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DICOM Instance Query

Language reference

This page describes the query language reference that allows you to search for DICOM instances in the Search and Export pages of the self-service portal, or to filter DICOM instances in the DICOMFilterQuery attribute of the de-identifier configuration file or the permissions configuration file.

A query is composed of one or more conditions, combined with AND or OR operands. You can also enclose multiple conditions and operands in parenthesis () in order to change the predecence of operands (e.g. (Condition1 OR Condition2) AND Condition3).

Each condition is defined as Tag Operator [Value] where a Value is required for some operators only.

Possible values for Tag

  • A case-sensitive keyword (e.g. Modality)
  • Or a hexadecimal number (e.g. 7FE00010)
  • Or a sequence of tags separated by dots (e.g. SequenceOfUltrasoundRegions.RegionSpatialFormat, 00186011.00186012 or 00186011.RegionSpatialFormat)

Possible values for Operator

Operator Value Description
Exists No value needed The data element must exist
NotExists No value needed The data element must not exist
Empty No value needed At least one value of the data element must be empty
NotEmpty No value needed At least one value of the data element must not be empty
StrEquals String that can eventually be enclosed with " or contains a wildcard character * At least one value of the data element must equals Value, or match Value if wildcard characters are used (case insensitive)
StrNotEquals String that can eventually be enclosed with " or contains a wildcard character * At least one value of the data element value must not equals Value, and must not match Value if wildcard characters are used (case insensitive)
NbEquals Integer or decimal value At least one value of the data element value must be an integer or a decimal, and must equals Value
NbNotEquals Integer or decimal value At least one values of the data element value must be an integer or a decimal, and must not equals Value
NbGreater Integer or decimal value At least one value of the data element value must be an integer or a decimal, and must be greater than Value
NbLess Integer or decimal value At least one value of the data element value must be an integer or a decimal, and must be less than Value

Examples

  • (Modality StrEquals CT OR Modality StrEquals MR) AND StudyDescription StrEquals "*chest*": The value of the data element Modality must equals CT or MR, and the value of the data element StudyDescription must contain chest.
  • ImageType StrEquals ORIGINAL AND Rows NbGreater 500 AND Rows NbLess 1000: At least one value of the data element ImageType must equals ORIGINAL (this is a multi-valued data element) and the value of the data element Rows must be between 500 and 1000 (500 and 1000 excluded).
  • 00190040.0019004A Exists: There must be a top-level data element 00190040 whose value representation is SQ, and one of its values must contain a data element 0019004A.

How does it work

This section is intended for advanced readers, and explains how the query language is implemented within the solution.

Each DICOM file stored in the second Orthanc server is indexed in a PostgreSQL database as a JSON document, derived from the output of the to_json function in pydicom.

PostgreSQL can store JSON data as a jsonb data type (see JSON data type) which supports the SQL/JSON path language from PostgreSQL 12 to efficiently query JSON data.

The solution translates human-readable queries into SQL/JSON path language, and executes the SQL/JSON path query in the PostgreSQL database to search for matching DICOM instances. For example, Modality StrEquals CT AND Rows NbGreater 1000 gives @.00080060 like_regex "CT" flag "i" && @.00280010.double() > 1000. This provides more granularity and performance than using the /tools/find Orthanc API or the DICOMweb API.