Operating instructions

HeartView CT
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ECG Pulsing
ECG pulsing is a dedicated technique used for online
dose modulation in ECG-gated spiral scanning. During
the spiral scan, the output of the X-ray tube is modu-
lated according to the patient’s ECG. It is kept at its
nominal value during a user-defined phase of the car-
diac cycle, in general the mid to end diastolic phase.
During the resting phase of the cardiac cycle, the tube
output is reduced to 20% of its nominal value. The
length of the plateau with full dose is 500 ms, which is
sufficient to retrospectively shift the image reconstruc-
tion interval for individual patient fine-tuning of the
image reconstruction phase. When properly placed in
the cardiac cycle this plateau length allows for a suffi-
cient phase shift of the reconstruction box to cover
both end-systolic and diastolic reconstructions. The
tube current is reduced and not switched off to allow
for image reconstruction throughout the entire cardiac
cycle. Even though their signal-to-noise ratio is
decreased, the low-dose images are sufficient for func-
tional evaluation. Clinical studies have demonstrated
dose reduction of up to 50% depending on the
patient’s heart rate using ECG pulsing. ECG pulsing
can be switched on/off by you on the Trigger tabcard.
When using ECG pulsing, the desired reconstruction
phase has to be estimated and entered into the Trigger
tabcard prior to scanning, since it determines the time
interval of maximum dose. ECG pulsing should not be
used for patients with irregular heart rates and
arrhythmia.