[FieldTrip] Orientation of headmodel with respect to sensors poisition

Susmita Sen susmitasen.ece at gmail.com
Wed Oct 19 08:02:25 CEST 2016

Dear FieldTrip community,

I am constructing headmodel using standard mri data. The meg data that I am
working with is recorded using yokogawa system. I have used the following


cfg = [];
cfg.coordsys = 'yokogawa';
cfg.viewresult = 'yes';
cfg.snapshot     = 'yes';
cfg.fiducial.nas    = mri.hdr.fiducial.mri.nas; %position of nasion
cfg.fiducial.lpa    = mri.hdr.fiducial.mri.lpa; %position of LPA
cfg.fiducial.rpa    = mri.hdr.fiducial.mri.rpa; %position of RPA
cfg.fiducial.zpoint =  [ 91 109 107];
[mri_realigned] = ft_volumerealign(cfg,mri);


cfg           = [];
cfg.output    = 'brain';
segmentedmri  = ft_volumesegment(cfg, mri_realigned);

%% create headmodel

cfg = [];
vol = ft_prepare_headmodel(cfg, segmentedmri);

%% visualize

vol = ft_convert_units(vol,'cm');
grad = ft_read_sens('D:\Data\all\raw_preproc_data\raw\ari.con'); % load grad

ft_plot_sens(grad, 'style', '*b');

hold on

However, I am facing a problem when I plotting headmodel with the sensors.
I noticed that the orienations of headmodel and sensors are not aligned. I
am attaching the figure with this mail. I would be very greatful if any
could kindly give me suggestions how to align these two.

[image: Inline image 1]

[image: Inline image 2]

Thanks and Regards,
Susmita Sen
Research Scholar
Audio and Bio Signal Processing Lab.
E & ECE Dept.
IIT Kharagpur
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