Sorry guys for not weighing in sooner, I was out of town. You should not use this intent code unless the data stored in the image conforms to the nifti spec for storing symmetric matrices. In short this spec requires that you store the unique elements of the matrix in a fixed order (same as `tensorfit.lower_triangular`) along the 5th dimension of the image. Specifying the intent code when the data does not conform to the spec is inappropriate and misleading.

http://nifti.nimh.nih.gov/nifti-1/documentation/nifti1fields/nifti1fields_pages/group__NIFTI1__INTENT__CODES.html#a29