DICOM PS3.3 2019c - Information Object Definitions
C.8.8.5.2 Frame of Reference Relationship Sequence and Transformation Matrix

Retired. See PS3.3-2011.

The concept of definition of registered Frame of References using the Frame of Reference Relationship Sequence (3006,00C0) formerly present in the Standard is retired. The use of Registration IODs is advised since the introduction of Spatial Registration IOD, which is a much stronger and more general concept, and independent from the specifics of RT Structure Sets. Additionally it is of importance that registrations are decoupled from image and segmentation objects.

DICOM PS3.3 2019c - Information Object Definitions