C.8.8.6 ROI Contour Module
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#### 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

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
ROI Contour Sequence | (3006,0039) | 1 | Sequence of Contour Sequences defining ROIs. One or more Items shall be included in this Sequence.
>Referenced ROI Number | (3006,0084) | 1 | Uniquely identifies the referenced ROI described in the Structure Set ROI Sequence (3006,0020).
>ROI Display Color | (3006,002A) | 3 | RGB triplet color representation for ROI, specified using the range 0-255.
>Recommended Display Grayscale Value | (0062,000C) | 3 | A default single gray unsigned value in which it is recommended that the contour be rendered on a monochrome display. The units are specified in P-Values from a minimum of 0000H (black) up to a maximum of FFFFH (white). ### Note The maximum P-Value for this Attribute may be different from the maximum P-Value from the output of the Presentation LUT, which may be less than 16 bits in depth.
>Recommended Display CIELab Value | (0062,000D) | 3 | A default triplet value in which it is recommended that the contour be rendered on a color display. The units are specified in PCS-Values, and the value is encoded as CIELab. See Section C.10.7.1.1.
>Contour Sequence | (3006,0040) | 3 | Sequence of Contours defining ROI. One or more Items are permitted in this Sequence.
>>Contour Number | (3006,0048) | 3 | Identification number of the contour. The value of Contour Number (3006,0048) shall be unique within the Contour Sequence (3006,0040) in which it is defined. No semantics or ordering shall be inferred from this attribute.
>>Attached Contours | (3006,0049) | 3 | List of Contour Number (3006,0048) defining lower-numbered contour(s) to which the current contour is connected.
>>Contour Image Sequence | (3006,0016) | 3 | Sequence of images containing the contour. One or more Items are permitted in this Sequence.
>>>Include Table 10-3 “Image SOP Instance Reference Macro Attributes” |
>>Contour Geometric Type | (3006,0042) | 1 | Geometric type of contour. See Section C.8.8.6.1. Enumerated Values: POINT single point OPEN_PLANAR open contour containing coplanar points OPEN_NONPLANAR open contour containing non-coplanar points CLOSED_PLANAR closed contour (polygon) containing coplanar points
>>Contour Slab Thickness | (3006,0044) | 3 | Thickness of slab (in mm) represented by contour, where Contour Data (3006,0050) defines a plane in the center of the slab, offset by the Contour Offset Vector (3006,0045) if it is present. See Section C.8.8.6.2.
>>Contour Offset Vector | (3006,0045) | 3 | Vector (x,y,z) in the patient based coordinate system described in Section C.7.6.2.1.1 that is normal to plane of Contour Data (3006,0050), describing direction and magnitude of the offset (in mm) of each point of the central plane of a contour slab from the corresponding original point of Contour Data (3006,0050). See Section C.8.8.6.2.
>>Number of Contour Points | (3006,0046) | 1 | Number of points (triplets) in Contour Data (3006,0050).
>>Contour Data | (3006,0050) | 1 | Sequence of (x,y,z) triplets defining a contour in the patient based 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:

- A Contour Geometric Type (3006,0042) of POINT indicates that the contour is a single point, defining a specific location of significance.

- 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 brachytherapy 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.

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