C.8.15.3.6 CT Geometry Macro
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##### C.8.15.3.6 CT Geometry Macro

Table C.8-122 specifies the attributes of the CT Geometry Functional Group Macro.

Table C.8-122. CT Geometry Macro Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
CT Geometry Sequence | (0018,9312) | 1 | Contains the attributes defining the CT geometry. Only a single Item shall be included in this sequence.
>Distance Source to Detector | (0018,1110) | 1C | Distance in mm from source to detector center. See Section C.8.15.3.6.1. ### Note This value is traditionally referred to as Source Image Receptor Distance (SID). Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.
>Distance Source to Data Collection Center | (0018,9335) | 1C | Distance in mm from source to data collection center. See Section C.8.15.3.6.1. Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL. May be present otherwise.

###### C.8.15.3.6.1 Relationships Between CT Geometric Attributes (Informative)

In Figure C.8-19 the relationship of the Geometric Attributes within the CT Geometry and CT Reconstruction functional groups is shown. Figure C.8-19, viewed from the front of the gantry (where the table enters the gantry), is informative only and is not meant to represent a standardization of an equipment-based frame of reference.

Figure C.8-19. Geometry of CT Acquisition System

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