An information entity (IE) is a representation or computer model of a real-world object.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 the entity-relationship (E/R) model. 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.
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.