Keywords:  Entity-relationship (E/R) model, Information Model, IE, Information Entity, E/R, Hanging Protocol
Information Model

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.

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.  

The E/R models are central to the information object definitions used in the standards, and should be studied carefully. There are many examples of interoperability problems due to the fact that vendors do not adhere strictly to the DICOM Information Model.

In order to provide hanging protocols, it is critical to know exactly how the images relate to each other. The DICOM Information Model provides the mechanism for standardizing these conventions. For hanging protocols, workstations typically rely on series identifications. So a study might have to be split (such as for the single CT scan that contains all images) so that, for example, the head images can be sent to a neuro specialist, while the remaining images sent to another.

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