Hi,
In a time series study, I only acquired one slice. I used spm99 to
realign images of the slice and plotted histograms of signal intensity
of the images. I noticed that the intensity distribution changed quite a
bit comparing a pair of pre- and post-realignment images. The histogram
of the pre-realignment image showed a 'bump' around 1000 (intensity
unit). This bump 'splitted' in the histogram of the post-realignment
image to two 'bumps', one centered at about 600 and the other one at
2000 with no overlap. That seems to imply that in addition to the
slightly smoothing effect introduced by the realignment procedure, a
certain filter had been applied to enhanced the image contrast between
gray and white matters. Is this true? How can I turn the filter off so
that I can use the original contrast for further quantitative
processing?
Thank you very much for your time.
Yi-Fen
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