能谱CT优化支气管动脉CT血管成像质量的最佳单能量值的初步研究

目的评价能谱CT单能量成像技术在显示支气管动脉中的应用价值,寻求其CTA图像质量最佳的单能量keV值或区间。方法回顾性分析18例患者影像资料,均采用能谱CT扫描技术行胸部增强扫描,符合研究标准的15例。数据采集完成后直接获取140 kVp混合能量和70keV单能量图像,再通过AW4.5工作站GSI viewer软件得到最佳单能量图像,并每隔5 keV对50-80 keV区间进行拆分,分别获取50 keV、55 keV、60 keV、65 keV、70 keV、75 keV、80 keV单能量图像,比较上述7组支气管动脉的对比噪声比(CNR)、信噪比(SNR),并采用Bonferroni法进行比较。结果本研究15例中,28支支气管动脉均符合研究要求。50 keV单能量组(CNR:33.21±10.03;SNR:38.54±10.53)略优于55 keV组(CNR:28.29±8.28;SNR:33.98±8.76),二者之间无显著统计学差异(P=0.211、0.517);但50 keV、55 keV均优于余下5组不同keV单能量组(CNR、SNR呈递减趋势),P0.05。GSI软件所测得较佳单能量水平均位于50-55 keV水平,以53 keV最多见(14/28,50%)。实际测量值与GSI viewer软件自动得到的最佳keV值相符。结论在50-80 keV区间7组不同水平单能量模式下的支气管供血动脉的显示中,最佳单能量位于50-55 keV水平间,最佳单能量keV值为53 keV。

A Preliminary Study on Optimizing Monoenergetic Parameters of CTA Imagning Quality of Bronchial Arteries in Spectral CT

Objective To investigate the value of the optimal monochromatic parameters of CT angiography（CTA） in displaying bronchial artery and find the optimized keV for displaying bronchial artery in CTA by spectral CT with gemstone spectral imaging （GSI） technique. Methods 18 patients were underwent chest enhanced CT scan by the GSI technique, and 15 ones meet a criterion. The clinical and imaging data were analyzed respectively. After scanning, the 140 kVp mixed energy images and 70 keV monochromatic images were obtained with standard algorithm. All the source images were transmitted into AW4.5 and obtained monochromatic images from 50 keV to 80 keV （every 5 keV） by GSI viewer software. CNR and SNR of 7 groups were analyzed. All data were analyzed by Bonferroni method. Results Totally 28 bronchial arteries were involved in this study. The CNR of bronchial artery from 50 keV to 80 keV were 33.21, 28.29, 24.60, 19.54, 16.79, 14.25, 12.27 respectively.The SNR of bronchial artery from 50 keV to 80 keV were 38.54, 33.98, 30.76, 25.36, 22.56, 20.16, 18.55 respectively. There was no statistical difference of CNR and SNR between 50 keV and 55 keV （P=0.211〉0.05, P=0.517〉0.05 respectively）.The CNR and SNR of 50 keV image and 55 keV image were statistically higher than those other keV groups （P〈0.05 respectively）, The optimal keV with optimal CNR by using GSI viewer software was from 50-55 keV, which was almost all in 53 keV [50%（14/28）]. Conclusion 50-55 keV was the optimized keV for displaying bronchial artery in the CTA, and 53 keV was the best.