Main DICOM Tags in DB


By default, Orthanc is saving a predefined subset of DICOM Tags in the DB. These are called the MainDicomTags.

Since they are stored in DB, these tags can be retrieved very quickly and can conveniently be used for filtering/finding resources while, to access other DICOM tags, Orthanc needs to re-open the DICOM file which is much slower.

As of Orthanc 1.4.2 (and later), the predefined list is:

  • Patients:
    • PatientName
    • PatentID
    • PatientBirthDate
    • PatientSex
    • OtherPatientIDs
  • Studies:
    • StudyDate
    • StudyTime
    • StudyID
    • StudyDescription
    • AccessionNumber
    • StudyInstanceUID
    • RequestedProcedureDescription
    • InstitutionName
    • RequestingPhysician
    • ReferringPhysicianName
  • Series:
    • SeriesDate
    • SeriesTime
    • Modality
    • Manufacturer
    • StationName
    • SeriesDescription
    • BodyPartExamined
    • SequenceName
    • ProtocolName
    • SeriesNumber
    • CardiacNumberOfImages
    • ImagesInAcquisition
    • NumberOfTemporalPositions
    • NumberOfSlices
    • NumberOfTimeSlices
    • SeriesInstanceUID
    • ImageOrientationPatient
    • SeriesType
    • OperatorsName
    • PerformedProcedureStepDescription
    • AcquisitionDeviceProcessingDescription
    • ContrastBolusAgent
  • Instances:
    • InstanceCreationDate
    • InstanceCreationTime
    • AcquisitionNumber
    • ImageIndex
    • InstanceNumber
    • NumberOfFrames
    • TemporalPositionIdentifier
    • SOPInstanceUID
    • ImagePositionPatient
    • ImageComments
    • ImageOrientationPatient

Adding more tags in DB

Since version 1.11.0, it is possible to customize a list of ExtraMainDicomTags to include in the DB through a new configuration option.

Since version 1.11.1, it is possible to include sequences in ExtraMainDicomTags. However, this should be considered as an “experimental” feature and you should not store large sequences (> 64KB) or sequences containing binary tags.

Below is a sample configuration that is well suited to optimize DICOMWeb routes in general, especially when you are using a DICOMWeb viewer:

    "ExtraMainDicomTags" : {
    "Instance" : [
    "Series" : [
    "Study": [
    "Patient": []

This configuration will apply only to newly added resources in Orthanc. If you want to apply this change to resources already in Orthanc, you may call the /studies/../reconstruct API route or use the Housekeeper plugin to automate this reconstruction process.


Since Orthanc 1.11.0, Orthanc issues a warning everytime it opens a DICOM file to access a DICOM tag that could have been saved in DB.

Orthanc will also issue a warning everytime it accesses a resource that has been saved with a ExtraMainDicomTags configuration that is different from the current one inviting you to call the /reconstruct route to fix this.

These warnings can be enabled/disabled through this configuration:

    "Warnings" : {
        "W001_TagsBeingReadFromStorage": true,
        "W002_InconsistentDicomTagsInDb": true