title: Quantitative assessment of emphysema distribution in smokers and patients with alpha1-antitrypsin deficiency.
abstract: BACKGROUND
  Identification of upper lobe emphysema is mandatory before lung volume reduction surgery (LVRS). Here we introduce a CT-based objective model for describing the distribution of different types of emphysema.
  
  
  METHODS
  Fifty COPD patients were included in the study. Half had alpha1-antitrypsin deficiency (alpha1-COPD) and the rest had smoking-induced emphysema (usual COPD). All patients were scanned 3 times. The relative area of emphysema in each CT slice was plotted against table position, and the cranio-caudal distribution was calculated as the slope of the regression line.
  
  
  RESULTS
  The variation in slopes within a patient was much less than the variation in slopes between patients (P<0.0001). There was a significant difference between slopes in the alpha1-COPD and the usual COPD groups (P<0.0001). In the alpha1-COPD group, 24/25 patients had lower lobe emphysema. In the usual COPD group, 4 patients had upper lope predominance, 5 patients had heterogeneous distributions, and 16 patients had lower lobe predominance.
  
  
  CONCLUSIONS
  The majority of patients with smoking-related emphysema have a homogeneous distribution and lower lobe predominance although not as noticeable as in alpha1-antitrypsin deficiency. An objective and quantitative method for determining the distribution of emphysema should be applied when selecting candidates for LVRS.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, University of Copenhagen, Rigshospitalet, 4011, Blegdamsvej 9, 2100 Copenhagen, Denmark. stavngaard@dadlnet.dk
authors.forename: Trine
authors.initials: T
authors.lastname: Stavngaard
authors.forename: Saher B
authors.initials: SB
authors.lastname: Shaker
authors.forename: Asger
authors.initials: A
authors.lastname: Dirksen
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000000981:diagnostic imaging; D011656:Pulmonary Emphysema / Q000150:complications* / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012907:Smoking / Q000009:adverse effects*; D014057:Tomography, X-Ray Computed / Q000592:standards*; D019896:alpha 1-Antitrypsin Deficiency / Q000150:complications*