How to retrieve user defined metadata and attachement ?

Hi there,

I have a question : How can I know what are the user defined metadata and attachment in an Orthanc installation ?

Here is what I want to do : I’m making an Orthanc Java tool to build user friendly services on the top of Orthanc server (using APIs).

One of the feature I want to create is to label Patients/Series/Studies with metadata, for example a user can have X ongoing clinical protocol and one day he might need free space and erase all studies that are not needed anymore because the clinical protocol has ended.

So I want to allow the users to label his patients/studies/Series to custom label and see the metadata in the interface.

I know about the custom metadata that can be set in the Orthanc.Json.

The problem is : I do not see any API that can tell me which value are available.
For example for declared AETs we have the /modalities API that give us the list of available modalities that way we can now what are the available destination to use for /store.

I don’t see anything similar for metadata and attachment so I do not know what metadata values are available to store custom metadata in the Orthanc installation (and similarly same problem for attachement).

Thanks for your help,



I have a question : How can I know what are the user defined metadata
and attachment in an Orthanc installation ?

Indeed you might find yourself at the boundary of the scope of Orthanc.
The metadata/attachment identifier/key spaces and name spaces are
defined "externally" and I don't think you have built-in solutions for
discoverability (short of scanning all resources and aggregating a
list), let alone standardization.

Right now I'd recommend you consider using a dedicated index beside
Orthanc. Others might have more creative solutions of course.

Good luck!


I confirm Thibault’s answer: User-defined metadata and attachments are assumed to be application-specific, and Orthanc provides no introspection mechanism to retrieve their list.

For the time being, the Orthanc Book references some well-known metadata/attachments in a so-called “central registry”:

You could retrieve metadata/attachments defined for one instance of Orthanc by creating a plugin that would parse the result of the “OrthancPluginGetConfiguration()” function:


Thanks Thibault and Sebastien for your answers,

I may start with an user instruction to ask users to set a specific metadata address where my software will store it’s metadata. This until I will get knowledge to make plugins in Orthanc to manage metadata or redirect their adress in Rest API.

Anyway It gives me more precise ideas,

Best regards,