The Study Of Quantitative Evaluation For Pulmona Embolism Detection And Curative Effect With Iodine-based Material Decomposition Techniques In Ct Spectral Imaging

Objective:To assess the clinical value of iodine-based material decomposition images and quantitative analysis with spectral computed tomography (CT) imaging in the diagnosis and treatment evaluation of pulmonary embolism (PE).Materials and methods:Fifty-six patients with suspicion of PE underwent CT pulmonary angiography (CTPA) with gemstone spectral imaging (GSI) mode. All patients were scanned on a GE Discovery CT750HD (HDCT) scanner. The monochromatic CTPA and material decomposition images (the water-based material decomposition image and iodine-based material decomposition image) were generated and the GSI data was analyzed with dedicated software of GSI Viewer. According to the positive findings of clots in CTPA images and/or density-decreased areas in the iodine-based material decomposition images, the patients were divided into PE group and normal group. The CTPA images were reviewed for the presence and localization of the embolus, as well as the grade of PE (occlusive or non-occlusive). The distribution of iodine in pulmonary parenchyma in the iodine-based material decomposition images was used to identify perfusion defects, which were then correlated to the CTPA findings. The number and location of perfusion defects were recorded. In quantitative analysis, lung field was divided into upper, middle and lower part on the iodine-based material decomposition images. The iodine densities of every part of the lung and perfusion defects areas were measured and compared intra-and inter-groups with independent-sample t-test. LSD-t test was used to compare the bilateral pulmonary parenchyma in the normal group. In the PE group, the iodine densities of the perfusion defect area were measured and compared to the normally perfused pulmonary parenchyma. Follow-up CT with GSI mode was performed3-month later in9patients with PE underwent anticoagulant treatment. The iodine densities of the perfusion defects before and after the treatment were also measured and compared.Results:1. HDCT showed symmetrical homogeneous perfusion in19normal cases, without significant perfusion defects on the iodine-based material decomposition images. The mean iodine density of the right upper, middle and lower lobe was (1.59±0.32)、(1.21±0.43)、(1.78±0.39) mg/mL respectively, and the mean iodine density of the left upper, middle and lower lobe was (1.56±0.44)、(1.13±0.32)、(1.75±0.41) mg/mL respectively. Quantitative analysis showed no significant difference was found between the counterpart of the bilateral pulmonary parenchyma (P>0.05), as well as between the upper and the lower part of the unilateral pulmonary parenchyma (P>0.05). The mean iodine density of the middle part was significantly different from the upper or lower part of the ipsilateral pulmonary parenchyma (P<0.001).2. A total of259clots (67occlusive and192nonocclusive) were detected in the pulmonary arteries in37patients with PE,21clots in the trunk,47in the lobar,102in the segment, and89in sub-segmental artery. There were150perfusion defects areas were detected on the iodine-based material decomposition images. All occlusive clots (100%) and68non-occlusive clots (35.4%) showed clear evidence of iodine distribution defects. With the Pearson χ2test, there was a significant difference (P<0.001) in the presence or absence of perfusion defects among normal CTPA, occlusive clots, and non-occlusive clots. Quantitative analysis showed that the iodine densities of the perfusion defects areas in the PE group were significantly different from the corresponding part of pulmonary parenchyma in the normal group(P<0.001). There was a significant difference in the iodine density between the normal lung parenchyma [(1.56±0.34) mg/mL] and perfusion defect parenchyma [(0.47±0.32) mg/mL] in the patients with PE(P<0.001).3. Most of the clots and perfusion defects either decreased or disappeared3months later in the follow up imaging in the nine PE patients after anticoagulant treatment. The iodine densities of perfusion defects areas before [(0.46±0.37) mg/mL] and after anticoagulation [(1.05±0.56) mg/mL] were significantly different (P<0.001).Conclusion:1Spectral CT imaging is a reliable method in the evaluation of pulmonary perfusion status in normal subjects.2Spectral CT imaging is a reliable method in the evaluation of pulmonary embolism both qualitatively and quantitatively. It helps to detect and precisely locate the embolism, and provide information regarding the severity of PE. Spectral CT imaging is a reliable method in monitoring therapeutic efficacy of PE.3Spectral CT imaging generated both monochromatic CTPA images for morphologic analysis of PE and material decomposition images for quantitative depiction of pulmonary perfusion with one scan, which shows good clinical feasibility and practicality.