C.8.27.6.3 Intravascular OCT Frame Content Macro
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##### C.8.27.6.3 Intravascular OCT Frame Content Macro

Table C.8.27.6.3-1 specifies the attributes of the Intravascular OCT Frame Content Functional Group.

Table C.8.27.6.3-1. Intravascular OCT Frame Content Macro Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Intravascular OCT Frame Content Sequence | (0052,0029) | 1 | A sequence that describes a general description of this image or frame. Only a single Item shall be included in this sequence.
>OCT Z Offset Correction | (0052,0030) | 1 | The amount to shift the frame along the axial direction, in pixels, to correct for interferometer path-length mismatch. See Section C.8.27.6.3.1 for further explanation.
>Seam Line Index | (0052,0036) | 1 | The A-line number (zero index) that coincides with the seam line as indicated with the First A-line Location (0052,0034) attribute.
>Number of Padded A-lines | (0052,0038) | 1C | The number of padded A-lines contained in the FOR PROCESSING image frame. Required if the FOR PROCESSING image contains padded A-lines. See Section C.8.27.6.3.2 for further explanation.

###### C.8.27.6.3.1 OCT Z Offset Correction

OCT Z Offset Correction (0052,0030) specifies the number of pixels to shift the A-lines of the frame to correct for the path length difference between the OCT Sample arm and Reference arm (in air). A positive value of Z Offset correction means pixels are shifted further away from the catheter optics. A negative value of Z Offset correction means pixels are shifted closer to the catheter optics. See Figure C.8.27-2

Figure C.8.27-2. OCT Z Offset Correction Example

###### C.8.27.6.3.2 A-line Padding

Padded A-lines shall not be used in FOR PRESENTATION frames. Padded A-lines shall only be encoded in the high order rows of the FOR PROCESSING frame and shall be contiguous. Padded A-lines may contain arbitrary pixel values.

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