The Referenced Instance Sequence (0008,114A) with a Purpose of Reference Code Sequence value of (121331, DCM, “Equivalent CDA Document”) identifies an HL7 Clinical Document Architecture (CDA) Document that contains clinical content equivalent to this SR Document SOP Instance. This referenced CDA Document may be a source document that was transformed to create this SR Document, or it may be a transcoding of the content created simultaneously for both the SR Document and the CDA Document.
Notes: 1. Reference to a CDA Document created as a transcoding of the SR Document subsequent to the creation of the SR SOP Instance would not be encodable in that SOP Instance.
2. There is no requirement that the transform or transcoding between DICOM SR and HL7 CDA be reversible. In particular, some attributes of the DICOM Patient, Study, and Series IEs have no corresponding standard encoding in the HL7 CDA Header, and vice versa. Such data elements, if transcoded, may need to be encoded in implementation-dependent “local markup” (in HL7 CDA) or private data elements (in DICOM SR) in an implementation-dependent manner; some such data elements may not be transcoded at all. It is a responsibility of the transforming application to ensure clinical equivalence.
3. Due to the inherent differences between DICOM SR and HL7 CDA, a transcoded document should have a different UID than the source document.
The Referenced SOP Instance UID (0008,1155) in Items of this Sequence is mapped to the native HL7 Instance Identifier through the HL7 Structured Document Reference Sequence (0040,A390) of the SOP Common Module (see Section C.12.1).