Dual-source computed tomography angiography image quality in patients with fast heart rates

Background

Dual-source computed tomography (DSCT) provides diagnostic quality images of the coronary arteries over a wide range of heart rates (HRs). Current dose reduction techniques, including electrocardiographic (ECG) dose modulation and prospective triggering, are optimized for use in patients with relatively slow (<70 beats/min) HRs by limiting radiation dose to the ideal phases of image acquisition.

Objective

We evaluated coronary vessel image quality (IQ) at different reconstruction phases in patients with fast HRs (>80 beats/min) to assess potential feasibility of prospective triggering techniques on DSCT.

Methods

Patients (n=101) underwent 64-slice DSCT with retrospective ECG-gating without β-blocker premedication. Image reconstructions were performed at 10% R-R wave phase intervals (0%–90%). Patients were grouped by mean HR: group A, <60 beats/min (n=22); group B, 60–80 beats/min (n=57); group C, >80 beats/min (n=22). Coronary artery IQ was assessed by 2 readers in consensus on a 5-point scale.

Results

Optimal IQ occurred at 70% phase for all arteries in groups A and B. In group C, optimal IQ occurred at 30% and 40% phases. The 70% phase achieved diagnostic IQ in 97% of group A and 86% of group B. A widened reconstruction window (30%–50%) was necessary for diagnostic IQ in a similar high proportion (84%) of group C.

Conclusion

Optimal IQ occurs during late-systolic phases for patients with fast HRs (>80 beats/min). Late-systolic phase prospective triggering is potentially feasible in these patients; however, given the widened reconstruction windows required, a higher radiation dose may be required compared with patients with slower HRs (<80 beats/min).

Keywords: Cardiac computed tomography, Coronary artery disease, Dual-source computed tomography, Prospective triggering, Retrospective gating