Quantitative Study Of Lung Structure Changes In Asymptomatic Smokers Based On Voxels

ObjectiveUsing dual-phase chest CT scan and voxel registration method,the changes of smokers’ lung structure were quantitatively measured,which provided basis for early detection of smokers’ lung structure injury.This study is divided into three parts:Part one: To analyze the small airway lesions and emphysema of asymptomatic smokers quantitatively by CT dual-gas registration technique,and to explore their correlation with lung function.Part two:CT dual-gas registration technique was used to quantitatively measure small airway lesions and emphysema of each lung lobe in asymptomatic smokers,and to explore the degree of injury of small airway lesions and emphysema and their correlation with lung function.Part three:The bronchial and pulmonary vascular parameters of smokers and non-smokers were quantitatively measured by respiratory and inspiratory CT,and the bronchial compliance was evaluated by the ratio of expiratory and inspiratory phase parameters,and the correlation between bronchial compliance and pulmonary function was discussed.Part one1.Materials and methods34 non-smokers and 65 smokers were included in the normal physical examination.According to the smoking index,they were divided into low smoking index group(30 cases)and high smoking index group(35 cases),and underwent dual-phase CT scanning and pulmonary function examination.The raw data were imported into digital lung quantitative analysis software for split lung and small airway registration analysis,and the whole lung CT quantitative indicators were obtained: normal lung tissue area percentage(PRMnormal%),small airway lesion area percentage(PRMfsad%),emphysema area percentage(PRMempha %).Other indexes are CT value corresponding to 15 th percentile of lung density histogram(PD15),percentage of pixels less than-950 HU in inspiratory phase(IN-950%),percentage of pixels less than-960 HU in inspiratory phase(IN-960%),average lung density in inspiratory phase(MLD-IN),average lung density in expiratory phase(MLD-EX)Lung function indicators: peak expiratory flow rate(PEF),percentage of measured peak expiratory flow rate to predicted value(PEF%),forced vital capacity(FVC),forced expiratory volume at the end of the first second(FEV1%),forced expiratory volume measured value to predicted value at the end of the first second(FEV1%)and FEV1 to FVC percentage(FEV1/FVC).The difference of CT quantitative index and lung function among the three groups was analyzed by one-way ANOVA or nonparametric test,and LSD method or paired comparison method was used for pairwise comparison.Pearson or Spearman was used to analyze the correlation between CT quantitative indexes and lung function.2.ResultsThere was no significant difference in CT quantitative indexes PD15 HU,IN-950%,IN-960% and MLD-IN among the three groups.There were significant differences in PRMnormal%,PRMfsad%,PRMempha%,MLD-EX,EXP-856(P<0.05).There were significant differences in pulmonary function indexes PEF,PEF%,FEV1% and FEV1/FVC among the three groups(P<0.05).There was no significant difference between FEV1 and FVC.There was significant difference in PRMfsad% among high smoking index group,low smoking index group and non-smoking group(P<0.05).There is no significant difference in PRMnormal%,PRMempha%,MLD-EX,EXP-856% between non-smoking group and low smoking index group,but there is significant difference among other groups.The PRMnormal% and MLD-EX of high smoking index group were smaller than those of low smoking index group and non-smoking group,and the PRMempha% and EXP-856% were higher than those of low smoking index group and non-smoking group.The quantitative CT indexes PRMnormal%,PRMfsad%,PRMempha%,MLD-EX,EXP-856% in the three groups were correlated with pulmonary function indexes PEF,PEF%,FEV1/FVC(P<0.05).There are correlations between PRMnormal%,PRMfsad%,PRMempha% and FEV1(P<0.05).There is a correlation between PRMfsad% and FEV1%(P<0.05).The correlation between PRMfsad% and PRMempha% and lung function was higher than other indexes.3.Brief summaryThe quantitative indexes of CT(EXP-856%,MLD-EX,PRMnormal%,PRMempha%,PRMfsad%)and lung function(PEF,PEF%,FEV1%,FEV1/FVC)were abnormal in smokers.There are differences in lung parenchyma between smokers and non-smokers in the quantitative indicators of respiratory and inspiratory biphasic CT(PRMnormal%,PRMempha%,PRMfsad%).Compared with single gas phase(EXP-856%,MLD-EX)quantitative indicators,dual gas phase voxel quantitative CT indicators have higher correlation with lung function.Two-phase voxel CT quantitative indicators(PRMempha%,PRMfsad%)are sensitive indicators for finding early damage of lung structure of smokers.Part two1.Materials and methodsSixty-five healthy asymptomatic smokers(the same as the first part)were enrolled.Biphasic CT scan of inpiration and expiration and pulmonary function examination were performed.The original data were imported into the digital lung quantitative analysis software for cleft lung segmentation and small airway registration analysis,and the quantitative indicators of CT of smokers’ right upper lobe(RUL),right middle lobe(RML),right lower lobe(RLL),left upper lobe(LUL)and left lower lobe(LLL)were obtained: small airway lesion area percentage(PRMfsad%),emphysema area percentage(PRM FSAD%)Lung function index: same as the first part.The differences of PRMfsad% and PRMempha% in each lung lobe of asymptomatic smokers were analyzed by one-way ANOVA or nonparametric test,and multiple comparisons were made by LSD or pairwise comparison.Pearson or