topoplot error

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Wed Jan 16 17:32:14 CET 2008

Hi Thomas,

On 6 Jan 2008, at 18:40, thomas gilbertson wrote:
> Does anyone know where to find the standardised montreal " average"
> mri in ctf format?

Maybe a bit late, but I'll give a short reply anyway.

If you read the canonical SPM MRI using mri=read_fcdc_mri(..), it
will have mri.transform describing the homogenous coordinate
transformation matrix that converts from voxel indices into SPM

In volumenormalise around line 153, there is a homogenous
transformation matrix that converts an MRI from CTF head coordinates
(linked to NAS/LPA/RPA) into SPM coordinates (linked to AC/PC). If
you multiply the inverse of that 4x4 matrix with mri.transform that
you obtained after reading the SPM canonical MRI, you should get the
canonical MRI reasonably aligned with the CTF headcoordinate system.

ent_head_and_mri_coordinate_systems_defined for further details on
coordinate systems, and the transformation matrix.

best regards

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