Dear Catherine,
> I understand that reslicing is important for individual data, but
> I was wondering if reslicing only adds additional error if one is
> normalizing. In other words, might it be better not to go through
> reslicing if one does realignment followed by normalization?
>
> When one realigns and reslices, the rI* images lose the pixels on
> the edge due to interpolation. If one then does normalization, one
> gets a second source of error from the interpolation in the normalization
> process. It seems that the realignment doesn't need the reslicing because
> the coregistration already appears in the Mat files of the I* files.
You are absolutely right. The only reason for rewriting after
normalisation is (i) you want to analyse non-normalised data or (ii) you
want to "adjust for sampling errors", which isn't terribly useful. An
important note: If you do not reslice immediately (ie reslice after
normalisation), make sure you use sinc interpolation. This is important,
because all volumes are slightly different (because of the realignment
parameters).
-Christian
--
Dr. Christian Buechel
Neurologische Universitaetsklinik, Haus B
Universitaets-Krankenhaus Eppendorf
Martinistr. 52
D-20246 Hamburg
Germany
Tel.: +49-40-42803-4726
Fax.: +49-40-42803-5086
email:[log in to unmask]
www.uke.uni-hamburg.de/kliniken/neurologie/pages/mitarbeiter/buechel_c.htm
www.uke.uni-hamburg.de/kliniken/neurologie/pages/forschung/cnl_index.htm
|