Spearman was used to analyze the correlation between PRMfsad%,PRMempha% and lung function.2.ResultsThere are significant differences in PRMfsad% and PRMempha% among different lung lobes(P<0.05).the PRMfsad% and PRMempha% values of RML are the largest,followed by LUL and RUL,and RLL and LLL are the smallestThe comparison of PRMfsad% and PRMempha% between lung lobes showed that RML was significantly different from RUL,RLL,LUL and LLL(P<0.05).RUL was significantly different from RLL and LLL(P<0.05).LUL was significantly different from RLL and LLL(P<0.05).There is no significant difference between RUL and LUL.There was no significant difference between RLL and LLL.The PRMempha% and PRMfsad% of RUL,RML,RLL,LUL and LLL were correlated with FEV1/FVC(P<0.05).The PRMfsad% was correlated with PEF,PEF% and FEV1(P<0.05).Except RML,the PRMempha% of the remaining lung lobes was correlated with PEF(P<0.05).Except RML and RLL,PRMempha% of the remaining lung lobes was correlated with FEV1 and PEF%(P<0.05).The correlation between PRMfsad%,PRMempha% and airflow restriction indexes PEF,FEV1,PRF%,FEV1/FVC in the upper lobe of double lungs(RUL+RML+LUL)is smaller than that in the lower lobe of double lungs(RLL+LLL),and the correlation in the middle lobe of right lung is the worst.The PRMempha% and PRMfsad% of some lung lobes were also correlated with other lung function indexes.3.Brief summaryRML is the most important factor in PRMempha% and PRMfsad% among the lungs of smokers,followed by LUL and RUL,and RLL and LLL are the lightest.The correlations between PRMempha% and PRMfsad% of both lower lungs and PEF,FEV1,PEF%,FEV1/FVC are higher than those of upper double lungs.Part three1.Materials and methodsThe objects included are the same as those in the first part.Import data into digital lung software to quantitatively analyze total bronchus and total pulmonary vessels,which can automatically extract and segment bronchial tree and pulmonary vascular tree,and measure inspiratory bronchus number(NB-IN),inspiratory bronchus length(BL-IN),inspiratory bronchus volume(BV-IN),inspiratory pulmonary vascular volume(PVV-IN),expiratory bronchus number(NB-EX),expiratory bronchus length(NB-EX)The ratio of bronchial parameters in inspiratory and expiratory CT was calculated: NB-E/I,BL-E/I,BV-E/I to evaluate bronchial compliance.Lung function indexes are the same as those in part one.One-way ANOVA or nonparametric test was used to compare the quantitative CT parameters of bronchial and pulmonary vessels and the ratio of respiratory bronchial parameters among the three groups.The pairwise comparison uses LSD method or paired comparison method;Pearson or Spearman was used to analyze the correlation between the quantitative parameters of expiratory CT and the ratio of bronchial parameters in respiratory phase and lung function.2.ResultsThere is no significant difference in NB-IN,BL-IN,BV-IN,PVV-IN,PVV-EX among the three groups.There are significant differences in NB-EX,BL-EX,BV-EX,NBE/I,BL-E/I and BV-E/I among the three groups(P<0.05).The NB-EX,BL-EX,BV-EX,NB-E/I,BV-E/I in high smoking index group were higher than those in low smoking index group and non-smoking group,but there was no significant difference between low smoking index group and non-smoking group.The lung function indexes among the three groups were the same as those in the first part,and the differences in PEF,PEF%,FEV1%,FEV1/FVC were statistically significant(P<0.05).There are correlations between FEV1/FVC and NB-EX,BL-EX,BV-EX,NB-E/I,BL-E/I and BV-E/I in three groups(P<0.05).There are correlations between NB-E/I,BLE/I,BV-E/I and FEV1(P<0.05).There is a negative correlation between NB-EX,BL-EX,BV-EX,NB-E/I,BL-E/I,BV-E/I and FEV1/FVC(r=-0.242,P< 0.05;r=-0.252,P<0.05;r=-0.340,P<0.05;r=-0.359,P<0.05;r=-0.356,P<0.05;r=-0.350,P<0.05).There is a negative correlation between NB-E/I,BL-E/I and BV-E/I and FEV1(r=-0.384,P<0.05;r=-0.406,P<0.05,r=-0.380,P<0.05).The relationship between NB-E/I,BL-E/I and BV-E/I and lung function is higher than that between NB-EX,BL-EX and BV-EX.With the increase of smoking index,the number,length and volume of bronchus in expiratory phase increased,and the compliance of bronchus decreased.3.Brief summaryThe quantitative bronchial indexes(NB-EX,BL-EX,BV-EX,NB-E/I,BL-E/I,BVE/I)of CT showed abnormal changes in smokers.The relationship between NB-E/I,BLE/I and BV-E/I and lung function is higher than that between NB-EX,BL-EX and BV-EX.With the increase of NB-E/I,BL-E/I and BV-E/I,the bronchial compliance of smokers decreased.The quantitative pulmonary vascular indexes PVV-IN and PVV-EX of CT showed no abnormal changes in smokers.ConclusionsQuantitative CT based on two-phase registration can accurately measure the small airway lesions and emphysema in asymptomatic smokers,and PRMfsad% and PRMempha% can more sensitively find the changes of lung function in asymptomatic smokers.The degree of small airway lesions and emphysema in each lung lobe of asymptomatic smokers is the heaviest in the middle lobe of right lung,followed by the upper lobe of both lungs and the lightest in the lower lobe of both lungs.The correlation between the lower lungs and lung function is better than that of the upper lungs.Asymptomatic smokers have airflow limitation mainly in the lower lungs.Inspiratory combined with expiratory quantitative CT can accurately measure the abnormal changes of bronchi in asymptomatic smokers.The increase of smoking degree will reduce bronchial compliance and lung function.Respiratory biphasic quantitative CT is insensitive to abnormal changes of pulmonary vessels in smokers.