双源CT单能量成像对肝癌检出影响的初步研究

目的 探索显示肝癌病灶对比噪声比(CNR)和图像质量的最佳keV条件,并与融合能量图像比较,探讨能谱CT单能量成像对肝癌检出的影响.方法 回顾性分析经双源CT双能量双期扫描的30例肝癌患者影像学表现.采用双源分析软件处理产生单能量(40～140 keV,间隔10 keV)图像,测定单能量图像、100 keV和140 keV图像中病灶的CNR和图像噪声.优化单能量图像中检测肝癌的最佳CNR值和图像噪声值.通过两相关样本的非参数秩和检验的方法对单能量图像和混合能量图像的结果进行比较.结果 动脉期图像中所有病灶的最佳CNR的单光子能量水平集中分布在70 keV,所占的比例为81.8％(27/33).图像噪声水平的最低点位于70 keV和80 keV.综合考虑图像质量和病变对比,笔者选择70 keV图像与融合图像进行比较.70 keV单能量图像的CNR与100 keV图像无显著性差异(1.68±1.04,1.88±1.59,P=0.149),>140 keV图像且有显著性差异(1.68±1.04,0.62±0.92,P=0.000).图像噪声<100 keV图像,差异有统计学意(6.52±1.53,8.55±1.11,P=0.000),与140 keV图像差异无统计学意义(6.52±1.53,7.60±2.73,P=0.050).结论 能谱CT 70 keV单能量图像可以在不降低图像质量的前提下有效提高肝癌病灶的CNR,这将有助于病灶的检出.

Preliminary study of dual-source CT monochromatic energy imaging on the detection of hepatocellular carcinomas

Objective To explore the best keV conditions of show hepatocellular carcinoma lesions with the best contrast-to-noise ratio (CNR)and image quality,and evaluate the effect of monochromatic energy imaging on the detection of hepatocellular carcinomas.Methods The dual-energy CT imaging of 30 patients with hepatocellular carcinoma were analyzed retrospectively.Monochromatic energy images (40 to 140 keV,interval 10 keV)were produced by the dual-engery software.CNR and image noise of monochromatic energy,100 keV and 140 keV images were measured respectively.The CNR and the imaging noise were optimized.The results between the monochromatic energy images and the mixed energy images were compared by using the two related samples of non-parameter rank test.Results In the arterial phase, the monochromatic energy level with the highest CNR was concentrated at 70 keV,and the lowest level of the image noises was at 70 and 80 keV.The images at 70 keV were chosen to be compared with the fusion images.The CNR values of the monochromatic images at 70 keV were similar as those at 100 keV (1 .68 ± 1 .04 vs 1 .88 ± 1 .59 ,P =0 .149 ),and significantly higher than those at 140 keV (1 .68 ± 1 .04 vs 0.62±0.92,P =0.000).The image noises at 70 keV were similar as those at 140 keV (6.52±1.53 vs 7.60±2.73,P =0.050), and significantly lower than those at 100 keV (6.52±1.53 vs 8.55±1.11,P =0.000).Conclusion The monochromatic energy imaging at 70 keV can improve the CNR of the hepatocellular carcinoma lesions without reducing the image quality,which will help the lesion detection.