A Primary Study Of Evaluating The Airway Dimension In COPD And Its Correlation With Airflow Limitation Using Multi-slice Spiral Computed Tomography

Objective:42 patients with chronic obstructive pulmonary disease(COPD) were scanning by using inspiratory and expiratory multi-slice spiral computed tomography (MSCT).To study the airway measurement on inspiratory and expiratory MSCT. To analyze the relationship between airflow limitation and airway dimensions from the third to the fifth generation of bronchi in patients with COPD.To study the clinical significance of the airway measurement.Materials and Methods:42 patients with COPD in our hospital from July 2009 to March 2010 were collected.These patients were scanning by using inspiratory and expiratory MSCT, The scanning parameters were:120kV,125mA, pitch 0.938, layer thickness 1mm, increament 0.5mm.The reconstitution was high resolution algorithm, matrix 512X512, field of view (FOV) 350.the workstation was MXV Philips,window width 1000HU, window level-400HU.the pulmonary function test (PFT)were performing after multisection CT were selected.The parameters of PFT included:forced expiratory volume at 1 second (FEV1%) and FEV1/FVC, the patients were sitted when examined. we developed a computer program (airway analysis)to measure the area of the bronchus. We use a phantom to validate the reliability of the program. The study bronchi were the apical bronchus of the right upper lobe (RBI) and the posterior basal bronchus of the right lower lobe (RB10), Using multiplanar reformats technology to choose the study transverse section of the bronchus which exactly perpendicular to the long axis. In each patient, airway luminal area from the third to the fifth generation of two bronchi (right B1,right B10) were measured by airway analysis which was a edited software at inspiratory CT and expiratory CT. In inspiratory CT the brochi were expressed IAx-By (x represent 3,4,5-class bronchial, y represent lung segement),in expiratory CT the brochi were expressed EAx-By,These measured airway luminal areas were normalized by using the body surface area as follows:measured airway luminal area/body surface area (mm2/m2).Using Spearman correlation analysis to evaluate the correlations between airway dimensions,change rate and pulmonary function test results.Result:â‘ IA5 had a correlation with PFT in inspiratoty CT(IA5:rFEV1%=0.352,pFEV1%=0.022;rFEV1/FVC=0.347,pFEV1/FVC=0.024), There were no significant correlations between IA3,IA4 and PFT.â‘¡The correlation coefficients between airway luminal area measured at expiratory CT and PFT were higher than those for inspiratory CT and improved as the airway size decreased (EA3:rFEV1%=0.192,pFEV1%=0.224;rFEV1/FVC=0.155,pFEV1/FVC=0.326,EA4:rFEV1%=0.546,pFEV1% < 0.001;rFEV1/FVC=0.536,pFEV1/FVC< 0.001, EA5:rFEV1%=0.725,pFEV1% < 0.001;rFEV1/FVC=0.711,pFEV1/FVC< 0.001);â‘¢The correlation coefficients between EA-B10and PFT were higher than EA-B1;â‘£EA4/IA4,EA5/IA5 had higher correlations with PFT (EA4/IA4:rFEV1%=0.542,pFEV1%< 0.001;rFEV1/FVC=0.416,PFEV1/FVC=0.006 EA5/IA5:rFEV1%=0.672,pFEV1%< 0.001;rFEV1/FVC=0.596,PFEV1/FVC< 0.001), There were no significant correlations between EA3/IA3 and PFT, The correlation coefficients between EA/IA and PFT improved as the airway size decreased.Conclusion:we could get the follow conclusions through the study:1:It is feasible to evaluate bronchial lumen area using inspiratory and expiratory MSCT and aided software.2:The distal airway lumen size in the role of airflow limitation higher than in proximal airways.3:The airway disease in the lower lobe make more contribution to airflow limitation than upper lobe.4:Bronchial lumen area in expiratory MSCT and the change rate of Bronchial lumen area in inspiratory and expiratory MSCT reflect the airway constriction included not only the fixed stenosis caused by anatomic abnormality,but also the dynamic stenosis caused by collapse of the lumen,so could better reflect the situation of expiratory flow limitation than inspiratory MSCT.