| Part one:Comparative study on image quality and radiation dose of different scanning protocols of dual source CT in pulmonary angiographyObjective: To evaluate image quality and radiation dose of dual-source CT in pulmonary angiography between dual-energy scanning protocol(dual-energy CT) and conventional scanning protocol(single-energy CT) and to investigate the optimal scanning protocols of dual-source CT in pulmonary angiography.Methods: 235 patients with clinically suspected pulmonary embolism underwent flash dual-source CT pulmonary angiography were consecutively collected, and divided randomly into three groups: group A(DE, 80/Sn140 k V, 179/76 m As)(n=77); group B(DE, 80/Sn140 k V, 89/76 m As)(n=80); group C(tube voltage was selected automatically by Care k V, 160 m As)(n=78). CT attenuation in ROIs of seven pulmonary arteries(the pulmonary trunk, right and left main pulmonary artery, right and left upper pulmonary artery, right and left lower pulmonary artery), dorsal muscle and background noise were measured, and corresponding signal to noise ratio(SNR) and contrast to noise ratio(CNR) were calculated. Two experienced radiologists independently assessed the image quality of the three groups with double blind method. Image quality and radiation exposure parameters(CTDIvol, DLP and ED) were compared between groups with one way ANOVA, chi-square test, fisher’s exact test, Mann-Whitney U test, and Kappa test. For all analyses, P<0.05 was considered statistically significant.Results: CT attenuation in bilateral upper lobe pulmonary artery did not differ significantly(P>0.05) in group A compared to group B and group C, which was lower in the group B compared with group C,the difference was statistically significant(P<0.05).There was no significant difference(P>0.05) in the rest of the pulmonary arteries CT values between groups. Compared to the other of two groups, image noise were higher in group A while the corresponding CNR and SNR for all measured pulmonary arteries were lower, difference was statistically significant(P<0.05). The image quality canmeet the diagnostic requirements for pulmonary embolism in all groups and the subjective image quality score were 1.36±0.61,1.28±0.55,1.26±0.50 respectively, differences were insignificant between the three groups(P>0.05) with good interobserver agreement, kappa was 0.767,0.781,0.821, respectively, and grade from good to excellent(1-2 score) of subjective image quality was achieved in 93.5%(72/77),95.0%(76/80),97.5%(76/78) of the cases, respectively, no significantly difference was found between the groups(P>0.05). However, radiation exposure significantly different between protocols: The values of CTDIvol, DLP, and ED were significantly lower in group A compared to group B and group C(P<0.05),and the mean ED values for group A were lower 46.8% than that of group C.Conclusions: The dual-energy scanning protocol at 80/Sn140 k V allows a significant radiation dose reduction when the image quality meet the diagnostic requirements in dual-source CTPA.Part two:The diagnostic value of dual energy software in dualsource CT for peripheral pulmonary embolismObjectives: To investigate the value of Lung PBV and Lung Vessels software in dual-source CT dual-energy pulmonary angiography for diagnosing peripheral pulmonary embolism(PE).Material and Methods: 143 patients with clinical suspicion of PE underwent CT pulmonary angiography with dual-energy technique on a flash dual-source CT scanner, 41 patients with PE and 41 patients without PE were enrolled in this study. All raw data were transported to a dedicated workstation and CT pulmonary angiography images, lung perfusion blood volume images and Lung Vessels images were obtained by Lung PBV and Lung Vessels software with color-coded imaging. Two experienced radiologists independently read CTPA images, Lung PBV images, Lung Vessels images and combinedimages Lung PBV with Lung Vessels and then combined CTPA with color-coded Lung PBV and Lung Vessels software respectively, and evaluated the presence or absence of emboli and counted the number and location of PE, each session was performed with at least a one month interval, and the color-coded Lung PBV and Lung Vessels images appearances and its relationship with CTPA images as well as pulmonary parenchyma abnormities were analyzed. The sensitivity, specificity, positive predictive value(PPV)and negative predictive value(NPV) of CTPA, Lung PBV software, Lung Vessels software, Lung PBV with Lung Vessels software for the diagnosis of PE were calculated respectively. The difference of CTPA alone and CTPA combined with Lung PBV and Lung Vessels software respectively in detection the total and different anatomical locations of emboli were compared with chi-square test on a number of clots basis. P<0.05 was considered statistically significant.Results: Pulmonary filling defects were found in 41 of 82 patients on CTPA images, both radiologists missed three patients who had isolated PE in a subsegmental and more distal pulmonary artery when they analyzed CTPA alone. Pulmonary embolism, fibrosis, masses, lung infection, emphysema or bullae of lung, pulmonary edema, chronic obstructive pulmonary disease, beam hardening and cardiac or diaphragmatic motion artifact can lead to perfusion abnormalities on Lung PBV images or vessels was coded color in red or gray on Lung Vessels images, but pulmonary embolism was demonstrated as wedge-shaped perfusion defect or decrease which consistent with embolic artery supply area on Lung PBV images and embolic pulmonary arteries color were coded red or gray on Lung Vessels images. The sensitivity, specificity, positive predictive value(PPV) and negative predictive value(NPV) were 92.7%/100%/100%/93.2%, 78.0%/34.1%/54.2%/60.9%, 97.6%/48. 9% /65.6%/95.2%, 75.6%/73.2%/73.8%/75.0%, respectively in images with CTPA, Lung PBV, Lung Vessels and Lung PBV with Lung Vessels. A total of 150 emboli were detected in 82 patients, Of these, 58 emboli were located in segmental pulmonary arteries, 64 in subsegmental pulmonary arteries, 28 in sub-subsegmental or more distal pulmonary arteries, in which two subsegmental below pulmonary arteries color were coded red on Lung Vessels and wedge-shaped perfusion defects were depicted on Lung PBV imageswithout the visualization of endoluminal thrombi within the corresponding arteries and no lung lesions on CTPA images. With CTPA alone, the detection rate for embolisms in all, segmental, subsegmental, and subsegmental below pulmonary arteries were 82%/98.3%/83.4%/42.9%, CTPA with Lung PBV software, 96.7%/100%/96.9%/89.3%, and CTPA with Lung Vessels software, 98%/100%/98.4%/92.9%, CTPA combined with Lung PBV and Lung Vessels software for detecting embolisms in all, subsegmental, and subsegmental below pulmonary arteries were significantly higher than CTPA alone(all P<0.05), in segmental pulmonary arteries was slightly higher than that of CTPA alone, but the difference was not statistically significant(P>0.05).Conclusion: Lung Vessels and Lung PBV software in dual-energy pulmonary angiography on dual source CT can directly show embolus and abnormal perfusion induced by PE, which have a high sensitivity and a low specificity in diagnosis peripheral PE, while a combination of both them can increases the specificity, and combined with CTPA, they can improve capability to detect peripheral PE, especially for subsegment and subsegment below PE. |
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