CT血管成像：噪声和血管增强程度对后处理图像质量的影响

目的探讨噪声和血管增强程度对CT血管成像（computed tomography angiography,CTA）后处理图像质量的影响。方法将临床需行下肢动脉CTA的61例患者随机分为3组,采用不同管电压和管电流扫描,对图像行容积再现（volume rendering,VR）和最大强度投影（maximum intensity projection,MIP）后处理并评价图像质量;测量血管增强CT值和对比度、图像噪声（N）、背景信号、信噪比（signal-to-noise ratio,SNR）和对比噪声比（contrast-to-noise ratio,CNR）,分析VR、MIP图像质量与CNR、SNR、N的相关性。结果 VR、MIP图像质量与CNR相关性最高,其次为SNR（P〈0.001）;3组病例之间血管增强CT值、背景信号和N的差异有统计学意义（P〈0.05）,而CNR与SNR的差异无统计学意义（P〉0.05）;3组病例间VR与MIP的图像质量无统计学差别（P〉0.05）。结论血管增强CT值和对比度是影响CTA后处理图像质量的关键因素。

Effect of noise and vascular contrast enhancement on post-processed images of computed tomography angiography

Objective To investigate the effect of noise and vascular contrast enhancement on quality of post-processed images of computed tomography angiography（CTA）.Methods 61 patients referred for lower extremity CTA were randomly divided into 3 groups with different tube current and kilovoltage during scanning.Quality of the volume rendering（VR） and maximum intensity projection（MIP） images,intravascular enhanced CT values and contrast,noise,background densities,signal-to-noise ratio（SNR） and contrast-to-noise ratio（CNR） were evaluated.The correlation between CNR,SNR,noise and image quality of VR and MIP was determined.Results CNR was most significantly（P〈0.001） correlated with image quality of VR and MIP,followed by SNR.There were significant differences（P〈0.05） in the intravascular enhanced CT values,background densities and noise among the 3 groups whereas differences in CNR and SNR as well as image quality of VR and MIP among the 3 groups were not significant（P〉0.05）.Conclusion Intravascular enhanced CT value and contrast are key factors in the quality of post-processed CTA images.