Objective:To prospectively research the correlation between the radiation dose and image quality in order to explore the optimization of exposure dose for digital radiography(DR).Methods:Simulated reticular

linear

and nodular structures were located in an anthropomorphic chest phantom.The phantom and resolution wedge were exposed by DR system with the same kilovoltage values(125 kVp)and different mAs sets.Four radiologists assessed all of the images.In addition

the entrance surface dose(ESD)

root mean squar(RMS)and resolution were measured.Results:ESD was increasing along with mAs’s enhancement

but RMS was decreasing when mAs was increasing.As long as the ESD increased to a certain degree

spatial resolution would go up to the limit.Images obtained with lower dose(EI<1 800)were obscure at the tiny nodular structure.Images of 2 000 EI value could show clearly the Simulated lesion.Conclusion:The optimization of exposure dose for DR imaging may effectively decrease radiation injuries under the precondition of DR image quality to be guaranteed.