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 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. Not having an E/R model as part of the specification means there is no true interoperability. In fact, there are many examples of interoperability problems due to the fact that vendors do not adhere strictly to the DICOM Information Model. A good example of that wood be a vendor who fails to specify the Series for the images (even if it is a "dummy"). |