DICOM PS3.3 2024a - Information Object Definitions
C.8.8.14.13 Angular Values in RT Beams Module

The Attributes that define angles refer to coordinate systems defined by [IEC 61217]. Where indicated in the DICOM Attribute definition, the angle uses the coordinate system (orientation of the rotation axis and the origin of the rotating coordinate system) defined in [IEC 61217], however DICOM makes no restrictions on the range of values stored. [IEC 61217] defines restrictions that only apply to user interface presentation.

DICOM PS3.3 2024a - Information Object Definitions