# C.8.19.6.11 X-Ray Table Position Macro

Table C.8.19.6-11 specifies the attributes of the X-Ray Table Position Functional Group macro.

Table C.8.19.6-11X-RAY TABLE POSITION MACRO ATTRIBUTES

 Attribute Name Tag Type Attribute Description Table Position Sequence (0018,9406) 1 A sequence that describes the geometrical position of the table top. Only a single Item shall be included in this sequence. >Table Top Vertical Position (300A,0128) 1 Table Top Vertical position with respect to an arbitrary chosen reference by the equipment in (mm). Table motion downwards is positive >Table Top Longitudinal Position (300A,0129) 1 Table Top Longitudinal position with respect to an arbitrary chosen reference by the equipment in (mm). Table motion towards LAO is positive assuming that the patient is positioned supine and its head is in normal position. >Table Top Lateral Position (300A,012A) 1 Table Top Lateral position with respect to an arbitrary chosen reference by the equipment in (mm). Table motion towards CRA is positive assuming that the patient is positioned supine and its head is in normal position. >Table Horizontal Rotation Angle (0018,9469) 1 Rotation of the table in the horizontal plane (clockwise when looking from above the table). >Table Head Tilt Angle (0018,9470) 1 Angle of the head-feet axis of the table in degrees relative to the horizontal plane. Positive values indicate that the head of the table is upwards. >Table Cradle Tilt Angle (0018,9471) 1 Angle of the left-right axis of the table in degrees relative to the horizontal plane. Positive values indicate that the left of the table is upwards.

## 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.

The Table Angle attributes of the Table Position Sequence (0018,9406) specify the rotation and tilt of the Table Top Plane with respect 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 shiftâ€¦), assuming that the patient position is fixed on the table. For more complex registration applications, and in order to properly handle the changes in the table angles, it is recommended to use the X-Ray Isocenter Reference System Macro attributes.

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Figure C.8.19.6-3Table Position Vectors