Hello SPM Community,
I am creating movies of some NIfTI files before preprocessing from EPI runs to get a better sense of my data (and because making brain movies is fun). I've noticed that many of the runs have what appears to be flickering in global signal instensity throughout the scan. This seems particularly prevalent on subjects with high motion, making me think that it is perhaps spin history artifacts, but even subjects who have very little motion have some of this flickering.
I don't have a sense of what a "normal" EPI should look like and if this kind of behavior is within the bounds of acceptable or is something I should be concerned about. Any thoughts on whether this is normal, what the primary causes could be, and if this is something that can/should be minimized (and how to) in future studies would be greatly appreciated.
Here is a link to one of these movies to give you a sense of what I'm talking about.
heuristicwondering.com/brainsharing/brainmovie.html
On this note too, I've seen labs at my campus engage in varying levels of visual inspection of data at different points along the analysis pipeline. What is your opinions on visual inspection best-practices? In particular, if you have very large studies, what are the essential images to look at to ensure things are going alright, what is optional? What is feasible?
Thank you in advance!
~Meg
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