title: Limits of normality of quantitative thoracic CT analysis.
abstract: BACKGROUND
  Although computed tomography (CT) is widely used to investigate different pathologies, quantitative data from normal populations are scarce. Reference values may be useful to estimate the anatomical or physiological changes induced by various diseases.
  
  
  METHODS
  We analyzed 100 helical CT scans taken for clinical purposes and referred as nonpathological by the radiologist. Profiles were manually outlined on each CT scan slice and each voxel was classified according to its gas/tissue ratio. For regional analysis, the lungs were divided into 10 sterno-vertebral levels.
  
  
  RESULTS
  We studied 53 males and 47 females (age 64 ± 13 years); males had a greater total lung volume, lung gas volume and lung tissue. Noninflated tissue averaged 7 ± 4% of the total lung weight, poorly inflated tissue averaged 18 ± 3%, normally inflated tissue averaged 65 ± 8% and overinflated tissue averaged 11 ± 7%. We found a significant correlation between lung weight and subject's height (P <0.0001, r2 = 0.49); the total lung capacity in a supine position was 4,066 ± 1,190 ml, ~1,800 ml less than the predicted total lung capacity in a sitting position. Superimposed pressure averaged 2.6 ± 0.5 cmH2O.
  
  
  CONCLUSIONS
  Subjects without lung disease present significant amounts of poorly inflated and overinflated tissue. Normal lung weight can be predicted from patient's height with reasonable confidence.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cressoni
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Gallazzi
authors.forename: Chiara
authors.initials: C
authors.lastname: Chiurazzi
authors.forename: Antonella
authors.initials: A
authors.lastname: Marino
authors.forename: Matteo
authors.initials: M
authors.lastname: Brioni
authors.forename: Federica
authors.initials: F
authors.lastname: Menga
authors.forename: Irene
authors.initials: I
authors.lastname: Cigada
authors.forename: Martina
authors.initials: M
authors.lastname: Amini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Lemos
authors.forename: Marco
authors.initials: M
authors.lastname: Lazzerini
authors.forename: Eleonora
authors.initials: E
authors.lastname: Carlesso
authors.forename: Paolo
authors.initials: P
authors.lastname: Cadringher
authors.forename: Davide
authors.initials: D
authors.lastname: Chiumello
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
mesh_terms: D000368:Aged; D001827:Body Height; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000033:anatomy & histology*; D008176:Lung Volume Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012016:Reference Values; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*