A.1.2 IOD Entity-Relationship Model

This Section of an IOD provides the Entity-Relationship (E-R) Model which depicts the relationships of the components or Information Entities (IE) of the specified IOD. It forms an IOD specific information model. This E-R model provides the complete context of how the composite instance information shall be interpreted when a composite instance is exchanged between two DICOM Application Entities.

Even though composite instances are sent as discrete individual components, each Composite Instance IOD E-R Model requires that all composite instances that are part of a specific study shall share the same context. That is, all composite instances within a specific patient study share the same patient and study information; all composite instances within the same series share the same series information; etc.

Figure A.1-1 is the DICOM Composite Instance IOD Information Model. It applies to all of the Composite Instance IODs defined in Annex A. However, a subset of this model may be specified by each individual Composite Instance IOD to accurately define the context for specific composite instance exchange.

Sections A.1.2.1 through A.1.2.10 describe the Information Entities (IE) which comprise the Composite Instance IODs defined in this Annex.

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Figure A.1-1 DICOM COMPOSITE INSTANCE IOD INFORMATION MODEL

Each Series shall contain at least one Presentation State IE, SR Document IE or Image IE.

A.1.2.1 PATIENT IE

The Patient IE defines the characteristics of a patient who is the subject of one or more medical studies.

Note: A patient may be a human or an animal.

The Patient IE is modality independent.

A.1.2.2 STUDY IE

The Study IE defines the characteristics of a medical study performed on a patient. A study is a collection of one or more series of medical images, presentation states, and/or SR documents that are logically related for the purpose of diagnosing a patient. Each study is associated with exactly one patient.

A study may include composite instances that are created by a single modality, multiple modalities or by multiple devices of the same modality.

The Study IE is modality independent.

A.1.2.3 SERIES IE

The Series IE defines the Attributes that are used to group composite instances into distinct logical sets. Each series is associated with exactly one Study.

The following criteria group composite instances into a specific series:

a. All composite instances within a series must be of the same modality

b. If a specific Composite Instance IOD specifies the support of a Frame of Reference IE, all composite instances within the series shall be spatially or temporally related to each other; therefore, each series is associated with exactly one Frame of Reference IE

c. If a specific Composite Instance IOD specifies the support of the Equipment IE, all composite instances within the series shall be created by the same equipment; therefore, each series is associated with exactly one Equipment IE

d. All composite instances within a series shall have the same series information

Presentation States shall be grouped into Series without Images (i.e. in a different Series from the Series containing the Images to which they refer). The Frame of Reference IE is irrelevant to the Presentation State IE.

Note: The Series containing Grayscale, Color and Pseudo-Color Softcopy Presentation States and the Series containing the Images to which they refer are both contained within the same Study, except for Blended Presentation States, which may refer to images from different Studies.

Waveforms shall be grouped into Series without Images. A Frame of Reference IE may apply to both Waveform Series and Image Series.

SR Documents shall be grouped into Series without Images. The Frame of Reference IE does not apply to SR Document Series.

A.1.2.4 EQUIPMENT IE

The Equipment IE describes the particular device that produced the series of composite instances. A device may produce one or more series within a study. The Equipment IE does not describe the data acquisition or image creation Attributes used to generate the composite instances within a series. These Attributes are described in the composite instance specific IEs (e.g. the Image IE).

A.1.2.5 FRAME OF REFERENCE IE

The Frame of Reference IE identifies the coordinate system that conveys spatial and/or temporal information of composite instances in a series.

When present, a Frame of Reference IE may be related to one or more series. In this case, it provides the ability to spatially or temporally relate multiple series to each other. In such cases, the series may share the UID of the Frame of Reference, or alternatively, a Registration SOP Instance may specify the spatial relationship explicitly, as a spatial transformation. A Frame of Reference IE may also spatially register a Frame of Reference to an atlas.

A.1.2.6 IMAGE IE

The Image IE defines the Attributes that describe the pixel data of an image. The pixel data may be generated as a direct result of patient scanning (termed an Original Image) or the pixel data may be derived from the pixel data of one or more other images (termed a Derived Image). An image is defined by its image plane, pixel data characteristics, gray scale and/or color mapping characteristics, overlay planes and modality specific characteristics (acquisition parameters and image creation information).

An image is related to a single series within a single study.

The pixel data within an Image IE may be represented as a single frame of pixels or as multiple frames of pixel data. The frames of a Multi-frame image (a cine run or the slices of a volume) are sequentially ordered and share a number of common properties. A few Attributes may vary between frames (eg.-Time, Angular Displacement, Slice Increment). All common Image IE Attributes refer to the first frame of a multiple frame image.

Overlay and Lookup Table data may be included within an Image IE only if this information is directly associated with the image.

