As Jörg says, for DICOM SR encoding, TID 2000 (which is the same
as what is used in the IHE Simple Image and Numeric Report SINR
profile) is the way to go if you want to do it in DICOM. There is
also TID 2005 Transcribed Diagnostic Imaging Report, when there are
no codes and measurements.
Sup 150 introduces TID 2006 Imaging Report With Conditional Radiation
Exposure and Protection Information, which specializes TID 2000 and
may be required in some situations (e.g., to satisfy the German
requirements).
As you mentioned (encapsulated) PDF is a good way to go if you
just need to exchange the rendered form of the report without
any structured content, and the DICOM encapsulation allows for
including it in the PACS or a DICOM archive. IHE XDS-I considers
the possibility of any one of three forms, DICOM SR, PDF, and
HL7 CDA wrapped plain text.
DICOM WG8 has been reviewing the RSNA's reporting templates effort,
and there is talk of turning these into a formal syntax that can
be encoded in multiple forms, such as DICOM SR and HL7 CDA, or
perhaps something else, as people discover that HL7 is a closed
standard (and that it is neither free to read nor free to
implement, unfortunately). You might want to look at CE/ISO 13606
(OpenEHR extract) instead of CDA.
As you can imagine, there is a lot of pressure in the US to use
CDA for documents other than radiology reports, despite the
fact that it is not an open standard, since the costs are low
for vendors (compared to their other costs), but since that
precludes the use of open source software (without the user
having to pay a fee), this seems undesirable, so it seems
likely that at least non-US sites will need a truly free and
open alternative to HL7 CDA.
DICOM SR may not be for everybody, but at least it is an open
standard, if that matters to you.
David