CTF mri import

Michael Wibral wibral at MPIH-FRANKFURT.MPG.DE
Thu Oct 4 12:35:00 CEST 2007


Dear Fieldtrippers,

I was wondering whether anyone has actually succefully imported a recent
ctf-mri into fieldtrip. The mri's we have are mistaken  to be ASA-mris
when I use read_fcdc_mri(MRIFILE). This does not generate an error but
never finishes. When I abort the function the error I get shows that
read_asa_mri has been used internally.

If I enforce the use of read_ctf_mri I get the following error:

??? Error using read_ctf_mri
unknown datasize in CTF mri file

This is due to the fact that hdr.dataSize is read as being 24397 instead
of 1 or 2 as its supposed to be. All of the above is quite obvioussly
due to the fact that the whole header inforamtion is read in a misplaced
fashion, because the software assumes ctf-mri of version2.2. E.g. the
mmPerPixel fields have values around 3.5e+9....etc.

Does anybody know / know how to:
(1) read CTF mris of version 4 and above ?
(2) the changes between version 2.2 and 4.x (I have documentation on the
4.x but not on the 2.x versions).
(3) downconvert CTF mris 4.1 and 4.0 to 2.2 ?
(4) donwgrade mri-viewer so that it produces version 2.2 images ?
(5) get the fiducial information into fieldtrip when not using ctf-mris
but spm-analyze mris?

I also thought about just using the ctf hdm and then to volume-normalize
everything to the MNI template and display things there. This is,
however not really optimal as segmentation of the brainshape is
unavailable for beamforing in that case...

Any help is greatly appreciated,
Michael


Michael Wibral
MEG Unit
Brain Imaging Center Frankfurt

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