双源CT增强大螺距扫描肺血管容积再现重组技术探讨

The Discussion of Scanning Techniques Using Dual-Source CT with High-Pitch Mode for Volume Rendering Reconstruction of Pulmonary Vessels

目的探讨双源CT增强大螺距扫描肺血管容积再现(VR)重组技术。方法85例患者行双源CT增强大螺距扫描肺血管VR重组,采用对比剂跟踪技术,监测点位于头臂静脉,随机分成三组:延迟4 s组(组1)、延迟5s组(组2)和延迟6 s组(组3)。测量各组肺动脉主干、左下肺动脉、左上肺静脉CT值,计算左下肺动-左上静脉CT值差值,计算并比较图像信噪比、对比噪声比以及肺动-静脉CT值差值在各组间差异。经VR重组各组肺部血管,规定亚段以上肺动脉为红色、肺静脉呈蓝色图像为优,段以上肺动脉为红色、亚段肺动脉和肺静脉呈蓝色图像为良,肺动脉和肺静脉色差不能明确区分为差,比较三组间各等级VR图像差异。结果组2、3与组1图像信噪比、对比噪声比有显著差异(均为P<0.05)。经Ridit分析,三组平均Ridit值分别为0.609、0.391和0.489,组2最小,影像效果最佳,三组VR图像优良率分别为75.9%、96.2%和76.7%(χ~2=4.916,P=0.086),优、良和差的肺动-静脉CT值差值分别为(228.63±83.551)HU、(155.38±38.83)HU和(88.07±54.53)HU。结论双源CT增强大螺距扫描肺血管成像,设置头臂静脉监测点,延迟5 s可以获得较高质量图像,VR重组图像上大多数病例的肺动脉、肺静脉具有良好色差。

Objective To discuss the scanning techniques using dual-source CT with high-pitch mode for volume rendering（VR）reconstruction of pulmonary vessels.MethodsThe study included 85 patients who had contrast-enhanced dual-source CT scan with high-pitch mode for volume rendering reconstruction of pulmonary vessels.The bolus tracking technique was applied with the ROI placed within the brachiocephalic veins.All subjects were divided randomly into three groups according to delay time：4 seconds-delay group（group 1）,5 seconds-delay group（group 2）and 6 seconds-delay group（group 3）.CT value of pulmonary arteries,left lower pulmonary arteries and left upper pulmonary veins were measured.Among the three groups,the signal-to-noise ratio（SNR）,contrast-to-noise ratio（CNR）and the differences of CT value between left lower pulmonary arteries and left upper pulmonary veins were calculated and compared.VR reconstruction was done and their image-grading criteria was as follows：excellent-above subsegmental pulmonary artery represented as red,pulmonary veins in blue,good-above segmental pulmonary artery presented rad,subsegmental artery and pulmonary veins in blue,poor-impossible to distinguish the colors between arteries and veins.The differences of VR image grades among the three groups were also compared.Results The SNR and CNR had significant differences between group 1 and group 2,group 1 and group 3.Among the three groups,Ridit analysis of VR images grading showed that the average Ridit values were 0.609,0.391 and 0.489 respectively,in which the VR images of group 2 were the best with minimal Ridit value,the percentage of excellent plus good images was 75.9%,96.2%and 76.7%respectively（χ~2=4.916,P=0.086）.The difference of CT values between arteries and veins of the grade excellent,good and poor images were（228.63±83.551）HU,（155.38±38.83）HU and（88.07±54.53）HU respectively.ConclusionDual-source CT can enhance the pulmonary angiography using a high-pitch scan and set up the monitoring site of the brachiocephalic veins.The quality of the pulmonary veins in the VR images can be improved by a delay of 5 seconds.