Abstract: ［Abstract］Objective〖HTSS〗To investigate the effects of  low-tube-voltage computed tomography(CT) venography of lower extremity on image quality and the radiation dose.
〖HTH〗〖WTHZ〗Methods〖HTSS〗Sixty patients suspected with venous diseases of lower extremity were randomly divided into low tube voltage group and control group, 30 cases in each group, All patients underwent lower extremity CT venography on a 64-detector CT scanner. Parameters for CT venography were as follows: 80 kV and 350 mAs in low tube voltage group, and 120 kV and 190 mAs in control group. Contrast-to-noise ratio(CNR) and single-to-noise ratio(SNR) of imaging, dose length product(DLP) and effective dose were statistical analyzed with the 2-tailed independent t test or the Mann-Whitney U test. The image quality were evaluated by two senior doctors using 5 mark system.
〖HTH〗〖WTHZ〗Results〖HTSS〗DLP,effective dose and dose of contrast material were significantly lower under low tube voltage group than control group(P＜0.05). The CNR and SNR of low tube voltage group and control group were no statistical difference between two groups(P＞0.05). The subjective scores of image quality between two groups were not statistically significant(P＞0.05).
〖HTH〗〖WTHZ〗Conclusion〖HTSS〗CT venography with a low-tubevoltage technique allows reducing the radiation dose and the amount of  contrast material without image quality degradation. 

Key words: tomography, spiral computed, low tube voltage, radiation dosage