A multiscale MDCT image-based breathing lung model with time-varying regional ventilation

• Published in: Journal of computational physics Vol. 244; pp. 168 - 192
• Main Authors: Yin, Youbing, Choi, Jiwoong, Hoffman, Eric A., Tawhai, Merryn H., Lin, Ching-Long
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2013
• Subjects: AIR FLOW; Airways; ALGORITHMS; ANIMAL TISSUES; Boundary condition; Breathing; COMPARATIVE EVALUATIONS; COMPUTERIZED TOMOGRAPHY; ENGINEERING; FLOW RATE; FLUID MECHANICS; Image registration; INTERPOLATION; LAMINAR FLOW; LARGE-EDDY SIMULATION; LUNGS; Mathematical analysis; Mathematical models; MDCT; Multiscale; Pulmonary air flow; Regional; Regional ventilation; RESPIRATION; Ventilation; Image registration; Pulmonary air flow; Boundary condition; MDCT; Multiscale; Regional ventilation; boundary condition; pulmonary air flow; regional ventilation; image registration
• ISSN: 0021-9991; 1090-2716
• DOI: 10.1016/j.jcp.2012.12.007

A novel algorithm is presented that links local structural variables (regional ventilation and deforming central airways) to global function (total lung volume) in the lung over three imaged lung volumes, to derive a breathing lung model for computational fluid dynamics simulation. The algorithm constitutes the core of an integrative, image-based computational framework for subject-specific simulation of the breathing lung. For the first time, the algorithm is applied to three multi-detector row computed tomography (MDCT) volumetric lung images of the same individual. A key technique in linking global and local variables over multiple images is an in-house mass-preserving image registration method. Throughout breathing cycles, cubic interpolation is employed to ensure C1 continuity in constructing time-varying regional ventilation at the whole lung level, flow rate fractions exiting the terminal airways, and airway deformation. The imaged exit airway flow rate fractions are derived from regional ventilation with the aid of a three-dimensional (3D) and one-dimensional (1D) coupled airway tree that connects the airways to the alveolar tissue. An in-house parallel large-eddy simulation (LES) technique is adopted to capture turbulent-transitional-laminar flows in both normal and deep breathing conditions. The results obtained by the proposed algorithm when using three lung volume images are compared with those using only one or two volume images. The three-volume-based lung model produces physiologically-consistent time-varying pressure and ventilation distribution. The one-volume-based lung model under-predicts pressure drop and yields un-physiological lobar ventilation. The two-volume-based model can account for airway deformation and non-uniform regional ventilation to some extent, but does not capture the non-linear features of the lung.