title: [Quantification of atelectases in artificial respiration: spiral-CT versus dynamic single-slice CT].
abstract: OBJECTIVE
  Dynamic CT (dCT) allows visualization and quantification of ventilated lung and atelectases with high temporal resolution during continuous ventilation. This study compares a quantitative image analysis in a subcarinal single slice dCT series versus a whole lung spiral-CT, in order to analyze, whether the distribution of atelectasis of a single dCT series is representative for the whole lung.
  
  
  METHODS
  dCT in sliding windows technique (slice thickness 1 mm, temporal increment 100 ms) was performed in 8 healthy pigs 3 cm caudal to the carina during continuous mechanical ventilation. Subsequently, a spiral-CT of the whole lung (slice thickness 2 mm; pitch 1.5; increment 2 mm) was acquired during inspiratory breath hold (airway pressure 20 mbar). Lung segmentation and planimetry of predefined density ranges were achieved using a dedicated software tool in both data-sets. Thus, the fractions of the following functional lung compartments were averaged over time: hyperinflated lung (- 1024 to - 910 HE), normal ventilated lung -900 to -300 HE) and atelectasis (-300 to +200 HE).
  
  
  RESULTS
  Quantitative analysis of dCT-series during continuous respiration correlated with the density analysis in spiral-CT as follows: hyperinflated lung r = 0.56; normal ventilated lung r = 0.83 and atelectases r = 0.84. Analysis of spiral-CT showed the following distribution of functional lung compartments: hyperinflated lung 3.1% normal ventilated lung 77.9% and atelectasis 19.0%. In dCT, hyperinflated lung represented 6.4%, normal ventilated lung 65.2% and atelectasis 28.4% of total the lung area.
  
  
  CONCLUSIONS
  The results of our study demonstrate that dCT allows monitoring of atelectasis formation in response to different ventilatory strategies. However, a deviation between dCT and spiral-CT has to be taken into account. In subcarinal dCT series, hyperinflated lung areas and atelectases were overestimated due to a craniocaudal gradient of atelectases, whereas normal ventilated lung was underestimated.
authors.affiliation: Klinik und Poliklinik für Radiologie, Johannes Gutenberg-Universität Mainz. cbletz@uni-mainz.de
authors.forename: C
authors.initials: C
authors.lastname: Bletz
authors.forename: K
authors.initials: K
authors.lastname: Markstaller
authors.forename: J
authors.initials: J
authors.lastname: Karmrodt
authors.forename: A
authors.initials: A
authors.lastname: Herweling
authors.forename: M
authors.initials: M
authors.lastname: Melvan
authors.forename: R
authors.initials: R
authors.lastname: Goetz
authors.forename: A
authors.initials: A
authors.lastname: Stepniak
authors.forename: B
authors.initials: B
authors.lastname: Eberle
authors.forename: H-U
authors.initials: HU
authors.lastname: Kauczor
authors.forename: C P
authors.initials: CP
authors.lastname: Heussel
authors.forename: M
authors.initials: M
authors.lastname: Thelen
mesh_terms: D000818:Animals; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging*; D013902:Radiography, Thoracic; D012119:Respiration; D012121:Respiration, Artificial; D013552:Swine; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed / Q000379:methods