The Value Of Dual-layer Detector Spectral CT In The Diagnosis Of Pulmonary Embolism

Objective:To evaluate the value of dual-layer detector spectral CT imaging in the qualitative and quantitative diagnosis of pulmonary embolism(PE).Materials and Methods:298 patients with suspected PE were scanned by dual-layer detector spectral CT.According to the standard of clinical comprehensive diagnosis,conventional pulmonary angiography(computed tomography pulmonary angiography,CTPA)map was compared with optimal monoenergetic map(40-65 ke V),iodine density map and effective atomic map to observe the presence of pulmonary emboli.The location and number of emboli on each type of image were recorded respectively.At the same time,the iodine density and effective atomic number of pulmonary perfusion defect area and normal area were quantitatively measured,and the subject operating characteristic curves of iodine density and effective atomic number were drawn to determine the threshold of the best probability value of whether PE exists or not.The qualitative data were compared by χ~2 test and the quantitative data were compared by Wilcoxon rank sum test.P < 0.05,it was considered that the difference was statistically significant.Results:1.Based on patient level,among the 63 patients with positive PE diagnosed clinically,53 cases of PE were found by CTPA,55 cases of PE were found by optimal monoenergetic map,61 cases of PE were found by iodine density map and effective atomic number map,respectively.All the diagnostic indexes of PE examined by DLCT were higher than those of conventional CTPA..2.Based on embolus level,a total of 127 emboli were detected by conventional CTPA images,including 32 pulmonary lobe and above pulmonary artery emboli,87 segmental pulmonary artery emboli and 8 pulmonary subsegmental and lower pulmonary artery emboli.144,172 and 172 emboli were detected in the optimal monoenergetic map,iodine density map and effective atomic number map,32,32 and 32 emboli in the lobe and above pulmonary arteries,92,94 and 94 emboli in segmental pulmonary arteries,and 20,46 and 46 emboli in pulmonary subsegments and lower pulmonary arteries,respectively.The optimal monoenergetic map,iodine density map and effective atomic number map were superior to conventional CTPA images in detecting emboli,especially in the detection of emboli in pulmonary subsegments and lower arteries.3.The iodine density and effective atomic number in perfusion defect area and normal lung parenchyma were 0.28mg/ml(0.19,0.39mg/ml),8.02(7.70,8.32),1.08mg/ml(0.89,1.37mg/ml) and 9.98(9.65,10.35),respectively.There were significant differences between iodine density and effective atomic number(Z =-11.38,-11.37,respectively,P < 0.05).According to the analysis of ROC curve,iodine density and effective atomic number were used to distinguish PE area from normal lung parenchyma area with 0.66mg/ml and 8.91.the sensitivity was 98.30% and 98.30%,respectively,and the specificity was 95.90% and 93.60%,respectively.The area under the curve is 0.991 and 0.992,respectively.Conclusion:Dual-layer detector spectral CT imaging can improve the detection rate of PE,especially PE of sub-segment and below and can be analyzed quantitatively.