Dear SPMers,
I am acquiring EPI data to standardize fMRI paradigm for one of my
studies. Unfortunately, the acquired EPI images are having artifacts in
the form of a chunk of missing data (images 1 & 2 attached for reference
are raw EPI images). Can someone confirm whether I can use any specific
analysis to correctly analyze this data. In order to see how SPM handles
such data, I have already performed pre-processing and GLM analysis. The
activation map is shifted down with respect to standard MNI glass brain
window (image 3 attached for reference, at p < 1 uncorrected).
I have several questions regarding this problem -
1. What may be the possible cause of this kind of artifact in the images?
What can be the remedy?
2. Are such image artifacts causing the normalization errors? If yes, then
I would expect 'SPM normalize' function to stretch EPI images up (to fill
the missing space). Why are the normalized images shifted down?
Thanks in anticipation.
-Vaibhav Tyagi
Speech and language laboratory
National brain research centre
Gurgaon, India
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