DICOM Associations

Abstract

DICOM association rules define low-level protocols for DICOM network connectivity. All high-level DIMSE networking we studied previously is based on this. The main goal of DICOM association protocols is to ensure that two communicating DICOM applications (AEs) are compatible and transfer data in a well-defined format and order. The main step toward achieving this goal is DICOM association establishment. It’s worth looking at DICOM associations from a couple of perspectives. From the perspective of TCP/IP networking, DICOM associations provide a more augmented and complex networking mechanism, tailored to transmit DICOM-specific messages. Basic TCP/IP deals with sending byte streams from one networked device to another; it does not make decisions and it does not know anything about data formats. DICOM association rules, built on top of TCP/IP, make TCP/IP smart enough to deal with DICOM objects and commands. For that reason, the DICOM association mechanism is often referred to in DICOM as the DICOM UL (Upper Layer protocol) to indicate that it extends basic TCP/IP networking to address DICOM-specific needs. The DICOM UL binds two AEs into an associated pair so that they know the functionality of one another, including data formats and SOP support. When this binding is established, the entire power of DICOM networking can be unleashed on higher DIMSE and SOP levels.