Hi Guys,
Thank you for your comments...
> I was told that it is not recommended to use data from different
> scanners for VBM. Differences among groups may be due to the
> different scanners, or you may get noisy results. Worth checking this
> before starting...
I agree with you Mauro! In principle, if gp1 = scanner A and group2 =
scanner B, then you have confounding effects between groups and
scanners, and the analysis is not possible (I think). However, as 1/6 of
the data (gp1&2) comes from a scanner A, 1/6 from a scanner B and 2/3
from a scanner C, i.e. the repartition of subjects from gp 1 & 2 is
approximately the same for each scanner. I don't think that future
differences between groups (I hope) would be due to differences between
scanners. First, because I will look at differences related to
differences in neuropsy data and second because the difference between
scanners will be modelled in the design matrix (as suggested by John).
Why do you think that my data would be noisier than with all data coming
from the same scanner?
> The segmentation procedure shouldn't have problem with that kind of
> data, should it ?
Regarding the segmentation, it should be OK. The 1st segmentation would
give different results (it is the case indeed) but the normalization on
MNI T1GM should resolve the pblm of different sizes.
Best,
Cyril
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