Application Of GSI Dual-energy CT In The Characterization Of Ground-glass Nodules(GGNs)

Background:Ground-glass nodule(GGN)is a localized lesion that is higher than the density of lung tissue,but its density is not enough to cover the bronchial blood vessels passing through in it.The ground glass lesions in lung can be considered as a wide variety of clinical features such as benign,malignant and inflammatory conditions.Radiologically,GGNs are divided into two categories:pure GGNs which has no solid component in it and mixed GGNs which contain both a pure GGN region and a consolidated regions.The risk factor of pulmonary ground-glass nodule for cancer can be assessed by using Imaging parameters including the size of the nodule,density,margin characteristics and peripheral signs.Generally,the nodules<4 mm is considered to be benign or active inflammatory,while those 4-10 mm in size are suggestive of malignancy but false positive results can occur in granulomatous inflammation or other active inflammation.However;the advent of.Dual-Energy CT(DECT)screening for lung cancer has increased the detection and differentiation rates of lung nodules.The aim of this research is to evaluate the nature of the GGNs by using DECT in order to make an early recognition of the nodule,early management and to give an appropriate treatment in patients with GGNs and to avoid misdiagnosing lung lesions or unnecessary process for non-cancerous nodules.Purpose of the thesis:The aim of this thesis is to explore the utility of contrast-enhanced DECT in the diagnosing and characterization of pulmonary ground-glass nodules(GGNs).The image display and data analysis of all cases in this study were used by Gemstone Spectral Imaging(GSI)viewer to determine whether DECT with GSI mode can differentiate malignant GGN from benign ones and other inflammatory GGN lesions.Subjects and Methods:A total of 41 patients with ground-glass nodules proved by pathology were enrolled in our study,and were divided into a malignant group(21 cases,51%),a benign group(11cases,27%)and inflammatory group(9 cases,22%).All patients underwent contrast-enhanced Dual-energy CT(Discovery CT750 HD scanner)with GSI mode.Five quantitative parameters including(net CT number enhancement,Water content(WC),Iodine Content(IC),Normalized Iodine Concentration(NIC)and the slope rate of the spectral curve(k HC)generated in gemstone spectral imaging dual-energy CT in 70KeV images have been used for analysis.Analysis of variance was used to analyze statistical differences between the three groups.The p-values less than 0.05 were used to consider the significant differences between three compared groups.For further evaluation we adopted Receiver operating characteristic(ROC)curves to calculate the sensitivity and specificity.The diagnostic capability was determined by calculating the area under the ROC curve(AUC).Results:The results of our research revealed that the Iodine Content(ICs),normalized iodine concentration(NICs)and the slope rate of spectral curve of the malignant and inflammatory GGNs were higher than those benign GGNs.the mean slope rates of malignant group,inflammatory group,benign group were 2.26±0.19λHU,2.36±0.24 λ,HU,and 1.35±0.20 λHU respectively,the NICs were 0.26±0.03,0.24±0.02 and 0.19±0.03 respectively,the WC were 421.50±48.45 mg/mL,434.05±33.95 mg/mL,284.93±74.91 mg/mL,respectively,The ICs were 25.43±3.43 mg/mL,24.24±2.47 mg/mL,and 20.6±3.67 mg/mL respectively.There were no statistical differences between malignant group and inflammatory group in water content.A further examine that we made by using ROC curve to determine the differential capacity with the net CT number enhancement in 70keV images,NIC,and λ HU had demonstrated that the net to have high diagnostic value in differentiating malignant and benign GGNs.The area under curve of Net CT Numbers was 0.926(0.838-1.000),with statistical significance of(P<0.05),the diagnostic value of Net CT Numbers was high,showing a sensitivity of 81.0%,and a specificity of 90.9%,with threshold of 86.540,Whereas NIC and λHU had shown areas under curve of 0.926 and 1.000 respectively,the Sensitivity and Specificity of NIC were:95.2%and 72.7%with Thresholds 0.215,the Sensitivity and Specificity of λHU were both reached 100%with threshold of 1.850.Conclusion:Dual-energy(spectral)CT plays a very important role in the modern medical imaging.The characterization of lung GGN by using contrast-enhanced DECT has proven to be very helpful for differentiating malignant from benign nodules for its quantitative parameters and monochromatic images.The results of our study showed that the WC,IC,NIC and slope rate of malignant group were higher than benign group,which can be explained as the higher IC,NIC and slope rate,the greater risk to be malignancy.The study also demonstrated that the net CT number enhancement,NIC and λHU have high sensitivity and specificity for differentiating benign and malignant GGNs.However,further researches are needed to provide a suitable and effective method for clinical diagnosis for patients with lung GGNs.