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.
The modality may:
In the Image SOP Instances:
create a Request Attributes Sequence containing two or more Items each containing the following Attributes:
Requested Procedure ID
Scheduled Procedure Step ID
Scheduled Procedure Step Description
Scheduled Protocol Code Sequence
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
select one value from the Modality Worklist or generate a new value for:
Study Instance UID
select one value from the Modality Worklist or generate a new value or assign an empty value for:
Accession Number
In the MPPS SOP Instance:
create a Scheduled Step Attributes Sequence containing two or more Items each containing the following Attributes:
Study Instance UID
Referenced Study Sequence
Accession Number
Requested Procedure ID
Scheduled Procedure Step ID
Scheduled Procedure Step Description
Scheduled Protocol Code Sequence
include the following Attribute value that may be generated during image acquisition, if supported:
Procedure Code Sequence
In both the Image SOP Instances and the MPPS SOP Instance
create a Performed Procedure Step ID
include the following Attribute values that may be generated during image acquisition, if supported:
Performed Procedure Step Start Date
Performed Procedure Step Start Time
Performed Procedure Step Description
Study ID
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:
For all Series in the MPPS, replicate the entire Series of Images using new Series Instance UIDs
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
In each of the Image SOP Instances, using values from the corresponding Requested Procedure:
create a Request Attributes Sequence containing an Item containing the following Attributes:
Requested Procedure ID
Scheduled Procedure Step ID
Scheduled Procedure Step Description
Scheduled Protocol Code Sequence
copy from the Modality Worklist:
Study Instance UID
Accession Number
create a Referenced Study Sequence containing an Item containing the following Attribute:
Study SOP Instance in the Referenced Study Sequence from the Worklist
In the MPPS SOP Instance (if supported):
create a Scheduled Step Attributes Sequence containing two or more Items each containing the following Attributes:
Study Instance UID
Referenced Study Sequence
Accession Number
Requested Procedure ID
Scheduled Procedure Step ID
Scheduled Procedure Step Description
Scheduled Protocol Code Sequence
include the following Attribute value that may be generated during image acquisition, if supported:
Procedure Code Sequence
In both the Image SOP Instances and the MPPS SOP Instance (if supported):
create a Performed Procedure Step ID
include the following Attribute values that may be generated during image acquisition, if supported:
Performed Procedure Step Start Date
Performed Procedure Step Start Time
Performed Procedure Step Description
Study ID