Low-dose adaptive sequential scan for dual-source CT coronary angiography in patients with high heart rate: comparison with retrospective ECG gating.

PURPOSE: To explore feasibility of dual-source CT (DS-CT) prospective ECG-gated coronary angiography in patients with heart rate (HR) higher than 70beat per minute (bpm), and evaluate image quality and radiation dose with comparison to retrospective ECG-gated spiral scan.

MATERIALS AND METHODS: One hundred patients who underwent DS-CT coronary angiography (DS-CTCA) with mean HR higher than 70bpm but below 110bpm were enrolled in the study, 50 were scanned by adaptive sequential scan and another 50 were analyzed by retrospectively gated CT scan. The imaging quality of coronary artery segments in the two groups was evaluated using a four-point grading scale by two independent reviewers. Patient radiation dose was calculated by multiplying dose length product by conversion coefficient of 0.017.

RESULTS: There was no significant difference between the two groups for mean HR (p=0.305), HR variability (p=0.103), body mass index (p=0.472), and scan length (p=0.208). There was good agreement for image quality scoring between the two reviewers (Kappa=0.72). Coronary evaluability of adaptive sequential scan was 99.7% (608 of 610 segments), while that of retrospective gated scan was 98.7% (614 of 622 segments), showing similar coronary evaluability (p=0.061). Effective doses of adaptive sequential scan and retrospective gated scan were 5.1±1.6 and 11.8±4.5mSv, respectively (p<0.001), showing that adaptive sequential scan reduced radiation dose by 57% compared with that of retrospective gated scan.

CONCLUSIONS: In patients with 70-110bpm HR, DS-CTCA adaptive sequential scan shows similar image quality as retrospective ECG-gated spiral scan with 57% reduction of radiation dose.