A.7.2 Updated Pattern Based on A_DicomCompositeObjectReference Minimal (COCT_RM830120UV)
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### A.7.2 Updated Pattern Based on A_DicomCompositeObjectReference Minimal (COCT_RM830120UV)

Figure A.7-2. A_DicomCompositeObjectReference Minimal

The A_DicomCompositeObjectReference minimal pattern has been updated for harmonization with the HL7 V3 assertion pattern. It is used to reference DICOM composite objects within HL7 Version 3 messages in the context of acts and observations. It provides detailed information on the referenced DICOM composite object such as images, presentation states and DICOM structured documents. Mappings from DICOM object attributes to the various Act attributes are provided. The CMETs for the HL7 V3 message DICOM composite object references and the corresponding CDA Release 2 section entries are structurally identical. For the CDA section entries different clone names are used according to the specified entry names in the CDA Release 2.

### Note

The A_DicomCompositeObjectReference minimal CMET COCT_RM830120 may be used in combination with COCT_RM830110 that provides a single location for lookup of referenced DICOM composite objects of an HL7 V3 message (identifying information on the DICOM study/series/instance hierarchy can be found there).

The following description of the act classes and act relationships contains the attribute mappings of HL7 V3 attributes to DICOM (Digital Imaging and Communications in Medicine) tags. The group and element number of the mapped DICOM tags are listed in parenthesis. The CDA mappings specify the use of the CMET act classes and act relationships as CDA Release 2 document section entries.

#### A.7.2.1 SopInstance

The SopInstance act class contains the DICOM Service Object Pair (SOP) Instance information for referenced DICOM composite objects. The SopInstance act class is used to reference both, image and non-image DICOM instances. The text attribute contains the DICOM WADO (PS 3.18 Web Access to DICOM Objects) reference.

Table A.7.2-1. DICOM Composite Object Reference in an HL7 V3 Act

Attribute | Data Type | Multiplicity | Value
--- | --- | --- | ---
classCode | CS | 1..1 | DGIMG
moodCode | CS | 1..1 | EVN
templateId | LIST<II> | 1..* |
id | II | 1..1 | < SOP Instance UID (0008,0018) as root property with no extension property> Uniquely identifies the SOP Instance.
code | CE | 1..1 | < SOP Class UID (0008,0016) as code property, 1.2.840.10008.2.6.1 as codeSystem property, DCMUID as codeSystemName property, SOP Class UID Name (from PS3.6) as displayName property>: Unique Identifier for the SOP Class as Code Property
title | ST | 0..1 | SOP Class UID derived name
text | ED | 0..1 | <"application/DICOM" as mediaType property, WADO reference (see Table A.7.2-2) as reference property>
effectiveTime | TS | 0..1 | < Content Date (0008,0023): The date the content creation (e.g., image pixel data, document) started; and Content Time (0008,0033): The time the content creation (e.g., image pixel data, document) started. >

The DGIMG classCode is used to reference all DICOM Composite Instances, not just diagnostic images.

WADO is a service that enables the Web Client System to retrieve DICOM Persistent Objects managed by a Web Enabled DICOM Server, through the HTTP/HTTPs protocol. The WADO reference uses an URI with query parameters (Table A.7.2-2). Access to the content of a data object is enabled by specifying a "link" pointing to a specific DICOM Persistent Object by means of its URL/URI and specifying its DICOM object Instance UID and the transfer syntax to be employed.

Table A.7.2-2. WADO Reference in HL7 DGIMG Observation.text

WADO Component | Source
--- | ---
<scheme>://<authority>/<path> | Configuration setting, used by the conversion process, identifying the WADO server
?requestType=WADO | Fixed
&studyUID=<uid> | Study Instance UID for referenced instance
&seriesUID=<uid> | Series Instance UID for referenced instance
&objectUID=<uid> | SOP Instance UID for referenced instance
&contentType=application/DICOM | Fixed

##### A.7.2.1.1 CDA Mapping (Class Name and Attributes used for CDA Documents)

- Act clone name of the CDA entry is "Observation" instead of "SopInstance". The attributes and attribute values of this CDA entry "Observation" are identical to those listed in table 1 and 2, except for the optional title attribute (Value: SOP Class UID derived name) that is not mapped because it is not supported by CDA Act Entries.

- templateId value (Table A.7.1-1): Set root portion of II to "2.16.840.1.113883.10.20.6.2.8" (identifies the template that defines constraints on "SopInstance Observation" of CDA Diagnostic Imaging Reports as specified by CDA R2 DIR IG).

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