# FFF.2.1.3.1.4 Example

In this example, the patient is on the table, in position “Head First Prone”. The table horizontal, tilt and rotation angles are equal to zero.

The positioner performs a rotation of 180 deg from the left to the right side of the patient, with the image detector going above the back of the patient, around an axis parallel to the head-feet axis of the patient.

[pic]

Figure FFF.2.1-14Detector Trajectory during Rotational Acquisition

Below are the encoded values of the key attributes of this example:

 Positioner Type (0018,1508) = CARM C-arm Positioner Tabletop Relationship (0018,9474) = YES … Per-Frame Functional Groups Sequence (5200,9230) Item 1 Frame 1 >Positioner Position Sequence (0018,9405) Item 1 >>Positioner Primary Angle (0018,1510) Item 1 >>Positioner Isocenter Primary Angle (0018,9463) = Item "N/2" Frame "N/2" >Positioner Position Sequence (0018,9405) Item 1 >>Positioner Primary Angle (0018,1510) Item 1 >>Positioner Isocenter Primary Angle (0018,9463) = Item "N" Frame "N" >Positioner Position Sequence (0018,9405) Item 1 >>Positioner Primary Angle (0018,1510) Item 1 Image XA/XRF Acquisition C.8.19.3 Specifies the relationship between the table and the positioner.

Table FFF.2. 1-34 ENHANCED XA IMAGE FUNCTIONAL GROUP MACROS

 Functional Group Macro PS 3.3 Reference Usage X-Ray Table Position C.8.19.6.11 Specifies the table position per-frame in three dimensions. X-Ray Isocenter Reference System C.8.19.6.13 Specifies the position and the angles of the table per-frame in equipment coordinates, for further applications based on the acquisition geometry (e.g., registration…).

FFF.2.1.3.2.3.1 XA/XRF Acquisition Module Recommendations

The usage of this module is recommended to specify the relationship between the table and the positioner.

Table FFF.2.1-35 XA/XRF ACQUISITION MODULE Example

 Attribute Name Tag Comment C-arm Positioner Tabletop Relationship (0018,9474) Both values YES and NO are applicable to this scenario. Note: On mobile systems where this attribute equals NO, it is possible to do table stepping. In such case, the system is not able to determine the absolute table position relative to the Isocenter, which is necessary for 2D-2D registration.

FFF.2.1.3.2.3.2 X-Ray Table Position Macro Recommendations

This macro is used in the per-frame context in this scenario.

Table FFF.2.1-36 X-RAY TABLE POSITION MACRO Example

 Attribute Name Tag Comment Table Position Sequence (0018,9406) >Table Top Vertical Position (300A,0128) The same value for all frames. >Table Top Longitudinal Position (300A,0129) The same value for all frames. >Table Top Lateral Position (300A,012A) Different values per frame, corresponding to the “stepping” intervals in the table plane. >Table Horizontal Rotation Angle (0018,9469) The same value for all frames. >Table Head Tilt Angle (0018,9470) The same value for all frames. >Table Cradle Tilt Angle (0018,9471) The same value for all frames.

FFF.2.1.3.2.3.3 X-Ray Isocenter Reference System Macro Recommendations

If the value of the C-arm Positioner Tabletop Relationship (0018,9474) is NO, the following macro may not be provided by the acquisition modality. This macro is used in the per-frame context in this scenario.

Table FFF.2.1-37 X-RAY ISOCENTER REFERENCE SYSTEM MACRO Example

 Attribute Name Tag Comment Isocenter Reference System Sequence (0018,9462) >Table X Position to Isocenter (0018,9466) X-position of a fixed point in the table top, it changes per-frame if table horizontal rotation is not zero >Table Y Position to Isocenter (0018,9467) Vertical position of a fixed point in the table top, it changes per-frame if table head tilt is not zero >Table Z Position to Isocenter (0018,9468) Z-position of a fixed point in the table top, it changes per-frame >Table Horizontal Rotation Angle (0018,9469) The same value for all frames. >Table Head Tilt Angle (0018,9470) The same value for all frames. >Table Cradle Tilt Angle (0018,9471) The same value for all frames.