Hi Sarika,
> I have been using ArtRepair to repair data obtained from
> children.Can this software be used to repair datasets with movement
> which is *slightly* larger than the voxel size itself? If the median
> filter option is used to repair such datasets, can they still be used
> provided they don't give rise to spurious patterns when grouped with
> low-motion data?
I think most people agree that there is no fixed absolute threshold
which can unambiguously be considered to be "too much" (well, I guess
there would be consensus that "leaving the field of view" would be too
much, but oh well :)
The good old "motion not exceeding 1 voxel size" is a rule of thumb that
may or may not be a good idea, as there is also the issue of how fast
this motion occurred. Moving away from the origin slowly and
systematically over the course of an imaging session so that, in the
end, you have moved more than one voxel size is not really that bad, but
jumping around in the scanner and moving 1/2 voxel size in the one
direction at timepoint 10 and 1/2 voxel into the other direction at
timepoint 11 is likely much worse. This is why Paul implemented the
"motion per TR" indicator in his excellent toolbox.
The issue of grouping good and bad data can be ameliorated by including
motion parameters into the first-level design matrix, which, however,
will remove some "true" activation and will reduce power. So I think
that your question cannot easily be answered with a yes or no but rather
a much less satisfying "it depends". Not sure this helps but I hope it
at least gives you some pointers.
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
____________________________________________________
|