Annex J Handling Of Identifying Parameters (Informative)

This Annex was formerly located in Annex M of PS 3.4 in the 2003 and earlier revisions of the standard.

J.1 PURPOSE OF THIS ANNEX

The DICOM Standard was published in 1993 and addresses medical images communication between medical modalities, workstations and other medical devices as well as data exchange between medical devices and the Information System (IS). DICOM defines SOP Instances with Patient, Visit and Study information managed by the Information System and allows to communicate the Attribute values of these objects.

Since the publication of the DICOM Standard great effort has been made to harmonize the Information Model of the DICOM Standard with the models of other relevant standards, especially with the HL7 model and the CEN TC 251 WG3 PT 022 model. The result of these effort is a better understanding of the various practical situations in hospitals and an adaptation of the model to these situations. In the discussion of models, the definition of Information Entities and their Identifying Parameters play a very important role.

The purpose of this Informative Annex is to show which identifying parameters may be included in Image SOP Instances and their related Modality Performed Procedure Step (MPPS) SOP Instance. Different scenarios are elucidated to describe varying levels of integration of the Modality with the Information System, as well as situations in which a connection is temporarily unavailable.

Note: In this Annex, “Image SOP Instance” is used as a collective term for all Composite Image Storage SOP Instances.

The scenarios described here are informative and do not constitute a normative section of the DICOM Standard.

J.2 Integrated Environment

"Integrated" means in this context that the Acquisition Modality is connected to an Information System or Systems that may be an SCP of the Modality Worklist SOP Class or an SCP of the Modality Performed Procedure Step SOP Class or both. In the following description only the behavior of "Modalities" is mentioned, it goes without saying that the IS must conform to the same SOP Classes.

The Modality receives identifying parameters by querying the Modality Worklist SCP and generates other Attribute values during image generation. It is desirable that these identifying parameters be included in the Image SOP Instances as well as in the MPPS object in a consistent manner. In the case of a Modality that is integrated but unable to receive or send identifying parameters, e.g. link down, emergency case, the Modality may behave as if it were not integrated.

The Study Instance UID is a crucial Attribute that is used to relate Image SOP Instances (whose Study is identified by their Study Instance UID), the Modality PPS SOP Instance which contains it as a reference, and the actual or conceptual Requested Procedure ( i.e. Study) and related Imaging Service Request in the IS. An IS that manages an actual or conceptual Detached Study Management entity is expected to be able to relate this Study Instance UID to the SOP Instance UID of the Detached Study Management SOP Instance, whether or not the Study Instance UID is provided by the IS or generated by the modality.

For a detailed description of an integrated environment see the IHE Radiology Technical Framework. This document can be obtained at:

http://www.ihe.net/

J.2.1 Modality Conforms to Modality Worklist and MPPS SOP Classes

The modality may:

  1. N-CREATE a MPPS SOP Instance and include its SOP Instance UID in the Image SOP Instances within the Referenced Performed Procedure Step Sequence Attribute.

  2. Copy the following Attribute values from the Modality Worklist information into the Image SOP Instances and into the related MPPS SOP Instance:

  3. Study Instance UID

  4. Referenced Study Sequence

  5. Accession Number

  6. Requested Procedure ID

  7. Scheduled Procedure Step ID

  8. Scheduled Procedure Step Description

  9. Scheduled Protocol Code Sequence

  10. Create the following Attribute value and include it into the Image SOP Instances and the related MPPS SOP Instance:

  11. Performed Procedure Step ID

  12. Include the following Attribute values that may be generated during image acquisition, if supported, into the Image SOP Instances and the related MPPS SOP Instance:

  13. Performed Procedure Step Start Date

  14. Performed Procedure Step Start Time

  15. Performed Procedure Step Description

  16. Study ID

J.2.2 Modality Conforms only to the Modality Worklist SOP Class

The modality may:

  1. In the absence of the ability to N-CREATE a MPPS SOP Instance, generate a MPPS SOP Instance UID and include it into the Referenced Performed Procedure Step Sequence Attribute of the Image SOP Instances. A system that later N-CREATEs a MPPS SOP Instance may use this UID extracted from the related Image SOP Instances.

  2. Copy the following Attribute values from the Modality Worklist information into the Image SOP Instances:

  3. Study Instance UID

  4. Referenced Study Sequence

  5. Accession Number

  6. Requested Procedure ID

  7. Scheduled Procedure Step ID

  8. Scheduled Procedure Step Description

  9. Scheduled Protocol Code Sequence

  10. Create the following Attribute value and include it into the Image SOP Instances:

  11. Performed Procedure Step ID

A system that later N-CREATEs a MPPS SOP Instance may use this Attribute value extracted from the related Image SOP Instances.

