C.8.15.3.4 CT Table Dynamics Macro
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##### C.8.15.3.4 CT Table Dynamics Macro

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.

###### C.8.15.3.4.1 Spiral Pitch Factor

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

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