Table Z Position to Isocenter Attribute
| Tag | (0018,9468) |
|---|---|
| Type | Optional (3) |
| Keyword | TableZPositionToIsocenter |
| Value Multiplicity | 1 |
| Value Representation | Single (FL) |
Z position of the Table Reference Point with respect to the Isocenter (mm).
See Section C.8.19.6.13.1.3 for further explanation.
Section C.8.19.6.13.1.3
C.8.19.6.13.1.3 Table Coordinate System
The table coordinate system (Ot, Xt, Yt, Zt) is defined as follows:
- Origin Ot, so-called Table Reference Point, is on the Table Top plane
- +Xt direction to the TABLE LEFT
- +Zt direction to the TABLE HEAD
- +Yt direction to the TABLE DOWN
The table coordinate system (Ot, Xt, Yt, Zt) 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 TX in Figure C.8.19.6-8) is defined as the translation of the Table Reference Point Ot 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 TY in Figure C.8.19.6-8) is defined as the translation of the Table Reference Point Ot 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 TZ in Figure C.8.19.6-8) is defined as the translation of the Table Reference Point Ot with respect to the Isocenter Coordinate System in the Z direction. Table motion toward +Z is positive.
Note
A translation of ( TX,TY,TZ ) = (0, 0, 0) means that the Table Reference Point Ot is at the System Isocenter.
Table Horizontal Rotation Angle (so-called At1 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 At2 in Figure C.8.19.6-9) is defined in the vertical plane containing Zt (i.e., YZt), as the angle of the +Zt 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 XtYt. Zero value is defined when +Zt 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 At3 in Figure C.8.19.6-9) is defined in the XtYt plane, as the angle of the +Xt axis relative to the intersection between the XtYt plane and the horizontal plane XZ. The axis of rotation of this angle is the axis Zt. Zero value is defined when +Xt 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 At1 , At2 and At3 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 Ot, 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