
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