A Study Of Multimodality CT Imaging Of Solitary Pulmonary Nodules

Objective : To explore the diagnostic value of multimodality CT imaging(including imaging of CT non-contrast scan,CT enhancement imaging,dual-energy CT imaging and CT perfusion imaging)for diagnosing benign and malignant solitary pulmonary nodules(SPN).Methods:From March 2017 to December 2018,a total of 146 consecutive patients with SPN who underwent multimodality CT imaging(including CT non-contrast scan,CT perfusion imaging and dual energy CT contrast-enhanced scan)with Siemens Somatom Definition Flash were enrolled and confirmed by pathology in the Affiliated Hospital of Zunyi Medical University.There were 98 males and 48 females,who were aged 19-78 years,with an average age of 56.38±1.04 years.Lung window images of CT non-contrast scan of SPN were reconstructed with a slice thickness of 1 mm,followed by the coronal and sagittal multiplanar reconstruction(MPR).CT perfusion images of SPN were post-processed by VPCT Body software in Siemens workstation to obtain perfusion parameters including blood volume(BV),blood flow(BF),permeability(PMB)and mean transit time(MTT).The dual energy CT contrast-enhanced scan of SPN can obtain both iodine maps and enhanced images in arterial and venous phase,the iodine maps of SPN were processed by the Liver VNC program in Dual Energy software to obtain parameters including the overlay value(OL),iodine concentration(IC)and normalized iodine concentration(NIC)in arterial and venous phase.the net-increased CT values could be obtained by measuring CT plain scan and enhanced CT values of SPN.CT perfusion parameters and dual-energy CT iodine map parameters were analyzed by independent-samples t test if they were in accordance with normal distribution or analyzed by Mann-Whitney test if not.Receiver operating characteristic(ROC)curve analysis was performed for parameters with statistical differences to determine the diagnostic threshold.Two senior doctors who have been engaged in chest CT diagnosis for more than 15 years were assigned to analyze the non-contrast CT images,three-dimensional reconstruction images and enhanced CT images of each SPN at random.When their diagnostic results were inconsistent,they were negotiated and unified.According to features of the non-contrast CT images of each SPN,the evaluation was based on the following five grades: 1 = definitely benign,2 = possibly benign,3 = uncertain,4 = possibly malignant,5= definitely malignant.Method A referred to the diagnosis by analyzing the non-contrast CT images combined with the net-increased CT values.Method B referred to the diagnosis by analyzing the non-contrast CT images combined with iodine map parameters.Method C referred to the diagnosis by analyzing the non-contrast CT images combined with CT perfusion parameters.Taking pathological diagnosis as the gold standard.146 cases of SPNs were divided into two groups: benign and malignant groups.There were 86 cases in the malignant group and 60 cases in the benign group.The sensitivity,specificity,accuracy,positive predictive value and negative predictive value of single or combined usage of multimodality CT imaging for the diagnosis of benign and malignant SPNs were calculated and the diagnostic efficacy was evaluated.P<0.05 was considered as statistically significant difference.Results:(1)The CT dose index volume(CTDIvol),the dose length product(DLP)and the effective dose(ED)were 74.89±3.98 m Gy,1011.67±10.29 m Gy.cm and 14.16±0.14 m Sv respectively by completing multimodality CT imaging of SPN once.(2)The evaluation results of five grades of non-contrast CT images in 146 cases of SPNs showed:in the benign group,there were 19 cases in grade 1,4 cases in grade 2,27 cases in grade 3,10 cases in grade 4 and 0 case in grade 5.In the malignant group,there was 0 case in grade1,2 cases in grade 2,22 cases in grade 3,10 cases in grade 4 and 52 cases in grade 5.(3)The CT perfusion parameters BV,BF,MTT and PMB in the malignant group were higher than those in the benign group.The difference in PMB was statistically significant(p <0.05)bwtween two groups,but there was no significant difference in BV,BF and MTT(p > 0.05).The area under the curve(AUC)was 0.741 by ROC curve analysis of PMB.When the diagnostic threshold was 10.22 ml/100ml/min,the sensitivity was 90.69% and the specificity was 58.33% for diagnosing benign and malignant SPNs.(4)The iodine map parameters in arterial and venous phase in the malignant group were higher than those in the benign group,the differences of all parameters were statistically significant(p < 0.05)bwtween two groups.ROC curve analysis showed that the AUC of all parameters including the artery-phase overlay value(a OL),vein-phase overlay value(v OL),artery-phase iodine concentration(a IC),vein-phase iodine concentration(v IC),artery-phase normalized iodine concentration(a NIC),vein-phase normalized iodine concentration(v NIC)were 0.627,0.630,0.617,0.643,0.620 and 0.815 respectively,of which the AUC of v NIC was the largest and the differences were statistically significant compared with the other parameters(p < 0.05).The sensitivity was 74.43% and the specificity was 78.33% for diagnosing benign and malignant SPNs when the diagnostic threshold was 0.31.(5)Taking pathological diagnosis as the gold standard,when method A,method B and method C were used singly,the specificity of method B was larger than that of method A,and the difference was statistically significant(p < 0.05).When method A,method B and method C were used in combination,the comparison between any two kinds of the following combinations: method A + B,method A + C,method B + C and method A+ B + C showed no significant difference in the diagnostic efficacy(p>0.05).However,the sensitivity of the above four combined methods was larger than that of method A,the difference was statistically significant(p < 0.05).The sensitivity of method A + C and method A + B + C was larger than that of method B,the difference was statistically significant(p < 0.05).The accuracy of method A + C was larger than that of method A,the difference was statistically significant(p < 0.05).Conclusion :(1)Multimodality CT imaging is helpful to improve the diagnostic efficiency of benign and malignant SPNs.(2)Chest CT scan combined with MPR is an important method for the diagnosis of benign and malignant SPNs.CT perfusion imaging and dual-energy CT imaging have certain value in the diagnosis of benign and malignant SPNs.