Abstract: Objectlve: To assess the image quality and radiation dose of 80 kV electrocardiography(ECG)-gated CCTA in subjects with a normal body mass index(BMI),compared to 120 kV ECG-gated CCTA.Method: The CCTA images of 140 subjects with BMIs ＜ 25 kg/m² were analyzed.Seventy subjects underwent 120 kV CCTA,and the other 70 subjects underwent 80kV CCTA.Two blinded observers independently evaluated the subjective image quality of the coronary arteries.The objective image quality(signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR)) and radiation dose were also measured in each group.Results: Although the objective image quality of the 80 kV protocol images was significantly poorer than that of 120 kV protocol images(P ＜ 0.05),there was no significant difference in the subjective image quality between the two groups(P ＞ 0.05).The radiation dose was reduced by 12mSv with the 80 kV protocol and by 82% with the 80 kV and ECG-based tube current modulation than one with the 120 kV protocol(P ＜ 0.05).Conclusion: The low tube voltage CCTA protocol using 80 kV allows significant reduction of the radiation dose without impairing the subjective image quality in subjects with normal BMIs.