[FieldTrip] Problem with Template Model for Source Reconstruction

[Britta Westner]

Dear Paolo,

I experienced similar problems and found that correcting the field bias
in the participant's MRI (e.g. doing a "bias correction" with SPM) can
help. My explanation would be that the field bias either leads to small
inaccuracies in the segmentation and volume which then "get visible"
when warping the grid based on the non-segmented MRI, or that the
warping algorithm itself is affected by this bias. Maybe you can give
that a try!

Hope this helps,
Britta



Am 17.02.2016 um 20:20 schrieb Paolo Belardinelli:
> Dear Fieldtrippers,
> we are encountering a problem with a template model for source
> reconstruction. In particular, we are warping (non linearly) a
> template grid to the individual subject's MRI.
> Doing that, it appears that the very top of the brain is not fully
> covered by dipole locations.
> We found that this issue has been already reported:
>
>  http://www.fieldtriptoolbox.org/template/sourcemodel 
>
> Apparently, since March 7th 2013, this issue has been fixed.
> However we are using August 28th 2015 Fieldtrip version and we are
> still dealing with the same issue.
> Any suggestions?
> Here are our code lines:
>
> cfg = [];
> cfg.grid.warpmni = 'yes';
> cfg.resolution = 6; % resolution of the template grid in mm
> cfg.grid.nonlinear = 'yes'; % use non linear normalization
> cfg.mri = mri_spm; % use subject's mri in mni coordinates
> cfg.grid.unit = 'mm';
> sourcemodel = ft_prepare_sourcemodel(cfg);
>
> Thank you in advance.
>
> Paolo
>
>
>
>  
> -- 
> --
> Paolo Belardinelli, PhD
> Neurology Department
> University Hospital Tuebingen
> Eberhard Karls University Tuebingen
> Hoppe-Seyler Str. 3
> D-72076 Tuebingen
> Tel: +49 7071 / 29 80478
>
>
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip


-- 
Britta Westner, M.Sc.
Neuroelectromagnetic Oscillations Laboratory

Fachbereich Psychologie
Universität Konstanz
Postfach 905
78457 Konstanz

Telefon: +49-(0)7531-88-5703
Fax: +49-(0)7531-88-5709 

www.psychologie.uni-konstanz.de/nemo-lab

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20160218/4d7cf85b/attachment-0002.html>