FFF.2.1.1 ECG Recording at Acquisition Modality

This application case is related to the results of an X-Ray acquisition and parallel ECG data recording on the same equipment.

FFF.2.1.1.1 User Scenario

The image acquisition system records ECG signals simultaneously with the acquisition of the Enhanced XA multi-frame image. All the ECG signals are acquired at the same sampling rate.

The acquisition of both image and ECG data are not triggered by an external signal.

The information can be exchanged via Offline Media or Network.

Synchronization between the ECG Curve and the image frames allows synchronized navigation in each of the datasets.

[pic]

Figure FFF.2.1-1Scenario of ECG Recording at Acquisition Modality

FFF.2.1.1.2 Encoding outline

The General ECG IOD is used to store the waveform data recorded in parallel to the image acquisition encoded as Enhanced XA IOD.

The Synchronization Module is used to specify a common time-base.

The option of encoding trigger information is not recommended by this case.

The solution assumes implementation on a single imaging modality and therefore the mutual UID references between the General ECG and Enhanced XA objects is recommended. This will allow faster access to the related object.

FFF.2.1.1.3 Encoding details

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

FFF.2.1.1.3.1 Enhanced XA Image

Table FFF.2.1-1ENHANCED X-RAY ANGIOGRAPHIC IMAGE IOD MODULES

IE Module PS 3.3 Reference Usage
Series General Series C.7.3.1 The General Series Module Modality (0008,0060) attribute description in PS 3.3 enforces the storage of waveform and pixel data in different Series IE.
Frame of Reference Synchronization C.7.4.2 Specifies that the image acquisition is synchronized. Will have the same content as the General ECG SOP Instance.
Equipment General Equipment C.7.5.1 Same as in the General ECG SOP Instance.
Image Cardiac Synchronization C.7.6.18.1 Contains information of the type of relationship between the ECG waveform and the image.
Enhanced XA/XRF Image C.8.19.2 Contains UID references to the related General ECG SOP Instance.

Table FFF.2. 1- 2 ENHANCED XA IMAGE FUNCTIONAL GROUP MACROS

Functional Group Macro PS 3.3 Reference Usage
Frame Content C.7.6.16.2.2 Provides timing information to correlate each frame to the recorded ECG samples.
Cardiac Synchronization C.7.6.16.2.7 Provides time relationships between the angiographic frames and the cardiac cycle.

FFF.2.1.1.3.1.1 Synchronization Module Recommendations

The usage of this Module is recommended to encode a “synchronized time” condition.

The specialty of Synchronization Triggers is not part of this scenario.

Table FFF.2.1-3 SYNCHRONIZATION MODULE Recommendations

Attribute Name Tag Comment
Synchronization Frame of Reference UID (0020,0200) Same UID as in the related General ECG SOP Instance.
Synchronization Trigger (0018,106A) In this scenario with no external trigger signal, the value “NO TRIGGER” is used.
Acquisition Time Synchronized (0018,1800) The value “Y” is used in this scenario.

FFF.2.1.1.3.1.2 General Equipment Module Recommendations

The usage of this Module is recommended to assure that the image contains identical equipment identification information as the referenced General ECG SOP Instance.

FFF.2.1.1.3.1.3 Cardiac Synchronization Module Recommendations

The usage of this module is recommended to indicate that the ECG is not used to trig the X-Ray acquisition, rather to time relate the frames to the ECG signal.

Table FFF.2.1-4 CARDIAC SYNCHRONIZATION MODULE Recommendations

Attribute Name Tag Comment
Cardiac Synchronization Technique (0018,9037) The value “REAL TIME” is used in this scenario.
Cardiac Signal Source (0018,9085) In this scenario, the value “ECG” is used to indicate that the cardiac waveform is an electrocardiogram.

FFF.2.1.1.3.1.4 Enhanced XA/XRF Image Module Recommendations

The usage of this module is recommended to reference from the image object to the related General ECG SOP Instance that contains the ECG data recorded simultaneously.

