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10.6 Resource ImagingSelection - Content

Imaging Integration Work Group

Maturity Level: 1

Trial Use

Security Category: Patient

Compartments: Group, Patient

A selection of DICOM SOP instances within a single Study and Series. This might include additional specifics such as a set of frames or an image region, allowing linkage to an Observation Resource.

10.6.3 References to this Resource

• Implements: Event
• Resource References: BodyStructure, itself and Observation

10.6.4 Resource Content

 

Additional definitions: Master Definition XML + JSON, XML Schema/Schematron + JSON Schema, ShEx (for Turtle) + see the extensions, the spreadsheet version & the dependency analysis

10.6.4.1 Terminology Bindings

Path	ValueSet	Type	Documentation
ImagingSelection.status	ImagingSelectionStatus	Required	The status of the ImagingSelection.
ImagingSelection.category	KeyObjectSelectionDocumentTitle	Preferred	Transitive closure of CID 7010 KeyObjectSelectionDocumentTitle
ImagingSelection.modality	Modality	Extensible	Transitive closure of CID 33 Modality
ImagingSelection.code	KeyObjectSelectionDocumentTitle	Example	Transitive closure of CID 7010 KeyObjectSelectionDocumentTitle
ImagingSelection.performer.function	ImagingStudySeriesPerformerFunction	Extensible	Performer function of an agent in an imaging study series
ImagingSelection.bodySite	SNOMEDCTBodyStructures	Example	This value set includes all codes from SNOMED CT where concept is-a 442083009 (Anatomical or acquired body site (body structure)).
ImagingSelection.instance.imageRegion2D.regionType	ImagingSelection2DGraphicType	Required	The type of 2D coordinates describing a 2D image region.
ImagingSelection.imageRegion3D.regionType	ImagingSelection3DGraphicType	Required	The type of coordinates describing a 3D image region.

10.6.4.2 Constraints

10.6.5 Notes

10.6.5.1 Imaging Selection Subsets

Some DICOM SOP Instances contain sub-resources, such as frames, segments, etc.

An Imaging Selection resource MAY specify the subset of these that are included in the selection using the following elements.

• instance.frameNumber - Frames selected from a multiframe SOP Instance
  • Corresponds to the value of DICOM Referenced Frame Number (0008,1160)
  • Each value specifies a frame included in the selection
  • Note: Frame number is implicit, and the first frame is denoted as frame 1
• instance.referencedContentItemIdentifier - Referenced Content Item Identifiers selected from a DICOM SR or other structured document SOP Instance
  • Corresponds to the value of DICOM Referenced Content Item Identifier (0040,DB73)
  • Each value specifies the node in the DICOM SR tree that is selected at each level
  • See DICOM PS 3.3 C.17.3.2.5
• instance.segmentNumber - Segments selected from a segmentation SOP Instance
  • Corresponds to the value of DICOM Referenced Segment Number (0062,000B)
  • Each value specifies a segment included in the selection
• instance.regionOfInterest - Regions of interest selected from a radiotherapy structure set SOP Instance
  • Corresponds to the value of DICOM Referenced ROI Number (0002,000E)
  • Each value specifies a region of interest included in the selection
• instance.waveFormChannel - Channels selected from a waveform SOP Instance
  • Specified as a pair of values (M,C), where the first value is the Item number of Waveform Sequence (5400,0100) in the referenced object (i.e., the Multiplex Group Number), and the second Value is the Item number of Channel Definition Sequence (003A,0200) (i.e., the Channel Number) within the multiplex group
  • Each value pair specifies a channel included in the selection

The value of the instance.sopClass element determines which type of subset may be present.

For example:

• If instance.sopClass has a value of urn:oid:1.2.840.10008.5.1.4.1.1.2.1, this indicates that the instance is Enhanced CT, which is a multiframe image instance and therefore instance.frameNumber can be included to specify a list of frames
• If instance.sopClass has a value of urn:oid:1.2.840.10008.5.1.4.1.1.88.22, this indicates that the instance is Enhanced SR and therefore instance.referencedContentItemIdentifier can be included to specify a list of content item identifiers

Note: Because an imaging selection instance is limited to a single DICOM Series and each DICOM Series can contain only one type of instance - image, SR document, radiotherapy object, etc. - each imaging selection instance can only contain one type of subset.

10.6.5.2 Use of ImagingSelection.code and ImagingSelection.category

The code and category element can be used to provide information relevant for applications that want to identify specific types of ImagingSelection resources.

For example, if an ImagingSelection is used to identify a set of images that make up a volume rendered view, the code could contain a code indicating Volume Rendering - such as RadLex RID35862 - and the category could contain values of the DICOM Image Type (0008,0008) attribute - such as DERVIED and SECONDARY.

