Comparative Study Of Image Quality Of Dual-source CT Dual-energy Pulmonary Angiography With Low Contrast Medium Doses

With the development of hardware and software of CT, multislice spiral CT pulmonary angiography has become the first-line diagnostic method for the diagnosis of pulmonary embolism. However, some patients are often accompanied by some complications, such as heart and lung diseases, whose hemodynamics are poor and can not hold one’s breathe for a long time. These cause examination failed or images can not be diagnosed. In addition, small emboli can cause a large area poor perfusion of lung tissue, but due to the limitations of technical conditions, diagnosis rate of pulmonary emboli located in subsegments and distal pulmonary arteries is not high. CT pulmonary angiography(CTPA)only provide anatomical information of pulmonary embolism, but lung perfusion changes that emboli caused are difficult to evaluate. In recent years dual-source CT has been widely used in clinic. Dual-energy scanning mode can not only get low-energy, high-energy, mix energy image, but also be able to get40-190keV monochromatic energy images. The iodinated contrast material distribution in different organs can be obtained through material composition parsing algorithm with different data, which display organ perfusion status.The purpose is to quantitativly evaluate image quality and value of different images of dual-source CT dual-energy pulmonary angiography, to select preliminarily contrast media volume and scanning parameters applying to DEPI. Part one The value of different energy images of dual-source CT dual-energy pulmonary angiography with low contrast medium dosesObjective:To quantitatively evaluate the quality and value of different images of dual-source CT low contrast medium doses dual-energy pulmonary angiography.Methods:31patients underwent dual-source CT dual-energy pulmonary angiography from July2011to July2012, got100kVp (group1),140kVp (group2), mixing energy (group3) and monochromatic images that the volume of contrast agent was30ml. CT values and SD values of pulmonary arteries were measured. The signal-to-noise ratio (SNR), contrast to noise ratio (CNR) were calculated. Monochromatic images in the peak of SNR and CNR were group4、5、6. CT values, SNR and CNR values were analyzed statistically. Two radiologists evaluate the quality of images.Results:During40-190keV, SNR values and CNR values between70-80keV were higher(70keV、80keV were group4、6),that reached the peak at74keV(group5). CT values of groupl and4were higher than the others. CT values of group5、6were not statistically significant compared with group3(P＞0.05). Image noise of group1was higher than other groups. Image noise of group4was higher than group3、5、6(P＜0.05). Image noise of group6was lower than group3(P＜0.05).There was no significant difference for Image noise between group5and3(P＞0.05). There was no significant difference for CNR values between groups(P＞0.05). There was no significant difference forSNR values between groupl and3(P＞0.05).SNR values of group5、6were higher than groupl(P<0.05). There was no significant difference for SNR values group4、5、6compared with group3(P＞0.05).Conclusion: The image quality of different energy images can meet the diagnostic requirements when the volume of contrast agent is30ml. There is no significant difference in the image quality between low-energy image and mixed energy images. Image quality and CT value of70-80keV image are equivalent with the low energy and mixed-energy image.74keV is the optimum monochromatic energy of pulmonary arteries. Part two Comparative study different contrast media volume and scanning parameters of dual energy lung perfusion imagingObjective:To compare image quality of dual-energy CT pulmonary angiography and lung perfusion blood volume (lung PBV) in different contrast media volume and scanning parameters groups.Methods:90patients underwent dual-sourceCT dual-energy pulmonary angiography from September2011to August2O12.Patients were randomly divided into30ml (group1) or50ml (group2) or40ml (group3),30cases in each group.The scan was initiated with a bolus-tracking technique. In group1and2, the arrival of the contrast bolus in the pulmonary trunk was detected at a threshold of50Hounsfield Units (HU) with delay3s, however, that is100HU in group3. Attenuation profiles of multiple pulmonary arteries bilaterally, superior vena cava, left atrium, right atrium, right ventricle were measured.The diagnostic quality of lung PBV was evaluated by two radiologists using a3-point scale and Kappa test. Measured the overlay and iodine content of perfusion defects and normal lung parenchyma which was scored3and analyzed statistically. Results:The average attenuation of pulmonary arteries in group3is greater than the other two groups. No statistically significant difference between groupl and group3was found regarding the pulmonary arteries attenuation except pulmonary trunk(P＜0.01). The CT value of superior vena cava in group2is greater than the other two groups. The image quality of lung PBV in group3is better than group1,2. Good interobserver agreement is found for lung PBV (Kappa=0.748, P＜0.001). The difference of overlay and iodine content of perfusion defects and normal lung parenchyma is statistically significant(P＜0.001). The overlay and iodine content of perfusion defects is lower than that of normal lung parenchyma.Conclusion:40ml contrast media combination with artificial intelligence monitor pulmonary trunk at a threshold of100HU with delay3s scanning is available for dual energy CTA and lung PBV. The perfusion of embolic parts is lower than normal lung parenchyma.