DICOM PS3.18 2017b - Web Services

6.4 WADO-WS Request/Response

The DICOM Web Service defines several action types. An implementation shall support at least one of these actions. The three action types are:

  1. RetrieveImagingDocumentSet

    This action retrieves a set of DICOM instances and other objects. This action corresponds to the IHE XDS-I.b transaction RAD-69. The DICOM instances are formatted in accordance with PS3.10, and encapsulated in a Web Services response.

  2. RetrieveRenderedImagingDocumentSet

    This action retrieves a set of DICOM instances that have been rendered into the requested format. For example, if rendering into JPEG was requested, these will be the JPEG renderings of the requested set of DICOM Objects.

  3. RetrieveImagingDocumentSetMetadata

    This action retrieves a set of DICOM instances presented as an Infoset with the bulk data removed. This service can retrieve either the full metadata, or a subset selected by XPath arguments. The XML encoding for the DICOM attributes is defined in PS3.19.

The Web Services actions shall be fully compliant with the Basic Profile of WS-I as defined in IHE IT Infrastructure Technical Framework Vol 2x Annex V. All <wsa:Action> elements shall have the mustUnderstand attribute set (mustUnderstand="1").

6.4.1 WS - RetrieveImagingDocumentSet

6.4.1.1 Request

The specific Web Services parameters to be used for the Retrieve Imaging Document Set action shall be as follows, in the order that they would appear in the WSDL definition:

  • The following types shall be imported (xsd:import) in the /definitions/types section:

    • namespace="urn:ihe:rad:xdsi-b:2009", schema="XDSI.b_ImagingDocumentSource.xsd"

    • The baseline XDS.b schema (namespace="urn:ihe:iti:xds-b:2007", schema="XDS.b_DocumentRepository.xsd")

    • The baseline DICOM WADO-WS schema (namespace="urn:dicom:wado:ws:2011", schema="dicom.wado.ws.2011.xsd")

  • The /definitions/message/part/@element attribute of the Retrieve Imaging Document Set Request message shall be an "iherad:RetrieveImagingDocumentSetRequest" as defined below.

  • The /definitions/message/part/@element attribute of the Retrieve Imaging Document Set Response message shall be an "ihe:RetrieveDocumentSetResponse" as defined below.

  • The /definitions/portType/operation/input/@wsaw:Action attribute for the Retrieve Imaging Document Set Request message shall be "urn:ihe:rad:2009:RetrieveImagingDocumentSet".

  • The /definitions/portType/operation/output/@wsaw:Action attribute for the Retrieve Imaging Document Set Response message shall be "urn:ihe:iti:2007:RetrieveDocumentSetResponse".

  • The /definitions/binding/operation/soap12:operation/@soapAction attribute shall be "urn:ihe:rad:2009:RetrieveImagingDocumentSet".

The <iherad:RetrieveImagingDocumentSetRequest/> element for use with the Retrieve Imaging Document Set Request Message is defined as:

  • One or more <iherad:StudyRequest/> elements each of which includes a "studyInstanceUID" attribute identifying the study associated with the DICOM images/ objects being retrieved. Each <iherad:StudyRequest/> element shall contain:

    • One or more <iherad:SeriesRequest/> elements each of which includes a "seriesInstanceUID" attribute identifying the series associated with the DICOM images/ objects being retrieved. Each <iherad:SeriesRequest/> element shall contain:

      • One or more <ihe:DocumentRequest/> elements, each one representing an individual document that the requestor wants to retrieve from the Web Server. Each <ihe:DocumentRequest/> element contains:

        • An optional <ihe:RepositoryUniqueId/> element that identifies the Web Server from which the document is to be retrieved. This value corresponds to XDSDocumentEntry.repositoryUniqueId. The RepositoryUniqueID is similar to a DICOM AETitle, but is a uniqueID assigned to the WADO-WS Web Server rather than a locally assigned string identifier. There will be a separate RepositoryUniqueID for each web service end point.

        • A required <ihe:DocumentUniqueId/> element that identifies the document within the source. For example, this value could be a SOP Instance UID obtained from a Key Object Selection (KOS) instance.

        • An optional <ihe:HomeCommunityId/> element. See the IHE Profiles for the definition and possible uses of this element.

        • An optional <wado:Anonymize/> element.

        • An optional <wado:FrameNumber/> element.

        • A required <iherad:TransferSyntaxUIDList/> element that contains a list of one or more <ihe:TransferSyntaxUID> elements. Each of the <iherad:TransferSyntaxUID> elements represent one of the transfer syntax encodings that the Imaging Document Consumer is capable of processing.

6.4.1.2 Response

A Web Server shall provide the document(s) indicated in the request. The Web Server shall return the document(s) or an error code when the document could not be returned. The pixel data shall be encoded using one of the DICOM transfer syntaxes included in the Retrieve Imaging Document Set Request Message. If the Imaging Document Source cannot encode the pixel data using any of the requested transfer syntaxes then an error status shall be returned.

6.4.1.2.1 Form of the Response

The <ihe:RetrieveDocumentResponse/> element for use with the Retrieve Imaging Document Set Response Message is defined as:

  • A required /ihe:RetrieveDocumentSetResponse/rs:RegistryResponse element

  • An optional sequence of <ihe:DocumentResponse/> elements containing

    • An optional <ihe:HomeCommunityId/> element. The value of this element shall be the same as the value of the /RetrieveImagingDocumentSetRequest/StudyRequest/SeriesRequest/DocumentRequest/HomeCommunityId element in the Retrieve Document Set Request Message. If the <ihe:HomeCommunityId/> element is not present in the Retrieve Document Set Request Message, this value shall not be present.

