Table C.8-120 specifies the attributes of the CT Table Dynamics Functional Group Macro.
Table C.8-120. CT Table Dynamics Macro Attributes
|
Attribute Name |
Tag |
Type |
Attribute Description |
|---|---|---|---|
|
CT Table Dynamics Sequence |
(0018,9308) |
1 |
Contains the attributes defining the movement of the CT table. Only a single Item shall be included in this sequence. |
|
>Table Speed |
(0018,9309) |
1C |
The distance in mm that the table moves in one second during the gathering of data that resulted in this frame. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL and Acquisition Type (0018,9302) is SPIRAL or CONSTANT_ANGLE. May be present otherwise if Frame Type (0008,9007) Value 1 of this frame is DERIVED and Acquisition Type (0018,9302) is SPIRAL or CONSTANT_ANGLE. |
|
>Table Feed per Rotation |
(0018,9310) |
1C |
Motion of the table (in mm) during a complete revolution of the source around the gantry orbit. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL and Acquisition Type (0018,9302) is SPIRAL. May be present otherwise if Frame Type (0008,9007) Value 1 of this frame is DERIVED and Acquisition Type (0018,9302) is SPIRAL. |
|
>Spiral Pitch Factor |
(0018,9311) |
1C |
Ratio of the Table Feed per Rotation (0018,9310) to the Total Collimation Width (0018,9307). See Section C.8.15.3.4.1 for further explanation and some examples. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL and Acquisition Type (0018,9302) is SPIRAL. May be present otherwise if Frame Type (0008,9007) Value 1 of this frame is DERIVED and Acquisition Type (0018,9302) is SPIRAL. |
The formula for Spiral Pitch Factor (0018,9311) in terms of Table Feed per Rotation (0018,9310) and Total Collimation Width (0018,9307) is:
Spiral Pitch Factor = (Table Feed per Rotation (mm))/(Total Collimation Width (mm))
An example calculation of Spiral Pitch Factor (0018,9311) for a single slice spiral acquisition of an image with a Total Collimation Width of 2.5mm and a Table Feed per Rotation of 10mm is:
Spiral Pitch Factor = (10 mm) / (2.5 mm) = 4.0
An example calculation of Spiral Pitch Factor (0018,9311) for a multiple slice spiral acquisition having a Total Collimation Width of 20mm and a Table Feed per Rotation of 10mm is:
Spiral Pitch Factor = (10 mm) / (20 mm) = 0.5