目的 探讨冠状动脉CT能谱成像(GSI)最佳单能量成像，以获得最好信噪比，得到最佳质量图像，为今后检查做出 指导。方法 应用宝石能谱CT(Discovery CT750 HD)，选取17例心率≤65次/min，波动≤3次/min，临床疑似冠 心病患者进行冠状动脉CT能谱扫描(GSI)，重建其140kVp混合能量图像及6组单能量图像(90、80、70、60、50和 40Kev)，测量、计算混合能量图像与各组单能量图像的背景噪声(SD)、图像信噪比(SNR)及对比噪声比(CNR)，筛 选出最佳单能量图像与混合能量图像的图像质量进行主客观评价。结果 70Kev单能量图像的SNR(39.39±5.56)及 CNR(30.47±4.77)均高于其他单能量图像与混合能量图像，与混合能量图像相比，差异有统计学意义(P＜0.05)； 90Kev、80Kev及70Kev单能量图像的背景噪声较140kvp混合能量图像分别减少32%、37%及30%；两组图像的主观评 分：70Kev单能量图像的质量评分为4.72±0.56，评5分血管段为177段，占85%(177/208)，混合能量图像评分为 4.57±0.58，评5分血管段为146，占71%(146/206)t值为25.01, P＜0.01。结论 70Kev单能量图像是冠状动脉CT能 谱成像的最佳单能量图像，图像质量明显优于140kvp混合能量图像。

Objective To investigate the optimal energy level for monochromatic reconstruction of coronary CT angiography with the use of cardiac spectral imaging. Methods 17 patients (HR<65/min,variation<3/min) underwent cardiac spectral imaging using GSI mode on a 64-slice CT scanner(Discovery CT 750 HD,GE healthcare). In 6 sets of monochromatic images(40,50,60,70,80 and 90kev), region of interest was put in the aortic root,signal-to-noise,contrast-to-noise and image quality(graded on a 5-point scale) were assessed in all monochromatic images and compared with the conventional polychromatic images. Results Compared with conventional polychromatic images and other monochromatic images, reconstruction with 70kev showed the highest SNR(39.39±5.56) and CNR (30.47±4.77). there was statistical difference on images noise (11.57±1.34vs16.63±1.97),subjective image score(4.72±0.56vs4.57±0.58),and percentage of segment of 5 point(85% vs 71%) between 70kev and polychromatic images(P<0.05). Conclustions Cardiac Spectral Imaging with reconstruction of 70kev offers best image quality of coronary CTangiography compared with other monochromatic images and polychromatic images.