    • An optional <ihe:RepositoryUniqueId/> that identifies the Imaging Document Source from which the document is to be retrieved. The value of this element shall be the same as the value of the /RetrieveImagingDocumentSetRequest/StudyRequest/SeriesRequest/DocumentRequest/RepositoryUniqueId element in the original Retrieve Imaging Document Set Request Message. This value corresponds to XDSDocumentEntry.repositoryUniqueId.

    • A required <ihe:DocumentUniqueId/> that identifies the document within the Imaging Document Source. The value of this element shall be the same as the value of the /RetrieveImagingDocumentSetRequest/StudyRequest/SeriesRequest/DocumentRequest/DocumentUniqueId element in the original Retrieve Imaging Document Set Request Message. This value corresponds to the SOP Instance UID in the Retrieve Document Request.

    • A conditional <wado:FrameNumber/> that identifies the frame within the source document. It shall be present if and only if <wado:FrameNumber/> was in the request

    • A required <ihe:Document/> element that contains the retrieved document as an XOP Infoset.

    • A required <ihe:mimeType/> element that indicates the media type of the retrieved document.

The /RetrieveDocumentSetResponse/rs:RegistryResponse/@status attributes provides the overall status of the request: It shall contain one of the following values:

  • urn:oasis:names:tc:ebxml-regrep:ResponseStatusType:Success

  • urn:ihe:iti:2007:ResponseStatusType:PartialSuccess

  • urn:oasis:names:tc:ebxml-regrep:ResponseStatusType:Failure

See ITI TF-2a: 4.1.13 Error Reporting for the interpretation of these values.

For each document requested in a /RetrieveImagingDocumentSetRequest/StudyRequest/SeriesRequest/DocumentRequest element:

  • If the document is successfully retrieved (without warning) then no /RetrieveDocumentSetResponse/rs:RegistryResponse/rs:RegistryErrorList/ rs:RegistryError element shall be present and a /RetrieveDocumentSetResponse/DocumentResponse/Document element shall be returned containing the document as base64binary encoded data.

  • If a warning is reported when retrieving the document, then a /RetrieveDocumentSetResponse/rs:RegistryResponse/rs:RegistryErrorList/ rs:RegistryError element shall be returned with:

    • @severity is urn:oasis:names:tc:ebxml-regrep:ErrorSeverityType:Warning

    • @errorCode is specified

    • @codeContext contains the warning message

    • @location contains the DocumentUniqueId of the document requested

    • The document shall be returned in an instance of /RetrieveDocumentSetResponse/DocumentResponse/Document as base64binary encoded data. The returned document and warning are correlated via the DocumentUniqueId.

  • If an error is reported when retrieving a document, then a /RetrieveDocumentSetResponse/rs:RegistryResponse/rs:RegistryErrorList/ rs:RegistryError element shall be returned with:

    • @severity is urn:oasis:names:tc:ebxml-regrep:ErrorSeverityType:Error

    • @errorCode is specified

    • @codeContext contains the error message

    • @location contains the DocumentUniqueId of the document requested

    • No corresponding RetrieveDocumentSetResponse/DocumentResponse element shall be returned

The error conditions for failures and associated error codes are given below in section 6.4.4. These errors shall be detected and the associated errorCode returned if that error occurs. Additional errors defined in the ebRS standard, in ITI TF-2: 4.1.13 "Error Reporting", and defined by the implementer may be returned.

6.4.1.2.2 JPIP

If the user agent specifies a transfer syntax field of 1.2.840.10008.1.2.4.94 (DICOM JPIP Referenced Transfer Syntax) or 1.2.840.10008.1.2.4.95 (DICOM JPIP Referenced Deflate Transfer Syntax), and the Web Server supports the requested transfer syntax the following behavior is expected:

  • If the DICOM Image Object(s) already have the same JPIP transfer syntax as the one indicated in the request, the Retrieve Imaging Document Set Response shall include the DICOM Image Objects unchanged.

  • If the DICOM Image Object(s) have a transfer syntax that differs from that of the request, the Retrieve Imaging Document Set Response shall include the DICOM image with the transfer syntax changed to the requested transfer syntax. In addition, the pixel data Attribute (7FE0,0010 tag) will have been removed and replaced with a Pixel Data Provider URL (0028,7FE0 tag). The URL represents the JPIP request and will include the specific target information.

  • Upon receipt of this Retrieve Imaging Document Set Response, the Imaging Document Consumer may request the pixel data from the pixel data provider using the supplied URL. Additional parameters required by the application may be appended to the URL when accessing the pixel data provider.

  • For example, a JPIP request for a 200 by 200 pixel rendition of the entire image can be constructed from the Pixel Data Provider URL as follows:

    • Pixel Data Provider URL (0028,7FE0) = https://server.xxx/jpipserver.cgi?target=imgxyz.jp2,

    • URL Generated by the application = https://server.xxx/jpipserver.cgi?target=imgxyz.jp2&fsiz=200,200

DICOM PS3.18 2017b - Web Services