Table 1.

Summary of scanning parameters for different types of CT scanners

Single source
64- and 80-detector row scanners (including “128- and 160-slice” systems)
HR < 65	Prospective gating with end-diastolic acquisition
HR > 65	Prospective gating with end-systolic acquisition
Exception	Where phase selection is not adjustable (e.g. on a scanner with prospective helical acquisition with diastolic phase acquisition only for slow HRs) There may be a role for retrospective gating (e.g. when the HR is >100 beats per minute) When retrospective acquisition is used, dose modulation outside the 30–80% cardiac cycle should be applied For scanners that have a retrospective mode with adaptive dose modulation, this may be used as an alternative for fast HRs
128-, 256- or 320-detector row scanners (including “256- and 640-slice” systems)
128–256 detector rows
HR < 75	Prospective gating with end-diastolic acquisition
HR > 75	Prospective gating with end-systolic acquisition
320 detector rows
HR independent	Non-gated helical acquisition with the middle 8-cm coverage (160 × 0.5 mm) can be used to image the thoracic aorta in 1–2 heartbeats with motion-free imaging of the aorta
Exception	If dedicated coronary assessment is required (e.g. in the context of known AAS or a high pre-test probability), then use following
HR < 65	Prospectively triggered ECG synchronization with 70–80% single pulse per volume
HR > 65	Prospectively triggered ECG synchronization with 30–80% single pulse per volume
Dual source
HR-dependent	HR-dependent prospectively ECG-synchronization protocols can be applied similar to the systems above
HR < 65	Prospective gating with end-diastolic acquisition
HR > 65	Prospective gating with end-systolic acquisition
	In a system that allows for high-pitch acquisition in conjunction with wide detector arrays, traditional ECG synchronization may not be required e.g. a pitch of >3 and gantry rotation time 0.28 s permit coverage of 9.6–11.6 cm s−1

AAS, acute aortic syndrome; ECG, electrocardiogram; HR, heart rate.