双能量CT增强扫描在肺部血管容积再现中的价值

Value of contrast-enhanced dual-energy CT scanning in volume rendering of pulmonary vessels

目的:探讨双能量CT增强扫描在肺部血管容积再现(VR)中的价值。方法:40例患者行胸部双源CT双能量增强扫描,把监测点设置在上腔静脉,分别获得80kV(组1)、140kV(组2)、M=0.6(组3)、最佳单能量(组4)和非线性融合(组5)图像。由两位影像科医师分别测量肺动脉干、左下肺动脉与左上肺静脉CT值并计算平均值,计算肺动脉干信噪比(SNR)、对比噪声比(CNR)、左下肺动脉与左上肺静脉CT值差值,使用单因素方差检验比较上述各指标在各组间的差异,获得最佳质量组图像并行VR重组,规定肺动脉为红色,肺静脉为蓝色,由两位影像科医师共同评价VR图像质量并取得一致意见,根据肺动静脉颜色差异把VR图像分成优、良和差三个等级,探讨VR图像的优缺点并分析其原因。结果:5组图像的SNR和CNR总体有显著差异(分别为F=25.049,P<0.001;F=24.882,P<0.001),组5具有最高的SNR、CNR,与其他各组差异均有统计学意义(均为P<0.05)),5组肺动静脉CT值差值总体有显著差异(F=21.120,P<0.001),组5肺动静脉CT值差值最高,与组1差异无统计学意义(P>0.05),与其它3组差异具有统计学意义(P<0.05)。采用非线性融合数据行VR重组,32例VR图像评为优,6例评为良,2例因呼吸运动导致监测点移位病例VR图像评为差。结论:双能量CT非线性融合图像具有很高的SNR、CNR,且肺动静脉CT值差值最大,VR重组时增加了肺动静脉色差,有利于肺段血管的精确定位。

Objective：To discuss the value of contrast enhanced dual-energy CT scan in volume rendering of pulmona- ry vessels. Methods：40 patients underwent contrast-enhanced dual-energy CT of chest with the region of interest （ROD of triggering position placed within superior vena cava. The original images were post-processed to create 80kV （group 1）, 140kV （group 2）, M = 0.6 （group 3）, optimal monoenergetic （group 4） and non-linear blending （group 5 ） images respectively. The CT values of pulmonary trunk, left lower pulmonary artery and left upper pulmonary vein were measured by two radiologists respectively. The value of SNR,CNR of pulmonary trunk and the difference of CT value between left lower pul- monary artery and left upper pulmonary vein were calculated. The difference of the above mentioned parameters among the five groups were compared using one-factor analysis of variance test. The VR reformation were performed using the best im ages of the above mentioned five groups, the pulmonary artery was defined as red coded, pulmonary vein as blue coded, the VR images quality was evaluated by two radiologist and reached in consensus. The quality of VR images were graded as excellent, good and poor according to the chromatism of pulmonary artery and vein. The advantage and disadvantage of VR im- ages and their causes were studied and analyzed. Results： SNR and CNR of the images in the 5 groups had significant statistical difference （F=25.049,P〈0.001,F=24.882,P〈0.001 ,respectively）,group 5 had the highest SNR and CNR value compared with the other 4 groups,with statistical significance （P〈0.05 ,P〈0.05 respectively）. The difference of CT value between left lower pulmonary artery and left upper pulmonary vein were significantly different among the 5 groups （F= 21. 120,P〈0. 001）,with the biggest difference value in group 5,yet there was no difference between group 1 and group 5 （P〉0.05）, the CT value difference of group 5 compared with group 2,3 and 4 showed statistical significance （P〈0.05）. When the VR images were reformed with non linear blending,the image quality was graded as excellent in 32 cases,good in 6,and poor in 2 which was due to the shift of ROI causing by respiratory movement. Conclusion：The images of dual-energy CT with non-linear blending showed higher SNR and CNR,which maximized the difference of CT value between pulmonary artery and vein and increased their chromatism,it is helpful for precise location of pulmonary vessels.