Does the format allow storing the transform to scanner coordinate space? Freesurfer needs this to relate a surface to a volume.

I assume the answer is yes, via the CoordinateSystemTransformationMatrix, DataSpace, TransformedSpace and MatrixData tags, and the NIFTI_XFORM_SCANNER_ANAT def.

Nick,

As you mentioned in your message, the CoordinateSystemTransformationMatrix and its children should meet your needs. As described in the GIFTI Surface Format document, the DataSpace indicates the space of the DATA element's contents and TransformedSpace indicates the space of the DATA element's contents after application of the matrix.

So, your DATA element could contain the data in the NIFTI_XFORM_SCANNER_ANAT space and the matrix could be used used to transform the data to another space such as NIFTI_XFORM_TALAIRACH. Of course, you could also load the DATA element with data in Talairach space and use the matrix to transform the data to the scanner space.

John

Can it store multiple transforms? For instance, a scanner space xform, and a talairach space xform?