Abstract: Objective To investigate the effect of different radiation doses on the accuracy of iodine quantification and CT value of virtual monochromatic image with a muti-spectral CT iodine phantom using second-generation dual-layer detector spectral CT (DLCT). Methods The second-generation DLCT scan abdominal phantom was used, which consisted of six different concentrations of iodine rods at 4, 8 and 12 g/L. The scan parameters were set at 100, 120 and 140 kVp tube voltages, and six radiation exposure sequences were scanned at each tube voltage: 5, 10, 15, 20, 25 and 30 mGy. Measure the iodine concentration value and the CT value at the single level of 50, 70 and 100 keV, and calculate the absolute error value of iodine concentration and CT value under different radiation exposure. SPSS 22.0 software single factor analysis of variance was used to compare the difference between the iodine concentration and the absolute error of CT value under different Radiation exposure, and LSD method was used to compare the two groups. Results The absolute error of CT value of 4 g/L iodine rod with 10~30 mGy scanning at 100 keV energy level was significantly higher than that of 12 g/L and 8 g/L(P＜0.05), and the absolute error of iodine concentration measurement of other iodine rods with different concentrations at different Radiation exposure had no statistical difference. Conclusions The second-generation double-layer detector spectral CT has high measurement stability for iodine concentration quantification and CT value accuracy under conditions of radiation dose greater than 5 mGy.

Key words: spectral CT, iodine quantification, radiation dose