[Eeglablist] Registering EGI 128 Channel GSN Electrode Locations to BESA/BEM Coordinates

[Michael Boyle]

Hey all,

I have been trying to get a good registration between the sensor locations
provided by EGI for their 128 channel geodesic sensor net and the default
BESA and BEM coordinate systems that DIPFIT provides, but the results are
quite unsatisfactory with the standard warping methods (no manual warping).
I have tried using the automatic warp when aligning just the 10-20 sensor
locations, the 10-10 sensor locations that EGI reports to be within 1cm of
an EGI GSN electrode (
ftp://ftp.egi.com/pub/documentation/technotes/HydroCelGSN_10-20.pdf), both
with and without fiducials, and even just assessing the correspondence
visually shows that the fits are quite poor. I was wondering if anyone has
had success getting a good registration particularly with the BESA
coordinates, since that is the dipole fitting method I've converged on. The
most noticeable issue with my registrations is with the frontal electrodes
in either model (the Fz's for example are clearly not well coregistered).
Possibly as a result, I have had, in a few cases, DIPFIT place the
well-fitting dipole for eye blink components slightly within the brain and
thus not automatically exclude them.

I can send pictures of my best attempts at registration to anyone
interested.

Thanks for your help!
Michael
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