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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