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C.8.19.6.13.1.3 Table Coordinate System

The table coordinate system (O_{t}, X_{t}, Y_{t}, Z_{t}) is defined as follows:

- Origin O_{t}, so-called Table Reference Point, is on the Table Top plane

- +X_{t} direction to the TABLE LEFT

- +Z_{t} direction to the TABLE HEAD

- +Y_{t} direction to the TABLE DOWN

The table coordinate system (O_{t}, X_{t}, Y_{t}, Z_{t}) is characterized, with respect to the Isocenter coordinate system (O, X, Y, Z), by a 3D translation and 3 angles describing the tilting and rotation:

**Table X Position to Isocenter**
**(0018,9466)**
(so-called
**T**_{X}
in Figure C.8.19.6-8) is defined as the translation of the Table Reference Point O_{t} with respect to the Isocenter Coordinate System in the X direction. Table motion toward +X is positive.

**Table Y Position to Isocenter**
**(0018,9467)**
(so-called
**T**_{Y}
in Figure C.8.19.6-8) is defined as the translation of the Table Reference Point O_{t} with respect to the Isocenter Coordinate System in the Y direction. Table motion toward +Y is positive.

**Table Z Position to Isocenter**
**(0018,9468)**
(so-called
**T**_{Z}
in Figure C.8.19.6-8) is defined as the translation of the Table Reference Point O_{t} with respect to the Isocenter Coordinate System in the Z direction. Table motion toward +Z is positive.

### Note

A translation of (
**T**_{X},T_{Y},T_{Z}
) = (0, 0, 0) means that the Table Reference Point O_{t} is at the System Isocenter.

**Table Horizontal Rotation Angle**
(so-called
**At**_{1}
in Figure C.8.19.6-9) is defined in the horizontal plane XZ, as the angle of the projection of the +Zt axis in the XZ plane relative to the +Z axis. The axis of rotation of this angle is the vertical axis crossing the Table Reference Point Ot. Zero value is defined when the projection of +Zt in the XZ plane is equal to +Z. Angle from +Z to +X is positive. The valid range of this angle is -180 to +180 degrees.

**Table Head Tilt Angle**
(so-called
**At**_{2}
in Figure C.8.19.6-9) is defined in the vertical plane containing Z_{t} (i.e., YZ_{t}), as the angle of the +Z_{t} axis relative to the horizontal plane XZ. The axis of rotation of this angle is defined as the intersection between the horizontal plane XZ and the plane X_{t}Y_{t}. Zero value is defined when +Z_{t} is contained in the horizontal plane XZ. Angle from horizontal (plane XZ) to -Y direction (upwards) is positive, indicating that the head of the table is above the horizontal plane. The valid range of this angle is -45 to +45 degrees.

**Table Cradle**
**Tilt Angle**
(so-called
**At**_{3}
in Figure C.8.19.6-9) is defined in the X_{t}Y_{t} plane, as the angle of the +X_{t} axis relative to the intersection between the X_{t}Y_{t} plane and the horizontal plane XZ. The axis of rotation of this angle is the axis Z_{t}. Zero value is defined when +X_{t} is contained in the horizontal plane XZ. Angle from horizontal (plane XZ) to -Y direction (upwards) is positive, indicating that the left of the table is above the horizontal plane. The valid range of this angle is -45 to +45 degrees.

### Note

The angles
**At**_{1}
,
**At**_{2}
and
**At**_{3}
are independent from any specific mechanical design of the table rotation axis defined by a manufacturer. In particular, they don't require the three rotation axis to cross on a single point. If a mechanical rotation axis does not cross the Table Reference Point O_{t}, a mechanical rotation around this axis will generate a change in one or more table angles as well as a translation of the Table Reference Point.

**Figure C.8.19.6-8. Table Translation with respect to the Isocenter Reference System**

**Figure C.8.19.6-9. Table Angulations with respect to the Isocenter Reference System**