Table FFF.2.1-5 ENHANCED XA/XRF IMAGE MODULE Recommendations

Attribute Name Tag Comment
Referenced Instance Sequence (0008,114A) Reference to “General ECG SOP Instance” acquired in conjunction with this image. Contains a single item.
>Referenced SOP Class UID (0008,1150) 1.2.840.10008.5.1.4.1.1.9.1.2” i.e. reference to an General ECG SOP Instance
>Referenced SOP Instance UID (0008,1155) Instance UID of referenced waveform
>Purpose of Reference Code Sequence (0040,A170) CID 7004 is used; identify clear reason for the Reference.

FFF.2.1.1.3.1.5 Cardiac Synchronization Macro Recommendations

If there is a specific ECG analysis that determines the time between the R-peaks and the angiographic frames, the usage of this macro is recommended.

As the frames are acquired at a frame rate independent of cardiac phases, this macro is used in a “per frame functional group” to encode the position of each frame relative to its prior R-peak.

FFF.2.1.1.3.1.6 Frame Content Macro Recommendations

In this scenario the timing information is important to correlate each frame to the recorded ECG.

If there is a specific ECG analysis, this macro allows the encoding of the position in the cardiac cycle that is most representative of each frame.

The following table gives recommendations for usage in this scenario.

Table FFF.2.1-6 FRAME CONTENT MACRO Recommendations

Attribute Name Tag Comment
Frame Content Sequence (0020,9111)
>Frame Reference Datetime (0018,9151) Exact Time taken from the internal clock.
>Frame Acquisition Datetime (0018,9074) Exact Time taken from the internal clock.
>Cardiac Cycle Position (0018,9236) Optional, if ECG analysis is available.

FFF.2.1.1.3.2 General ECG Object

This IOD will encode the recorded ECG waveform data, which is done by the image acquisition system. Since this is not a dedicated waveform modality device, appropriate defaults for most of the data have to be recommended to fulfill the requirements according to PS 3.3.

Table FFF.2. 1-7 General ECG IOD Modules

IE Module PS 3.3 Reference Usage
Series General Series C.7.3.1 The General Series Module Modality (0008,0060) attribute description in PS 3.3 enforces the storage of waveform and pixel data in different Series IE.
Frame of Reference Synchronization C.7.4.2 Specifies that the waveform acquisition is synchronized. Will have the same content as the image.
Equipment General Equipment C.7.5.1 Same as in the image.
Waveform Waveform Identification C.10.8 Contains references to the related image object.
Waveform C.10.9 Contains one multiplex group with the same sampling rate.

FFF.2.1.1.3.2.1 General Series Module Recommendations

A new Series is created to set the modality “ECG” for the waveform.

Most of the attributes are aligned with the contents of the related series level attributes in the image object.

The Related Series Sequence (0008,1250) is not recommended because instance level relationship can be applied to reference the image instances.

Table FFF.2. 1-8 GENERAL SERIES MODULE Recommendations

Attribute Name Tag Comment
Modality (0008,0060) “ECG”
Series Instance UID (0020,000E) Different from the one of the image object.
Series Date (0008,0021) Identical to the contents of related image object
Series Time (0008,0031) Identical to the contents of related image object.
Other attributes of General Series Module Match contents of related image object, if set there.

FFF.2.1.1.3.2.2 Synchronization Module Recommendations

The usage of this Module is recommended to encode a “synchronized time” condition, which was previously implicit when using the curve module.

Table FFF.2.1-9 SYNCHRONIZATION MODULE Recommendations

Attribute Name Tag Comment
Synchronization Frame of Reference UID (0020,0200) Same UID as in the related image object.
Synchronization Trigger (0018,106A) The value “NO TRIGGER” is used in this scenario with no external trigger signal.
Acquisition Time Synchronized (0018,1800) The value “Y” is used to allow synchronized navigation.

FFF.2.1.1.3.2.3 General Equipment Module Recommendations

The usage of this Module is recommended to assure that the General ECG SOP Instance contains identical equipment identification information as the referenced image objects.