  {
    "resource": {
      "resourceType": "ImagingSelection",
      "id": "fa8e0948175f3117a3b8c4be2ff972ec",
      "subject": {
        "reference": "Patient/acb045960122378999c97cd7ca532f8b"
      },
      "code": {
        "coding": [
          {
            "system": "http://radlex.org/",
            "code": "RID12769",
            "display": "volume rendering"
          }
        ]
      },
      "category": [
        {
          "text": "DERIVED"
        },
        {
          "text": "SECONDARY"
        }
      ]
    }
  }

10.6.5.3 Element Requirements by Selection Type

This section outlines several imaging selection types, each listing a set of resource elements that are required and/or typically present in the selection. Some types require only a minimal set of elements, while others require a comprehensive list to ensure clarity.

10.6.5.3.1 Single-Frame Image Selection

An imaging selection that points to one single-frame image requires:

• studyUid to identify the DICOM Study that contains the image
• seriesUid to identify the Series within the Study that contains the image
• instance containing a single entry that specifies:
  • uid to identify the SOP Instance UID of the selected image

While not required, this type of selection typically includes:

• frameOfReferenceUid to identify the coordinate system of the image
• instance.sopClass to specify the SOP Class UID of the selected image

See Single-Frame Image Selection example.

10.6.5.3.2 Multiframe Image Selection

An imaging selection that points to frames in a multiframe image requires:

• studyUid to identify the DICOM Study that contains the image
• seriesUid to identify the Series within the Study that contains the image
• instance containing a single entry that specifies:
  • uid to identify the SOP Instance UID of the selected image
  • frameNumber to identify the list of frames included in the selection

While not required, this type of selection typically includes:

• frameOfReferenceUid to identify the coordinate system of the image
• instance.sopClass to specify the SOP Class UID of the selected image

See Multiframe Image Selection example.

10.6.5.3.3 2D Image Selection

An imaging selection that points to a 2D region on an image requires:

• studyUid to identify the DICOM Study that contains the image
• seriesUid to identify the Series within the Study that contains the image
• instance containing a single entry that specifies:
  • uid to identify the SOP Instance UID of the selected image
  • imageRegion2D containing
    • regionType specifying the type of image region
    • coordinate specifying the x and y coordinates that define the image region in image pixel space

While not required, this type of selection typically includes:

• frameOfReferenceUid to identify the coordinate system of the image
• instance.sopClass to specify the SOP Class UID of the selected image

See 2D Image Region Selection example.

10.6.5.3.4 3D Image Selection

An imaging selection that points to a 3D region requires:

• frameOfReferenceUid to identify the coordinate system that includes the specified coordinates
• imageRegion3D containing
  • regionType specifying the type of image region
  • coordinate specifying the x, y and z coordinates that define the 3D region

This type of selection may also specify a set of images but this is not required. The 3D region selection can be applied to any images that share the same Frame of Reference UID.

See 3D Image Region Selection example.

10.6.5.4 ImagingSelection Endpoints

The ImagingSelection.endpoint elements indicate network services that can be used to access the imaging data referenced by the imaging selection; for example, a DICOM WADO-RS server. Systems can determine if the relevant imaging data is available or offline by interacting with the endpoint.

Different Endpoint connection types MAY have different capabilities, protocols or requirements. Furthermore, the specified Endpoint.address identifies the DICOM Web Service Base URI (see DICOM PS 3.18 Section 8.2 ). The URL needed to retrieve image data may need to be constructed from this base URL. See below for the details on use of imaging-related Endpoint connection types.

10.6.5.4.1 WADO-RS

An Endpoint.connectionType of code dicom-wado-rs, system http://terminology.hl7.org/CodeSystem/endpoint-connection-type, identifies a DICOM WADO-RS service.

The DICOM WADO-RS (Web Access to DICOM Objects, RESTful mode) service uses a RESTful approach to instance retrieval. This service allows for retrieval of native DICOM SOP instances, or instances “rendered” into other formats, including JPEG and MPEG. The media type of a response is specified by the request Accept header (preferred); or, by the accept query parameters. Supported media types depend on the capabilities of the WADO-RS server and the classification of the instance as "single frame", "multi-frame", "video", "text", or "other". The WADO-RS service also allows retrieval of study or series level information.

The path to retrieve a DICOM instance is constructed by appending the appropriate sub-resource paths to the Endpoint.address value.

