FFF.2.2 Review
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### FFF.2.2 Review

#### FFF.2.2.1 Variable Frame-rate Acquisition With Skip Frames

This application case provides information on how X-Ray acquisitions with variable time between frames can be organized by groups of frames to be reviewed with individual group settings.

##### FFF.2.2.1.1 User Scenario

The image acquisition system performs complex acquisition protocols with groups of frames to be displayed at different frame rates and others to be skipped.

Allow frame-rates in viewing applications to be different than acquired rates.

##### FFF.2.2.1.2 Encoding Outline

The XA IOD provides only one group of frames between start and stop trim.

The Enhanced XA/XRF IOD allows encoding of multiple groups of frames (frame collections) with dedicated display parameters.

The Enhanced XA IOD provides an exact acquisition time for each frame.

##### FFF.2.2.1.3 Encoding Details

This section provides detailed recommendations of the key attributes to address this particular scenario.

Table FFF.2.2-1. Enhanced X-Ray Angiographic Image IOD Modules

IE | Module | PS3.3 Reference | Usage
--- | --- | --- | ---
Image | XA/XRF Multi-frame Presentation | C.8.19.7 | Specifies the groups of frames and their display parameters.

###### FFF.2.2.1.3.1 XA/XRF Multi-frame Presentation Module Recommendations

The usage of this module is recommended to encode the grouping of frames (one or more groups) for display purposes and the related parameters for each group.

Table FFF.2.2-2. XA/XRF Multi-frame Presentation Module Recommendations

Attribute Name | Tag | Comment
--- | --- | ---
Preferred Playback Sequencing | (0018,1244) | Specifies the direction of the playback.
Frame Display Sequence | (0008,9458) | Specifies the details on how frames are grouped for display purposes.

##### FFF.2.2.1.4 Example

An example of a 4 position peripheral stepping acquisition with different frame-rates is provided. One group is only 2 Frames (e.g., due to fast contrast bolus) and will be skipped for display purposes.

The whole image is reviewed in looping mode:

- The first group, from frames 1 to 17, is to be reviewed at 4 frames per second;

- The second group, from frames 18 to 25, is to be reviewed at 2 frames per second;

- The third group, of frames 26 and 27, is not to be displayed;

- The fourth group, from frames 28 to 36, is to be reviewed at 1.5 frames per second.

The encoded values of the key attributes of this example are shown in Figure FFF.2.2-1.

Figure FFF.2.2-1. Attributes of the Example of the Variable Frame-rate Acquisition with Skip Frames

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