FFF.2.1.1.3.2.4 Waveform Identification Recommendations

The usage of this module is recommended to relate the acquisition time of the waveform data to the image acquired simultaneously.

The module additionally includes an instance level reference to the related image.

Table FFF.2.1-10 WAVEFORM IDENTIFICATION MODULE Recommendations

Attribute Name Tag Comment
Acquisition Datetime (0008,002A) Exact start of the waveform acquisition taken from common (or synchronized) clock. Note: In case the ECG acquisition started before the image acquisition itself, the given datetime value is not the same as for the image.
Referenced Instance Sequence (0008,114A) Only one item used in this application case.
>Referenced SOP Class UID (0008,1150) 1.2.840.10008.5.1.4.1.1.12.1.1” i.e. Enhanced XA
>Referenced SOP Instance UID (0008,1155) Instance UID of Enhanced XA Image Object to which this parallel ECG recording is related.
>Purpose of Reference Code Sequence (0040,A170) The referenced image is related to this ECG.

FFF.2.1.1.3.2.5 Waveform Module Recommendations

The usage of this module is a basic requirement of the General ECG IOD.

Any application displaying the ECG is recommended to scale the ECG contents to its output capabilities (esp. the amplitude resolution).

If more than one ECG signal needs to be recorded, the grouping of the channels in multiplex groups depends on the ECG sampling rate. All the channels encoded in the same multiplex group have identical sampling rate.

Table FFF.2.1-11 WAVEFORM MODULE Recommendations

Attribute Name Tag Comment
Waveform Sequence (5400,0100) Only one item is used in this application case, as all the ECG signals have the same sampling rate.
> Multiplex Group Time Offset (0018,1068) If needed, specify the Group Offset from the Acquisition Datetime.
> Waveform Originality (003A,0004) The value “ORIGINAL” is used in this scenario.

FFF.2.1.1.4 Examples

In the two following examples, the Image Modality acquires a multi-frame image of the coronary arteries lasting 4 seconds, at 30 frames per second.

Simultaneously, the same modality acquires two channels of ECG from a 2-Lead ECG (the first channel on Lead I and the second on Lead II) starting one second before the image acquisition starts, and lasting 5 seconds, with a sampling frequency of 300 Hz on 16 bits signed encoding, making up a number of 1500 samples per channel. The first ECG sample is 10 ms after the nominal start time of the ECG acquisition. Both ECG channels are sampled simultaneously. The time skew of both channels is 0 ms.

[pic]

Figure FFF.2.1-2Example of ECG Recording at Acquisition Modality

FFF.2.1.1.4.1 Enhanced XA image without cardiac synchronization

In this example, the Enhanced XA image does not contain information of the cardiac cycle phases.

The attributes that define the two different SOP Instances (Enhanced XA and General ECG) of this example are described in the following figures:

ENHANCED XA SOP INSTANCE

Study Instance UID (0020,000D) = UID “A”
Modality (0008,0060) = XA
Synchronization Trigger (0018,106A) = NO TRIGGER
Acquisition Time Synchronized (0018,1800) = Y
Referenced Instance Sequence (0008,114A)
Item 1
>Referenced SOP Class UID (0008,1150)
Series Instance UID (0020,000E) = UID “F”
Modality (0008,0060) = ECG
Synchronization Frame of Reference UID (0020,0200) = UID “C”
Synchronization Trigger (0018,106A) = NO TRIGGER
Acquisition Time Synchronized (0018,1800) = Y
SOP Instance UID (0008,0018) = UID “E”
Referenced Instance Sequence (0008,114A)
Item 1
>Referenced SOP Class UID (0008,1150) = 1.2.840.10008.5.1.4.1.1.12.1.1
>Referenced SOP Instance UID (0008,1155) = UID “D”
>Purpose of Reference Code Sequence (0040,A170)
Item 1
Item 1 Only one ECG Multiplex Group
>Multiplex Group Time Offset (0018,1068) = 10
>Waveform Originality (003A,0004) = ORIGINAL
>Number of Waveform Channels (003A,0005) = 2
>Number of Waveform Samples (003A,0010) = 1500
>Sampling Frequency (003A,001A) = 300
>Channel Definition Sequence (003A,0200)
Item 1
>Waveform Sample Interpretation (5400,1006) = SS

