双能量CT肺动脉成像不同混和能量图像质量对比分析

目的 评估双能量CT肺动脉成像(CTPA)上不同能量图像的图像质量,以确定双能量CTPA的最佳能量混合方式.方法 装满不同浓度碘水的模型及27例怀疑肺动脉栓塞的患者行胸部双能量CT扫描,将140kV和80kV图像传送至后处理工作站,按照不同的能量比例混合生成9种权重因子的混合能量图像.比较140kV图像、9种不同权重因子混合能量图像和80kV图像上模型内碘水的CT值、噪声和信噪比(SNR),同时比较27例患者140kV图像、9种混合能量图像和80kV图像上肺动脉的CT值、噪声、SNR和对比噪声比(CNR),并对所有患者的权重因子为0.3的混合能量图像、80kV图像和最佳混合能量图像的肺动脉图像质量进行评分.结果 在实验研究及临床应用中,权重因子为0.3的混合能量图像噪声均最小,而权重因子为0.5的混合能量图像肺动脉的SNR值最大,其次为权重因子为0.6的混合能量图像,临床应用中权重因子为0.5和0.6的混合能量图像上肺动脉的CNR值最大.权重因子为0.3、0.5、0.6的混合能量图像和80kV图像的评分结果总体比较,差异有统计学意义(x2 =25.65,P=0.00),其中权重因子为0.6的混合能量图像评分最高.结论 双能量CTPA中,权重因子为0.5和0.6的混合能量图像能提供最佳肺动脉SNR和CNR,并能够提高CTPA的图像质量.

Comparative study of image quality of dual-energy CT pulmonary angiography at different energy levels

Objective To evaluate the image quality of various energy images of dual-energy CT pulmonary angiography （CTPA） so as to determine the optimum energy-mix methods of dual-energy CTPA. Methods A model filled with various density iodine and 27 patients who suspected pulmonary embolism underwent thoracic dual-energy CT scan, and the images of 140 kV and 80 kV were sent to post processing computer, then 9 sets mixed energy images were made form 140 kV and 80 kV images with various methods. The CT value, noise and signal-to-noise rate （SNR） of iodine in model were com- pared among 140 kV, 9 sets mixed energy and 80 kV images, and the CT value, noise., SNR and contrast-to-noise rate （CNR） of 27 patients＇ pulmonary were also compared among 140 kV, 9 sets mixed energy and 80 kV images, then the im- age quality score was ranked among mixed energy images with weight factored 0.3, 80 kV images and optimum mixed en- ergy images. Results Based on empirical study, the noise of mixed energy images with weight factor 0.3 was minimum, and the SNR of iodine of mixed energy images with weight factor 0.5 was maximum. Based on clinical study, the noise of mixed energy images with weight factor 0.3 was minimum, the SNR of pulmonary of mixed energy images with weight factor 0.5 was maximum, and the second was on the mixed energy images with weight factor 0.6, and the CNR of pulmo- nary of mixed energy images with factor 0.5 and 0.6 were maximum. There was statistic difference among 80 kV images, mixed energy images with weight factor 0.3, 0.5 and 0.6 （x2 =25.65, P =0.00）, and the scores of mixed energy with weight factor 0.6 were maximum. Conclusion The mixed energy images with weight factor 0.5 and 0.6 can provide the maximum SNR and CNR of pulmonary, and increase the image quality of dual-energy CTPA.