E/R Diagram | DICOM E/R Diagram

The DICOM Information Model specifies the relationship between DICOM objects and real-world entities such as a study, a series, images, etc. The information model is mostly referred to as an entity-relationship (E/R) model.

An information entity (IE) is a representation or computer model of a real-world object.
Rectangular boxes in the E/R diagram represent DICOM information entities. The diamond shapes connected to the entities with directional lines represent the relationships between entities. It is important to note that the connecting lines do not represent data or information flow but the relationships between entities.

The E/R models define the information models used for exchanging data. These models represent DICOM information entities and the relationships between entities. For example, the Patient IE represents the characteristics associated with a real patient; the Study IE represents the characteristics of a real study, and so forth.
Part of the information model deals with the Patient-Image relationship: Each patient can have one or more studies (1,n). Each study can contain multiple series (1,n), and each series can contain zero or multiple images (0,n). The E/R models are central to the information object definitions used in the standards, and should be studied carefully.

The DICOM Information Models are the structure of Information Object Definitions (IODs). IODs represent a class of related real-world objects that share the same properties. An IOD is instantiated (becomes a real-world Information Object such as “CT Image”) by providing values for the attributes that describe the entities in the information model. When so instantiated, an IOD becomes a DICOM Object. This is the information part of what is to be communicated. The other necessary part describes what to do with the information. DICOM builds the various services that imaging systems provide or use through the other fundamental part of a DICOM Message – the Service primitives. Putting together the service (what to do) with the information object instance (the information to be acted on) results in the basic unit of DICOM Communications; the Service-Object Pair, or SOP.