[Mne_analysis] Alignment Problems

[Matti Hamalainen]

Hi Tom,

On Apr 5, 2009, at 8:17 PM, Thomas Wallis wrote:

> Hello,
>
> I am having trouble aligning MEG position and the MRI. I have  
> attempted to attach some pictures to illustrate.
>
> I can get the data to the mne_analyze stage. When I check the  
> viewer, the head is shown protruding through the MEG helmet.  
> Consequently, the source estimates are problematic.
>
> As can be seen in the original alignment pictures  
> (Alignment_Original_1 and _2), the digitizer data and head position  
> information is shown far above the scalp and rotated forwards. I  
> manually re-aligned the digitizer data in the mne_analyze viewer  
> (see Realigned_1 and _2). I then saved the alignment as a COR-.fif  
> file, and re-calculated the forward models and the inverse operator.
>
> When I load the data back into mne_analyze, the digitizer data looks  
> as I aligned it, but the scalp is still protruding from the MEG  
> helmet (see Realigned_Failure_1 and _2).
>
> Where have I gone wrong? Any help would be greatly appreciated.

There is obviously some problem with the head position information.  
Some more information is needed to go forward:

1. I am guessing from your geographical location that the data come  
from a KIT MEG system. Correct?

2. Have you done this successfully before? I suspect there is some  
problem in the fif conversion process. It is also possible that the  
KIT MEG data formats have changed.

Best,
Matti




-------------

Matti Hamalainen, Ph.D.
Athinoula A. Martinos Center for Biomedical Imaging
Massachusetts General Hospital
Building 149, 13th Street, Mailcode 149-2301
Charlestown, MA 02129-2060
USA

e-mail          msh at nmr.mgh.harvard.edu
Tel             +1 617 726 0323
FAX             +1 617 726 7422



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