Hi,
I'm currently analysing brain volumetric changes in
patients' with Alzheimers. I have two 3D MR datasets
from the same subject taken six months apart and I'm
looking for changes in brain volume at the voxel level
(looking for voxels whose intensities have changed by a
certain amount).
Prior to any analysis, I have realigned the two images
together and then carried out a 6-parameter
normalisation on them. However, what I'm finding is
that the number of voxels within each volume changes
drastically following realignment, and not by the same
amount either ie following realignment, the actual
difference in volume between both datasets increases
significantly. I have tried to make the images as
similar as possible before realignment. Why should the
brain volume change following realignment?? I
understand that it will change at the normalisation
stage but surely by the same amount for both datasets.
Thanks in advance,
Carol.
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carol docherty
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