Figure FFF.2.1-3Attributes of ECG Recording at Acquisition Modality

FFF.2.1.1.4.2 Enhanced XA image with cardiac synchronization

In this example, the heart rate is 75 beats per minute. As the image is acquired during a period of four seconds, it contains five heartbeats.

The ECG signal is analyzed to determine the R-peaks and to relate them to the angiographic frames. Thus the Enhanced XA image contains information of this relationship between the ECG signal and the frames.

[pic]

Figure FFF.2.1- 4 Example of ECG information in the Enhanced XA image

The attributes that define the two different SOP Instances (Enhanced XA and General ECG) of this example are described in the figures of the previous example, in addition to the attributes described in the following figures:

ENHANCED XA SOP INSTANCE

Cardiac Synchronization Technique (0018,9037) = REALTIME
Cardiac Signal Source (0018,9085) = ECG
Cardiac RR Interval Specified (0018,9070) = 800
Intervals Acquired (0018,1083) = 5
Intervals Rejected (0018,1084) = 0
Per-Frame Functional Groups Sequence (5200,9230)    
  Item i     Frame “i”
    >Cardiac Synchronization Sequence (0018,9118)    
      Item 1      
       
Frame of Reference Synchronization C.7.4.2 Specifies that the image acquisition is time synchronized with the ECG acquisition. Will have the same content as the General ECG SOP Instance.
Image Enhanced XA/XRF Image C.8.19.2 Specifies the date and time of the image acquisition.

Table FFF.2. 1-13 ENHANCED XA IMAGE FUNCTIONAL GROUP MACROS

Functional Group Macro PS 3.3 Reference Usage
Frame Content C.7.6.16.2.2 Provides timing information to correlate each frame to any externally recorded waveform.

FFF.2.1.2.1.3.1.1 Synchronization Module Recommendations

This Module is used to document the synchronization of the two modalities.

Table FFF.2.1-14 SYNCHRONIZATION MODULE Recommendations

Attribute Name Tag Comment
Synchronization Frame of Reference UID (0020,0200) The UTC Synchronization UID “1.2.840.10008.15.1.1” is used in this case.
Synchronization Trigger (0018,106A) The value “NO TRIGGER” is used for the case of time synchronization via NTP.
Acquisition Time Synchronized (0018,1800) The value “Y” is used in this scenario.
Time Source (0018,1801) The same value as in the related General ECG SOP Instance is used in this scenario.
Time Distribution Protocol (0018,1802) The value “NTP” is used in this scenario.
NTP Source Address (0018,1803) The same value as in the related General ECG SOP Instance is used in this scenario.

FFF.2.1.2.1.3.1.2 Enhanced XA/XRF Image Module Recommendations

This module includes the acquisition date and time of the image, which is in the same time basis as the acquisition date and time of the ECG in this scenario.

FFF.2.1.2.1.3.1.3 Frame Content Macro Recommendations

In this scenario the timing information is important to correlate each frame to any externally recorded waveform.

Table FFF.2.1-15 FRAME CONTENT MACRO Recommendations

Attribute Name Tag Comment
Frame Content Sequence (0020,9111)
>Frame Reference Datetime (0018,9151) Exact date and time taken from the synchronized clock.
>Frame Acquisition Datetime (0018,9074) Exact date and time taken from the synchronized clock.

FFF.2.1.2.1.3.2 Waveform Object

The ECG recording system will take care of filling in the waveform-specific contents in the General ECG SOP Instance. This section will address only the specifics for attributes related to synchronization.

