ABSTRACT
Objective To investigate the influence of low-tube current in combination with simultaneous iterative reconstruction algorithm on bone mineral density (BMD) of T12 and image quality with a chest phantom.Methods An adult male chest phantom was selected.CT scan of the chest was performed at tube voltage of 120 kV and five different tube currents (20,30,40,50,60 mAs) in combination with filtered back projection (FBP),iDose4 (Level 4) and iterative model reconstruction (IMR,Level 2),respectively.BMD of T12 in chest phantom and objective evaluation results on different tube currents and simultaneous iterative reconstruction techniques were compared.The subjective scoring of mediastinum and lung window imaging qualities at tube current of 20 mAs with IMR and tube current of 60 mAs with FBP were compared.The consistency between two observers was evaluated.Results There was no significant difference between BMD values nor CT values on different tube currents and simultaneous iterative reconstruction techniques of chest phantom (all P＞ 0.05),but the differences between SD values were statistically significant (P＜ 0.001).SD values obtained with IMR were lower than those of iDose4 and FBP at same tube currents (all P＜0.001).At tube current of 60 mAs with FBP,the consistency of two observers in mediastinum window was the best (Kappa=1,P＜0.001),while in lung window was medium (Kappa=0.64,P=0.002).At tube current of 20 mAs with IMR,the consistency of two observers in mediastinum window was medium (Kappa=0.64,P=0.002),while in lung window was the best (Kappa=1.00,P＜0.001).Conclusion Low-tube current in combination with simultaneous iterative reconstruction algorithm can reduce radiation dose without affecting the accuracy of BMD.