Encapsulated pdf - create-dicom defaults Modality to "OT" always

Hi,

I am using Orthanc for storing and communicating with other PACS and I am creating dicom within Orthanc using its Rest API but even if I set the Modality in the query to be “CR” or “SR”, the encapsulated pdf (sop class uid=1.2.840.10008.5.1.4.1.1.104.1) , Orthanc always creates the dicom with Modality = “OT”.

Could you please help troubleshoot this issue within Orthanc?

Thank you,
Rajshree

Hello,

This is a feature, not a bug. To the best of my knowledge, DICOM files embedding PDF should have “Modality” set to “OT” (which stands for “Other”):
https://dicom.nema.org/medical/dicom/current/output/chtml/part03/sect_C.7.3.html#sect_C.7.3.1.1.1

This behavior is implemented at this part of the source code of Orthanc:
https://hg.orthanc-server.com/orthanc/file/Orthanc-1.9.7/OrthancFramework/Sources/DicomParsing/ParsedDicomFile.cpp#l1467

If this sounds like a misunderstanding on my part, I’ll happily fix this behavior. Please provide me with a reference (you can for instance ask the question to the “comp.protocols.dicom” Google Group).

Regards,
Sébastien-

Thank you Sebastien for the prompt response.

I have asked in the group (comp.protocols.dicom). I will get back.

Rajshree

Here is the reference from the group:
https://groups.google.com/g/comp.protocols.dicom/c/jgsvKDA6pc0

Hope this helps,

Thank you,
Rajshree

Thanks for having investigated this issue and for providing the reference.

The following changeset that is pending in the mainline of Orthanc fixes your issue:
https://hg.orthanc-server.com/orthanc/rev/d7d5d63985c8

Sébastien-

Thanks. I noticed the same thing previously. Anything that I put there was being overwritten by 'OT". I’ll have to check to see if the change is going to break anything.
Will the series number be set to the next available then ?

As can be seen in the source code, the line corresponding to the “Series Number” tag is commented, so the value provided by the caller is not overwritten.