Z.4.1 C-GET Operation

SCUs of the Composite Instance Retrieve Without Bulk Data Service shall generate retrievals using the C-GET operation as described in PS 3.7. The C-GET operation allows an application entity to instruct another application entity to transfer SOP Instances without the Attributes as described in Section Z.1.3 to the initiating application entity using the C-STORE operation. Support for the C-GET service shall be agreed upon at Association establishment time by both the SCU and SCP of the C-GET in order for a C-GET operation to occur over the Association. The C-STORE Sub-operations shall be accomplished on the same Association as the C-GET operation. Hence, the SCP of the Query/Retrieve Service Class serves as the SCU of the Storage Service Class.

Note: The Application Entity that receives the stored SOP Instances is always the originator of the C-GET operation.

Z.4.2.1 C-GET Service Parameters

Z.4.2.1.1 SOP Class UID

The SOP Class UID identifies the Query/Retrieve Information Model against which the C-GET is to be performed. Support for the SOP Class UID is implied by the Abstract Syntax UID of the Presentation Context used by this C-GET operation.

Z.4.2.1.2 Priority

The Priority Attribute defines the requested priority of the C-GET operation and corresponding C-STORE sub-operations with respect to other DIMSE operations being performed by the same SCP.

Processing of priority requests is not required of SCPs. Whether or not an SCP supports priority processing, and the meaning of the different priority levels shall be stated in the Conformance Statement of the SCP. The same priority shall be used for all C-STORE sub-operations.

Z.4.2.1.3 Identifier

The C-GET request shall contain an Identifier. The C-GET response shall conditionally contain an Identifier as required in C.4.3.1.3.2.

Note: The Identifier is specified as U in the definition of the C-GET primitive in PS 3.7 but is specialized for use with this service.

Z.4.2.1.3.1 Request Identifier Structure

An Identifier in a C-GET request shall contain:

– the Query/Retrieve Level (0008,0052) that defines the level of the retrieval

– SOP Instance UID(s) (0008,0018)

Query/Retrieve Level (0008,0052) shall be IMAGE.

Specific Character Set (0008,0005) shall not be present.

The Keys at each level of the hierarchy and the values allowable for the level of the retrieval are defined in the SOP Class definition for the Query/Retrieve Information Model.

Z.4.2.1.4 Status

The status code values that might be returned in a C-GET response shall be as specified in Table Z.4-1

Table Z.4-1 C-GET RESPONSE STATUS VALUES FOR INSTANCE ROOT RETRIEVE

Service Status Further Meaning Status Codes Related Fields
Failure Refused: Out of Resources – Unable to calculate number of matches A701 (0000,0902)
Refused: Out of Resources – Unable to perform sub-operations A702 (0000,1020) (0000,1021) (0000,1022) (0000,1023)
Identifier does not match SOP Class A900 (0000,0901) (0000,0902)
Unable to process Cxxx (0000,0901) (0000,0902)
Cancel Sub-operations terminated due to Cancel Indication FE00 (0000,1020) (0000,1021) (0000,1022) (0000,1023)
Warning Sub-operations Complete – One or more Failures or Warnings B000 (0000,1020) (0000,1021) (0000,1022) (0000,1023)
Success Sub-operations Complete – No Failures or Warnings 0000 (0000,1020) (0000,1021) (0000,1022) (0000,1023)
Pending Sub-operations are continuing FF00 (0000,1020) (0000,1021) (0000,1022) (0000,1023)

Z.4.2.1.5 Number of Remaining Sub-Operations

Inclusion of the Number of Remaining Sub-operations shall be as specified in C.4.3.1.5

Z.4.2.1.6 Number of Completed Sub-Operations

Inclusion of the Number of Completed Sub-operations shall be as specified in C.4.3.1.6

Z.4.2.1.7 Number of Failed Sub-Operations

Inclusion of the Number of Failed Sub-operations shall be as specified in C.4.3.1.7

Z.4.2.1.8 Number of Warning Sub-Operations

Inclusion of the Number of Warning Sub-operations shall be as specified in C.4.3.1.8.

