基于光谱CT的单能级图像评估经颈静脉肝内门体分流术术后支架内情况

Monochromatic images based on spectral CT for stent evaluation after transjugular intrahepatic portosystemic shunt

目的:探讨双层探测器光谱CT单能级图像显示经颈静脉肝内门体分流术(TIPS)术后支架内管腔情况的最佳单能级水平。方法:回顾性收集2019年12月至2021年7月于西安国际医学中心医院在双层探测器光谱CT上行门静脉CT血管成像(CTA)的TIPS术后患者29例。通过重建获得混合迭代图像(常规组)及单能级图像(40 keV组、50 keV组、60 keV组和70 keV组)。在横断面重建图像的支架内和同层面竖脊肌内分别放置圆形感兴趣区,获得相应的平均CT值、噪声,通过计算得到对比噪声比(CNR)和信噪比(SNR)。由2名医师以4分制对各组的图像质量进行主观评分。组间整体分析采用单因素方差分析或Kruskal-Wallis H秩和检验,组内两两比较采用LSD检验或Dunn-Bonforoni检验。结果:5组间噪声值差异无统计学意义(P>0.05);5组间图像的CNR、SNR差异有统计学意义(F=72.28、56.45,P<0.001)。40 keV组图像的CNR、SNR最高,分别为50.4±15.7、59.3±18.4,与其他组图像均差异具有统计学意义(P<0.001)。5组间整体主观评分均差异具有统计学意义(χ2=101.61,P<0.001),40 keV组主观评分高于60 keV组、70 keV组及常规组(P<0.001),与50 keV组的主观评分相比差异无统计学意义(P>0.05)。结论:双层探测器光谱CT的40 keV单能级图像是观察TIPS术后支架内管腔情况的最佳单能级图像。

Objective To investigate the optimal monochromatic level for evaluation of in-stent lumen after transjugular intrahepatic portosystemic shunt(TIPS)by dual-layer detector CT.Methods Twenty-nine patients after TIPS were retrospectively enrolled who underwent abdomen enhanced examinations with portal venous phases by a dual-layer detector CT between December 2019 and July 2021.The mixed iterative image(conventional group)and monochromatic images(40 keV group,50 keV group,60 keV group and 70 keV group)were obtained by reconstruction.Circular regions of interest were placed in the in-stent of the cross-sectional reconstructed image and in the vertical spinal muscle on the same plane to obtain the corresponding average CT value and noise.The contrast to noise ratio(CNR)and signal to noise ratio(SNR)were calculated.Then 4-point scale was performed to evaluate image quality subjectively by 2 physicians blindly and separately.One-way ANOVA or Kruskal Wallis H rank-sum test was used for the overall analysis between groups,and LSD test or Dunn′s Bonforoni test was used for pairwise comparison within groups.Results There was no significant difference in noise values among the 5 groups(P>0.05).The difference of CNR and SNR between the 5 groups was statistically significant(F=72.28,56.45,P<0.001).The CNR and SNR in the 40 keV group were the highest,which were 50.4±15.7 and 59.3±18.4 respectively,and the difference was statistically significant(P<0.001).Subjective scores showed statistically significant differences among the 5 groups(χ²=101.61,P<0.001).The score of the 40 keV group was higher than that of the 60 keV group,70 keV group,and conventional group(P<0.001),and there was no significant difference when compared with the subjective score of the 50 keV group(P>0.05).Conclusions The 40 keV monochromatic image of dual detector spectral CT is the best image to observe the lumen of the stent after TIPS.