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 80kV 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 >27.5kg/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, 120kV 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 80kV group than 100 and 120 groups (P<0.001), while SNR was not (P=0.097). The effective dose of 80kV group (0.36±0.03mSv) was significantly lower than that of 100kV group (0.86±0.08mSv) and 120kV group (1.77±0.18mSv). The mean±SD of HR in all patients was 54.8±5.1bpm. 80kV HPS CCTA is feasible for patient with BMI≤22.5kg/m² which can save 58% dose than 100kV group, while maintain diagnosable image quality.