title: Dynamic computed tomography of the neonatal lung: volume calculations and validation in an animal model.
abstract: OBJECTIVE
  The purpose of this study was to evaluate and validate dynamic volume calculation by respiratory-gated multislice computed tomography (CT) in small neonatal animals.
  
  
  METHODS
  Six mechanically ventilated newborn piglets were imaged in a multislice CT with 0.5-mm slice thickness (4:16 pitch, 0.5-second rotation time, 120 kV). The respirator was connected to the CT unit for recording the respiratory signal. Simultaneously, tidal volume was measured by the respirator and functional residual capacity (FRC) using a multiple-breath washin-washout technique (MBW) with heptafluoropropane (HFP) as tracer gas. Complete volume datasets were reconstructed throughout the respiratory cycle in increments of 10% using retrospective half-scan gating. All animals were scanned in 3 different ventilator settings. Dynamic lung volumes (tidal volumes) were calculated by means of segmentation of the lung parenchyma during the respiratory cycle using work-in-progress software.
  
  
  RESULTS
  The mean (+/-standard deviation) FRC determined by CT was 24.7+/-8.6 mL versus 24.8+/-7.3 mL for the MBW technique. There was no statistically significant difference (P=0.555). Pearson's correlation coefficient showed a strong correlation between the data obtained with CT and that obtained with the MBW technique (r=0.886). After exclusion of one outlier, tidal volumes showed a similar correlation (r=0.837) without significant differences in the mean values (CT: 8.9+/-2.4 mL and respirator: 8.7+/-2.4 mL, P=0.566).
  
  
  CONCLUSIONS
  Dynamic multislice CT with respiratory gating allows for calculation of lung volumes and may be useful for future CT applications in human neonatal lung imaging.
authors.affiliation: Department of Radiology and the Clinic of Neonatology, Campus Charité Mitte, Universitätsmedizin Berlin, Berlin, Germany. thomas.elgeti@charite.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Elgeti
authors.forename: Hans
authors.initials: H
authors.lastname: Proquitté
authors.forename: Noga E
authors.initials: NE
authors.lastname: Rogalla
authors.forename: Jürgen
authors.initials: J
authors.lastname: Mews
authors.forename: Roland
authors.initials: R
authors.lastname: Wauer
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamm
authors.forename: Gerd
authors.initials: G
authors.lastname: Schmalisch
authors.forename: Patrik
authors.initials: P
authors.lastname: Rogalla
mesh_terms: D000465:Algorithms; D000818:Animals; D000831:Animals, Newborn; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology*; D008176:Lung Volume Measurements / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D013990:Tidal Volume / Q000502:physiology*; D014057:Tomography, X-Ray Computed / Q000379:methods*