I am working with 275 channels MEG system from CTF and I am running DICS for
source localization comparing MEG with an external reference channel
(surface bipolar EMG).
As I ran the method I got curious results and therefore I was looking inside
the code for debugging.
I found a problem with which i am stuck in the forward solution with a
single sphere conductive model used in compute_leadfield.m
By comparing the results with CTF's forward solution routine i simulated a
single dipole in a known position/orientation and i have got different
results for the lead field.
What could be the problem?
Maybe i am using bad settings...
I attach the code i am using for the lead field computation in Fieldtrip:
% 1) Initialize the gradients' structure
% ctf read in function - ds: ctf info struct
position = ctf_getSensPos(ds);
grad.pnt = [position(:,1:3);position(:,7:9)];
grad.ori = [position(:,4:6);position(:,10:12)];
MEGlist = strmatch('M',ds.res4.chanNames);
for fkk=1:length(MEGlist)
grad.label(fkk) = cellstr(ds.res4.chanNames(MEGlist(fkk),1:5));
end
grad.label = grad.label';
grad.tra = [eye(275), -eye(275)];
% 2) Initialize the grid structure
grids.resolution = 0.5;
grids.xgrid = 'auto';
grids.ygrid = 'auto';
grids.zgrid = 'auto';
% prepare the head model
cfg = [];
cfg.grad = grad;
cfg.grid = grids;
cfg.hdmfile = 'myhead.hdm';
[vol, sens, cfg] = prepare_headmodel(cfg, data);
% compute the lead field (dipole_pos and dipole_mom are known and fixed)
lf = compute_leadfield(dipole_pos, grad, vol,
'singlesphere','yes')*dipole_mom';
% compute lead field with ctf routine
lf_ctf = ctf_leadField(ds,dipole_pos,dipole_mom);
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