C.7.6.16.2.7 Cardiac Synchronization Macro

Table C.7.6.16-8 specifies the attributes of the Cardiac Synchronization Functional Group macro.

Table C.7.6.16-8CARDIAC SYNCHRONIZATION MACRO ATTRIBUTES

Attribute Name Tag Type Attribute Description
Cardiac Synchronization Sequence (0018,9118) 1 Sequence that describes the frame specific cardiac synchronization parameters. Only a single Item shall be included in this sequence.
>Nominal Percentage of Cardiac Phase (0020,9241) 1C The nominal time relative to the preceding R peak divided by the nominal R-R interval multiplied by 100. Required if used as a dimension index, may be present otherwise.
>Nominal Cardiac Trigger Delay Time (0020,9153) 1 The nominal time in ms from the time of the previous R-peak to the value of the Frame Reference DateTime (0018,9151) expressed as a positive value. See C.7.6.16.2.7.1 for further explanation.
>Actual Cardiac Trigger Delay Time (0020,9252) 1C The actual time in ms from the time of the previous R-peak to the value of the Frame Reference DateTime (0018,9151) expressed as a positive value . See C.7.6.16.2.7.1 for further explanation. Required if Intervals Acquired (0018,1083) is present and has a value of 1. May be present otherwise.
>Nominal Cardiac Trigger Time Prior to R-peak (0020,9154) 3 The nominal time in ms from the time of the next R-peak to the value of the Frame Reference DateTime (0018,9151) expressed as a negative value. See C.7.6.16.2.7.1 for further explanation.
>Actual Cardiac Trigger Time Prior to R-peak (0020,9155) 3 The actual time in ms from the time of the next R-peak to the value of the Frame Reference DateTime (0018,9151) expressed as a negative value. See C.7.6.16.2.7.1 for further explanation.
>Intervals Acquired (0018,1083) 3 Number of R-R intervals acquired.
>Intervals Rejected (0018,1084) 3 Number of R-R intervals rejected.
>Heart Rate (0018,1088) 3 Average number of heart beats per minute for the collection period for this frame. This shall include all accepted beats as well as rejected beats. Note: During prolonged acquisitions the average heart rate may differ from the reciprocal of the nominal R-R interval.
>R-R Interval Time Nominal (0020,9251) 1C Nominal R-peak - R-peak interval time in ms for the cardiac cycle used for the acquisition of this frame. See C.7.6.16.2.7.1 for further explanation. Required if Cardiac Synchronization Technique (0018,9037) equals other than NONE or REALTIME. May be present otherwise.
>Low R-R Value (0018,1081) 3 R-R interval low limit for beat rejection, in ms.
>High R-R Value (0018,1082) 3 R-R interval high limit for beat rejection, in ms.

C.7.6.16.2.7.1 Relationship of Cardiac Timing Attributes

The Nominal Cardiac Trigger Delay Time (0020,9153) is the nominal trigger delay time in ms from the previous R-peak to the value of the Frame Reference DateTime (0018,9151). When frames are acquired with prospective gating, that is, the data acquisition actually begins in response to a timed delay from the R-peak, it may be that Actual Cardiac Trigger Delay Time (0020,9252) and the Nominal Cardiac Trigger Delay Time (0020,9153) have the same value.

However, when frames are the result of retrospective gating, that is, the data is continuously acquired and then later compared with a simultaneously acquired ECG waveform and fitted into time slots corresponding to nominal phases of the cardiac cycle, then Nominal Cardiac Trigger Delay Time (0020,9153) and the Actual Cardiac Trigger Delay Time (0020,9252) may have different values. When applicable the same is valid for the Nominal Cardiac Trigger Time Prior to R-peak (0020,9154) and the Actual Cardiac Trigger Time Prior to R-peak (0020,9155) attributes.

When multiple cardiac cycles are averaged together, then the Low R-R Value (0018,1081), and High R-R Value (0018,1082) are an average of the cardiac cycles that were accepted in the frame.

Note: For cardiac gated acquisitions the choice of the Frame Reference DateTime (0018,9151) is influenced by the Nominal Cardiac Trigger Delay Time (0020,9153). For respiratory gated acquisitions the choice of the Frame Reference DateTime (0018,9151) is influenced by the Nominal Respiratory Trigger Delay Time (0020,9255).

Figure C.7.6.16-5a depicts the usage.

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Figure C.7.6.16-5aCardiac Timing Tags

Nominal Cardiac Trigger Time Prior to R-peak (0020,9154) and the Actual Cardiac Trigger Time Prior to R-peak (0020,9155) attributes can be used to store a time of the next R-peak to the value of the Frame Reference DateTime (0018,9151) expressed as a negative value. In this case the Actual Cardiac Trigger Delay Time (0020,9252), when present, and the Nominal Cardiac Trigger Delay Time (0020,9153) shall contain a value calculated based on the R-R interval applicable for this frame. See Figure C.7.6.16-5b.

[pic]

Figure C.7.6.16-5bCardiac Timing Relationships

Note: Specifying the time interval prior to the R-peak is relevant for applications such as capturing P- and Q-wave related morphology.