[FieldTrip] fit volume segment and sensors

[s.rombetto at cib.na.cnr.it]

Dear Fieldtrippers

I 'm trying to perform source analysis on MEG data.
I use an AtB system (usually it is described as 'itab' in fieldtrip)

First I have preprocessed my data and I have calculated the cross  
spectral density matrix

Then I have constructed the forward model

  mri = ft_read_mri('Subject01.mri');
cfg = [];
cfg.write      = 'no';
cfg.coordsys   = 'ctf';
[segmentedmri] = ft_volumesegment(cfg, mri);

and segmented the brain surface:

cfg = [];
cfg.method = 'singleshell';
vol = ft_prepare_headmodel(cfg, segmentedmri);

With the command ft_read_sens I have also read the sensors positions.

Before going on I have checked the results plotting the volume and the  
sensors using the commands
vol = ft_convert_units(vol,'cm');
sens = ft_read_sens(rawdataname);
figure
ft_plot_sens(sens, 'style', '*b');
hold on
ft_plot_vol(vol);

and I have noticed that the result is wrong because the volume soesn't  
fit the sensors as shown in the attachment
Moreover, following some topics in the mailing list I have used

ft_determine_coordsys(mri)
ft_determine_coordsys(vol)
ft_determine_coordsys(sens)

and I have found that the coordinate systems are diffeerent.

As far as I understand I should use the ctf coordinate system to  
perform the source analysis. But even if I try to specify this  
coordinate system it did not work.
Any suggestion to solve this problem?

Kind regards
-------------------------
  Dott.ssa Sara Rombetto
  Istituto di Cibernetica
  "E. Caianiello"
  Via Campi Flegrei, 34
  80078 Pozzuoli (NA)
  Italy
  mob +39 3401689815
  tel +39 0818675361
  fax +39 0818675128
--------------------------
"I disapprove of what you say, but I will defend to the death your  
right to say
it." [Evelyn Beatrice Hall, The Friends Of Voltaire]

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