Abstract： Objective To assess the influence of tube current and tube voltage on the CT attenuation,radiation dose,and image quality.Methods A total of 113 saline solutions with decreasing dilution of contrast medium (370 mg I/ml) was produced.MDCT scan was performed with 15 series of different settings of tube current and tube voltage.CT attenuations with 15 series of different settings were all measured,and influence of tube current and tube voltage on CT attenuations was analyzed.CT dose index (CTDIvol) was recorded.The CT attenuations with different tube voltage and current were compared with one-way ANOVA and Kruskal-Wallis rank sum test.The correlation of CT attenuation with different tube voltage and the influence of tube voltage and current on radiation dose and image quality were tested by correlation analysis.Results Tube current (250,200,150,100,and 50 mA) had no significant effect on CT attenuation (F =0.001,0.008,0.075,P ＞ 0.05),while tube voltage (120,100,and 80 kV) had significant effect (H =17.906,17.906,13.527,20.124,23.563,P ＜ 0.05).The correlation between CT attenuation and tube voltage was determined with equation:CT attenuatio N100 kV =1.561 × CT attenuatio N120kv + 4.0818,CT attenuatio N80kV =1.2131 × CT attenuatio N120kv + 0.9283.The influence of tube voltage on radiation dose and image quality was also analyzed,and equations were also obtained:N120 kV =-5.9771Ln(D120 kV) + 25.412,N100 kV =--10.544Ln (D100 kV) + 36.262,N80 kV =-25.326Ln(D80kv) +62.816.According to the results of relationship among CT attenuation,radiation dose,and image quality,lower tube voltage with higher tube current can reduce the radiation dose.Conclusions Lower tube voltage can reduce the radiation dose.However,CT attenuation was influenced,and correction should be done with the equations.