The art_global function tries to automatically detect bad image volumes according
to the criteria of unusual global signal, or large scan-to-scan motion,
or large total motion from baseline. Use it after realignment, because
it uses the rp.txt file. When used just before estimation, it is
easier to compare estimation results with and without it, to see if
it helps on a particular data set.
The clip function marks a volume for repair if the total motion from
baseline is > 3mm, which may be useful for short duration artifacts when
no motion regressors are used in the design matrix.
Handling artifacts is tricky, and the best method may not yet be known.
Consequently, the admittedly limited "manual" on the website does not give
strong guidance on the best choices of parameters.
Note there are alternative (and better documented!) approaches to the artifact
problem, including removing volumes by inspection (Luo and Nichols, 2003)
or by the art_detect utility (Whitfield-Gabrieli), adding scan null regressors
(Lemieux, 2007), and adaptive weighting of the scans (RobustWLS toolbox).
Also, motion regressors (e.g. Lund, 2005) are helpful for removing
the effect of many artifacts.
-Paul
----- Original Message -----
From: "Sanne Boesveldt" <[log in to unmask]>
To: [log in to unmask]
Sent: Wednesday, May 13, 2009 7:15:12 AM GMT -08:00 US/Canada Pacific
Subject: [SPM] Art_Repair, Art_Global
Dear all
I am trying to use art_repair/art_global in SPM5, but what exactly does
Art-global do? And when do I use it, after realignment, or after
normalization and smoothing? And what is the function of the 'clip' button
in the program?
The only manual I could find are the short .txt and .pdf files from
http://cibsr.stanford.edu/tools/ArtRepair/ArtRepair.htm, but those don't
give that much info unfortunately. Is there a better manual out there?
Thanks!
Sanne Boesveldt, PhD
Postdoctoral Fellow
Monell Chemical Senses Center
3500 Market Street
Philadelphia, PA 19104
USA
+1 267 519 4688
[log in to unmask]
--
Paul K. Mazaika, PhD.
Center for Interdisciplinary Brain Sciences Research
Stanford University School of Medicine
Office: (650)724-6646 Cell: (650)799-8319
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