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Foundations

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Standards

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Flagship messages

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Tools

ImagingSelection — Subset of DICOM instances

A new resource introduced in FHIR R5. It identifies a precise subset of a DICOM study — series, instances, frames, geometric regions. The bridge between the global ImagingStudy and the radiologic content relevant to a clinical report.

Purpose of the resource

A DICOM study may contain thousands of images. For a radiology report, the radiologist points to only a small subset that justifies the interpretation: 3 axial slices showing a suspicious lesion, two frames of a coronary angiography showing a stenosis. ImagingSelection is the container that unambiguously identifies that subset.

Before R5, FHIR used ImagingManifest (deprecated in R4 and removed). The new resource is explicitly aligned with DICOM PS3.4 KOS (Key Object Selection) and with TID 1500 Structured Reports, which allows direct convertibility between the two worlds.

Key fields

FieldTypeCardinalityRole
identifierIdentifier[]0..*External identifiers for the selection.
statuscode1..1State: available, entered-in-error, unknown.
subjectReference(Patient | Group | Device | Location)0..1Patient or group the selection refers to.
issueddateTime0..1Date the selection was issued (= report date).
performerBackboneElement[]0..*Author(s) of the selection with their role (radiologist, technologist…).
basedOnReference(CarePlan | ImagingStudy | ServiceRequest)[]0..*Originating request.
categoryCodeableConcept[]0..*Classification (key image, teaching file…).
codeCodeableConcept0..1Selection type (DICOM TID 1500 concept names).
studyUidid0..1DICOM UID of the source study.
derivedFromReference(ImagingStudy | DocumentReference)[]0..*Originating ImagingStudy or DICOM KOS.
endpointReference(Endpoint)[]0..*WADO-RS, WADO-URI, QIDO-RS from which to fetch pixels.
seriesUidid0..1DICOM UID of the selected series.
seriesNumberunsignedInt0..1DICOM series number.
frameOfReferenceUidid0..1DICOM Frame of Reference (shared 3D space).
bodySiteBackboneElement0..1Anatomic site (SNOMED CT or DICOM CID).
focusReference(ImagingSelection)[]0..*Parent or sibling selections (e.g. before/after comparison).
instanceBackboneElement[]0..*List of selected DICOM instances with UID, SOP class, frames, regions.
instance.imageRegion2DBackboneElement[]0..*2D region inside the image (point, polyline, rectangle, ellipse).
instance.imageRegion3DBackboneElement[]0..*3D region inside the frameOfReference (point, sphere, ellipsoid).

JSON example

A radiologist marks a roughly 4×4 cm lesion on axial slice 42 of an abdominal CT series. The selection references the study by its DICOM studyUid, points at the WADO-RS server hosting the pixels, and carries an imageRegion2D of polyline type.

json imagingselection-example.json 
{
  "resourceType": "ImagingSelection",
  "id": "example-keyimage",
  "status": "available",
  "subject": { "reference": "Patient/example" },
  "issued": "2026-05-16T10:25:30+02:00",
  "performer": [{
    "function": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/v2-0912",
        "code": "REF",
        "display": "Referring"
      }]
    },
    "actor": { "reference": "Practitioner/dr-jones" }
  }],
  "studyUid": "1.2.840.113619.2.176.2025.1499492.7040.1171286242.109",
  "derivedFrom": [{ "reference": "ImagingStudy/example" }],
  "endpoint": [{ "reference": "Endpoint/dicom-wado-rs" }],
  "seriesUid": "1.2.840.113619.2.176.2025.1499492.7040.1171286242.111",
  "seriesNumber": 3,
  "frameOfReferenceUid": "1.2.840.113619.2.176.2025.1499492.7040.1171286242.219",
  "bodySite": {
    "concept": {
      "coding": [{
        "system": "http://snomed.info/sct",
        "code": "12921003",
        "display": "Anatomic site of pelvis"
      }]
    }
  },
  "instance": [{
    "uid": "1.2.840.113619.2.176.2025.1499492.7040.1171286242.345",
    "number": 42,
    "sopClass": {
      "system": "urn:ietf:rfc:3986",
      "code": "urn:oid:1.2.840.10008.5.1.4.1.1.2"
    },
    "subset": ["1", "2"],
    "imageRegion2D": [{
      "regionType": "polyline",
      "coordinate": [100.0, 110.0, 130.0, 110.0, 130.0, 150.0, 100.0, 110.0]
    }]
  }]
}

Typical use cases

  • Radiology report: each assertion of a DICOM TID 1500 SR can be converted into an ImagingSelection attached to an Observation.
  • Key images: flag the key images of a study for another clinician or an MDT (Multi-Disciplinary Team).
  • Teaching files: case libraries with annotations.
  • Annotations: lesion contour, 2D/3D ROI for longitudinal follow-up (RECIST).
  • Radiation therapy: identify target structures inside a dosimetric plan.
  • AI / CADx: traceability of the region analysed by an algorithm and its output.

Common pitfalls

  • Duplicate DICOM UIDs: studyUid, seriesUid and instance.uid must exactly match those of the associated ImagingStudy. Any mismatch breaks the WADO-RS resolution.
  • Selection without endpoint: the consumer will not know where to fetch the pixels. Always provide at least an Endpoint typed dicom-wado-rs or equivalent.
  • Misaligned 2D coordinates: imageRegion2D.coordinate is expressed in the pixel space of the instance. For physical 3D coordinates, use imageRegion3D together with frameOfReferenceUid.
  • Confusion with ImagingStudy: ImagingStudy models the whole study; ImagingSelection only references a subset. One does not replace the other.
  • Missing SOP class: instance.sopClass is required so a consumer can tell what kind of DICOM object is referenced (CT, MR, US, segmentation, structured report…).
  • ImagingStudy — the global DICOM study referenced via derivedFrom.
  • DiagnosticReport — the radiology report that may embed one or more ImagingSelection in media.
  • Observation — the structured clinical assertion carried by the selection (lesion measurement, BI-RADS, TI-RADS…).
  • Endpoint — the WADO-RS / QIDO-RS / STOW-RS service endpoint.
  • BodyStructure — anatomy pointed to by the selection.

See also: ImagingStudy — the global DICOM study and DiagnosticReport — radiology report.