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

Abstract

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.