O.3 System Interaction
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## O.3 System Interaction

Figure O.3-1 shows the system interaction of storage operations for a registration of MR and CT using the Spatial Registration SOP Class. The Image Plane Module attributes of the CT Series specify the spatial mapping to the RCS of its DICOM Frame of Reference.

Figure O.3-1. Stored Registration System Interaction

The receiver of the Registration SOP Instance may use the spatial transformation to display or process the referenced image data in a common coordinate system. This enables interactive display in 3D during interpretation or planning, tissue classification, quantification, or Computer Aided Detection. Figure O.3-2 shows a typical interaction scenario.

Figure O.3-2. Interaction Scenario

In the case of coupled acquisition modalities, one acquisition device may know the spatial relationship of its image data relative to the other. The acquisition device may use the Registration SOP Class to specify the relationship of modality B images to modality A images as shown below in Figure O.3-3. In the most direct case, the data of both modalities are in the same DICOM Frame of Reference for each SOP Class Instance.

Figure O.3-3. Coupled Modalities

A Spatial Registration instance consists of one or more instances of a Registration. Each Registration specifies a transformation from the RCS of the Referenced Image Set, to the RCS of this Spatial Registration instance (see PS3.3) identified by the Frame of Reference UID (0020,0052).

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