title: Limitations of airway dimension measurement on images obtained using multi-detector row computed tomography.
abstract: OBJECTIVE
  (a) To assess the effects of computed tomography (CT) scanners, scanning conditions, airway size, and phantom composition on airway dimension measurement and (b) to investigate the limitations of accurate quantitative assessment of small airways using CT images.
  
  
  METHODS
  An airway phantom, which was constructed using various types of material and with various tube sizes, was scanned using four CT scanner types under different conditions to calculate airway dimensions, luminal area (Ai), and the wall area percentage (WA%). To investigate the limitations of accurate airway dimension measurement, we then developed a second airway phantom with a thinner tube wall, and compared the clinical CT images of healthy subjects with the phantom images scanned using the same CT scanner. The study using clinical CT images was approved by the local ethics committee, and written informed consent was obtained from all subjects. Data were statistically analyzed using one-way ANOVA.
  
  
  RESULTS
  Errors noted in airway dimension measurement were greater in the tube of small inner radius made of material with a high CT density and on images reconstructed by body algorithm (p<0.001), and there was some variation in error among CT scanners under different fields of view. Airway wall thickness had the maximum effect on the accuracy of measurements with all CT scanners under all scanning conditions, and the magnitude of errors for WA% and Ai varied depending on wall thickness when airways of <1.0-mm wall thickness were measured.
  
  
  CONCLUSIONS
  The parameters of airway dimensions measured were affected by airway size, reconstruction algorithm, composition of the airway phantom, and CT scanner types. In dimension measurement of small airways with wall thickness of <1.0 mm, the accuracy of measurement according to quantitative CT parameters can decrease as the walls become thinner.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Oguma
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Hirai
authors.forename: Akio
authors.initials: A
authors.lastname: Niimi
authors.forename: Hisako
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Shigeo
authors.initials: S
authors.lastname: Muro
authors.forename: Michio
authors.initials: M
authors.lastname: Shigematsu
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishimura
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Kubo
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mishima
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D061827:Dimensional Measurement Accuracy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D012137:Respiratory System / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*