For example, using the following information in a fictional ImagingSelection resource:

• the WADO-RS service base URL of https://pacs.hospital.org/wado-rs found in an ImagingSelection.endpoint.address,
• the DICOM Study Instance UID of 1.2.250.1.59.40211.12345678.678910 found in an ImagingSelection.identifier having Identifier.system of “urn:dicom:uid”,
• the DICOM Series Instance UID of 1.2.250.1.59.40211.789001276.14556172.67789 found in ImagingSelection.series.uid, and
• the DICOM SOP Instance UID of 1.2.250.1.59.40211.2678810.87991027.899772.2 found in ImagingSelection.series.instance.uid

we can construct the WADO-RS URL to issue an HTTP GET for a native DICOM PS3.10 instance file (if consistent with the Accept header):

https://pacs.hospital.org/wado-rs/studies/1.2.250.1.59.40211.12345678.678910/series/1.2.250.1.59.40211.789001276.14556172.67789/instances/1.2.250.1.59.40211.2678810.87991027.899772.2

10.6.5.4.2 WADO-URI

An Endpoint.connectionType of code dicom-wado-uri, system http://terminology.hl7.org/CodeSystem/endpoint-connection-type, identifies a DICOM WADO-URI service.

The DICOM WADO-URI (Web Access to DICOM Objects, URI mode) service uses HTTP query parameter syntax. This service allows for retrieval of native DICOM instances, or instances “rendered” into other formats, including JPEG and MPEG. The media type of a response is specified by the request Accept header (preferred); or, by the contentType query parameter. Supported media types depend on the classification of the instance as "single frame", "multi-frame", "video", "text", or "other."

The query to retrieve a DICOM instance is constructed by appending the appropriate query parameters to the Endpoint.address value.

For example, using the following information in a fictional ImagingSelection resource:

• the WADO-URI service base URL of https://pacs.hospital.org/wado-uri found in an ImagingSelection.endpoint.address,
• the DICOM Study Instance UID of 1.2.250.1.59.40211.12345678.678910 found in an ImagingSelection.identifier having Identifier.system of urn:dicom:uid,
• the DICOM Series Instance UID of 1.2.250.1.59.40211.789001276.14556172.67789 found in ImagingSelection.series.uid, and
• the DICOM SOP Instance UID of 1.2.250.1.59.40211.2678810.87991027.899772.2 found in ImagingSelection.series.instance.uid

we can construct the WADO-URI URL to issue an HTTP GET for a native DICOM PS3.10 instance file (if consistent with the Accept header):

https://pacs.hospital.org/wado-uri?requestType=WADO&studyUID=1.2.250.1.59.40211.12345678.678910&seriesUID=1.2.250.1.59.40211.789001276.14556172.67789&objectUID=1.2.250.1.59.40211.2678810.87991027.899772.2

10.6.5.5 Body Site and Laterality

The bodySite element may include the laterality of the (possibly paired) anatomic structures examined – e.g. left knee, bilateral lungs, etc. This can be conveyed in several ways:

• bodySite contains an anatomic code that includes laterality, e.g.

  "bodySite": {
    "concept": {
      "coding": [{
        "system": "http://snomed.info/sct",
        "code": "5951000",
        "display": "Left wrist"
      }]
    }
  }
        

• bodySite contains a reference to a BodyStructure resource whose includedStructure.structure element contains an anatomic code that includes laterality
• bodySite contains a reference to a BodyStructure resource whose includedStructure element includes a laterality value. See this example BodyStructure representation of the Left Wrist, with laterality and SNOMED coding for anatomical structure.

10.6.6 Search Parameters

Search parameters for this resource. See also the full list of search parameters for this resource, and check the Extensions registry for search parameters on extensions related to this resource. The common parameters also apply. See Searching for more information about searching in REST, messaging, and services.

Name	Type	Description	Expression	In Common
based-on	reference	The request associated with an imaging selection	ImagingSelection.basedOn (Appointment, CarePlan, Task, ServiceRequest)
body-site	token	The body site code associated with the imaging selection	ImagingSelection.bodySite.concept
body-structure	reference	The body structure associated with the imaging selection	ImagingSelection.bodySite.reference
category	token	The imaging selection category	ImagingSelection.category
code	token	The imaging selection description text or code	ImagingSelection.code	20 Resources
derived-from	reference	The imaging study from which the imaging selection was derived	ImagingSelection.derivedFrom (ImagingStudy, DocumentReference)
identifier	token	Identifiers for the imaging selection	ImagingSelection.identifier	65 Resources
issued	date	The date / time the imaging selection was created	ImagingSelection.issued
modality	token	The modality of the selection	ImagingSelection.modality
patient	reference	Who the study is about	ImagingSelection.subject.where(resolve() is Patient) (Patient)	66 Resources
status	token	The status of the imaging selection	ImagingSelection.status
study-uid	token	The DICOM Study Instance UID from which the images were selected	ImagingSelection.studyUid
subject	reference	The subject of the Imaging Selection, such as the associated Patient	ImagingSelection.subject (Practitioner, Group, Specimen, Device, Medication, Patient, Procedure, Substance)