A SOP Class defined in the DICOM Standard extended in an implementation with additional Type 3 Attributes. The additional Attributes may either be drawn from the Data Dictionary in PS 3.6, or may be Private Attributes. The semantics of the related Standard SOP Class shall not be modified by the additional Type 3 Attributes when absent. Therefore, the Standard Extended SOP Class utilizes the same UID as the related Standard SOP Class.
Note: IODs from a Standard Extended SOP Class may be freely exchanged between DICOM implementations since implementations unfamiliar with the additional Type 3 Attributes would simply ignore them.