DICOM Specification Overview: Information Object Definitions Subtopics

Subtopics related to Information Object Definitions:

Composite IOD
Normalized IOD
Attributes
Normalized and Composite SOP Classes
Modules
Definitions

 Composite IOD

A Composite IOD is an Information Object Definition which represents parts of several entities included in the DICOM Model of the Real-World. This Model is introduced in Section 7. Such an IOD includes Attributes which are not inherent in the Real-World Object that the IOD represents but rather are inherent in related Real-World Objects.

These related Real-World Objects provide a complete context for the exchanged information. When an instance of a Composite IOD is communicated, this entire context is exchanged between Application Entities. Relationships between Composite IOD Instances shall be conveyed in this contextual information.

 Normalized IOD

A Normalized IOD is an Information Object Definition which generally represents a single entity in the DICOM Model of the Real-World.

In this Standard, strict definition of Normalized Object Definitions has not been applied. Application of strict definitions would often result in unnecessary complexity and reduced performance of implementations for several applications.

 Attributes

The Attributes of an IOD describe the properties of a Real-World Object Instance. Related Attributes are grouped into Modules which represent a higher level of semantics documented in the Module Specifications found in Annex C of the DICOM Standard.

Attributes are encoded as Data Elements using the rules, the Value Representation and the Value Multiplicity concepts specified in PS 3.5 of the DICOM Standard. For specific Data Elements, the Value Representation and Value Multiplicity are specified in the Data Dictionary in PS 3.6 of the DICOM Standard.

When multiple modules containing the same Attributes(s) are included in an IOD, the Attribute shall be encoded only once into a Data Element. If one of the modules is a specialization of the other (e.g., General Image and CT Image) the Attribute definition contained in the more specialized module shall be used.

 Normalized and Composite SOP Classes

DICOM defines two types of SOP Classes, Normalized and Composite. Normalized SOP Classes are defined as the union of a Normalized IOD and a set of DIMSE-N Services. Composite SOP Classes are defined as the union of a Composite IOD and a set of DIMSE-C Services.

 Modules

Mandatory Modules

For each IOD, Mandatory Modules shall be supported per the definitions, semantics and requirements defined in Annex C.

Conditional Modules

Conditional Modules are Mandatory Modules if specific conditions are met. If the specified conditions are not met, this Module shall not be supported; that is, no information defined in that Module shall be sent.

User Option Modules

User Option Modules may or may not be supported. If an optional Module is supported, the Attribute Types specified in the Modules in Annex C shall be supported.

 Definitions

The following definitions pertain to Information Object Definitions and are commonly used in the DICOM Standard.

Attribute tag: A unique identifier for an Attribute of an Information Object composed of an ordered pair of numbers (a Group Number followed by an Element number).

Composite IOD: an Information Object Definition which represents parts of several entities in the DICOM Application Model. Such an IOD includes Attributes which are not inherent in the Real-World Object that the IOD represents but rather are inherent in related Real-World Objects.

Derived image: an image in which the pixel data was constructed from pixel data of one or more other images (source images).

DICOM information model: an Entity-Relationship diagram which is used to model the relationships between the Information Object Definitions representing classes of Real-World Objects defined by the DICOM Application Model.

DICOM application model: an Entity-Relationship diagram used to model the relationships between Real-World Objects which are within the area of interest of the DICOM Standard.

Information entity: that portion of information defined by a Composite IOD which is related to one specific class of Real-World Object. There is a one-to-one correspondence between Information Entities and entities in the DICOM Application Model.

Information object definition (IOD): a data abstraction of a class of similar Real-World Objects which defines the nature and Attributes relevant to the class of Real-World Objects represented.

Module: A set of Attributes within an Information Entity or Normalized IOD which are logically related to each other.

Multi-frame image: Image that contains multiple two-dimensional pixel planes.

Normalized IOD: an Information Object Definition which represents a single entity in the DICOM Application Model. Such an IOD includes Attributes which are only inherent in the Real-World Object that the IOD represents.

Cine run: A set of temporally related frames acquired at constant or variable frame rates. This term incorporates the general class of serialography.