目的 评估正弦图确定迭代重建（sinogram-affirmed iterative reconstruction,SAFIRE）和滤波反投影重建（filtered back projection,FBP）对于低剂量胸部CT筛查图像质量的影响。方法 收集304名行低剂量胸部CT筛查的体检者,均用双源CT以管电压120 kV、有效管电流40 mA·s进行扫描,图像使用不同技术进行重建,包括1个FBP和5个不同重建强度的SAFIRE序列（S1至S5）。由2名影像科医师分别记录噪声值和主观评价图像噪声、伪影。结果 患者的平均体重为（66.3±12.8） kg,体质量指数为23.4±3.2,平均剂量-长度乘积为（95.2±30.6） mGy·cm,平均有效辐射剂量为（1.6±0.5） mSv。2位医师评价的图像噪声等级、伪影等级、图像总体质量间的一致性较好（r分别为0.785、0.595 和0.512）。在6个序列中,无论主观还是客观图像噪声,都是FBP最高,而图像噪声随着SAFIRE的重建强度的上升而下降,其中S3得到的图像质量最好。结论 与FBP相比,SAFIRE可显著提高低剂量胸部CT筛查的图像质量,其中S3适用于低剂量胸部CT筛查。
Objective: To compare the performance difference on image quality between sinogram-affirmed iterative reconstruction (SAFIRE) and filtered back projection （FBP）in low-dose lung CT screening. Methods: A total of 304 patients receiving annual low-dose lung CT screening were examined by a dual-source CT system at 120 kV with reference tube current of 40 mA·s. Six image serials were reconstructed, including one dataset of FBP and five datasets of SAFIRE with different reconstruction strengths from 1 to 5 (S1 to S5). Image noise and subjective scores of image noise were recorded. Images artifacts and overall image quality were also assessed by two radiologists. Results: The mean weight and the body mass index of patients were （66.3±12.8） kg and 23.4±3.2, respectively. The mean dose-length product was (95.2±30.6） mGy·cm, and the effective dose was （1.6±0.5） mSv. The observation agreement for image noise grade, artifact grade and the overall image quality was in good consistency (r=0.785, 0.595 and 0.512). Among the overall six datasets, both the scores of measured mean objective image noise and the subjective image noise of FBP were the highest, and the image noise decreased with the increasing of SAFIRE reconstruction strength. The datasets of S3 obtained were the highest quality scores for image. Conclusions: Compared with FBP, SAFIRE reconstruction may significantly improve image quality in low-dose lung CT screening and SAFIRE with reconstruction strength 3 is a pertinent choice for low-dose lung CT.
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