| Objective To compare radiation dose,image quality and the amount of contrast medium(CM)of second-generation and third-generation dual source CT(DSCT)for CT pulmonary angiography(CTPA).Methods A total of 70 patients were randomly divided into 2 groups.(1)Group A(n=35)underwent CTPA at(90,Sn150)kV with 30ml CM and 30ml normal saline(NS)on third-generation dual source CT;(2)Group B(n=35)underwent CTPA at(100,Sn140)kV with 60ml CM and 30ml NS on second-generation dual source CT.Mean attenuation values of pulmonary artery and muscle,standard deviation of air presternally in front of the patient were measured.CT dose index volume(CTDIvol)、dose-length product(DLP)were recorded.Signal to noise ratio(SNR),contrast to noise ratio(CNR)and effective dose(ED)were calculated.And overall image quality assessed by two blinded radiologists were recorded.The Cohen k analysis was performed to determine interobserver agreement for subjective image quality scoring.Subjective image quality scoring were compared with the Mann-Whitney U-test.Patient age,body mass index(BMI),DLP,CTDIvol,ED,attenuation values,SNR,CNR were compared with the independent samples t-test.Results SNR、CNR and subjective image quality scoring were no statistically significant difference between group A and group B.Agreement between the readers for scoring the subjective image quality was good(Kappa=0.677,P=0.000).The median effective dose was 1.68mSv in group A vs 3.17mSv in group B which corresponds to a mean radiation dose reduction of 47%.Conclusion The dual-energy mode of third-generation dual-source CT can achieve satisfactory image quality with 50%contrast medium savings,while significantly reducing the radiation dose.Objective To investigate the effect of virtual monoenergetic imaging(VMI)and non-linear blending(NLB)on imaging quality in indirect computed tomography venography(CTV)by dual energy CT(DECT).Methods 35 patients underwent indirect CTV with third-generation dual-source CT(Somatom Force;Siemens Medical Solutions,Forchheim,Germany)with dual energy mode(tube voltage:70 and Sn150kVp)were analyzed.Raw data were reconstructed using ADMIRE-3,and linear blending(LB)was performed with weighting factors 0.5.Furthermore,three sets of images generated with monoenergetic technology and NLB including group VMICNR、group VMI50keV and group NLB were also included in this research.The subjective and objective images of the inferior vena cava and lower extremity deep veins were evaluated respectively in group 70kV and the other four sets of images generated from LB,VMI and NLB.CT values,SNR,CNR and background noise(BN)were measured.The difference of the CT value,SNR,CNR and BN among the five groups were analyzed by the one-way ANOVA.And overall image quality assessed by two blinded radiologists were recorded.The Cohen k analysis was performed to determine interobserver agreement for subjective image quality scoring.Subjective image quality scoring were compared with the Kruskal-Wallis H-test.Results Group VMI50keV was found to provide the highest CT value for the inferior vena cava and lower extremity deep veins,and it followed by group 70kV.The CT value of the group VMICNR and group NLB were better than those of group LB.Group NLB provided the best SNR for femoral common vein,and group VMICNR provided the best SNR for the other five veins.Group 70kV provided the best CNR for the inferior vena cava,superficial femoral vein and popliteal vein,and group VMI50keV provided the best CNR for the other three veins.And group VMICNR and group NLB provided better CNR than group LB.The background noise(BN)in group VMI50keV was significantly increased comparing with the others,and it followed by group 70kV which was significantly increased comparing with group LB,NLB and VMICNR(P≤0.010).Agreement between the two radiologists for scoring the subjective image quality was good(Kappa=0.714,P=0.000).There was significant difference among the five groups for subjective image quality analysis(H=14.684,P=0.005).And there was no significant difference among group LB、NLB and VMICNR(P≥0.28).Conclusion The application of VMI and NLB could improve the image quality compared with LB algorithm in the indirect CTV examination.And it had important clinical significance. |
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