title: Lung hyperaeration assessment by computed tomography: correction of reconstruction-induced bias.
abstract: Computed tomography (CT) reconstruction parameters, such as slice thickness and convolution kernel, significantly affect the quantification of hyperaerated parenchyma (VHYPER%). The aim of this study was to investigate the mathematical relation between VHYPER% calculated at different reconstruction settings, in mechanically ventilated and spontaneously breathing patients with different lung pathology.
  
  
  
  In this retrospective observational study, CT scans of patients of the intensive care unit and emergency department were collected from two CT scanners and analysed with different kernel-thickness combinations (reconstructions): 1.25 mm soft kernel, 5 mm soft kernel, 5 mm sharp kernel in the first scanner; 2.5 mm slice thickness with a smooth (B41s) and a sharp (B70s) kernel on the second scanner. A quantitative analysis was performed with Maluna® to assess lung aeration compartments as percent of total lung volume. CT variables calculated with different reconstructions were compared in pairs, and their mathematical relationship was analysed by using quadratic and power functions.
  
  
  
  43 subjects were included in the present analysis. Image reconstruction parameters influenced all the quantitative CT-derived variables. The most relevant changes occurred in the hyperaerated and normally aerated volume compartments. The application of a power correction formula led to a significant reduction in the bias between VHYPER% estimations (p < 0.001 in all cases). The bias in VHYPER% assessment did not differ between lung pathology nor ventilation mode groups (p > 0.15 in all cases).
  
  
  
  Hyperaerated percent volume at different reconstruction settings can be described by a fixed mathematical relationship, independent of lung pathology, ventilation mode, and type of CT scanner.
authors.affiliation: Department of Surgical Sciences and Integrated Diagnostics, IRCCS AOU San Martino-IST, University of Genoa, Genoa, Italy. lorenzo.ball@edu.unige.it.
authors.forename: Lorenzo
authors.identifier: 0000-0002-3876-4730
authors.initials: L
authors.lastname: Ball
authors.affiliation: Anaesthesia and Intensive Care, E.O. Ospedali Galliera, Genova, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Brusasco
authors.affiliation: Anaesthesia and Intensive Care, E.O. Ospedali Galliera, Genova, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Corradi
authors.affiliation: Radiology Department, E.O. Ospedali Galliera, Genova, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Paparo
authors.affiliation: Dipartimento di Diagnostica per Immagini, IRCCS-Azienda Ospedaliera Universitaria-IST, Genova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Garlaschi
authors.affiliation: Department of Anaesthesiology, Emergency and Intensive Care Medicine, University of Göttingen Medical Center, Göttingen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Herrmann
authors.affiliation: Department of Anaesthesiology, Emergency and Intensive Care Medicine, University of Göttingen Medical Center, Göttingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Quintel
authors.affiliation: Department of Surgical Sciences and Integrated Diagnostics, IRCCS AOU San Martino-IST, University of Genoa, Genoa, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D008176:Lung Volume Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012119:Respiration; D012121:Respiration, Artificial; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*