Table FFF.2. 1-16 Waveform IOD Modules

IE Module PS 3.3 Reference Usage
Frame of Reference Synchronization C.7.4.2 Specifies that the ECG acquisition is time synchronized with the image acquisition. Will have the same content as the Enhanced XA SOP Instance. See section FFF.2.1.2.1.3.1.1.
Waveform Waveform Identification C.10.8 Provides timing information to correlate the waveform data to any externally recorded image.

FFF.2.1.2.1.3.2.1 Waveform Identification Recommendations

The usage of this module is recommended to relate the acquisition time of the waveform data to the related image(s).

Table FFF.2.1-18 WAVEFORM IDENTIFICATION MODULE Recommendations

Attribute Name Tag Comment
Acquisition Datetime (0008,002A) Exact start of the waveform acquisition: taken from synchronized clock.

FFF.2.1.2.1.4 Example

In this example, there are two modalities that are synchronized with an external clock via NTP. The Image Modality acquires three multi-frame images within the same Study and same Series. Simultaneously, the Waveform Modality acquires the ECG non-stop during the same period, leading to one single Waveform SOP Instance on a different Study.

In this example, there is no UID referencing capability between the two modalities.

[pic]

Figure FFF.2.1-7Example of Multi-modality Waveform Synchronization

The attributes that define the relevant content in the two different SOP Instances (Enhanced XA and General ECG) are described in the following figure:

ENHANCED XA SOP INSTANCES

Study Instance UID (0020,000D) = UID “A”
Series Instance UID (0020,000E) = UID “B”
Modality (0008,0060) = XA
Synchronization Frame of Reference UID (0020,0200) = 1.2.840.10008.15.1.1
Synchronization Trigger (0018,106A) = NO TRIGGER
Acquisition Time Synchronized (0018,1800) = Y
Time Source (0018,1801) = Clock System ID
Time Distribution Protocol (0018,1802) = NTP
NTP Source Address (0018,1803) = aaa.bbb.ccc.ddd
SOP Instance UID (0008,0018) = UID “D1”, “D2” and “D3” resp.

GENERAL ECG SOP INSTANCE

Study Instance UID (0020,000D) = UID “E”
Series Instance UID (0020,000E) = UID “F”
Modality (0008,0060) = ECG
Synchronization Frame of Reference UID (0020,0200) = 1.2.840.10008.15.1.1
Synchronization Trigger (0018,106A) = NO TRIGGER
Acquisition Time Synchronized (0018,1800) = Y
Time Source (0018,1801) = Clock System ID
Time Distribution Protocol (0018,1802) = NTP
NTP Source Address (0018,1803) = aaa.bbb.ccc.ddd
SOP Instance UID (0008,0018) = UID “H”

Figure FFF.2.1-8Attributes of Multi-modality Waveform NTP Synchronization

FFF.2.1.2.2 One Modality Sends Trigger to the other Modality

FFF.2.1.2.2.1 User Scenario

Image runs are taken by the image acquisition modality. Waveforms are recorded by waveform recording modality. Both modalities are time synchronized via NTP. The acquisition in one modality is triggered by the other modality. The resulting objects will include the time synchronization and trigger synchronization concepts.

There are two cases depending on the triggering modality:

  1. At X-Ray start, the image modality sends a trigger signal to the waveform modality.

  2. The waveform modality sends trigger signals to the image modality to start the acquisition of each frame.

[pic]

Figure FFF.2.1- 9 Scenario of Multi-modality Waveform Synchronization

FFF.2.1.2.2.2 Encoding outline

Dedicated Waveform IODs exist to store captured waveforms. In this case, General ECG IOD is used to store the waveform data.

With the Synchronization Module information, the method to implement the triggers can be documented.

The Enhanced XA IOD provides per-frame encoding of the timing information related to each frame.

FFF.2.1.2.2.3 Encoding details

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

FFF.2.1.2.2.3.1 Enhanced XA Image

Table FFF.2. 1- 19 ENHANCED X-RAY ANGIOGRAPHIC IMAGE IOD MODULES

IE Module PS 3.3 Reference Usage
Frame of Reference Synchronization C.7.4.2 Specifies that the image acquisition triggers (or is triggered by) the ECG acquisition, and that they are time synchronized.
Image Enhanced XA/XRF Image C.8.19.2 Specifies the date and time of the image acquisition. .

