Материал: part17

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N.5 IVUS Report​

The IVUS Report contains one or more vessel containers, each corresponding to the vessel (arterial location) being imaged. Each​ vessel is associated with one or more IVUS image pullbacks (Ultrasound Multi-frame Images), acquired during a phase of a catheter-​ ization procedure. Each vessel may contain one or more sub-containers, each associated with a single lesion. Each lesion container​ includes a set of IVUS measurements and qualitative assessments. The resulting hierarchical structure is depicted in Figure N.5-1.​

CONTAINS

Image Reference

IMAGE

CONTAINS

Image Reference

IMAGE

Figure N.5-1. IVUS Report Structure​

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O Registration (Informative)​

O.1 Spatial Registration and Spatial Fiducials SOP Classes​

These SOP Classes allow describing spatial relationships between sets of images. Each instance can describe any number of regis-​ trations as shown in Figure O.1-1. It may also reference prior registration instances that contribute to the creation of the registrations​ in the instance.​

A Reference Coordinate System (RCS) is a spatial Frame of Reference described by the DICOM Frame of Reference Module. The​ chosen Frame of Reference of the Registration SOP Instance may be the same as one or more of the Referenced SOP Instances.​ In this case, the Frame of Reference UID (0020,0052) is the same, as shown by the Registered RCS in the figure. The registration​ information is a sequence of spatial transformations, potentially including deformation information. The composite of the specified​ spatial transformations defines the complete transformation from one RCS to the other.​

Image instances may have no DICOM Frame of Reference, in which case the registration is to that single image (or frame, in the​ case of a Multi-frame Image). The Spatial Registration IOD may also be used to establish a coordinate system for an image that has​ no defined Frame of Reference. To do this, the center of the top left pixel of the source image is treated as being located at (0, 0, 0).​ Offsets from the first pixel are computed using the resolution specified in the Source IOD. Multiplying that coordinate by the Trans-​ formation matrix gives the patient coordinate in the new Frame of Reference.​

A special case is an atlas. DICOM has defined Well-Known Frame of Reference UIDs for several common atlases. There is not ne-​ cessarily image data associated with an atlas.​

WhenusingtheSpatialRegistrationorDeformableRegistrationSOPClassestherearetwotypesofcoordinatesystems.Thecoordinate​ system of the referenced data is the Source RCS. The coordinate system established by the SOP instance is the Registered RCS.​

ThesenseofthedirectionoftransformationdiffersbetweentheSpatialRegistrationSOPClassandtheDeformableSpatialRegistration​ SOP Class. The Spatial Registration SOP Class specifies a transformation that maps Source coordinates, in the Source RCS, to​ Registered coordinates, in the Registered RCS. The Deformable Spatial Registration SOP Class specifies transformations that map​ Registered coordinates, in the Registered RCS, to coordinates in the Source RCS.​

The Spatial Fiducials SOP Class stores spatial fiducials as implicit registration information.​

Figure O.1-1. Registration of Image SOP Instances​

O.2 Functional Use Cases​

Multi-Modality Fusion: A workstation or modality performs a registration of images from independent acquisition modalities-PET,​ CT, MR, NM, and US-from multiple series. The workstation stores the registration data for subsequent visualization and image pro-​ cessing. Such visualization may include side-by-side synchronized display, or overlay (fusion) of one modality image on the display​

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of another. The processes for such fusion are beyond the scope of the Standard. The workstation may also create and store a ready-​ for-displayfusedimage,whichreferencesboththesourceimageinstancesandtheregistrationinstancethatdescribestheiralignment.​

Prior Study Fusion: Using post processing or a manual process, a workstation creates a spatial object registration of the current​ Study's Series from prior Studies for comparative evaluation.​

AtlasMapping:AworkstationoraCADdevicespecifiesfiducialsofanatomicalfeaturesinthebrainsuchastheanteriorcommissure,​ posteriorcommissure,andpointsthatdefinethehemisphericfissureplane.ThesystemstoresthisinformationintheSpatialFiducials​ SOP Instance. Subsequent retrieval of the fiducials enables a device or workstation to register the patient images to a functional or​ anatomical atlas, presenting the atlas information as overlays.​

CAD: A CAD device creates fiducials of features during the course of the analysis. It stores the locations of the fiducials for future​ analysis in another imaging procedure. In the subsequent CAD procedure, the CAD device performs a new analysis on the new data.​ As before, it creates comparable fiducials, which it may store in a Spatial Fiducials SOP Instance. The CAD device then performs​ additional analysis by registering the images of the current exam to the prior exam. It does so by correlating the fiducials of the prior​ and current exam. The CAD device may store the registration in Registration SOP Instance.​

Adaptive Radiotherapy: A CT Scan is taken to account for variations in patient position prior to radiation therapy. A workstation​ performs the registration of the most recent image data to the prior data, corrects the plan, and stores the registration and revised​ plan.​

Image Stitching: An acquisition device captures multiple images, e.g., DX images down a limb. A user identifies fiducials on each​ oftheimages.ThesystemstorestheseinoneormoreFiducialSOPInstances.Thentheimagesare"stitched"togetheralgorithmically​ by means that utilize the Fiducial SOP Instances as input. The result is a single image and optionally a Registration SOP Instance​ that indicates how the original images can be transformed to a location on the final image.​

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.​

Modality CT

CT

Information

Network Workstation

MR

or CAD

CT MR Registration

Workstation

or CAD

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, quantific-​ ation, or Computer Aided Detection. Figure O.3-2 shows a typical interaction scenario.​

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Images A

Images B

Images A

Images B

Registration

Images A

Images B

Registration

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​ imagesasshownbelowinFigureO.3-3.Inthemostdirectcase,thedataofbothmodalitiesareinthesameDICOMFrameofReference​ 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​ theRCSoftheReferencedImageSet,totheRCSofthisSpatialRegistrationinstance(seePS3.3)identifiedbytheFrameofReference​ UID (0020,0052).​

O.4 Overview of Encoding​

Figure O.4-1 shows an information model of a Spatial Registration to illustrate the relationship of the Attributes to the objects of the​ model. The DICOM Attributes that describe each object are adjacent to the object.​

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