Embedded Files
what is ecg gating?
what is ecg gating?
Cardiac gating or ECG gated angiography in CT is an acquisition technique that triggers a scan during a specific portion of the cardiac cycle.
why do we gate our scans?
why do we gate our scans?
To try and obtain images with minimal pulsatile artifact from the heart movement to allow for the visualisation of small vessels and valves. Where possible we try to gate all of our CTA Chest scans at RCH to maximise the amount of information within our angiograms.
non-gated scan
non-gated scan
gated scan
gated scan
when will the scans trigger?
when will the scans trigger?
We want the scans to be performed when the heart is the stillest for the longest period of time.
The heart is most still in End Diastole and End Systole but when is the longest period?
end diastole
end diastole
Prior to the P wave
end systole
end systole
Immediately after the T wave
The longest period of stillness is dictated by the heart rate of the patient.
An increase in heart rate will decrease the amount of time between R peaks (seen in image below, left).
At low heart rates (<65bpm) the longest window is the end diastole window. As heart rate increases this window length will decrease.
End systole window is relatively unaffected by heart rate and stays consistent at 100ms.
Therefore in heart rates <65bmp the scans will trigger in End Diastole.
In heart rates >65bpm the scans will trigger in End Systole.
This setting of the trigger point is prebuilt into our Under_65bpm_CTA_Gated_Chest and Over_65bpm_CTA_Gated_Chest and is the only difference between the two scan protocols.
tips for obtaining a good trace
tips for obtaining a good trace
Link to Teams: Tips for Gating - FR Draft.docx
rch gated chest protocol
rch gated chest protocol
Link to Gated Chest Protocol in Teams: Force CT-CP-713 Gated CTA Chest FD Edited.docx
Link to Test Bolus Instructions in Teams: Force CT-CP-712 CTA Test Bolus Instructions. 2024.docx
Important points:
The CTA Gated Protocol has two different recon boxes within the one flash scan.
Recon job 1 & 2 (Green) is to sit around the heart. This is where you are saying you want the scan to gate (obtain scan at this point when the heart is the most still).
Recon job 3 & 4 determines the extra scan coverage of the chest. This box does not dictate the gated portion.
The scan is a turbo flash scan so has a 38cm run up and very quick scan time. This scan is not suitable for patients on ECMO.
Test bolus works best with this scan technique. It is possible to do bolus tracking however there is a minimum trigger to scan start time of 5 seconds due to the table needing to move into its run up position and for the scan to predict the heart rhythm for gating.
Page updated
Google Sites
Report abuse