Table FFF.2. 1-20 ENHANCED XA IMAGE FUNCTIONAL GROUP MACROS

Functional Group Macro PS 3.3 Reference Usage
Frame Content C.7.6.16.2.2 Provides timing information of each frame.

FFF.2.1.2.2.3.1.1 Synchronization Module Recommendations

The usage of this Module is recommended to document the triggering role of the image modality.

Table FFF.2.1-21 SYNCHRONIZATION MODULE Recommendations

Attribute Name Tag Comment
Synchronization Frame of Reference UID (0020,0200) The UTC Synchronization UID “1.2.840.10008.15.1.1” is used in this case.
Synchronization Trigger (0018,106A) The value “SOURCE” is used when the image modality sends a trigger signal to the waveform modality. The value “EXTERNAL” is used when the image modality receives a trigger signal from the waveform modality.
Trigger Source or Type (0018,1061) If Synchronization Trigger (0018,106A) equals SOURCE, then ID of image equipment. If Synchronization Trigger (0018,106A) equals EXTERNAL, then ID of waveform equipment if it is known.
Acquisition Time Synchronized (0018,1800) The value “Y” is used in this scenario.
Time Source (0018,1801) The same value as in the related General ECG SOP Instance is used in this scenario.
Time Distribution Protocol (0018,1802) The value “NTP” is used in this scenario.
NTP Source Address (0018,1803) The same value as in the related General ECG SOP Instance is used in this scenario.

FFF.2.1.2.2.3.1.2 Enhanced XA/XRF Image Module Recommendations

This module includes the acquisition date and time of the image.

Table FFF.2.1-22 ENHANCED XA/XRF IMAGE MODULE Recommendations

Attribute Tag Comment
Acquisition DateTime (0008,002A) Exact date and time taken from the synchronized clock.

FFF.2.1.2.2.3.1.3 Frame Content Macro Recommendations

In this scenario the timing information does not allow relating each frame to any externally recorded waveform.

Table FFF.2.1-23 FRAME CONTENT MACRO Recommendations

Attribute Name Tag Comment
Frame Content Sequence (0020,9111)
>Frame Reference Datetime (0018,9151) Exact date and time taken from the synchronized clock.
>Frame Acquisition Datetime (0018,9074) Exact date and time taken from the synchronized clock.

FFF.2.1.2.2.3.2 Waveform Object

The recording system will take care of filling in the waveform-specific contents, based on the IOD relevant for the type of system (e.g., EP, Hemodynamic, etc.). This section will address only the specifics for attributes related to synchronization.

Table FFF.2. 1-24 Waveform IOD Modules

IE Module PS 3.3 Reference Usage
Frame of Reference Synchronization C.7.4.2 Specifies that the ECG acquisition triggers (or is triggered by) the image acquisition, and that they are time synchronized.
Waveform Waveform Identification C.10.8 Specifies the date and time of the ECG acquisition.
Waveform C.10.9 Specifies the time relationship between the trigger signal and the ECG samples.

FFF.2.1.2.2.3.2.2 Synchronization Module Recommendations

The usage of this Module is recommended to document the triggering role of the waveform modality.

Table FFF.2.1-25 SYNCHRONIZATION MODULE Recommendations

Attribute Name Tag Comment
Synchronization Frame of Reference UID (0020,0200) The UTC Synchronization UID “1.2.840.10008.15.1.1” is used in this case.
Synchronization Trigger (0018,106A) The value “EXTERNAL” is used when the waveform modality receives a trigger signal from the image modality. The value “SOURCE” is used when the waveform modality sends a trigger signal to the image modality.
Trigger Source or Type (0018,1061) If Synchronization Trigger (0018,106A) equals SOURCE, then ID of Waveform equipment. If Synchronization Trigger (0018,106A) equals EXTERNAL, then ID of image equipment if it is known.
Synchronization Channel (0018,106C) Number or ID of Synchronization channel recorded in this waveform.
Acquisition Time Synchronized (0018,1800) The value “Y” is used in this scenario.
Time Source (0018,1801) The same value as in the related image SOP Instance is used in this scenario.
Time Distribution Protocol (0018,1802) The value “NTP” is used in this scenario.
NTP Source Address (0018,1803) The same value as in the related image SOP Instance is used in this scenario.

