自适应统计迭代重建算法对肝脏低剂量CT能谱成像质量的影响

目的 探讨自适应统计迭代重建算法(ASIR)在肝脏低剂量CT能谱成像(GSI)中降低辐射剂量、优化图像质量的价值。方法 将60例行肝脏CT能谱成像患者按就诊顺序分为2组,每组30例:A组为低剂量GSI扫描组,采用ASIR重建,按不同ASIR权重值分别重建A1组(ASIR 0%)图像和A2组(ASIR 50%)图像;B组为常规剂量GSI扫描组,采用滤波反投影法(FBP)重建图像。由2名放射科医师对3组GSI图像质量进行评价,并比较A、B两组辐射剂量的差异。结果 A组和B组的有效剂量(E)分别为(3.2±0.2)和(5.8±0.2)mSv(Z=-6.874,P<0.05)。A1组、A2组和B组GSI图像的噪声、信噪比(SNR)和对比噪声比(CNR)差异均有统计学意义(F=24.013、15.646和8.285,P<0.05)。与A1组图像相比,A2组和B组图像的噪声均较低,但SNR值和CNR值均较高(P<0.05);而A2组和B组图像的噪声、SNR和CNR差异均无统计学意义(P>0.05)。3组图像的主观评价结果差异有统计学意义(F=102.38、105.768,P<0.05),主观评分结果一致性较好(Kappa=0.819,P<0.05)。结论 应用低管电流CT能谱成像技术联合ASIR算法可以显著降低肝脏增强门静脉期GSI扫描的辐射剂量,并可得到较好的图像质量。

Effect of adaptive statistical iterative reconstruction algorithm on the imaging quality in low-dose spectral CT scanning of the liver

Objective To investigate the value of the adaptive statistical iterative reconstruction (ASIR) algorithm for reducing the radiation dose and optimizing the image quality in the low-dose spectral CT scanning in GSI (Gemstone spectral imaging) of the liver. Methods A total of 60 patients who underwent hepatic spectral CT scanning in GSI were enrolled in this study. The patients were randomly divided into two groups according to priority with 30 cases per group. Low-dose spectral CT scanning was used for group A, and images were reconstructed by ASIR 0 and 50%, marked as A1 and A2. Group B was scanned with conventional dose of spectral CT, and images were reconstructed by Filtered back projection (FBP). Effective doses (E) for each group were calculated. Image quality was assessed by two radiologists, and the radiation doses were compared between groups A and B. Results All image quality of each group were good enough for clinical diagnosis. E for group A and B were (3.2±0.2) and (5.8±0.2) mSv, respectively. There was statistical difference with image noise between group A and B(Z=-6.784,P<0.05). The image noise, SNR and CNR had statistical differences between group A and B (F=24.013, 15.646, 8.285, P<0.05). Compared with group A1, the image noise was lower, and the SNR and CNR were higher in groups A2 and B(P<0.05). There were no statistical differences of image noise, SNR and CNR between groups A2 and B (P>0.05). There were no statistical differences of the image quality score between groups A1, A2 and B (F=102.38,105.768,P0.05). Conclusions ASIR combined with low-dose spectral CT scanning was helpful to reduce radiation dose and could obtain better image quality in hepatic CT examination.