低管电流联合迭代重建算法对胸部体模T12骨密度值准确性和胸部图像质量的影响

摘要

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.%目的 探讨低管电流联合迭代重建算法对仿真胸部体模T12骨密度(BMD)的准确性和胸部图像质量的影响.方法 选用成年男性胸部体模,管电压120 kV,管电流分别为20、30、40、50、60 mAs,联合滤波反投影算法(FBP)、混合迭代重建技术(iDose4,Level 4)及迭代模型重建(IMR,Level 2)行胸部扫描.比较采用不同管电流和重建技术时胸部体模T12的BMD及客观评价结果;比较管电流20 mAs、采用IMR算法与管电流60 mAs、采用FBP迭代算法的纵隔窗和肺窗图像质量的主观评分,并评价观察者间的一致性.结果 管电流、重建技术不同时,胸部体模T12的BMD和CT值差异均无统计学意义(P均＞0.05),而SD值差异有统计学意义(P均＜0.001).相同管电流下,采用IMR算法获得的SD值明显低于iDose4和FBP(P均＜0.001).管电流60 mAs、采用FBP算法时,2名观察者观察纵隔窗的一致性较好(Kappa=1,P＜0.001),观察肺窗的一致性中等(Kappa=0.64,P=0.002);管电流20 mAs、采用IMR时,2名观察者观察纵隔窗的一致性中等(Kappa=0.64,P=0.002),观察肺窗的一致性较好(Kappa=1,P＜0.001).结论 低管电流联合迭代重建算法可降低辐射剂量,同时满足骨密度测值的准确性及胸部图像诊断.