title: Quantitative assessment of peripheral airway obstruction on paired expiratory/inspiratory thin-section computed tomography in chronic obstructive pulmonary disease with emphysema.
abstract: OBJECTIVE
  We examined the hypothesis that paired inspiratory/expiratory computed tomography (CT) scans in a limited-lung area that excludes emphysema may provide a more accurate evaluation of peripheral airway obstruction in patients with chronic obstructive pulmonary disease (COPD) with emphysema.
  
  
  METHODS
  This study included 32 patients with COPD. The cross-sectional area between -500 and -1024 HU was segmented as whole-lung. The relative areas (RA) less than -950 HU for the whole-lung (RA<-950) were segmented as emphysema, and pixels less than -900 HU for the whole-lung (RA<-900) were segmented to evaluate air trapping. Next, the cross-sectional area between -500 and -950 HU that excludes emphysema was segmented as limited-lung, and pixels between -900 and -950 HU for the limited-lung (RA900-950) were segmented. The changes in RA<-900 (RA<-900-change) and RA900-950 (RA900-950-change) between inspiration and expiration were calculated. Correlations between CT measurements and the results of pulmonary function tests (PFT) were evaluated.
  
  
  RESULTS
  There was no significant difference between the mean inspiratory RA<-950 and expiratory RA<-950 (P = 0.245), but the mean expiratory RA900-950 decreased significantly compared with the mean inspiratory RA900-950 (P < 0.001). The correlation coefficients between PFT parameters and the RA900-900-change in the limited-lung without emphysema were higher than that of the RA<-900-change in the whole-lung.
  
  
  CONCLUSIONS
  The paired inspiratory/expiratory CT measurements in the limited-lung without emphysema correlated more closely with the PFTs. Our observations suggest that paired inspiratory/expiratory CT scans in the limited-lung excluding emphysema are sensitive for the evaluation of airway obstruction in COPD with emphysema.
authors.affiliation: From the Department of Radiology, St. Marianna University School of Medicine, Kawasaki City, Kanagawa, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kurihara
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Yagihashi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakajima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D045853:Exhalation; D005260:Female; D006801:Humans; D001239:Inhalation; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012129:Respiratory Function Tests; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*