ITK orientation codes

The orientation code maps the voxel coordinate system I (column) J (row) K (slice) to right-handed coordinate system X Y Z. Minor rank notation is used, characters R (right), L (left), A (anterior), P (posterior), I (inferior), S (superior) identify from direction.

E.g. RAI, the ITK default orientation, means

  • X: patient Right to left
  • Y: patient Anterior to posterior
  • Z: patient Inferior to superior
Note: sometimes major rank notation (towards) is used, the same coordinate system may be called DICOM LPS or Nrrd left-posterior-superior (right to Left, etc.)


Spatial position, orientation and geometry of DICOM series (CT, MR, PET and other IODs) are examined. If the image is recognized as uniform volume, it receives green ITK orientation code in information widget.

Fig. 1