[Eeglablist] Co-registration procedure DIPFIT

Arnaud Delorme arno at ucsd.edu
Thu Feb 18 08:46:14 PST 2010


Dear Katy and Kelly,

the latest version of EEGLAB does recognize automatically EGI location  
flles (in fact, it will automatically import channel locations for you  
when you import a binary file).
For co-registration in Dipfit, you still have to rotate the channel  
location manually or you can also try to automatically align the  
fiducials to the template in the graphic interface.

Best regards,

Arno

On Feb 16, 2010, at 3:45 AM, Katy Ericson wrote:

> Hi Kelly,
> thanks a lot for your reply. I think i understand what you mean  
> (sorry if i don't ;) ). As i understood ,this is a standard way,  
> when you have a 10-10 or 10-5 marking of your electrodes, which  
> corresponds to the standard 10-5 marking of the file, given in  
> DIPFIT. The problem in my case was, that i have a custom system with  
> E1-E129 electrode marking, which does not correspond to the DIPFIT  
> file. In this case wrap function does not recognize those locations  
> and, from my point of view, there are two options:
> 1. Do a co-regestaration manually, which takes tons of time
> 2. Find a .loc file with custom electrodes from EGI in spherical  
> format, that will represent my 129 electrodes with the names E1- 
> E129, and set it as a template file. In this case the wrap function  
> will be able to recognize location names and will do wrapping  
> automatically. I'm not sure that this will work in EEGLAB, right now  
> looking for an appropriate file to do try this out.
> Best regards,
> Katy
>
>
> From: Kelly.Kaneswaran <kelly.kaneswaran at ul.ie>
> To: Katy Ericson <katy.ericson at yahoo.com>
> Sent: Mon, February 15, 2010 3:34:02 PM
> Subject: RE: [Eeglablist] Co-registration procedure DIPFIT
>
> Katy,
>
> I had similar problem before, follow the turorial it explains a way  
> of doing it that speeds it up. First you should have a channel  
> location file with all the locations in an acceptable  
> format .sph .loc etc. from the locate dipole using dipfit menu ,  
> choose head and model settings , leave the default settings and  
> choose manual co registration. then a spherical model pops up ,  
> choose warp montage , the list shows the models fudicials and you  
> can select corresponding electrode locations that your model has  
> exact. then press ok , the montage is warped to fit the model and  
> press ok it will generate the tailrach co-ordinates.
>
> i could be way off so apologies if I mis-understood what you were  
> trying to do
>
> Kelly
>
> From: eeglablist-bounces at sccn.ucsd.edu [mailto:eeglablist-bounces at sccn.ucsd.edu 
> ] On Behalf Of Katy Ericson
> Sent: 11 February 2010 18:20
> To: EEGLAB
> Subject: [Eeglablist] Co-registration procedure DIPFIT
>
> Dear all,
> I'm new to the EEGLAB, this seems to be a nice software. Anyway i  
> have some trouble, if one can call it a trouble at all. I need to  
> find the locations of equivalent dipoles for my ICA components. My  
> recordings are done on EGI 128 channel system and then the exact  
> locations of the sensors are modeled with Photogrametry procedure.  
> As i understand, in order to get more or less correct locations of  
> dipoles, i have to do a co-registration procedure (my net does not  
> correspond exactly to any of 10-5 or 10-10 systems and sensor  
> locations are "scanned" for every patient).
> I was trying to do the co-registration using a standard  
> standard-10-5-cap385.elp file as the template file and spherical  
> model. This analysis takes quite a long time, when one has to pair  
> all 128 channels to template locations, because my system has  
> channels numbered as E1 till E128 and Cz as a reference. It may be  
> unreasonable use of time to sit for several hours trying to co- 
> register electrodes to the standard template. On the other hand  
> there was a study, which calculated correspondences of E1:E128  
> channel names to the 10-5 names. Which may really speed up the  
> process, but the pairing may be done with a greater distances  
> between electrodes.
> It would be a great help from you, if some one could answer my  
> questions:
> 1. How big can the errors be, if i use no co-registration and file  
> with the scanned locations.
> 2. Is there a way to speed up the process or some other solution of  
> co-registration and dipole fitting in my case (i should mention  
> though, if it concerns accuracy, we would rather take a longer  
> processing time, rather than do the work inaccurately).
> 3. We have a possibility to export location file from EGI in  
> spherical and in Cartesian coordinates, will there be a difference  
> in accuracy and time consume during co-registration procedure  
> between files in these 2 coordinate systems.
> 4. When one does the co-registration, the locations of electrodes  
> are changed (custom locations are aligned with predefined ones), how  
> does this affect the accuracy of dipole fitting.
> Thank a lot for your answers and the great mailing lists:)
> Cheers!
> Katy
>
>
>
> <ATT00001..txt>

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