Hi Daniel,
if you "only" want to do realign & unwarp (without having acquired a
fieldmap), then this will realign the images and additionally correct
for motion*B0 interaction effects. It will not undo the distortions
induced by using EPI in the first place.
If you want to do that, you need an additional set of images coming from
a dedicated fieldmap sequence. If you have those images, you can/must
enter the TE of the early and late echo of the fieldmap, not the EPI
(click Toolbox, Fieldmap), which will then allow you to properly unwarp
the EPI images (a kind of "realign & unwarp & unwarp"). I don't think
field strength is explicitly used anywhere as the fieldmap must of
course be from the same subject, session, and thus, scanner.
Hope this helps,
Marko
Daniel ROQUET wrote:
> Hello SPM'ers
> I have two EPI data-sets (with distinct TE) which I want to realign and
> unwarp. I wonder whether FieldMap-Toolbox takes (1) the TE of the EPI
> images which have to be corrected, and (2) the strength of the magnetic
> field, into account . If it doesn't, why ? if it does, where can we
> change these parameters ?
> Best wishes
> --
> Daniel ROQUET
> PhD student
> Clinique Psychiatrique
> Unité INSERM 666
> 1 Place de l'Hôpital
> 67091 Strasbourg
--
____________________________________________________
PD 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
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