Материал: part03

C.8.19.6.11.1 X-Ray Table Position Macro Attribute Description​

The Table Top Position Attributes of the Table Position Sequence (0018,9406) specify the geometrical position of the Table in the​ three spatial directions (i.e., Vertical, Longitudinal and Lateral) relative to the Table Top plane (see Figure C.8.19.6-3). The absolute​ reference point to which the Table positions are related is arbitrarily defined by the manufacturer.​

TheTableAngleAttributesoftheTablePositionSequence(0018,9406)specifytherotationandtiltoftheTableTopPlanewithrespect​ to a plane arbitrarily defined by the manufacturer (usually the horizontal plane).​

The Table Top Position Attributes allow to describe the incremental translation of the Table top between frames of the same Multi-​ frame image, and between frames of different images, provided that the Table Angles are not modified between these frames.​

When the table angles are modified between two frames, the Table Position Sequence (0018,9406) does not allow to characterize​ the relationship between the two table positions in an absolute reference coordinate system. For this purpose, the X-Ray Isocenter​ Reference System Macro has to be used.​

Note​

The incremental table translation may be used, in conjunction with the Positioner Position Sequence Attributes (0018,9405),​ for simple 2D-2D registration applications (object tracking, pixel shift…), assuming that the patient position is fixed on the​ table.Formorecomplexregistrationapplications,andinordertoproperlyhandlethechangesinthetableangles,itisrecom-​ mended to use the X-Ray Isocenter Reference System Macro Attributes.​

+ Lateral Position

+ Longitudinal Position

Figure C.8.19.6-3. Table Position Vectors​

C.8.19.6.12 X-Ray Collimator Macro​

Table C.8.19.6-12 specifies the Attributes of the X-Ray Collimator Functional Group Macro.​

Table C.8.19.6-12. X-Ray Collimator Macro Attributes​

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row of the origin vertex;​ column of the origin vertex.​

Two or more pairs of values follow and are the effective pixel row and​ columncoordinatesoftheotherverticesofthepolygoncollimator.Polygon​ collimators are implicitly closed from the last vertex to the origin vertex​ and all edges shall be non-intersecting except at the vertices. See​ Section C.8.19.6.12.1.​

C.8.19.6.12.1 X-Ray Collimator Attributes​

The top left pixel of the image has a pixel row and column value of 1.​

C.8.19.6.13 X-Ray Isocenter Reference System Macro​

Table C.8.19.6-13 specifies the Attributes of the X-Ray Isocenter Reference System Functional Group Macro.​

Table C.8.19.6-13. X-Ray Isocenter Reference System Macro Attributes​

Only a single Item shall be included in this Sequence.​

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See Section C.8.19.6.13.1.3 for further explanation.​

C.8.19.6.13.1 Isocenter Reference System Attribute Description​

The Isocenter Reference System Attributes describe the 3D geometry of the X-Ray equipment composed by the X-Ray positioner​ and the X-Ray table.​

These Attributes define three coordinate systems in the 3D space:​

•​Isocenter coordinate system​

•​Positioner coordinate system​

•​Table coordinate system​

The Isocenter Reference System Attributes describe the relationship between the 3D coordinates of a point in the table coordinate​ system and the 3D coordinates of such point in the positioner coordinate system (both systems moving in the equipment), by using​ the Isocenter coordinate system that is fixed in the equipment.​

Note​

Annex FFF “Enhanced XA/XRF Encoding Examples (Informative)” in PS3.17 describes the transformations necessary to​ transpose between coordinate systems.​

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C.8.19.6.13.1.1 Isocenter Coordinate System​

The Isocenter coordinate system (O,X,Y,Z) of the equipment is defined as follows:​ •​Origin O is on the System Isocenter​

•​+Y DOWNWARD (gravity)​

•​+X, +Z directions in the horizontal plane (gravity plane). Directions arbitrarily defined by the manufacturer​

+ Z

+ X

Gravity (downward)

Figure C.8.19.6-4. Isocenter Coordinate System​

C.8.19.6.13.1.2 Positioner Coordinate System​

The Positioner Coordinate System (Op, Xp, Yp, Zp) is defined as follows:​ •​Origin Op, is the origin of the Isocenter coordinate system O​

•​Xp axis is parallel to the horizontal scan-lines of the detector (rows). Positive direction from left to right of the detector plane looking​ towards the source.​

•​Zp axis is parallel to the vertical scan-lines of the detector (columns). Positive direction from bottom to top of the detector plane​ looking towards the source.​

•​Yp is the axis from the isocenter to the X-Ray source. Positive direction from the Isocenter to the X-Ray Source. This axis is so-​ called the X-Ray center beam.​

Figure C.8.19.6-5. Positioner Coordinate System​

Note​

The quantities SID and ISO are specified by the Attributes Distance Source to Detector (0018,1110) and Distance Source​ to Isocenter (0018,9402) respectively.​

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The Positioner Coordinate System (Op, Xp, Yp, Zp) is characterized, with respect to the Isocenter Coordinate System (O, X, Y, Z), by​ two angles describing the X-Ray center beam, and a third angle describing the rotation of the X-Ray detector plane. These angles​ are relative to the Isocenter reference system, and independent from the patient position on the equipment.​

Positioner Isocenter Primary Angle (0018,9463) (so-called Ap1 in Figure C.8.19.6-6) is defined in the plane XY, as the angle between​ the plane YZ and the plane YpZ. The axis of rotation of this angle is the Z axis. Angle from -Y to +X is positive. The valid range of this​ angle is -180 to +180 degrees.​

Positioner Isocenter Secondary Angle (0018,9464) (so-called Ap2 in Figure C.8.19.6-6) is defined in the plane YpZ, as the angle of​ the X-Ray Center Beam (i.e., Yp) relative to the XY plane. The axis of rotation of this angle is perpendicular to the plane YpZ. Angle​ from the plane XY to +Z is positive. The valid range of this angle is -180 to +180 degrees.​

Positioner Isocenter Detector Rotation Angle (0018,9465) (so-called Ap3 in Figure C.8.19.6-6 and in Figure C.8.19.6-7) is defined in​ the detector plane, as the angle of the vertical scan-lines of the detector (i.e., Zp) relative to the intersection between the detector​ plane and the plane YpZ. The sign of this angle is positive clockwise when facing on to the detector plane (see Figure C.8.19.6-7).​ The valid range of this angle is -180 to +180 degrees.​

X-Ray Source

Figure C.8.19.6-6. Positioner Isocenter Angles​

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