DICOM PS3.3 2019b - Information Object Definitions
C.8.8.7.2 Referenced ROI Number

There shall be a one-to-one correspondence between Referenced ROI Number (3006,0084) and the Sequence of ROIs defined in the Structure Set Module and ROI Contour Module. The RT Dose ROI Module shall only contain references to structures that are dose-related (i.e., dose points and isodose curves).

DICOM PS3.3 2019b - Information Object Definitions