Anonymization and modification

Orthanc 0.5.0 introduces the anonymization of DICOM resources (i.e. patients, studies, series or instances). This page summarizes how to use this feature.

Anonymization of a Single Instance

Orthanc allows to anonymize a single DICOM instance and to download the resulting anonymized DICOM file. Anonymization consists in erasing all the tags that are specified in Table E.1-1 from PS 3.15 of the DICOM standard 2008 or 2017c (default). Example:

$ curl http://localhost:8042/instances/6e67da51-d119d6ae-c5667437-87b9a8a5-0f07c49f/anonymize -X POST -d '{}' > Anonymized.dcm

It is possible to control how anonymization is achieved by specifying a JSON body:

$ curl http://localhost:8042/instances/6e67da51-d119d6ae-c5667437-87b9a8a5-0f07c49f/anonymize -X POST -d '{"Replace":{"PatientName":"Hello","0010-1001":"World"},"Keep":["StudyDescription", "SeriesDescription"],"KeepPrivateTags": true, "DicomVersion" : "2017c"}' > Anonymized.dcm


  • New UUIDs are automatically generated for the study, the series and the instance.
  • The DICOM tags can be specified either by their name (PatientName) or by their hexadecimal identifier (in the example above, 0010-1001 corresponds to Other Patient Names).
  • Replace is an associative array that associates a DICOM tag with its new string value. The value is dynamically cast to the proper DICOM data type (an HTTP error will occur if the cast fails). Replacements are applied after all the tags to anonymize have been removed.
  • Keep specifies a list of tags that should be preserved from full anonymization.
  • If KeepPrivateTags is set to true in the JSON request, private tags (i.e. manufacturer-specific tags) are not removed by the anonymization process. The default behavior consists in removing the private tags, as such tags can contain patient-specific information.
  • DicomVersion specifies which version of the DICOM standard shall be used for anonymization. Allowed values are 2008 and 2017c (default value if the parameter is absent). This parameter has been introduced in Orthanc 1.3.0. In earlier version, the 2008 standard was used.

Modification of a Single Instance

Orthanc allows to modify a set of specified tags in a single DICOM instance and to download the resulting anonymized DICOM file. Example:

$ curl http://localhost:8042/instances/6e67da51-d119d6ae-c5667437-87b9a8a5-0f07c49f/modify -X POST -d '{"Replace":{"PatientName":"hello","PatientID":"world"},"Remove":["InstitutionName"],"RemovePrivateTags": true, "Force": true}' > Modified.dcm


  • The Remove array specifies the list of the tags to remove.
  • The Replace associative array specifies the substitions to be applied (cf. anonymization).
  • If RemovePrivateTags is set to true, the private tags (i.e. manufacturer-specific tags) are removed.
  • The Force option must be set to true, in order to allow the modification of the PatientID, as such a modification of the DICOM identifiers might lead to breaking the DICOM model of the real-world. In general, any explicit modification to one of the PatientID, StudyInstanceUID, SeriesInstanceUID, and SOPInstanceUID requires Force to be set to true, in order to prevent any unwanted side effect.

Modification of Studies or Series

It is possible to modify all the instances from a study or from a series in a single request. In this case, the modified instances are stored back into the Orthanc store. Here is how to modify a series:

$ curl http://localhost:8042/series/95a6e2bf-9296e2cc-bf614e2f-22b391ee-16e010e0/modify -X POST -d '{"Replace":{"InstitutionName":"My own clinic"}}'

The parameters are identical to those used to modify a single instance. Orthanc will answer a JSON message that tells where the modified series has been stored:

  "ID" : "3bd3d343-82879d86-da77321c-1d23fd6b-faa07bce",
  "Path" : "/series/3bd3d343-82879d86-da77321c-1d23fd6b-faa07bce"

Similarly, here is an interaction to modify a study:

$ curl http://localhost:8042/studies/ef2ce55f-9342856a-aee23907-2667e859-9f3b734d/modify -X POST -d '{"Replace":{"InstitutionName":"My own clinic"}}'
  "ID" : "1c3f7bf4-85b4aa20-236e6315-5d450dcc-3c1bcf28",
  "Path" : "/studies/1c3f7bf4-85b4aa20-236e6315-5d450dcc-3c1bcf28"

Modification of Patients

Starting with Orthanc 0.7.5, Orthanc can also modify all the instances of a patient with a single REST call. Here is a sample:

$ curl http://localhost:8042/patients/6fb47ef5-072f4557-3215aa29-f99515c1-6fa22bf0/modify -X POST -d '{"Replace":{"PatientID":"Hello","PatientName":"Sample patient name"},"Force":true}'
  "ID" : "f7ff9e8b-7bb2e09b-70935a5d-785e0cc5-d9d0abf0",
  "Path" : "/patients/f7ff9e8b-7bb2e09b-70935a5d-785e0cc5-d9d0abf0",
  "PatientID" : "f7ff9e8b-7bb2e09b-70935a5d-785e0cc5-d9d0abf0",
  "Type" : "Patient"

Please note that, in this case, you have to set the value of the PatientID (0010,0020) tag for Orthanc to accept this modification: This is a security to prevent the merging of patient data before and after anonymization, if the user does not explicitly tell Orthanc to do so.

Anonymization of Patients, Studies or Series

Study and series can be anonymized the same way as they are modified:

$ curl http://localhost:8042/patients/6fb47ef5-072f4557-3215aa29-f99515c1-6fa22bf0/anonymize -X POST -d '{}'
$ curl http://localhost:8042/studies/ef2ce55f-9342856a-aee23907-2667e859-9f3b734d/anonymize -X POST -d '{}'
$ curl http://localhost:8042/series/95a6e2bf-9296e2cc-bf614e2f-22b391ee-16e010e0/anonymize -X POST -d '{}'

As written above, the anonymization process can be fine-tuned by using a JSON body.