Z.4.2.2 C-GET SCU and C-STORE SCP Behavior

An SCU conveys the following semantics with a C-GET request:

– The SCU shall specify one Instance UID or a list of Instance UIDs.

– The SCU shall have proposed sufficient presentation contexts at Association establishment time to accommodate expected C-STORE sub-operations that will occur over the same Association. The SCU of the Query/Retrieve Service Class shall serve as the SCP of the Storage Service Class.

– The SCP of the Storage Service Class shall not store the incomplete SOP Instance; rather the behavior is implementation defined.

– The SCU shall accept C-GET responses with status equal to Pending during the processing of the C-STORE sub-operations. These responses indicate the number of Remaining, Completed, Failed and Warning C-STORE sub-operations.

– The SCU shall interpret a C-GET response with a status equal to Success, Warning, Failure, or Refused as a final response. The final response indicates the number of Completed sub-operations and the number of Failed C-STORE sub-operations resulting from the C-GET operation. The SCU shall interpret a status of:

– The SCU may cancel the C-GET operation by issuing a C-GET-CANCEL request at any time during the processing of the C-GET request. A C-GET response with a status of Canceled shall indicate to the SCU that the retrieve was canceled. Optionally, the C-GET response with a status of Canceled shall indicate the number of Completed, Failed, and Warning C-STORE sub-operations. If present, the Remaining sub-operations count shall contain the number of C-STORE sub-operations that were not initiated due to the C-GET-CANCEL request.

– The SCP of the Storage Service Class shall not return a status of “Error: Dataset does not match SOP Class” (A9xx) or “Warning: Dataset does not match SOP Class” (B007) due to the absence of the Attributes described in Section Z.1.3.

Z.4.2.3 C-GET SCP and C-STORE SCU Behavior

An SCP conveys the following semantics with a C-GET response:

– The SCP shall identify a set of Entities at the level of the transfer based upon the values in the Unique Keys in the Identifier of the C-GET request.

– The SCP shall initiate C-STORE sub-operations for the identified SOP Instances, but shall not include in this C-STORE sub-operation the Attributes described in section Z.1.3. The SCP of the Query/Retrieve Service Class shall serve as an SCU of the Storage Service Class.

– Apart from the Attributes listed in section Z.1.3, the SOP Instance sent via the C-STORE sub-operation shall be unchanged, and no corresponding changes to other attributes shall be made.

Note: In particular, the Study, Series and SOP Instance UIDs and SOP Class UID will not be altered.

– The SCP shall initiate C-STORE sub-operations over the same Association for all SOP Instances specified in the C-GET request.

– A sub-operation is considered a Failure if the SCP is unable to initiate a C-STORE sub-operation because the Query/Retrieve SCU did not offer an appropriate presentation context for a given stored SOP Instance.

– Optionally, the SCP may generate responses to the C-GET with status equal to Pending during the processing of the C-STORE sub-operations. These responses shall indicate the number of Remaining, Completed, Failure, and Warning C-STORE sub-operations.

– When the number of Remaining sub-operations reaches zero, the SCP shall generate a final response with a status equal to Success, Warning or Failed. The status contained in the C-GET response shall contain:

– The SCP may receive a C-GET-CANCEL request at any time during the processing of the C-GET request. The SCP shall interrupt all C-STORE sub-operation processing and return a status of Canceled in the C-GET response. The C-GET response with a status of Canceled shall contain the number of Completed, Failed, and Warning C-STORE sub-operations. If present, the Remaining sub-operations count shall contain the number of C-STORE sub-operations that were not initiated due to the C-GET-CANCEL request.

– If the SCP manages images in multiple alternate encodings (see C.6.1.1.5.1), only one of the alternate encodings of an image shall be used as the existing SOP Instance from which frames are to be extracted.