FFF.2.1.2.2.3.2.3 Waveform Identification Module Recommendations

This module includes the acquisition date and time of the waveform, which may be different than the acquisition date and time of the image in this scenario.

Table FFF.2.1-26 WAVEFORM IDENTIFICATION MODULE Recommendations

Attribute Name Tag Comment
Acquisition Datetime (0008,002A) Exact date and time taken from the internal clock of the Waveform modality. It may be different from the acquisition datetime of the Enhanced XA SOP instance.

FFF.2.1.2.2.3.2.4 Waveform Module Recommendations

The usage of this module is recommended to encode the time relationship between the trigger signal and the ECG samples.

Table FFF.2.1-27 WAVEFORM MODULE Recommendations

Attribute Name Tag Comment
Waveform Sequence (5400,0100) Only one item is used in this application case, as all the ECG signals have the same sampling rate.
>Multiplex Group Time Offset (0018,1068) If needed, specify the Group Offset from the Acquisition Datetime.
>Waveform Originality (003A,0004) The value “ORIGINAL” is used in this scenario.
>Trigger Time Offset (0018,1069) In case the waveform recording started with a synchronization trigger from the image modality, this value allows specifying the time relationship between the trigger and the ECG samples.
>Trigger Sample Position (0018,106E) In case the waveform recording started with a synchronization trigger from the image modality, this value allows specifying the waveform sample corresponding to the trigger sent from the image modality.

FFF.2.1.2.2.4 Examples

FFF.2.1.2.2.4.1 Image modality sends trigger to the waveform modality

In this example, there are two modalities that are synchronized with an external clock via NTP. The Image Modality acquires three multi-frame images within the same Study and same Series. Simultaneously, the Waveform Modality acquires the ECG non-stop during the same period, leading to one single Waveform SOP Instance on a different Study. The ECG sampling frequency is 300 Hz on 16 bits signed encoding, making up a number of 1500 samples per channel. The first ECG sample is acquired at nominal start time of the ECG acquisition.

The image modality sends a trigger to the waveform modality at the start time of each of the three images. This signal is stored in one channel of the waveform modality, together with the ECG signal.

In this example, there is no UID referencing capability between the two modalities.

[pic]

Figure FFF.2.1-10Example of Image Modality as Source of Trigger

The attributes that define the relevant content in the two different SOP Instances (Enhanced XA and General ECG) are described in the following figure:

ENHANCED XA SOP INSTANCES

Study Instance UID (0020,000D) = UID “A”
Series Instance UID (0020,000E) = UID “B”
Modality (0008,0060) = XA
Synchronization Frame of Reference UID (0020,0200) = 1.2.840.10008.15.1.1
Synchronization Trigger (0018,106A) = SOURCE
Trigger Source or Type (0018,1061) = Imaging System ID
Acquisition Time Synchronized (0018,1800) = Y
Time Source (0018,1801) = Clock System ID
Time Distribution Protocol (0018,1802) = NTP
NTP Source Address (0018,1803) = aaa.bbb.ccc.ddd
SOP Instance UID (0008,0018) = UID “D1”, “D2” and “D3” resp.

