Boubts about Orthanc SOPInstanceUID and instances uuid assignation


At my workplace we have 2 Orthanc servers, one for incoming studies and another for backup. The backup server is configured to receive all studies from the incoming server and store it on object storage. This configuration works pretty well, but after some time we’ve detect a problem in a very small number of studies, sometimes the SOPInstanceUID of the instances are different between the incoming and backup server or the uuid of the instances are different.

This is a problem because our algorithm to check studies consistency between both servers, fails in this cases, despite the fact that the instances are the same on the dicom viewer for both servers.

The first thing we thought was that there could be duplicate IDs in the backup server studies, but then we verified that is not the case.

In what cases could Orthanc assign Ids different from those of the origin modality?

Thanks in advance,
Best regards.

Orthanc never modifies DICOM UIDs unless you call /anonymize or /modify routes explicitly. There must be something else involved …