title: Analysis of discrete and continuous distributions of ventilatory time constants from dynamic computed tomography.
abstract: In this study, an algorithm was developed to measure the distribution of pulmonary time constants (TCs) from dynamic computed tomography (CT) data sets during a sudden airway pressure step up. Simulations with synthetic data were performed to test the methodology as well as the influence of experimental noise. Furthermore the algorithm was applied to in vivo data. In five pigs sudden changes in airway pressure were imposed during dynamic CT acquisition in healthy lungs and in a saline lavage ARDS model. The fractional gas content in the imaged slice (FGC) was calculated by density measurements for each CT image. Temporal variations of the FGC were analysed assuming a model with a continuous distribution of exponentially decaying time constants. The simulations proved the feasibility of the method. The influence of experimental noise could be well evaluated. Analysis of the in vivo data showed that in healthy lungs ventilation processes can be more likely characterized by discrete TCs whereas in ARDS lungs continuous distributions of TCs are observed. The temporal behaviour of lung inflation and deflation can be characterized objectively using the described new methodology. This study indicates that continuous distributions of TCs reflect lung ventilation mechanics more accurately compared to discrete TCs.
authors.affiliation: Department of Radiology, Johannes Gutenberg-University Mainz, Germany. doebrich@uni-mainz.de
authors.forename: Marcus
authors.initials: M
authors.lastname: Doebrich
authors.forename: Klaus
authors.initials: K
authors.lastname: Markstaller
authors.forename: Jens
authors.initials: J
authors.lastname: Karmrodt
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Balthasar
authors.initials: B
authors.lastname: Eberle
authors.forename: Norbert
authors.initials: N
authors.lastname: Weiler
authors.forename: Manfred
authors.initials: M
authors.lastname: Thelen
authors.forename: Wolfgang G
authors.initials: WG
authors.lastname: Schreiber
mesh_terms: D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D016247:Information Storage and Retrieval / Q000379:methods; D007700:Kinetics; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology*; D008954:Models, Biological; D012123:Pulmonary Ventilation / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*