Hi Gabor,
> I also read the Wilcke 2012 Neuroimage paper on the motion
> fingerprint and found the Pythagorean Displacement and Motion
> Regressors script, but I'm looking for something in which I could
> enter the coordinates of the origin, the coordinates of a "point" on
> the sphere, some translation and rotations parameters, with the exact
> displacement as an output. My maths is limited, I'm afraid, and maybe
> someone already has a script like that. Sorry to bother you!
I have not done this but the functions in my script could pretty easily
be generalized to achieve what you want. It is basically calculating the
Euclidian norm in 3D. People have done that in the past, but given the
number of voxels it may take some time if you do not vectorize the
calculations nicely.
I am not sure you want to continue thinking of a sphere, though, as you
really are looking for the distance of every single voxel from the
origin, which as you correctly state, is only relevant for the
rotational component. The sphere is a helpful construct if you want to
have some generalizable metric without calculating it for every voxel in
the brain; the 65 mm used in the art repair toolbox are a pragmatic
approximation (and a good one at that :), as is the 50 mm used by
others. Translations are less of a problem here as they induce global,
i.e. constant displacements over the whole volume, irrespective of
distances.
Cheers,
Marko
--
____________________________________________________
PD Dr. med. Marko Wilke
Facharzt für Kinder- und Jugendmedizin
Leiter, Experimentelle Pädiatrische Neurobildgebung
Universitäts-Kinderklinik
Abt. III (Neuropädiatrie)
Marko Wilke, MD, PhD
Pediatrician
Head, Experimental Pediatric Neuroimaging
University Children's Hospital
Dept. III (Pediatric Neurology)
Hoppe-Seyler-Str. 1
D - 72076 Tübingen, Germany
Tel. +49 7071 29-83416
Fax +49 7071 29-5473
[log in to unmask]
http://www.medizin.uni-tuebingen.de/kinder/epn/
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