CT Evaluation Of Pulmonary Adenocarcinoma In Situ(AIS)

[OBJECTIVE] 1.To investigate the characteristics of peripheral lung adenocarcinoma in situ lesions on CT images and related clinical features.2.To compare the methods of assessment of pulmonary nodule size and density and evaluate its value in AIS precise diagnosis.[METHODS] This study retrospectively reviewed 97 patients with 100 lesions,confirmed by surgical excision.To investigate the characteristics of peripheral lesions of lung adenocarcinoma in situ on CT images and related clinical features,including position,type,density and homogeneity,size,shape,boundary,margin,vacuole sign,spiculation,and pleural indentation.Lesion diameters,including maximal diameter and vertical diameter,were measured on the maximal dimension of the pulmonary nodules in both the cross-sectional thin section and modified MPR images,meanwhile the mean diameter was calculated.Comparison of the two diameters on the two measurement methods were analysed to diagnose lung AIS lesions accurately.In the evaluation of p GGNs,the average CT value of ground-glass component in papers were used as a reference standard,the concept of the CT value in the representative region of interest(representative ROI)was proposed and the accuracy of diagnosis between the two methods was compared.[RESULTS] 1.General clinical and imaging features 97 patients(34 males,63 females,age ranged from 24 to 79 yrs,mean 50.3±12.0 yrs)with 100 lung adenocarcinom in situ lesions(3 cases of double lesions)confirmed by operation pathology were included in this study.100 cases of lung AIS,including 81 pure ground-glass nodules,and the ground-glass opacity in 43 of 81 cases appeared as inhomogeneous.19 lesions were characterized by mixed ground-glass nodules,14 cases had mixed ground-glass opacity and nodular solid component,and 5 cases had mixed ground-glass opacity and patchy solid component.All cases were well-demarcated,65 cases had smooth margin,35 cases had irregular margin.No spiculation was shown in this group,pleural indentation sign was shown in 7 cases and vacuole sign in 7 cases.2.General lesion size characteristics and comparison of measurement methods In p GGN,maximal diameter on cross-section was 8.8±2.3mm,mean diameter was 8.0±2.0mm,maximal diameter on modified MPR was 9.5±2.8mm,mean diameter was 8.5±2.3mm.In m GGN,maximal diameter on cross-section was 10.6±3.3mm,mean diameter was 9.4±2.5mm,maximal diameter on modified MPR was 11.1±4.1mm,mean diameter was 9.8±3.0mm.In p GGN and m GGN,there was no significant difference in the data obtained from the two measurement methods of the maximal diameter in the cross-sectional thin section and modified MPR images.Both two methods could be used to represent the size of the lesions.The maximal diameter of solid component in m GGN on modified MPR was 4.1±1.5mm,mean diameter was 3.6±1.3mm.The proportion of solid components was 40%.3.Density characteristics in p GGN and comparison of different methods of measurement In 81 p GGN lesions,38 cases were homogeneous and their mean CT value was -637.2±101.5HU(95%:-669.5~-604.9HU),43 cases were heterogeneous and their mean CT value was-566.7±99.8HU(95%:-596.5~-536.9HU),CT value of representative ROI was-438.6±117.2HU(95%:-473.6~-403.6 HU).[CONCLUSION] 1.Lung nodules of adenocarcinoma in situ were more common in women,with a trend of becoming younger.The lesions were mostly characterized by round and well-demarcated heterogeneously pure ground-glass nodules.Some were showed as mixed ground-glass nodules.Vacuole sign and pleural indentation could be seen in some cases.2.Both the maximal diameter in the cross-sectional thin section and modified MPR images could be used to represent the size of the lesions.In each measurement data,the pure ground-glass nodule was smaller than that of the mixed ground-glass nodule.The maximal diameter of the solid component in m GGN on modified MPR was less than 5mm.3.In p GGN,the mean CT value of homogeneous nodules was-637.2±101.5HU(95%CI:-669.5~-604.9HU),heterogeneous nodules was-566.7±99.8HU(95%CI:-596.5~-536.9HU),CT value of representative ROI was-438.6±117.2HU(95%CI:-473.6~-403.6HU),the average CT value of 81 p GGN were-599.7±106.1HU(95%CI:-622.8~-576.6HU).