Материал: part17

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SSSUseofImageLibrariesinSRDocuments​ (Informative)​

This Annex contains examples of the use of Image Library templates within SR Documents.​

SSS.1 Image Library for PET-CT Example​

This PET-CT example dillustrates an Image Library in which Attributes of images for two modalities are described, with common At-​ tributes factored out of the individual image references.​

Note​

1.​OnlytheAttributesofrelevancetoSUVandspatialmeasurementsareincluded,notacompletedescriptionofallaspects​ of acquisition.​

2.​Only two images for each modality are described, rather than all slices acquired, since it is usually only necessary to​ describe images that are referenced elsewhere in the SR content tree, e.g., on which a region of interest is specified​ from which measurements are made.​

Table SSS.1-1. Image Library for PET-CT Example​

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TTT X-Ray 3D Angiographic Image Encoding​

Examples (Informative)​

TTT.1 General Concepts of X-Ray 3D Angiography​

This chapter describes the general concepts of the X-Ray 3D Angiography: the acquisition of the projection images, the 3D recon-​ struction, and the encoding of the X-Ray 3D Angiographic Image SOP instances. They provide better understanding of the different​ application cases in the rest of this Annex.​

TTT.1.1 Process of Creating An X-Ray 3D Angiography​

Two main steps are involved in the process of creating an X-Ray 3D Angiographic Instance: The acquisition of 2D projections and​ the 3D reconstruction of the volume.​

Figure TTT.1.1-1. Process flow of the X-Ray 3D Angiographic Volume Creation​

TTT.1.1.1 Acquisition of 2D Projections​

The X-Ray equipment acquires 2D projections at different angles. The Acquisition Context describes the technical parameters of a​ set of 2D projection acquisitions that are used to perform a 3D reconstruction. In the scope of the X-Ray 3D Angiographic SOP Class,​ all the projections of an Acquisition Context share common parameter values, such as:​

•​Detector settings, anti-scatter grid, field of view characteristics​

•​Distances from the X-Ray source to the Isocenter and to the detector, table position and table angles​

•​Focal spot, spectral filters​

•​Contrast injection details​

If one value of such common parameters changes during the acquisition of the projections, then more than one Acquisition Context​ will be defined.​

TypicallytheprojectionsofanAcquisitionContextaretheresultofarotationalacquisitionwheretheX-Raypositionerfollowsacircular​ trajectory. However, it is possible to define an Acquisition Context as the set of multiple projections at different X-Ray incidences​ without a particular spatial trajectory.​

An Acquisition Context is characterized by a period of time in which all the projections are acquired. Some other parameters are used​ to describe the Acquisition Context: start and end DateTime, average exposure techniques (mA, kVp, exposure duration, etc.), posi-​ tioner start, end and increment angles.​

Additionally, other technical parameters that change at each projection can be documented in the X-Ray 3D Angiographic SOP Class​ on a per-projection basis:​

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•​kVp, mA, exposure duration​ •​Collimator shape and dimensions​ •​X-Ray positioner angles​

TTT.1.1.2 3D Reconstruction​

The 3D Reconstruction Application performing the 3D Reconstruction can be located in the same X-Ray equipment or in another​ workstation.​

A 3D Reconstruction in the scope of the X-Ray 3D Angiographic SOP Class is the creation of one X-Ray 3D Angiographic volume​ fromasetofprojectionsfromoneormoreAcquisitionContext(s).Therefore,one3DReconstructioninthisscopereferstotheresulting​ volume, and not to the application logic to process the projections. This application logic is out of the scope of this SOP Class, the​ same encoding will result whether several 3D Reconstructions are performed in a single or in multiple application steps to create​ several volumes (e.g., low and high resolution volumes) from the same set of projections.​

One 3D Reconstruction is characterized by some parameters like name, version, manufacturer, description and the type of algorithm​ used to process the projections.​

The 3D Reconstruction can use one or more Acquisition Contexts to generate one single X-Ray 3D Angiographic Volume. Several​ 3D Reconstructions can be encoded in one single X-Ray 3D Angiographic Instance.​

TTT.1.2 X-Ray 3D Angiographic Real World Entities Relationships​

This section describes the relationships between the real world entities involved in X-Ray 3D Angiography.​

The X-Ray equipment creates one or more acquisition contexts (i.e., one or more rotational acquisitions with different technical​ parameters). The projections can be kept internal to the equipment (i.e., not exported outside the equipment) or can be encoded as​ DICOMinstances.InthescopeoftheX-Ray3DAngiographicSOPClass,theprojectionscanbeencodedeitherasX-RayAngiography​ SOP Class or Enhanced XA SOP Class.​

If the projections are encoded as DICOM Instances, they can be referenced in the X-Ray 3D Angiographic image as Contributing​ Sources. Each Acquisition Context refers to all the DICOM instances involved in that context. If the projections are kept internal to​ the equipment, the X-Ray 3D Angiographic image can still describe the technical parameters of each acquisition context without ref-​ erencing any DICOM instance.​

The 3D Reconstruction Application creates one or more 3D Reconstructions, each 3D Reconstruction uses one or more Acquisition​ Contexts. One or more 3D Reconstructions can be encoded in one single X-Ray 3D Angiographic Instance.​

Figure TTT.1.2-1. Relationship between the creation of 2D and 3D Instances​

TTT.1.3 X-Ray 3D Angiographic Pixel Data Characterization​

Similarly to other 3D modalities like CT or MR, the X-Ray 3D Angiographic image is generated from original source data (i.e., original​ projections) which can be kept internal to the equipment. In this sense, the 3D data resulting from the reconstruction of the original​

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