Alignment Problems

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.

Regards,

Tom Wallis

-------------- next part --------------
A non-text attachment was scrubbed...
Name: Alignment_Pics.zip
Type: application/zip
Size: 228691 bytes
Desc: not available
Url : http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20090406/31a02fd4/attachment.zip
-------------- next part --------------

Hi Tom,

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