Image quality and dose performance of 80 kV low dose scan protocol in high-pitch spiral coronary CT angiography: feasibility study

To investigate the image quality and dose performance of 80 kV high-pitch spiral (HPS) coronary CT angiography (CCTA). 106 patients consecutively enrolled into prospectively ECG-triggering HPS CCTA (pitch = 3.4) exam using kV/ref. mAs = 80/400, 100/370, and 120/370 when patient BMI was ≤22.5 (n = 40), between 22.5 and 27.5 (n = 53) and >27.5 kg/m² (n = 13). Image quality was assessed per-segment by two observers independently using a 4-point scale (1—excellent, 4—non-diagnosable). Image noise and signal-to-noise ratio (SNR), contrast-to-noise ratio were measured. Diagnostic image quality was obtained in 503 of 507, 687 of 693, 164 of 167 coronary segments in 80, 100, 120 kV groups without significant difference ( P = 0.482). The proportions of segments with score 1–4 were not significantly different among three kV groups (all P > 0.05). Image noise were significantly higher in 80 kV group than 100 and 120 groups ( P < 0.001), while SNR was not ( P = 0.097). The effective dose of 80 kV group (0.36 ± 0.03 mSv) was significantly lower than that of 100 kV group (0.86 ± 0.08 mSv) and 120 kV group (1.77 ± 0.18 mSv). The mean ± SD of HR in all patients was 54.8 ± 5.1 bpm. 80 kV HPS CCTA is feasible for patient with BMI ≤ 22.5 kg/m² which can save 58% dose than 100 kV group, while maintain diagnosable image quality.