Материал: part03

C.8.8.6 ROI Contour Module​

In general, a ROI can be defined by either a sequence of overlays or a sequence of contours. This Module, if present, is used to​ define the ROI as a set of contours. Each ROI contains a sequence of one or more contours, where a contour is either a single point​ (for a point ROI) or more than one point (representing an open or closed polygon).​

Table C.8-42. ROI Contour Module Attributes​

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Coordinate System described in Section C.7.6.2.1.1 (mm). See​

Section C.8.8.6.1 and Section C.8.8.6.3.​

Note​

Contour Data may not be properly encoded if Explicit VR​ Transfer Syntax is used and the VL of this Attribute exceeds​ 65534 bytes.​

C.8.8.6.1 Contour Geometric Type​

A contour can be one of the following geometric types:​

•​AContourGeometricType(3006,0042)ofPOINTindicatesthatthecontourisasinglepoint,definingaspecificlocationofsignificance.​

•​A Contour Geometric Type (3006,0042) of OPEN_PLANAR indicates that the last vertex shall not be connected to the first point,​ and that all points in Contour Data (3006,0050) shall be coplanar.​

•​A Contour Geometric Type (3006,0042) of OPEN_NONPLANAR indicates that the last vertex shall not be connected to the first​ point, and that the points in Contour Data (3006,0050) may be non-coplanar. Contours having a Geometric Type (3006,0042) of​ OPEN_NONPLANAR can be used to represent objects best described by a single, possibly non-coplanar curve, such as a brachy-​ therapy applicator.​

•​A Contour Geometric Type (3006,0042) of CLOSED_PLANAR indicates that the last point shall be connected to the first point,​ where the first point is not repeated in Contour Data (3006,0050). All points in Contour Data (3006,0050) shall be coplanar.​

C.8.8.6.2 Contour Slab Thickness​

A set of Contour slabs may define a multi-slab Volume of Interest. Contour Slab Thickness (3006,0044) shall specify the thickness​ of a slab, the central plane of which shall be defined by the set of points offset from Contour Data (3006,0050) by the value of Contour​ Offset Vector (3006,0045). One contour slab may contain one to many sets of Contour Data (3006,0050) that may define regions of​ one complex Volume of Interest. If no valid value of Contour Slab Thickness (3006,0044) is present, then the offset value shall be​ (0,0,0) and the original Contour Data (3006,0050) shall define the central plane of the Contour slab.​

C.8.8.6.3 Representing Inner and Outer Contours on an Image​

When a single ROI describes an excluded inner volume, this can be encoded with a single contour, using a "keyhole" technique. In​ this method, an arbitrarily narrow channel is used to connect the outer contour to the inner contour, so that it is drawn as a single​ contour. An example of such a structure is shown in Figure C.8.8.6-1​

Points in space lying along the path defined by the contour are considered to be inside the ROI.​

Figure C.8.8.6-1. Example of ROI with excluded inner volume​

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C.8.8.7 RT Dose ROI Module​

RT Dose ROI provides ancillary dose-related information to the ROI data defined within the Structure Set Module and ROI Contour​ Module, which may be included in the RT Dose IOD composite object. These Modules in combination provide for the definition of​ dose data in the form of isodose curves or named or unnamed dose points. Isodose curves in radiation oncology are simply contours​ identifying a set of points with the same dose value.​

Table C.8-43. RT Dose ROI Module Attributes​

Note​

1.​The Structure Set ROI Sequence (3006,0020) defining the dose point and surfaces is defined in the Structure Set​ Module. ROI Number (3006,0022) is unique within the Structure Set ROI Sequence, and is referenced from the RT​ Dose ROI Module using Referenced ROI Number (3006,0084).​

2.​The RT Dose ROI Module defines the Attributes that describe references to ROIs contained within the associated​ Structure Set Module and ROI Contour Module. Note that the RT Dose IOD Module table specifies that either all or​ none of the Structure Set Module, ROI Contour Module, and RT Dose ROI Module must be present in the RT Dose​ IOD.​

C.8.8.7.1 Contour Geometric Type of Referenced ROI​

ROIs referenced in the RT Dose ROI Module shall have a Contour Geometric Type (3006,0042) of POINT, OPEN_PLANAR or​ CLOSED_PLANAR.​

C.8.8.7.2 Referenced ROI Number​

There shall be a one-to-one correspondence between Referenced ROI Number (3006,0084) and the Sequence of ROIs defined in​ the Structure Set Module and ROI Contour Module. The RT Dose ROI Module shall only contain references to structures that are​ dose-related (i.e., dose points and isodose curves).​

C.8.8.7.3 Dose Value​

Dose Value (3004,0012) shall be the dose value corresponding to the referenced isodose curve, named dose point, or unnamed dose​ point.​

C.8.8.8 RT ROI Observations Module​

The RT ROI Observations Module specifies the identification and interpretation of an ROI specified in the Structure Set Module and​ ROI Contour Module.​

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DICOM PS3.3 2020a - Information Object Definitions​ Page 729​

Table C.8-44. RT ROI Observations Module Attributes​

See Note 2.​

>>Include Table 8.8-1 “Code Sequence Macro Attributes”​ For dose measurement devices Baseline CID 7026 “Radiotherapeutic​ Dose Measurement Devices”.​

Modifier Code Sequence​

One or more Items are permitted in this Sequence.​

>>>Include Table 8.8-1 “Code Sequence Macro Attributes”​DCID 244 “Laterality”.​

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One or more Items are permitted in this Sequence.​

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