双层探测器光谱CT虚拟单能量CTA技术对脑血管成像的价值

The Value of Virtual Monoenergetic Computed Tomography Angiography with Dual-layer Detector Spectral Computed Tomography for Imaging Cerebral Vessels

目的:探讨双层探测器光谱CT虚拟单能量(VMI)(≤70 keV)CTA技术对脑小血管成像的应用价值。方法:回顾性分析在Philips IQon CT行头颈部CTA检查的52例患者的影像资料,获得常规120 kVp混合能量图像和光谱数据重建的40~70 keV(间隔10 keV)CTA图像。测量大脑中动脉M1段的CT值、信噪比(SNR)、对比噪声比(CNR)和同层面血管旁脑实质的CT值和噪声(SD),并由两名医师以5分法分别对中大脑中动脉的容积再现(VRT)图像和豆纹动脉的最大密度投影(MIP)图像评分并进行比较。结果:于40~70 keV VMI测得的血管CT值、SNR、CNR随着能级降低显著递增,SD值仅稍增,与常规图像相比差异多有统计学意义;主观评价中,40 keV和50 keV组VRT图像评分为5(5,5)、5(4,5);MIP图像评分为4(3,4)、4(3,5),两组主观评分均优于其他组,两组间差异均无统计学意义。结论:双层探测器光谱CT小于70 keV的虚拟单能量CTA技术可以有效提高脑血管远端分支和豆纹动脉的显示效果,常规推荐50 keV VMI。

Objective:This study aimed to investigate the application value of virtual monoenergetic(VMI)(≤70 keV)computed tomography angiography(CTA)in imaging small cerebral vessels with dual-layer detector spectral CT.Methods:The imaging data of 52 patients who underwent head and neck CTA using Philips IQon CT were retrospectively analyzed.Conventional 120 kVp mixed energy images and 40~70 keV(10 keV interval)VMI CTA images reconstructed using spectral data were obtained.The CT value,signal-to-noise ratio(SNR),contrast noise ratio(CNR),and CT value and noise(SD)of the paravascular cerebral parenchyma at the same level were measured in the M1 segment of the middle cerebral artery.The image quality of the middle cerebral artery in volume reconstruction(VRT)and lepidopleural artery in maximum density projection(MIP)was scored by two physicians using a 5-point Likert scale.The evaluation results between the different groups were compared.Results:The CT,SNR,and CNR values of blood vessels at 40~70 keV VMI increased with a decrease in energy level,and the SD values increased slightly,with more statistically significant differences compared with conventional images.In the subjective evaluation,the VRT images in the 40 keV and 50 keV groups were 5(5,5)and 5(4,5),respectively,and the MIP image scores were 4(3,4)and 4(3,5),respectively.The subjective scores of both groups were better than those of the other groups,with no statistically significant difference.Conclusion:Virtual monoenergetic CTA technology with dual-layer spectral CT<70 keV can effectively improve the display effect of the distal branch of the cerebral small vessels and legume artery,and 50 keV VMI CTA is recommended.