[FieldTrip] Fiducial registration issue

[Alex Williams]

Hello Fieldtrip community,

  I was curious if anyone here has come across this issue. I'm currently in
the process of registering fiducials to a participant from the CamCan
study. The meeg data, D, I'm using has been converted from SPM to
fieldtrip using
the function. spm2fieldtrip(). The converted data itself has been defined,
and has undergone pre-processing and time-locking in SPM. ft_read_mri()
used a .nifti MRI file and an empty configuration. I have used the
fiducials applied to the segmented mri model's configuration and
subsequently used the configuration to realign the segmented mri using
ft_volumerealign() with cfg.coordsys='neuromag'. After, segmentation was
done using ft_volumesegment(), again with an empty configuration. However,
it seems as though the gradiometer array and the headmodel aren't properly
aligned to one another after plotting both. The unit of the grad, mri and
headmodel are all in 'mm'.

%% Sensors

grad = ft_read_sens([Path1,Path2], 'senstype', 'meg');
%% MRI Read

mri = ft_read_mri([Path1,Path3]);
%% Reslice Volume

cfg = [];
cfg.resolution = 1;
mri = ft_volumereslice(cfg, mri);
%% Realign Coord Sys.

cfg=[];
cfg.fiducial.nas = D2.datareg.fid_eeg.fid.pnt(1,:);
cfg.fiducial.lpa = D2.datareg.fid_eeg.fid.pnt(2,:);
cfg.fiducial.rpa = D2.datareg.fid_eeg.fid.pnt(3,:);
nas=cfg.fiducial.nas;
lpa=cfg.fiducial.lpa;
rpa=cfg.fiducial.rpa;
cfg.coordsys='neuromag';
cfg.method='fiducial';
mri = ft_volumerealign(cfg, mri);
ft_sourceplot([],mri)

-Alex
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