Modeling the Nonlinear Motion of the Rat Central Airways

Abstract

Advances in volumetric medical imaging techniques allowed the subjectspecific modeling of the bronchial flow through the first few generations of the central airways using computational fluid dynamics (CFD). However, a reliable CFD prediction of the bronchial flow requires modeling of the inhomogeneous deformation of the central airways during breathing. This paper addresses this issue by introducing two models of the central airways motion. The first model utilizes a nodetonode mapping between the discretized geometries of the central airways generated from a number of successive computed tomography (CT) images acquired dynamically (without breath hold) over the breathing cycle of two SpragueDawley rats. The second model uses a nodetonode mapping between only two discretized airway geometries generated from the CT images acquired at endexhale and at endinhale along with the ventilator measurement of the lung volume change. The advantage of this second model is that it uses just one pair of CT images, which more readily complies with the radiation dosage restrictions for humans. Threedimensional computer aided design geometries of the central airways generated from the dynamicCT images were used as benchmarks to validate the output from the two models at sampled timepoints over the breathing cycle. The central airway geometries deformed by the first model showed good agreement to the benchmark geometries within a tolerance of 4%. The central airway geometry deformed by the second model better approximated the benchmark geometries than previous approaches that used a linear or harmonic motion model.