Hi,
the object of this message is to report a possible SIENA misfunction when
applied on coronal brains to warn possible users.
In order to test SIENA we have adquiered three 3d's of 5 healthy volunteers,
two in the same session another one, one or two weeks later.
The results of SIENA on some of those studies was quite disappointing since
variations over 2% were reported.
After rejecting some hypotesis related to image format, we have checked
SIENA carefully step by sted and we have noticed that, in some cases,
talairach masking fails because registration with talairach template is
wrong (the brain is in 180º respect to tempalte). That could happen when
orbits anb soft tissue under skull basis is not removed enterely by BET so
the brain to register is practically symmetric, in terms of volume, respect
X-Z plain.
The problem is easely removed by orienting coronal images in axial order
(with avwswapdim, for instance) before running SIENA and keeping search
angles below 90 degrees in flirt.
Yours,
Carles Falcon
University of Barcelona
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