Long Primitive Point Index List Attribute
| Tag | (0066,0040) |
|---|---|
| Type | Conditionally Required (1C) |
| Keyword | LongPrimitivePointIndexList |
| Value Multiplicity | 1 |
| Value Representation | OL |
A list of point indices. See Section C.37.1.2.1.1.
Required if Graphic Type (0070,0023) is POLYLINE or POLYGON.
Section C.37.1.2.1.1
C.37.1.2.1.1 Type, Points, Polygons, Parameterized and Rotated Shapes and Indices
All the Annotations in a single Item of Annotation Group Sequence (006A,0002) share the same value for Graphic Type (0070,0023).
If Annotation Coordinate Type (006A,0001) is 2D, then the coordinates are interpreted as image-relative, either relative to an individual frame or the Total Pixel Matrix, with units of pixels, as defined in Section C.10.4 Displayed Area Module. If Pixel Origin Interpretation (0048,0301) is FRAME, then a single frame of a single image shall be specified in Referenced Image Sequence (0008,1140). If Pixel Origin Interpretation (0048,0301) is VOLUME, then a single image shall be specified in Referenced Image Sequence (0008,1140) without a subset of frames designated, and the coordinates are relative to the Total Pixel Matrix of that image. The referenced image shall not be an instance of a Concatenation; i.e., in the case of Concatenations, references shall be relative to the SOP Instance UID of Concatenation Source (0020,0242).
Note
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The referenced image need not be any particular resolution layer of a WSI pyramid. I.e., it may or may not be the highest resolution layer. The user may annotate images that are not at the highest resolution, but such Annotations may be projected onto any resolution layer that is available (or computed). If the referenced image is no longer stored or accessible, the ability to project the Annotations onto other layers may be lost.
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A reference to a single frame means that all Annotations in this instance are on that frame; no mechanism is provided to span frames, or to specify more than one frame.
If Annotation Coordinate Type (006A,0001) is 3D, then the X, Y and Z coordinates are interpreted as volume relative, with units of mm, in the Cartesian space defined by the Frame of Reference UID.
Note
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A single referenced image may be specified even if Annotation Coordinate Type (006A,0001) is 3D. It need not be any particular resolution layer of a WSI pyramid, but may be interpreted as a suitable layer on which to render, select from or otherwise apply the Annotation. In particular, it may not be the highest resolution layer. Regardless, the Annotations are applicable to any image in the same Frame of Reference.
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The use of millimeters as the unit for the Z coordinates is inconsistent with the use of microns for the Z Offset in Slide Coordinate System (0040,074A) in the Section C.8.12.2 Slide Coordinates Module.
If the Annotations are points, then
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Graphic Type (0070,0023) shall have a value of POINT.
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All the points in the group shall be encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022), concatenated one after another, with Z factored out into Common Z Coordinate Value (006A,0010), if common.
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Long Primitive Point Index List (0066,0040) shall not be present, because there is no need for a separate index of each Annotation.
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Number of Annotations (006A,000C) will contain the number of points, which shall also be the number of coordinate tuples in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022).
If the Annotations are open polylines, then
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Graphic Type (0070,0023) shall have a value of POLYLINE.
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The points of each polyline shall be encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022), concatenated one after another, with Z factored out into Common Z Coordinate Value (006A,0010), if common.
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The order of the encoded points is from the first point to the last point of the polyline.
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The index in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022) of each successive polyline is encoded in Long Primitive Point Index List (0066,0040), which shall contain Number of Annotations (006A,000C) values.
If the Annotations are closed polygons, then
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Graphic Type (0070,0023) shall have a value of POLYGON.
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The points of each polygon shall be encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022), concatenated one after another, with Z factored out into Common Z Coordinate Value (006A,0010), if common.
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The order of the encoded points is from the first point to the last point of the polygon. The first point and the last point shall not be the same, but rather they are implicitly joined to close the polygon.
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The index in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022) of each successive polygon is encoded in Long Primitive Point Index List (0066,0040), which shall contain Number of Annotations (006A,000C) values.
Note
This closed polygon representation differs from that used in Presentation States (Section C.10.5.1.2 Graphic Data and Graphic Type) and Structured Reports (Section C.18.6.1 Spatial Coordinates Macro Attribute Descriptions and Section C.18.9.1 3D Spatial Coordinates Macro Attribute Descriptions), none of which are implicitly closed, and required replication of the first point as the last point.
If the Annotations are circles or ellipses, then
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Graphic Type (0070,0023) shall have a value of ELLIPSE.
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The end points of the major and minor axes of the ellipses in the group shall be encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022), with Z factored out into Common Z Coordinate Value (006A,0010) if common.
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Long Primitive Point Index List (0066,0040) shall not be present, because the index of each Annotation can be computed. Number of Annotations (006A,000C) will contain the number of ellipses, which shall also be one quarter of the number of coordinate tuples in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022).
Note
If the length of the major and minor axes are the same, then the ellipse is a circle; a simpler (e.g., 2 point) encoding of a circle is not defined, since the plane of the circle would be unspecified without a third point.
If the Annotations are squares or rectangles, then
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Graphic Type (0070,0023) shall have a value of RECTANGLE.
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All the corner points of the rectangles in the group shall be encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022), with Z factored out into Common Z Coordinate Value (006A,0010) if common.
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Long Primitive Point Index List (0066,0040) shall not be present, because the index of each Annotation can be computed. Number of Annotations (006A,000C) will contain the number of rectangles, which shall also be one quarter of the number of coordinate tuples in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022).
Note
If the lengths of the perpendicular edges are the same, then the rectangle is a square. This rectangle representation is the same as if the rectangle were encoded as an implicitly closed polygon, except that the number of points is fixed and Long Primitive Point Index List (0066,0040) is absent. A simpler (e.g., 2 point TLHC, BRHC) encoding of a rectangle is not defined, since the plane of the rectangle would then be unspecified without a third point.
The index used in Long Primitive Point Index List (0066,0040) of the first value of the first coordinate tuple in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022) shall be 1.
The polylines and polygons encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022) shall be in the same order as Long Primitive Point Index List (0066,0040). I.e., the values of Long Primitive Point Index List (0066,0040) are strictly increasing.
Open polylines and implicitly closed polygons shall have their vertices encoded in Point Coordinates Data (0066,0016) or Double Point Coordinates Data (0066,0022) in clockwise winding order when viewed from the top surface of the slide towards the bottom, per Section C.8.12.2.1 Slide Coordinates Module Attribute Descriptions. The line segments shall not cross (i.e., shall be simple polygons, not complex polygons), and shall not contain holes (i.e., the keyhole technique described for RT Structure Sets (Section C.8.8.6.3 Representing Inner and Outer Contours), shall not be used).
The plane of the coplanar points is not required to correspond to an image plane or be parallel to the slide surface; the points are only required to be coplanar in a geometric sense (i.e., they need not all have the same Z coordinate value).