A.1.2.7 OVERLAY IE

The Overlay IE defines the Attributes that describe an independent set of Overlay Planes. The Overlay IE may represent in a bit-map format, graphics or text and is used to indicate such items as region of interest, reference marks and annotations. Sufficient information shall be available to allow an overlay to be presented at a display station superimposed on a particular image with which it is associated. An Overlay IE shall be related to only one Series IE.

An Overlay Plane may be represented as a single frame (when associated with a single frame image) or as multiple frames of overlay planes (when associated with a Multi-frame image).

A.1.2.8 CURVE IE

Retired. See PS 3.3 2004.

A.1.2.9 MODALITY LUT IE

The Modality LUT IE defines the Attributes that describe the transformation of manufacturer dependent pixel values into pixel values which are manufacturer independent (e.g. Hounsfield units for CT, Optical Density for film digitizers, etc.). The Modality LUT may be contained within an image, or a presentation state that references an image. When the transformation is linear, the Modality LUT is described by Rescale Slope (0028,1053) and Rescale Intercept (0028,1052). When the transformation is non-linear, the Modality LUT is described by Modality LUT Sequence (0028,3000).

A.1.2.10 VOI LUT IE

The VOI LUT IE defines the Attributes that describe the transformation of the modality pixel values into pixel values that are meaningful for print, display, etc. This transformation is applied after any Modality LUT. The VOI LUT may be contained within an image, or a presentation state that references an image. When the transformation is linear, the VOI LUT is described by the Window Center (0028,1050) and Window Width (0028,1051). When the transformation is non-linear, the VOI LUT is described by VOI LUT Sequence (0028,3010). A non-linear interpretation of Window Center (0028,1050) and Window Width (0028,1051) may be defined by VOI LUT Function (0028,1056).

A.1.2.11 PRESENTATION STATE IE

The Presentation State IE defines how a referenced image (or images) will be presented (e.g. displayed) in a device independent grayscale space (i.e. in P-Values) or color space (i.e. in PCS-values), and what graphical annotations and spatial and grayscale contrast transformations will be applied to the referenced image pixel data.

A.1.2.12 WAVEFORM IE

The Waveform IE represents a multi-channel time-based digitized waveform. The waveform consists of measurements of some physical qualities (e.g., electrical voltage, pressure, gas concentration, or sound), sampled at constant time intervals. The measured qualities may originate, for example, in any of the following sources:

a. the anatomy of the patient,

b. therapeutic equipment (e.g., a cardiac pacing signal or a radio frequency ablation signal),

c. equipment for diagnostic synchronization (e.g., a clock or timing signal used between distinct devices),

d. the physician’s voice (e.g., a dictated report).

The sample data within a Waveform IE may represent one or more acquired channels. Several signal channels acquired at the same sampling rate can be multiplexed (by interleaving samples) in a single multiplex group. (See also PS 3.17 Annex on Waveforms.)

A.1.2.13 SR DOCUMENT IE

The SR Document IE defines the Attributes that describe the content of an SR Document. These include semantic context as well as Attributes related to document completion, verification and other characteristics. An SR Document SOP Instance is related to a single Series within a single Study.

A.1.2.14 MR SPECTROSCOPY IE

The MR Spectroscopy IE defines the attributes that describe the data of a MR spectroscopy acquisition created by a magnetic resonance spectroscopy device.

A.1.2.15 RAW DATA IE

The Raw Data IE defines the attributes that describe a data set that may be used for further processing to produce image data or other data.

Note: For example, raw data may be used with CT and MR systems to reconstruct sets of images or for MR to reconstruct spectroscopic data. The format of the raw data is vendor specific.

A.1.2.16 ENCAPSULATED DOCUMENT IE

The Encapsulated Document IE defines the Attributes that describe the content of a non-DICOM formatted document that is encapsulated in a DICOM Attribute. These include Attributes related to document origin, title, and other characteristics. An Encapsulated Document SOP Instance is related to a single Series within a single Study.

A.1.2.17 REAL WORLD VALUE MAPPING IE

The Real World Value Mapping IE defines the attributes that describe the mapping of stored pixel data to real world values.

A.1.2.18 SURFACE IE

The Surface IE defines the Attributes that describe a surface in a spatial coordinate system. A surface is defined by its shape and can be further defined by normals on that shape. The surface may be reconstructed from either spatial scans (e.g. laser scanners) or based on images. A surface is described by its finite volume and manifold property, gray scale and color mapping characteristics, presentation type, opacity, and modality specific characteristics.

A surface is related to a single Series.

A.1.2.19 MEASUREMENTS IE

The Measurement IE defines the Attributes that describe the measurements taken by medical instruments.