DICOM association and networking

DICOM accesses DIMSE services through SOP. These SOPs are wrapped within an upper level networking protocol that works using PDUs (Protocol Data Units). The format of the PDUs are:

In addition to the DICOM network data transfer vehicle, PDUs can also form sessions (DICOM associations) between the Modalities (Application Entities [AE]).

Forming a DICOM association is essentially an exchange of capabilities and preferences of peer AEs. These are remembered for the duration of the DICOM association. DICOM associations are established every time a set of DICOM data needs to be exchanged.

The items that are highlighted are:

  • # Peer AE pair

    This indicates the SCU (Service Class User) and SCP (Service Class Provider) AE names. This is remembered by Cloverleaf for the duration of association.

  • #2 Presentation context ID (request)

    This is the presentation context ID of the presentation data that is requested or accepted. Presentation context ID are generated for this purpose by SCU. Accepted IDs are remembered by Cloverleaf for the duration of the association.

  • #3 Abstract syntax

    This is the type of data that is being sent without specifying the actual format. This is similar to SOPs in individual messages. For example, "I must send X-Ray images."

    See DICOM abstract syntax values.

  • #4 Transfer syntax

    This is the format of the data, for example, if you require to send compressed JPEGs and numbers are Big Endian. Some transfer syntax items are remembered by Cloverleaf for the duration of association:

    • Implicit VR Endian: Default Transfer Syntax for DICOM

      UID: 1.2.840.10008.1.2

    • Explicit VR Little Endian

      UID: 1.2.840.10008.1.2.1

    • Deflated Explicit VR Big Endian

      UID: 1.2.840.10008.1.2.1.99

    • Explicit VR Big Endian

      UID: 1.2.840.10008.1.2.2

      See DICOM transfer syntax values.

  • #5 Presentation Context ID

    This is the presentation context ID used to transfer data, with no mention of AE’s or Transfer syntax. This ID is used by Cloverleaf to encode and decode data to additional routes.

  • #6 DICOM Message

    This is the actual DICOM message as indicated in "DICOM format."

    See LDL Configurator.