Tag | (0018,9464) |
---|---|
Type | Required (1) |
Keyword | PositionerIsocenterSecondaryAngle |
Value Multiplicity | 1 |
Value Representation | Single (FL) |
Position of the X-Ray center beam in the isocenter reference system in the Z direction (deg).
See Section C.8.19.6.13.1.2 for further explanation.
Part of the X-Ray Isocenter Reference System Functional Group Macro with usage: U
The Positioner Coordinate System (O_{p}, X_{p}, Y_{p}, Z_{p}) is defined as follows:
Origin O_{p}, is the origin of the Isocenter coordinate system O
X_{p} 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.
Z_{p} 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.
Y_{p} 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
The quantities SID and ISO are specified by the Attributes Distance Source to Detector (0018,1110) and Distance Source to Isocenter (0018,9402) respectively.
The Positioner Coordinate System (O_{p}, X_{p}, Y_{p}, Z_{p}) 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 Ap_{1} in Figure C.8.19.6-6) is defined in the plane XY, as the angle between the plane YZ and the plane Y_{p}Z. 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 Ap_{2} in Figure C.8.19.6-6) is defined in the plane Y_{p}Z, as the angle of the X-Ray Center Beam (i.e., Y_{p}) relative to the XY plane. The axis of rotation of this angle is perpendicular to the plane Y_{p}Z. 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 Ap_{3} 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., Z_{p}) relative to the intersection between the detector plane and the plane Y_{p}Z. 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.
Figure C.8.19.6-6. Positioner Isocenter Angles
Figure C.8.19.6-7. Positioner Isocenter Detector Rotation Angle when Ap_{1} = 0 and Ap_{2} = 0