目的 评价256层iCT 联合iDose4 迭代重建技术在胸部低剂量CT扫描中的应 用价值。方法 将150名健康体检者随机分 为常规剂量组(100mAs)、低剂量50mAs组 和低剂量25mAs组，分别采用100、50、 25mAs进行胸部CT扫描，100mAs采用FBP重 建作为常规对照组，两组低剂量扫描组均 采用FBP及iDose4对图像进行重建。比较 不同毫安秒和重建算法的辐射剂量、CT图 像噪声(MSD)、对比信噪比(CNR)、信噪比 (SNR)以及主观图像质量。结果 低剂量采 用iDose4组与常规对照组主观图像质量比 较差异无统计学意义。50mAs采用iDose4 重建图像的MSD、CNR及SNR与常规对照 组差异有统计学意义(P<0.05)；25mAs采 用iDose4与对照组比较差异无统计学意 义。50mAs组较常规对照组辐射剂量降低 约53.3％，25mAs相比对照组剂量降低 76.4％。结论 与常规剂量FBP重建相比， 50和25 mAs采用iDose4重建能有效降低辐 射剂量，同时不影响图像质量。

Objective To evaluate application value of 256-slice iCT associated with iDose4 iterative reconstruction technique in chest low dose CT. Methods 150 patients were randomly assigned into three groups: 100 mAs group as control group (n=50),50 mAs group (n=50), and 25 mAs group (n=50). Images from control group were reconstructed by FBP, and low dose groups were reconstructed by FBP and iDose4 . Quantitative noise, SNR, CNR, subjectively image quality, and radiation dose were compared and analyzed statistically. Results The subjectively image quality of low dose groups have no statistical significance compared with control group. MSD, CNR and SNR in 50 mAs with iDose4 were improved compared with control group(P<0.05). MSD, CNR and SNR in 25 mAs with iDose4 have no statistical significance compared with control group. Radiation dose were respectively reduced by 53.3％ and 76.4％ In 50mAs and 25 mAs. Conclusion Compared with FBP, 50mAs and 25 mAs groups with iDose4 could maintain or improve image quality on chest CT while reducing radiation dose effectively