What do the various status displayed in a series header mean?

A series can be assigned a status by Orthanc. I can list as unknown, missing, inconsistent or complete.

The status is meant to convey the completeness of the series, as known by Orthanc.

As a general rule, since there is no generic DICOM tag that contains the number of DICOM instances that are contained in a given series, and since there is no generic tag that contains the index of a DICOM instance inside its parent series, it is in general impossible to know if a series is complete in terms of its instances. This is the meaning of the Unknown status displayed by Orthanc.

However, for some types of images (such as cardiac MRI), the DICOM modules might specify a tag that contains this information. If such a tag is available for a series, Orthanc will either report a Complete status (if all the instances have been received), Incomplete (if some instances are [still] missing) or Inconsistent if there is an error inside the numbering of the instances.