[FieldTrip] generating single / multiple local sphere model using brain surface from segmented MRI

[Andreas Wollbrink]

Hi all,

I just tried to generate a multiple local sphere model using a brain 
surface from a segmented MRI following the instructions on

http://fieldtrip.fcdonders.nl/example/make_leadfields_using_different_headmodels#local_spheres_model_from_fieldtrip_using_brain_surface_from_segmented_mri

The actual matlab code is:

hdr = ft_read_header('example.ds');
cfg                       = [];
cfg.grad                  = hdr.grad;
ft_segment                = ft_prepare_localspheres(cfg,segmentedmri);


The error message is as follows:

??? Attempted to access cfg.numvertices(1); index out of bounds because 
numel(cfg.numvertices)=0.

Error in ==> prepare_mesh_segmentation at 67
   [pnt, tri] = triangulate_seg(seg, cfg.numvertices(i), ori);

Error in ==> ft_prepare_mesh at 104
   bnd = prepare_mesh_segmentation(cfg, mri);

Error in ==> ft_prepare_localspheres at 93
   headshape = ft_prepare_mesh(cfg, mri);


The same error occurred when I tried to generate a single local sphere 
model based on a brain surface derived a segmented MRI.


After defining a value for cfg.numvertices = 3000 I got a reasonable 
good volume conductor model.

Since I am not quite sure which value I should use for the numvertices 
parameter I like to ask for some explanations and suggestions.

Thanks in advance!

Andreas
-- 


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   Andreas Wollbrink, Biomedical Engineer

   Institute for Biomagnetism and Biosignalanalysis       	
   Muenster University Hospital

   Malmedyweg 15         phone:   +49-(0)251-83-52546
   D-48149 Muenster      mobil:   +49-(0)160-98527553
   Germany               fax:     +49-(0)251-83-56874	
                         e-Mail: a.wollbrink at uni-muenster.de

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