  1. Include the following Attribute values that may be generated during image acquisition, if supported, into the Image SOP Instances:

  2. Performed Procedure Step Start Date

  3. Performed Procedure Step Start Time

  4. Performed Procedure Step Description

  5. Study ID

A system that later N-CREATEs a MPPS SOP Instance may use these Attribute values extracted from the related Image SOP Instances.

J.2.3 Modality Conforms only to the MPPS SOP Class

The modality may:

  1. N-CREATE a MPPS SOP Instance and include its SOP Instance UID in the Image SOP Instances within the Referenced Performed Procedure Step Sequence Attribute.

  2. Create the following Attribute values and include them in the Image SOP Instances and the related MPPS SOP Instance:

  3. Study Instance UID

  4. Performed Procedure Step ID

  5. Copy the following Attribute values, if available to the Modality, into the Image SOP Instances and into the related MPPS SOP Instance:

  6. Accession Number

  7. Patient ID

  8. Patient’s Name

  9. Patient’s Birth Date

  10. Patient’s Sex

If sufficient identifying information is included, it will allow the Image SOP Instances and the MPPS SOP Instance to be later related to the Requested Procedure and the actual or conceptual Detached Study Management entity.

  1. Include the following Attribute values that may be generated during image acquisition, if supported, into the Image SOP Instances and the related MPPS SOP Instance:

  2. Performed Procedure Step Start Date

  3. Performed Procedure Step Start Time

  4. Performed Procedure Step Description

  5. Study ID

J.3 Non-Integrated Environment

"Non-Integrated" means in this context that the Acquisition Modality is not connected to an Information System Systems, does not receive Attribute values from an SCP of the Modality Worklist SOP Class, and cannot create a Performed Procedure Step SOP Instance.

The modality may:

  1. In the absence of the ability to N-CREATE a MPPS SOP Instance, generate a MPPS SOP Instance UID and include it into the Referenced Performed Procedure Step Sequence Attribute of the Image SOP Instances. A system that later N-CREATEs a MPPS SOP Instance may use this UID extracted from the related Image SOP Instances.

  2. Create the following Attribute values and include them in the Image SOP Instances:

  3. Study Instance UID

  4. Performed Procedure Step ID

A system that later N-CREATEs a MPPS SOP Instance may use these Attribute values extracted from the related Image SOP Instances.

  1. Copy the following Attribute values, if available to the Modality, into the Image SOP Instances:

  2. Accession Number

  3. Patient ID

  4. Patient’s Name

  5. Patient’s Birth Date

  6. Patient’s Sex

If sufficient identifying information is be included, it will allow the Image SOP Instances to be later related to the Requested Procedure and the actual or conceptual Detached Study Management entity.

  1. Include the following Attribute values that may be generated during image acquisition, if supported, into the Image SOP Instances:

  2. Performed Procedure Step Start Date

  3. Performed Procedure Step Start Time

  4. Performed Procedure Step Description

  5. Study ID

A system that later N-CREATEs a MPPS SOP Instance may use these Attribute values extracted from the related Image SOP Instances.

J.4 One MPPS is Created in Response to two or more Requested Procedures

In the MPPS SOP Instance, all the specific Attributes of a Scheduled Procedure Step or Steps are included in the Scheduled Step Attributes Sequence. In the Image SOP Instances, these Attributes may be included in the Request Attributes Sequence. This is an optional Sequence in order not to change the definition of existing SOP Classes by adding new required Attributes or changing the meaning of existing Attributes.

Both Sequences may have more than one Item if more than one Requested Procedure results in a single Performed Procedure Step.

Because of the definitions of existing Attributes in existing Image SOP Classes, the following solutions are a compromise. The first one chooses or creates a value for the single valued Attributes Study Instance UID and Accession Number. The second one completely replicates the Image data with different values for the Attributes Study Instance UID and Accession Number.

