Hi,
On 13 Dec 2010, at 16:54, Ivan Maximov wrote:
> Sorry for the newbie's question but what the b-values range is useful and has a sense
> in DTI tool? I mean can I apply FDT to [0 1000] and for [0 1000 2500] b-values? Or even to
> [0 1000 3000 5000 7000]?
Supposing that you are interested in the orientations (hence the high b values), bedpostx does not currently handle multiple b-value data. You can however use any single-shell HARDI protocol with b=1000-3000 being a reasonable range (going higher than that will possibly induce many noise artifacts). I would take a look at (Behrens et al, NeuroImage, 2007, 144-155) to get a feeling for the effect of b value on resolving crossing propulations.
> How is FDT evaluating rotational invariants (MD, FA etc)?
> How is it evaluating a fibretracking?
For fitting a tensor, a linear least squares scheme is employed. For estimating fibre orientation distributions used in tractography, a Bayesian MCMC scheme is used. You can take a look at FDT's documentation for an overview of the tool and the relevant theory.
http://www.fmrib.ox.ac.uk/fsl/fdt/index.html
>
> Thanks in adnvace
> Ivan
>
Cheers,
Stam
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