Hello Natalia,
I do not think there is a hard rule how you have to do things in this
respect, but one argument for using the structural as the target is that
you will usually use this one for spatial normalization, and that it
should therefore be nicely aligned along the principal axes (as this
makes the affine mapping more stable). I actually usually first do an
alignment of the structural (taking all functionals along) and then
coregister the mean of the first session to the anatomical, again taking
along all functionals. As you only have to write to the header in this
case (not the data itself), there is no interpolation issue.
Whichever way you do it, you should never generate "9 different
anatomicals" as all images of one subject should be normalized using the
same set of parameters, determined from one image that is in register
with all functionals. SPM knows this, so if you do a realignment across
sessions, the second session will automatically be realigned to be in
the space of the first, as will be all other sessions if entered as such
in the bach system. You can therefore register the mean of the first
session to the anatomical, if you then specify all other functionals as
"other images", this should work.
Cheers
Marko
Natalia Yakunina schrieb:
> Hello all,
>
> The question is probably very basic, but it suddenly made me stumble. I
> always used a structural image as reference, and mean (or first) EPI
> image as source image, assuming SPM will wiggle mean and the rest of the
> EPIs to match structural which is then normalized. So far it seems to be
> working just fine. But now that I've taken a closer look, SPM 12 manual
> has it vice versa - have mean functional image as reference, and wiggle
> the structural image as source image. Is it a better approach than the
> one I've been using? If so, why? If I have 9 runs, and I realign each
> run separately, I will have 9 means, which means I will have 9 different
> structural images. Is it a better approach to normalize it this way?
>
> Sincerely,
> Natalia Yakunina
--
____________________________________________________
Prof. Dr. med. Marko Wilke
Facharzt für Kinder- und Jugendmedizin
Leiter, Experimentelle Pädiatrische Neurobildgebung
Universitäts-Kinderklinik
Abt. III (Neuropädiatrie)
Marko Wilke, MD, PhD
Pediatrician
Head, Experimental Pediatric Neuroimaging
University Children's Hospital
Dept. III (Pediatric Neurology)
Hoppe-Seyler-Str. 1
D - 72076 Tübingen, Germany
Tel. +49 7071 29-83416
Fax +49 7071 29-5473
[log in to unmask]
http://www.medizin.uni-tuebingen.de/kinder/epn/
____________________________________________________
|