The coordinate system should be as described here and are essentially the same
directions as used by Talairach:
Basically, it is up to you to ensure that the data are viewed in this
orientation. If you can convert your DICOM using the DICOM button of SPM,
then all should be well. The image orientations and positions encoded in the
DICOM headers are converted to the equivalent directions for T&T space.
If you have SPM8/SPM8 then the file format is NIfTI, which is extensively
documented at http://nifti.nimh.nih.gov/pub/dist/src/niftilib/nifti1.h .
Look about 2/3 down the page for the orientation information.
On Monday 25 May 2009 11:39, Markus Mertens wrote:
> Dear Prof. Ashburner,
> I am confused about some parameters shown when I use the DISPLAY button in
> I have a volume consisting of 128 coronal slices (XZ-plane in
> DICOM-coordinates); slice distance 1.5 mm. Each slice consists of a 256x256
> matrix. Voxel size in plane is 0.898 x 0.898. But when I load this volume
> into SPM I get the following values:
> Dimensions: 256 x 256 x 128
> Vox size: -0.898 x 0.898 x 1.5
> It seems to me that y- and z-direction are exchanged which has the side
> effect that the loaded head volume looks in opposite direction and left and
> right sides of the head are switched. This could also be explained be the
> negative x-value for the voxel size. I would expect the following:
> Dimensions: 256 x 128 x 256
> Vox size: 0.898 x 0.898 x 1.5
> How could I verify that the volume is shown correctly? Which coordinate
> system is used and shown in SPM5/8? Is it DICOM?
> Kind and hopeful regards,
> Markus Mertens
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