Behavior of Instance Level Attributes at Series Level in ExtraMainDicomTags

General
1

Hi everyone! I have a question regarding the configuration option ExtraMainDicomTags. Let’s say I have an Instance level attribute configured as an extra tag at the series level, e.g.,

  "ExtraMainDicomTags" : {
    "Series": [
      ...
      "AcquisitionTime",
      ...
    ]
  },

Can the behavior for which instance-level value be controlled (e.g., max or min acquisition time)? Or does Orthanc just use the value arbitrarily from the first instance that was uploaded for the series?

I could not find information on this in the docs, so I did some experimentation by adding InstanceNumber at the series level extra tags and found the value to be somewhat arbitrary, leading me to believe Orthanc uses the value from the first uploaded instance.

2

Hi @matt_hancock

This system was not designed to store Instance level tags at series level therefore, indeed, the result is kind of arbitrary.

Alain.

3

Makes sense. Should it be considered a bug that you can add lower-level attributes to “extra dicom tags” at a higher level (e.g., adding instance level tags to a series), or should the fact that it works but results are arbitrary be documented in faq/main-dicom-tags.rst?

4

Actually, Orthanc does not really know what is the “level” of a each DICOM tag so I have added a warning in the documentation:

Note: You should only include tags from the same or from a higher level: E.g. Storing StudyDescription at Series level is possible since all series are supposed to share the same StudyDescription . But, adding SeriesDescription at Study level will lead to unpredictible results. Orthanc will not check that the tags levels are adequate.

Thanks for your suggestion

Alain

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