J.4.1 Choose or Create a Value for Study Instance UID and Accession Number

The modality may:

  1. In the Image SOP Instances:

  2. create a Request Attributes Sequence containing two or more Items each containing the following Attributes:

  3. Requested Procedure ID

  4. Scheduled Procedure Step ID

  5. Scheduled Procedure Step Description

  6. Scheduled Protocol Code Sequence

  7. create a Referenced Study Sequence containing two or more Items sufficient to contain the Study SOP Instance UID values from the Modality Worklist for both Requested Procedures

  8. select one value from the Modality Worklist or generate a new value for:

  9. Study Instance UID

  10. select one value from the Modality Worklist or generate a new value or assign an empty value for:

  11. Accession Number

  12. In the MPPS SOP Instance:

  13. create a Scheduled Step Attributes Sequence containing two or more Items each containing the following Attributes:

  14. Study Instance UID

  15. Referenced Study Sequence

  16. Accession Number

  17. Requested Procedure ID

  18. Scheduled Procedure Step ID

  19. Scheduled Procedure Step Description

  20. Scheduled Protocol Code Sequence

  21. include the following Attribute value that may be generated during image acquisition, if supported:

  22. Procedure Code Sequence

  23. In both the Image SOP Instances and the MPPS SOP Instance

  24. create a Performed Procedure Step ID

  25. include the following Attribute values that may be generated during image acquisition, if supported:

  26. Performed Procedure Step Start Date

  27. Performed Procedure Step Start Time

  28. Performed Procedure Step Description

  29. Study ID

J.4.2 Replicate the Image IOD

An alternative method is to replicate the entire Image SOP Instance with a new SOP Instance UID, and assign each Image IOD it’s own identifying Attributes. In this case, each of the Study Instance UID and the Accession Number values can be used in their own Image SOP Instance.

Both Image SOP Instances may reference a single MPPS SOP Instance (via the MPPS SOP Instance UID in the Referenced Performed Procedure Step Sequence).

Each individual Image SOP Instance may reference it’s own related Study SOP Instance, if it exists (via the Referenced Study Sequence). This Study SOP Instance has a one to one relationship with the corresponding Requested Procedure.

If an MPPS SOP Instance is created, it may reference both related Study SOP Instances.

The modality may:

  1. For all Series in the MPPS, replicate the entire Series of Images using new Series Instance UIDs

  2. Create replicated Image SOP Instances with different SOP Instance UIDs that use the new Series Instance UIDs, for each of the two or more Requested Procedures

  3. In each of the Image SOP Instances, using values from the corresponding Requested Procedure:

  4. create a Request Attributes Sequence containing an Item containing the following Attributes:

  5. Requested Procedure ID

  6. Scheduled Procedure Step ID

  7. Scheduled Procedure Step Description

  8. Scheduled Protocol Code Sequence

  9. copy from the Modality Worklist:

  10. Study Instance UID

  11. Accession Number

  12. create a Referenced Study Sequence containing an Item containing the following Attribute:

  13. Study SOP Instance in the Referenced Study Sequence from the Worklist

  14. In the MPPS SOP Instance (if supported):

  15. create a Scheduled Step Attributes Sequence containing two or more Items each containing the following Attributes:

  16. Study Instance UID

  17. Referenced Study Sequence

  18. Accession Number

  19. Requested Procedure ID

  20. Scheduled Procedure Step ID

  21. Scheduled Procedure Step Description

  22. Scheduled Protocol Code Sequence

  23. include the following Attribute value that may be generated during image acquisition, if supported:

  24. Procedure Code Sequence

  25. In both the Image SOP Instances and the MPPS SOP Instance (if supported):

  26. create a Performed Procedure Step ID

  27. Include the following Attribute values that may be generated during image acquisition, if supported:

  28. Performed Procedure Step Start Date

  29. Performed Procedure Step Start Time

  30. Performed Procedure Step Description

  31. Study ID

J.5 MPPS SOP Instance Created by Another System (not the Modality)

If for some reason the Modality was unable to create the MPPS SOP Instance, another system may wish to perform this service. This system must make sure that the created PPS SOP Instance is consistent with the related Image SOP Instances.

Depending on the availability and correctness of values for the Attributes in the Image SOP Instances, these values may be copied into the MPPS SOP Instance, or they may have to be coerced, e.g. if they are not consistent with corresponding values available from the IS.

For example, if the MPPS SOP Instance UID is already available in the Image SOP Instance (in the Referenced Performed Procedure Step Sequence), it may be utilized to N-CREATE the MPPS SOP Instance. If not available, a new MPPS SOP Instance UID may be generated and used to N-CREATE the MPPS SOP Instance. In this case there may be no MPPS SOP Instance UID in the Referenced Performed Procedure Step Sequence in the corresponding Image SOP Instances. An update of the Image SOP Instances will restore the consistency, but this is not required.

J.6 MAPPING OF STUDY INSTANCE UIDS TO THE STUDY SOP INSTANCE UID

Retired. See PS 3.17 2004.