DICOM PS3.17 2019a - Explanatory Information

KKK.9 Uncertainty Principle

When does a converted view come into existence? By definition, when it is "observed". However, a practical question is when to start conversion. A Study is never, theoretically, complete, yet the semantics for conversion and consistency are defined at the Study level.

Another practical question is whether or not to make the received instances available, even though the converted ones may not yet have been created.

In the absence of the concept of "study completion" in DICOM, no firm rules can be defined. However, in practice, most systems have an internal "completion" concept, which may or may not be related to the completion of the Performed Procedure Steps that are related to the sets of instances in question, or may be established through some other mechanism, such as operator intervention, possibly via a RIS message (e.g., after QC checks are signed off as complete, or after a Study has been declared as "ready to read").

A system may elect to "dynamically" begin conversion as instances arrive and update the information in the conversion as new instances are encountered, or it may wait until some state is established that allows it to perform the conversion "statically". In either case, the information in the converted view via the query/retrieval mechanisms should be immutable once made available. I.e., once a conversion has been "distributed", it would be desirable for the system to block subsequent changes to the Study, except to the extent that there is a need for correction and management of errors (in which case mechanisms such as IHE Image Object Change Management (IOCM) may be appropriate).

DICOM PS3.17 2019a - Explanatory Information