title: Effect of inspiration on airway dimensions measured in maximal inspiration CT images of subjects without airflow limitation.
abstract: OBJECTIVE
  To study the effect of inspiration on airway dimensions measured in voluntary inspiration breath-hold examinations.
  
  
  METHODS
  961 subjects with normal spirometry were selected from the Danish Lung Cancer Screening Trial. Subjects were examined annually for five years with low-dose CT. Automated software was utilized to segment lungs and airways, identify segmental bronchi, and match airway branches in all images of the same subject. Inspiration level was defined as segmented total lung volume (TLV) divided by predicted total lung capacity (pTLC). Mixed-effects models were used to predict relative change in lumen diameter (ALD) and wall thickness (AWT) in airways of generation 0 (trachea) to 7 and segmental bronchi (R1-R10 and L1-L10) from relative changes in inspiration level.
  
  
  RESULTS
  Relative changes in ALD were related to relative changes in TLV/pTLC, and this distensibility increased with generation (p < 0.001). Relative changes in AWT were inversely related to relative changes in TLV/pTLC in generation 3--7 (p < 0.001). Segmental bronchi were widely dispersed in terms of ALD (5.7 ± 0.7 mm), AWT (0.86 ± 0.07 mm), and distensibility (23.5 ± 7.7%).
  
  
  CONCLUSIONS
  Subjects who inspire more deeply prior to imaging have larger ALD and smaller AWT. This effect is more pronounced in higher-generation airways. Therefore, adjustment of inspiration level is necessary to accurately assess airway dimensions.
  
  
  CONCLUSIONS
  Airway lumen diameter increases and wall thickness decreases with inspiration. The effect of inspiration is greater in higher-generation (more peripheral) airways. Airways of generation 5 and beyond are as distensible as lung parenchyma. Airway dimensions measured from CT should be adjusted for inspiration level.
authors.affiliation: Department of Computer Science, University of Copenhagen, Nørre Campus, Universitetsparken 5, 2100, Copenhagen Ø, Denmark, phup@diku.dk.
authors.forename: Jens
authors.initials: J
authors.lastname: Petersen
authors.forename: Mathilde M W
authors.initials: MM
authors.lastname: Wille
authors.forename: Lars Lau
authors.initials: LL
authors.lastname: Rakêt
authors.forename: Aasa
authors.initials: A
authors.lastname: Feragen
authors.forename: Jesper H
authors.initials: JH
authors.lastname: Pedersen
authors.forename: Mads
authors.initials: M
authors.lastname: Nielsen
authors.forename: Asger
authors.initials: A
authors.lastname: Dirksen
authors.forename: Marleen
authors.initials: M
authors.lastname: de Bruijne
mesh_terms: D000368:Aged; D055088:Early Detection of Cancer / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012137:Respiratory System / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013997:Time Factors; D014109:Total Lung Capacity