title: A technique for determination of lung outline and regional lung air volume distribution from computed tomography.
abstract: BACKGROUND
  Determination of the lung outline and regional lung air volume is of value in analysis of three-dimensional (3D) distribution of aerosol deposition from radionuclide imaging. This study describes a technique for using computed tomography (CT) scans for this purpose.
  
  
  METHODS
  Low-resolution CT scans of the thorax were obtained during tidal breathing in 11 healthy control male subjects on two occasions. The 3D outline of the lung was determined by image processing using minimal user interaction. A 3D map of air volume was derived and total lung air volume calculated. The regional distribution of air volume from center to periphery of the lung was analyzed using a radial transform and the outer-to-inner ratio of air volume determined.
  
  
  RESULTS
  The average total air volume in the lung was 1,900±126 mL (1 SEM), which is in general agreement with the expected value for adult male subjects in the supine position. The fractional air volume concentration increased from the center toward the periphery of the lung. Outer-to-inner (O/I) ratios were higher for the left lung [11.5±1.8 (1 SD)] than for the right [10.1±0.8 (1 SD)] (p<0.001). When normalized for the region sizes, these ratios were 1.37±0.16 and 1.20±0.04, respectively. The coefficient of variation of repeated measurement of the normalized O/I ratio was 5.9%.
  
  
  CONCLUSIONS
  A technique for outlining the lungs from CT images and obtaining an image of the distribution of air volume is described. The normal range of various parameters describing the regional distribution of air volume is presented, together with a measure of intrasubject repeatability. This technique and data will be of value in analyzing 3D radionuclide images of aerosol deposition.
authors: 1 National Institute of Health Research Biomedical Research Unit in Respiratory Disease , University Hospital Southampton NHS Foundation Trust, Southampton, UK .
authors: John
authors: J
authors: Fleming
authors: Joy
authors: J
authors: Conway
authors: Caroline
authors: C
authors: Majoral
authors: Michael
authors: M
authors: Bennett
authors: Georges
authors: G
authors: Caillibotte
authors: Spyridon
authors: S
authors: Montesantos
authors: Ira
authors: I
authors: Katz
mesh_terms: D000328:Adult; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D008168:Lung / Q000000981:diagnostic imaging*; D008176:Lung Volume Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012119:Respiration; D016683:Supine Position; D014057:Tomography, X-Ray Computed; D055815:Young Adult