个体化最佳单能量图像在能谱双低冠状动脉成像中的应用

Application of Individualized Optimal Monochromatic Energy Images in Low Radiation Dose and Contrast Dose Spectral Coronary CT Angiography

目的探讨能谱CT个体化最佳单能量冠状动脉成像在降低辐射剂量、减少碘负荷中的应用价值。资料与方法选择临床疑似冠心病患者60例,随机分为两组,每组30例,A组采用常规扫描,B组采用能谱低剂量模式,两组对比剂分别为350 mg I/ml和300 mg I/ml。扫描后A组重建常规序列,B组采用Optimal CNR软件获取最佳单能量值后重建单能量断层图像,分别导入工作站进行后处理。采用双盲法对图像质量进行主观评分,并测量冠状动脉各节段CT值及主动脉窦部的噪声(SD)、信噪比(SNR)和对比噪声比(CNR)。比较两组辐射剂量、碘摄入量,统计B组最佳单能量范围。结果两组冠状动脉图像质量主观评分、冠状动脉各节段CT值、SD、SNR、CNR差异无统计学意义(P>0.05);B组的有效辐射剂量和碘摄入量均较A组低,差异有统计学意义(P<0.05)。B组最佳能量点为60~75 ke V,平均(66.50±3.91)ke V。结论能谱CT低剂量、低碘负荷冠状动脉血管成像中,选择个体化最佳能量点,结合迭代重建可有效降低辐射剂量和碘负荷,并可获得优于常规扫描的图像。

Purpose To explore the value of spectral coronary CT angiography（CCTA） in reducing radiation dose and contrast dose using individualized optimal monochromatic imaging. Materials and Methods Sixty patients with suspected coronary disease were recruited in the study, who were randomly divided into two groups： group A（n=30） using conventional CT protocol with 350 mg I/ml contrast agent; group B（n=30） using low dose spectral CT imaging mode with 300 mg I/ml contrast agent. The images of group A were reconstructed with conventional process, and the images of group B were reconstructed with Optimal CNR to obtain the optimal monochromatic energy images. The images of both groups were transferred to an Advanced Workstation for analysis. Double-blinded method was carried out to qualify the images. CT values of coronary artery segments, as well as standard deviations（SD）, the signal-to-noise ratio（SNR）, contrast-to-noise ratio（CNR） of aortic sinus were measured. Radiation doses and iodine intake were compared between the two groups. The optimal ke V distribution in group B was analyzed. Results There was no significant difference for the subjective scoring of image quality, CT value of each coronary artery segment, SD, SNR, and CNR values between the two groups（P〉0.05）. The effective radiation dose and total iodine load in group B were less than that in group A（P〈0.05）. The optimal energy distribution for group B was 60-75 ke V, average at（66.50±3.91） ke V. Conclusion Compared with the conventional CT protocol, spectral CT imaging at optimal energy levels combined with iterative reconstruction can effectively reduce the radiation dose and iodine load, and obtain better images than usual protocol.