GENERAL ECG SOP INSTANCE

Study Instance UID (0020,000D) = UID “E”
Series Instance UID (0020,000E) = UID “F”
Modality (0008,0060) = ECG
Synchronization Frame of Reference UID (0020,0200) = 1.2.840.10008.15.1.1
Synchronization Trigger (0018,106A) = EXTERNAL
Trigger Source or Type (0018,1061) = Imaging System ID
Synchronization Channel (0018,106C) = 1\2
Acquisition Time Synchronized (0018,1800) = Y
Time Source (0018,1801) = Clock System ID
Time Distribution Protocol (0018,1802) = NTP
NTP Source Address (0018,1803) = aaa.bbb.ccc.ddd
SOP Instance UID (0008,0018) = UID “H”

Waveform Sequence (5400,0100)
Item 1 Only one ECG Multiplex Group
>Multiplex Group Time Offset (0018,1068) = 0
>Waveform Originality (003A,0004) = ORIGINAL
>Number of Waveform Channels (003A,0005) = 2
>Number of Waveform Samples (003A,0010) = 1500
>Sampling Frequency (003A,001A) = 300
>Channel Definition Sequence (003A,0200)
Item 1
>Waveform Sample Interpretation (5400,1006) = SS

Figure FFF.2.1-11Attributes when Image Modality is the Source of Trigger

FFF.2.1.2.2.4.2 Waveform modality sends trigger to the image modality

In this example, there are two modalities that are synchronized with an external clock via NTP.

The Image Modality starts the X-Ray image acquisition and simultaneously the Waveform Modality acquires the ECG and analyzes the signal to determine the phases of the cardiac cycles. At each cycle, the waveform modality sends a trigger to the image modality to start the acquisition of a frame. This trigger is stored in one channel of the waveform modality, together with the ECG signal.

The ECG sampling frequency is 300 Hz on 16 bits signed encoding, making up a number of 1500 samples per channel. The first ECG sample is acquired 10 ms after the nominal start time of the ECG acquisition.

In this example, there is no UID referencing capability between the two modalities.

[pic]

Figure FFF.2.1-12Example of Waveform Modality as Source of Trigger

The attributes that define the relevant content in the two different SOP Instances (Enhanced XA and General ECG) are described in the following figure:

ENHANCED XA SOP INSTANCES

Study Instance UID (0020,000D) = UID “A”
Series Instance UID (0020,000E) = UID “B”
Modality (0008,0060) = XA
Synchronization Frame of Reference UID (0020,0200) = 1.2.840.10008.15.1.1
Synchronization Trigger (0018,106A) = EXTERNAL
Trigger Source or Type (0018,1061) = ECG Equipment ID
Acquisition Time Synchronized (0018,1800) = Y
Time Source (0018,1801) = Clock System ID
Time Distribution Protocol (0018,1802) = NTP
NTP Source Address (0018,1803) = aaa.bbb.ccc.ddd
SOP Instance UID (0008,0018) = UID “D”

GENERAL ECG SOP INSTANCE

Study Instance UID (0020,000D) = UID “E”
Series Instance UID (0020,000E) = UID “F”
Modality (0008,0060) = ECG
Synchronization Frame of Reference UID (0020,0200) = 1.2.840.10008.15.1.1
Synchronization Trigger (0018,106A) = SOURCE
Trigger Source or Type (0018,1061) = ECG Equipment ID
Synchronization Channel (0018,106C) = 1\2
Acquisition Time Synchronized (0018,1800) = Y
Time Source (0018,1801) = Clock System ID
Time Distribution Protocol (0018,1802) = NTP
NTP Source Address (0018,1803) = aaa.bbb.ccc.ddd
SOP Instance UID (0008,0018) = UID “H”

Waveform Sequence (5400,0100)
Item 1 Only one ECG Multiplex Group
>Multiplex Group Time Offset (0018,1068) = 10
>Waveform Originality (003A,0004) = ORIGINAL
>Number of Waveform Channels (003A,0005) = 2
>Number of Waveform Samples (003A,0010) = 1500
>Sampling Frequency (003A,001A) = 300
>Channel Definition Sequence (003A,0200)
Item 1
>Waveform Sample Interpretation (5400,1006) = SS

Figure FFF.2.1-13Attributes when Waveform Modality is the Source of Trigger