CT Pulmonary Angiography With Dual-energy CT:the Feasibility With Gd-DTPA

Objective: To evaluate the feasibility of Gd-DTPA for CT pulmonary angiography with dual-energy CT,and provide an alternative program for patients who are unable to CTPA for iodine contrast agents.Methods: 69 patients who received CTPA from March 2019 to November 2019 was collected,and divided into three groups by the random draw.In group A,a total of 25 patients were subjected to large-pitch scanning with the tube voltage of 100 k V.The contrast agent was iohexol injection(Onapec)with a dose of 0.6ml/kg.In group B,a total of 23 patients were scanned with large-pitch spiral scan.The tube voltage was 70 k Vp,the contrast agents was Gd-DTPA(Magnevist),and the dose was 0.6ml/kg(0.3mmol / kg).In group C,21 patients were scanned with dual energy scan.The tube voltage was 70/150 Snk Vp,the contrast agents was Gd-DTPA(Magnevist)with a dose of 0.6ml/kg.The CT value of pulmonary artery,SNR,CNR,CTDIvol,DLP,vascular branching series,beam hardening artifacts in superior vena and subjective score of image quality were compared.The original images of group C were mixed linearly with a weighting factor of 0.5 to obtain the reconstructed images of group Cm0.5.At the same time,the images was reconstructed by VMI at 40 ke V,50 ke V,60 ke V,70 ke V,80 ke V,90 ke V,100 ke V and 110 ke V energy levels,respectively.Compared the reconstructed images on CT value of pulmonary artery,SNR,CNR,vascular branching series,beam hardening artifacts in superior vena and subjective score of image quality between each group.Finally,compared the differences between the group C40 ke V with group A,B and C in CT value of pulmonary artery,SNR,CNR,vascular branching series,beam hardening artifacts in superior vena cava and subjective score of image quality.Results:(1)The basic information and clinical characteristics of the subjects: there were no statistically significant differences in clinical characteristics and basic information in groups A,B and C(P > 0.05).(2)Comparison between groups A,B,and C(1)Comparison of CT value of pulmonary artery: the average CT value of main pulmonary trunk,left pulmonary artery and right pulmonary artery in group A was higher than that in group B and group C,the difference was statistically significant(P < 0.05).In pairwise comparison,there was no significant difference between group B and group C(P ? 0.05).(2)Comparison of image quality: in group A,SNR and CNR were higher than those in group B and group C(P < 0.05).There was no significant difference in SNR and CNR between the two groups(P ? 0.05).Among the three groups,group A had the highest proportion of beam hardening artifact in superior vena cava,the second was group B and the least was group C,with the difference was statistically significant(P < 0.05).Among the three groups,the vascular branching series was not the same.The number of branches was 6,which respectively were 16%,47.8% and42.9% in three groups.Among them,group B was better than group A,the difference was statistically significant(P = 0.025).There was no statistical significance between group A and group C,group B and group C(P ? 0.05).There was no significant difference in the subjective score of image quality among the three groups(P ?0.05).(3)Comparison of radiation dose: among the three groups,CTDIvol and DLP was the highest in group C,followed by group A,and the lowest in group B.In pairwise comparison,group B was significantly lower than group A and group C.(3)Comparison between reconstructed images of linear mixing and VMI(1)Comparison of pulmonary artery CT value: the average CT value of main pulmonary trunk,left pulmonary artery and right pulmonary artery in group C40 ke V was higher than that of other reconstructed images,and the difference was statistically significant(P <0.05).(2)Comparison of image quality: The differences of SNR,CNR,vascular branching series and subjective scores in the reconstructed images were not all the same,among which group C40 ke V was the highest.However,in multiple comparisons there was no statistical significance in difference(P?0.05)with group Cm0.5?C50ke V?C60ke V?C70ke V,while there was statistical significance in difference(P<0.05)with group C80 ke V?C90ke V?C100ke V?C110ke V.In all reconstructed images,the beam hardening artifact of superior vena cava was the most in group C50 ke V,followed by group C40 ke V.The difference in group C50 ke V and C40 ke V was not statistically significant(P ?0.05).(4)Comparison between group C40 ke V and group A,B and C(1)Comparison of pulmonary artery CT value: The average CT value of main pulmonary trunk,left pulmonary artery and right pulmonary artery in group C40 ke V was higher than that of in group B and group C,but lower than that of in group A.The difference was statistically significant.(2)Comparison of image quality: Compared with group A,group C40 ke V showed higher vascular branching series than group A(P <0.05),while SNR,CNR and the proportion of beam hardening artifact in superior vena cava were lower than group A.The difference was statistically significant(P <0.05).Compared with group B,group C40 ke V showed higher vascular branching series and subjective score than group B and the difference was statistically significant(P <0.05).Compared with group C,the vascular series of group C40 ke V was higher than that of group C,and the difference was statistically significant(P <0.05).Conclusions:(1)Gd-DTPA can be used for CTPA.For patients who are not suitable for iodinated contrast agent,Gd-DTPA can be considered as a substitute.(2)Dual-energy CT using high-pitch spiral scan and dual-energy scan can both be used for CTPA of Gd-DTPA.The radiation of high-pitch spiral scan is relatively low,but the dual-energy scan can improve the contrast in the blood vessels,the display of blood vessels in pulmonary artery branch and reduce beam hardening artifact in superior vena cava through VMI.