Hi - yes, this is quite straightforward as long as you can trust that
the scanner calibration hasn't changed between the timepoints. Looking
for longitudinal change with SIENA should be more sensitive than
running two independent analyses (e.g. with SIENAX) and comparing
them, as it is explicitly tuned to maximise accuracy on longitudinal
analyses. You can change the calls to pairreg in $FSLDIR/bin/
siena_flirt to just call flirt with -dof 6 instead and ignore the
skulls. Let us know if you need more details on this approach.
Cheers, Steve.
On 12 Nov 2007, at 03:16, Linda Campbell wrote:
> Hi there,
> I am looking for software to analyze longitudinal structural MRI
> data acquired in the same subjects at
> two time periods (3 years apart). I have been recommended to look at
> Siena. However, reading the
> explanations of Siena I noticed that it uses the skull size (T1 and
> T2) during registration. Since my
> sample contains adolescents three years might have made a difference
> in their actual skull size and
> might therefore not be appropriate. Would anyone be able to advise
> me if I still can use Siena
> (perhaps not using skull size) and obtain reliaible data or can
> anyone recommend any alternate
> software. I would like to do a within group comparison and a between
> group comparison, ie I have
> both patient and control data from both time points using the same
> scanner and identical
> parameters.
>
> I would be most grateful for your advice
>
> Linda
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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
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