Abstract: Objective:To compare the radiation dose between two different collimations on chest low-dose screen and normal using a 16-slice spiral CT,in order to provide guideline for lung low-dose screen.Methods:100 physical examination objectors use 1.5 mm × 16(24 mm) collimation in lung low-dose screen of anomalous.Then use 0.75 mm × 16(12 mm) collimation to screen.They use KVP,Effective mAs,time of ration and image of thick were the same.120 kV,20 mAs,0.5 s/rotation,5 mm.To different overlap 50% reconstruct 2 mm and 1mm thick images for 3D-process.To compare image quality.Results:Four screen technique to display the focus and normal organization of the Lung were not difference.Image quality were excellent,use the wide collimation screen time and X-ray radiation protection too decrease.Conclusion:Radiation dose of 1.5 mm collimation.In lung low-dose screen is less of 0.75 mm collimation,and scan time is low.The radiation dose(CTDIvol) only for the narrow(0.75mm) detector and the conventional dose scanning for 20%,but can provide similar diagnostic information.So a collimation of 1.5mm is recommended in lung low-dose screen using a 16-slice spiral CT.