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Objective: To evaluate image quality of low-voltage coronary artery computed tomographic (CT) angiography with low contrast agent in comparison with image quality., Methods: Forty-five patients underwent coronary artery computed tomographic (CT) angiography. They were randomly assigned to 3 groups, group A (n = 15) were scanned in 120 kVp with 350 mgI/ml iodinated contrast agent mode, group B (n = 15) were scanned in 100 kVp with 350 mgI/ml iodinated contrast agent mode, group C (n = 15) were scanned in 100 kVp with 270 mgI/ml iodinated contrast agent mode. Then measured CT attenuation value of three main branches (RCA, LAD and CX) of coronary artery, And compare the SNR, CNR, the effective radiation dose(ED) and iodine intake. The Kappa test were used to quantify inter- and intra-reader agreement in detecting quality of the images under different scanning solutions., Results: Three groups of coronary artery CT image quality was no statistically significant differences (all P values >0.05), Good inter- and intra-reader agreement ( k = 0.754, P < 0.05) for the detection of noise in all the patients. There was significant difference in the CT attenuation of RCA, LAD and CX among the 3 groups (P < 0.05), the CT attenuation was the highest in group B, the CT value of RCA, LAD and CX were 537 ± 90, 505 ± 90, 484 ± 75 HU, respectively.the CT attenuation was the lowest in group C, the CT value of RCA, LAD and CX were 357 ± 126, 360 ± 95, 378 ± 121 HU, respectively. There was no significant difference in the SNR and CNR among the 3 groups (P > 0.05). There was significant difference in the ED among the 3 groups (P < 0.05). The ED value of the group A was bigger than the value of the group B and C. There was no significant difference between the group B and C. Compared the group A and B, the iodine intake of the group C had fallen by 23%., Conclusions: The coronary artery CT angiography using 100 kVp with 270 mgI/ml iodinated contrast agent provide similar objective or subjective image quality compared with the (350 mgI/ml) and the 100 kVp (350 mgI/ml), thus enabling effective dose and iodine intake reduction without loss of diagnostic information.