[FieldTrip] Problem with Template Model for Source Reconstruction

[Paolo Belardinelli]

Dear Britta,
I was deeply involved in the processing and I forgot to update this post.
Thank you: it worked out!
Eliminating the bias from MRI images (using light/very light
regularization) leads to more accurate grids and correct results.

Best,

Paolo



On Thu, Feb 18, 2016 at 10:10 AM, Britta Westner <
britta.westner at uni-konstanz.de> wrote:

> 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 listfieldtrip at donders.ru.nlhttp://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
>
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>



-- 
--
Paolo Belardinelli, PhD
Neurology Department
University Hospital Tuebingen
Eberhard Karls University Tuebingen
Hoppe-Seyler Str. 3
D-72076 Tuebingen
Tel: +49 7071 / 29 80478
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