Art_global can be used at any point in preprocessing, and it needs the rp.txt file of realignment parameters to find the image volumes with large scan-to-scan to motion.
Art_slice was designed to suppress a particular kind of scanner noise, which hopefully is not present in your data. Head motion may cause spin history artifacts on a few slices, but the resulting image distortion often corrupts an entire volume after realignment. So, art_global is more effective to suppress artifacts from rapid head motions because it repairs whole volumes.
The interpolation method reduces the residual variance and may reduce the sensitivity of a contrast. Deweighting attempts to correct for these two types of errors, but generally these errors are small anyway. It is easier to do an analysis without it.
- Paul
-------- Original Message --------
Subject: [SPM] ArtRepair
Date: Fri, 21 Sep 2012 13:44:07 +0000
From: Krisa, Laura <[log in to unmask]>
Reply-To: Krisa, Laura <[log in to unmask]>
To: [log in to unmask]
Dear SPM'ers,
I am having a similar problem to Pieter with movement however, I do
not want to eliminate the entire block. I have been trying to use
ArtRepair to correct for motion but I have not found any concrete
instructions about how to use the program. I have the instructions form
the website along with the power points and other presentations.
However, I am unsure about what to use and when. Does anyone have
instructions other than what is on the website?
Some questions I have are..
I know Art Slice should only be used on noisy, raw images but if this
does not take away all the motion can I also use Art Global on the same
block of data?
When using Art_ Global it states that the images should be realigned.
Can they also be smoothed and normalized or should these steps be
completed after using Art_Global?
If you select that you have realigned files for Art_Global the first box
asks you to select the files however I am not sure what to select for
the second box when it ask to select movement parameters. Is this the
rp file?
Once I get the Art_Global graphs and I repair the files do I then
deweight the images? I will be using motion regressors. Is it best not
to adjust the threshold?
Any information anyone can provide will be greatly appreciated.
Thank you,
Laura
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