Hi,
You wrote:
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I was wondering why smoothing should be done after realigning and normalizing
and not before. First, realignment of smoothed images should be more robust
because high frequency noise is removed. No other effect should be produced if
all the voxels are convolved with the same gaussian kernel. Second, images are
normalized to a very smooth template. As I understand it is easier (in terms of
time computing) normalizing smoothed image to a smoothed template than doing to
non smoothed images; and the result shouldn't be affected.
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In fact the images are smoothed before calculating the realignment parameters
8mm PET, 6mm FMRI), and also before calculating the normalization parameters
(8mm), then the transformations are applied to the unsmoothed versions. I
guess you could smooth beforehand, then not smooth during the calculations,
but then you would have to be happy that you wanted the same smoothing for the
realignment, normalization and statistics, which might be unlikely...
Best,
Matthew
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