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目的比较256排螺旋CT低剂量迭代算法与滤波反投影算法(filtered back projection,FBP)图像差异,找出迭代算法诊断肺结节的最优水平。方法 75例肺结节患者分别行FBP和低剂量迭代算法扫描与薄层重建,比较FBP与低剂量迭代算法薄层重建图像的肺组织信噪比、对比噪声比及小结构可见性、诊断确信程度、空间分辨率、密度分辨率评分。结果 FBP重建图像肺结节信噪比、肺组织信噪比、对比噪声比分别为1.13±1.02、10.59±3.28、11.25±7.40,小结构可见性、诊断确信程度、空间分辨率、密度分辨率评分分别为3.46±0.50、3.48±0.68、3.88±0.33、3.60±0.49;迭代算法重建图像iDose4~7肺结节信噪比、肺组织信噪比、对比噪声比,iDose1~4小结构可见性,iDose1~7诊断确信程度、空间分辨率及密度分辨率评分与FBP重建图像比较差异均无统计学意义(P>0.05)。结论 256排CT螺旋低剂量迭代算法重建中iDose 4在肺结节筛查中为最优水平,图像质量最接近FBP图像,且辐射剂量明显降低。
Objective To compare the differences between low-dose iterative 256-slice CT and filtered back projection (FBP) images and to find out the optimal level of diagnosis of pulmonary nodules by iterative algorithm. Methods Seventy-five patients with pulmonary nodules underwent scanning and thin-layer reconstruction with FBP and low-dose iterative algorithms respectively. The lung tissue signal-to-noise ratio, contrast-to-noise ratio and small structure visibility were compared between FBP and low-dose iterative algorithms. Degree, Spatial Resolution, Density Resolution. Results The signal to noise ratio of pulmonary nodules, lung tissue signal to noise ratio and contrast-to-noise ratio were 1.13 ± 1.02, 10.59 ± 3.28 and 11.25 ± 7.40 in FBP reconstruction images respectively. Small structure visibility, diagnostic confidence, spatial resolution and density resolution The scores were 3.46 ± 0.50,3.48 ± 0.68,3.88 ± 0.33,3.60 ± 0.49 respectively. The iterative algorithm was used to reconstruct the image of iDose4 ~ 7 pulmonary nodules, the signal to noise ratio of lung tissue, the contrast ratio of noise, the iDose1 ~ 4 small structure visibility There was no significant difference between iDose 1 ~ 7 diagnostic confidence, spatial resolution and density resolution scores and FBP reconstructed images (P> 0.05). Conclusions iDose 4 is the optimal level for lung nodule screening in 256-slice CT spiral low-dose iterative reconstruction. The image quality is the closest to that of FBP images and the radiation dose is significantly reduced.