The Study On Differential Diagnosis Of Solitary Pulmonary Nodule With Five-phase Enhanced Multi-slice SpiralCT(MSCT) Scanning

ObjectiveTo retrospectively analyze imaging features of benign and malignant solitary pulmonary nodules(SPN) by using five-phase enhanced multi-slice spiral CT(MSCT)scanning,illustrate its clinical efficacy in differential diagnosis between benign and malignant pulmonary nodules.MethodsTo collect 44 patients with solitary pulmonary nodules(SPN)which diameter≤4CM(ineluding 27 malignant SPNs,9 tuberculomas,8 inflammatory lesions) in Clifford Hospital from January,2006 to March,2007,they were confirmed by operation,pathohistology or clinic follow-uP.Methods of CT scanning:Patients were performed firstly routine spiral scan with 4-row detector CT(GE LightSpeed QX/2.0 System),then were performed SPN thin slice CT scan,slice thickness is 1.25～2.5mm.Thirdly,95ml Iohexol (300mgI/ml)was injected at a rate of 2.0～3.0ml/s via forearm superficial vein by a high-press injector,and perform SPN five-phase enhanced thin slice scan began at 30s,60s,150s,240s,and at 90s it is routine spiral scan.The CT values of SPNs and descending aorta at the same slice before and after the enhancement in various time period were measured.Then the time -attenuation curves were drawn.The number of CT signs about the SPNs(including lobulation,short spiculation,little spinous process,vacuole sign,air bronchogram,vascular convergence and pleural indentation) were recorded.Enhanced peak CT value and SPN-to-aorta enhanced ratio(S/A ratio) of each SPN were calculated,and according to those data of the malignant nodules with inflammatory nodules and malignant nodules with tuberculomas the ROC curves were drawn.Results1.The TDC appeared differently for the malignant SPN,tuberculoma,and inflammatory lesion.Malignant TDC described as typeⅠcurve,showed rapidly increase to the peak height at 60s and maintained a plateau.Inflammatory curve,described as typeⅡcurve,showed sharply increase at the first 30s, then moderate increase at 30s to 150s,at 150s reach to peak height and then slightly decreased.The peak heigh of TDC of the malignant SPN was higher than the inflammatory lesion.The TDC of tuberculomas showed little or a little increase after injection of contrast material.2.The enhanced peak CT value of inflammatory lesions was significantly higher than that of tuberculomas(P=0.019＜0.05).But no statistically significant difference in the enhanced peak CT value was found between malignant and inflammatory lesions(P=0.109＞0.05),neither malignant nodules and tuberculomas(P=0.255＞0.05).3.The SPN-to-aorta enhanced ratio of inflammatory lesions was significantly higher than those of malignant nodules and tuberculomas (P=0.022,0.003＜0.05).No statistically significant difference in the SPN-to-aorta enhanced ratio was found between malignant nodules and tuberculomas(P=0.142＞0.05).4.According to the data of the malignant and inflammatory nodules/the malignant nodules and tuberculomas,the ROC curves about the enhanced peak CT value and the S/A ratio were drawn.The area under the curves of the enhanced peak CT value(0.771/0.728) was smaller than that of the S/A ratio (0.856/0.745).5.To differentiate between the malignant and inflammatory nodules:the peak height of 49Hu was considered as threshold(equal to or less than 49Hu were considered as malignant)and sensitivity would be 88.89%,specificity 62.50%,and accuracy 82.86%.The positive predictive value was 88.9%and negative predictive value 62.5%.If the ratio of SPN-to-aorta of 25.42%was threshold(equal to or less than 25.42%were considered as malignant),the sensitivity was 100%,specificity 62.50%,accuracy 91.43%,and the positive and negative predictive values were 90.0%,100%respectively.6.To differentiate between the malignant nodules and tuberculomas:the peak height of 19Hu was considered as threshold(higher than 19Hu were considered as malignant) and sensitivity would be 100%,specificity 66.67%,and accuracy 91.67%.The positive predictive value was 90.0%and negative predictive value 100%.If the ratio of SPN-to-aorta of 7.48%was threshold (higher than 7.48%were considered as malignant),its statistical result as the same as the peak height of 19Hu was considered as threshold.7.The number of CT signs of malignant nodules was significantly higher than those of inflammatory lesions and tuberculomas(P=0.014,0.003＜0.05).No statistically significant difference in the number of CT signs was found between inflammatory lesions and tuberculomas(P=0.689＞0.05).Conclusions1.The technique of five-phase enhanced multi-slice spiral CT(MSCT) scanning is helpful for the diagnosis and differential diagnosis of SPN.2.The diagnostic efficacy of the ratio of SPN-to-aorta would be higher than that of peak height in differential diagnosis of SPN.3.The number of peak height between(19Hu,49Hu]and the ratio of SPN-to-aorta between(7.48%,25.42%]would predict a malignant nodule.And the number less than that would predict a tuberculomas,higher than that would predict a inflammatory lesion.If increasing the sample size,the threshold of the ratio of SPN-to-aorta between the malignant nodules and inflammatory nodules would down to the number between 20%to 25.42%.4.The number of CT signs of SPN is helpful for the differential diagnosis of SPN.